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Compensatory life history responses of a mesopredator may undermine carnivore management efforts
Journal of Applied Ecology
Abstract
Lethal carnivore management, aimed at reducing carnivore impacts, is a global phenomenon threatening the persistence of many carnivores. Black‐backed jackals Canis mesomelas , the dominant cause of livestock predation in southern Africa, are widely hunted to reduce livestock predation. Despite centuries of lethal management, jackals persist. Smaller canids, like jackals, are highly adaptable and display variable responses to mortality sources, which may affect management outcomes.
The effects of killing carnivores will depend on their behaviour, social organization, reproduction and dispersal patterns. We predicted that hunted jackals will alter demographic and reproductive patterns to compensate for increased mortality. Here, we collected demographic and reproductive information from harvested jackals and compared it between continually hunted (farms) and unmanaged populations (reserves).
The removal of jackals from farms results in a decrease in median age from 5–6 years (reserves) to 2–3 years (farms). Hunting also changed the age structure of jackal populations from a stable population to an expanding population. This may be ascribed to the compensatory immigration of individuals from neighbouring unmanaged areas, suggesting the formation of a source–sink system. Unmanaged areas may act as source populations exporting young, dispersing individuals to hunted areas which may act as sinks. This is likely driven by disruptions in the normal, mutually exclusive territorial system resulting in low densities of conspecifics on farms.
The low density of conspecifics allows younger individuals that would be socially precluded from reproducing to reproduce. Jackals on farms compensated for increased mortality by increasing the pregnancy rate of young individuals and increasing the litter size at younger ages, thereby increasing reproductive output.
Synthesis and applications . The lethal management of predators is the prevailing strategy to reduce livestock predation. However, the highly adaptable nature of jackals and the combination of compensatory mechanisms such as increased reproduction and potential for immigration allow these predators to persist in the face of severe anthropogenic mortality, possibly through the formation of a source–sink system. These compensatory processes will continue to counter population management actions as long as recruitment from unmanaged areas persists.
... Used in isolation, predator culling does not always lead to increased prey survival and can be counterproductive. Predator removal can lead to population expansions of other predators and herbivores (Edwards & Edwards, 2011), disruptions to predator social systems (Doherty & Ritchie, 2017), compensatory immigration (Doherty & Ritchie, 2017;Minnie et al., 2015;Thomson et al., 2000), and increased birth rates (Doherty & Ritchie, 2017;Minnie et al., 2015). Further, some techniques become less effective over time, for example, the use of poison baits can lead to bait resistance or shyness (Allsop et al., 2017). ...
... Used in isolation, predator culling does not always lead to increased prey survival and can be counterproductive. Predator removal can lead to population expansions of other predators and herbivores (Edwards & Edwards, 2011), disruptions to predator social systems (Doherty & Ritchie, 2017), compensatory immigration (Doherty & Ritchie, 2017;Minnie et al., 2015;Thomson et al., 2000), and increased birth rates (Doherty & Ritchie, 2017;Minnie et al., 2015). Further, some techniques become less effective over time, for example, the use of poison baits can lead to bait resistance or shyness (Allsop et al., 2017). ...
... Our findings indicate that CTA has the potential to modify fox behavior. There is substantial evidence that management and harvesting practices have led to unintended consequences, driving evolution that counteracts their effectiveness (Allsop et al., 2017;Manning et al., 2021;Minnie et al., 2015;Shefferson et al., 2018;Thomson et al., 2000). With greater attention given to evolution-focused tactics, taking animal learning and adaptation into account (Evans et al., 2022;Manning et al., 2021), we may be able to develop fox impact mitigation regimes that minimize the need for culling and removal actions that may lead to undesirable evolutionary consequences (Bischof & Zedrosser, 2009), while still addressing the negative impacts of predator species . ...
Predation by invasive mammalian species is one of the key drivers of native species' population declines and extinctions. Current management of invasive species focuses on their removal from the landscape. However, total removal can be difficult, costly and even impossible. If eradication is not achieved, reductions in predator numbers are often temporary. New tactics are needed to target predators in situ, to reduce their negative impacts. We test the efficacy of conditioned taste aversion (CTA), a tactic that could reduce the impact of predation on target prey species. By associating nausea with a specific food source, it may be possible to condition an aversion to a target bait, and ultimately to live animals in the wild. To assess if wild invasive red foxes (Vulpes vulpes) can be conditioned to avoid a specific food source, we used baits (fried deboned chicken) containing encapsulated levamisole, an anthelmintic agent known to induce nausea leading to emesis and/or diarrhea at high dosages with no long-term side effects. We buried baits at 30 stations across an open landscape. After treatment, reductions in control baits taken (at least 30%) were observed for 68 days, indicating the use of CTA had successfully reduced bait consumption by red foxes in a wild context. To our knowledge, this study represents the first successful test of CTA to a meat bait in a wild red fox population. Our results suggest that CTA shows promise as a tool to reduce the pre-dation of vulnerable animals providing an alternative tactic to manage the impacts of invasive mammalian predators where eradication is currently impossible. K E Y W O R D S conditioned taste aversion, invasive predator, red fox
... Predator management may have both perverse outcomes (e.g. Minnie, Gaylard & Kerley (2016) show earlier reproduction in managed jackal populations) and unexpected positive outcomes for biodiversity (e.g. show that livestock are sometimes withdrawn from high risk areas, leading to a relaxation of domestic herbivore pressures). ...
... Clearly, and as demonstrated in this Scientific Assessment, the system is complex, and there may be unforeseen or perverse outcomes of management interventions (e.g. Minnie et al., 2016). The PredSA assessment identifies many management approaches to mitigating livestock predation. ...
... These techniques consist of lethal and nonlethal methods and are generally implemented as a precautionary (≈ preventative) measure to decrease the risk of livestock predation or as a remedial (≈ reactive) action following predation (PMF, 2016). In South Africa, many livestock producers persist in attempting to reduce predator numbers through unselective, lethal methods (Du Plessis, 2013; McManus, Dickman, Gaynor, Smuts & MacDonald, 2015;Minnie, Gaylard & Kerley, 2016). There are, however, an increasing number of producers who are moving away from an eradication-only approach to non-lethal and more target-specific methods . ...
This assessment provides a policy relevant synthesis on the topic of livestock predation and its management in South Africa, as well as recommendations for future research.
See also https://predsa.mandela.ac.za/
... A growing body of evidence, however, suggests that removing carnivores-whether via general culling or targeted removal-may not address the real causes of carnivore-livestock conflict (e.g., cheetah, Acinonyx jubatus, social behaviors; Melzheimer et al., 2020), or that removals may even exacerbate the problem by leaving the culprits in place or disrupting carnivore social networks (Haber, 1996;Woodroffe et al., 2006;Santiago-Avila et al., 2018;Nattrass et al., 2020). Several recent studies of pumas (Puma concolor), gray wolves (Canis lupus), black-backed jackals (Canis mesomelas) and caracals (Caracal caracal), among other carnivores, suggest that killing one or more carnivores can increase risks for remaining livestock (Peebles et al., 2013;Minnie et al., 2016;Teichman et al., 2016;Santiago-Avila et al., 2018;Nattrass et al., 2020;Dellinger et al., 2021;Grente, 2021); also (Krofel et al., 2011) and coyotes (C. latrans) (Conner et al., 1998). ...
... Lethal removal creates a vacancy on the landscape, and following species-specific time lags, a greater number of new carnivores may immigrate in to fill the void than the original number of residents that were removed (Adams et al., 2008;Cooley et al., 2009a;Cooley et al., 2009b;Minnie et al., 2016). The allure of vacant habitat may also attract residents of neighboring ranges to shift their territories or expand them. ...
... The allure of vacant habitat may also attract residents of neighboring ranges to shift their territories or expand them. Some carnivores also respond to heavy mortality by increasing litter sizes and reducing the average age of initial female reproduction (e.g., black-backed jackals, Minnie et al., 2016). ...
Human-carnivore conflict is still characterized by lethal control, even while some evidence suggests that carnivore removal may not affect the likelihood of future livestock predation, or that it may even exacerbate the problem. Here we propose five non-exclusive, and likely additive, hypotheses for why lethal removals could fail to mitigate livestock-carnivore conflict. We also propose a methodological change in the scale of conflict analyses from populations to smaller social networks, and encourage public education that includes discussions about the potential consequences for communities with livestock following the killing of carnivores, in addition to broader outreach about both the costs and benefits of living with carnivores.
... Allerdings gibt es zunehmend Hinweise, dass die vorherrschende Art der Bejagung von Mesoprädatoren wie Rotfüchsen, Schakalen oder Kojoten die Bestände nicht im gewünschten Umfang und somit die verursachten Schäden nicht nachhaltig reduziert werden können. Denn das Dispersionsverhalten, das flexible Sozialverhalten und die dichteabhängige Reproduktion gleichen die Verluste durch die Jagd wieder aus (Funk 1994;Baker et al. 2002;Rushton et al. 2006;Minnie et al. 2016;Kämmerle et al. 2019b). Zudem hat ein Teil der jagdlichen Mortalität einen kompensatorischen Charakter: Aufgrund der hohen natürlichen Mortalität würden viele Füchse ohnehin sterben, bevor sie reproduzieren (Harris und Smith 1987). ...
... Verschiedene Studien zeigen, dass mit der aktuell praktizierten Fuchsjagd die Bestände nicht reguliert werden können, weil die grundlegenden Anforderungen an ein Wildtiermanagement nicht erfüllt sind (Heydon und Reynolds 2000;Baker et al. 2002;Rushton et al. 2006;Minnie et al. 2016;Kämmerle et al. 2019b). Für ein modernes Fuchsmanagement braucht es zum einen 1) ein besseres Verständnis für die Populationsdynamik des Rotfuchses, 2) verlässliche Datengrundlagen zu den Beständen, 3) eine klare Definition quantitativ messbarer Ziele und Massnahmen sowie 4) die Überprüfung, ob die Massnahmen wirken und gegebenenfalls angepasst werden müssen (Doherty und Ritchie 2017;Robin et al. 2017). ...
... Diese Methoden können jedoch höchstens bei zeitlich und räumlich intensiver Durchführung ihren funktionalen Zweck -die Bestände zu reduzieren -erfüllen. Dies ist aufgrund des grossen Aufwands und der oft fehlenden Ressourcen erfahrungsgemäss kein realistisches Szenario (Minnie et al. 2016;Doherty und Ritchie 2017;Kämmerle et al. 2019a). Zudem sollten die von Füchsen erbrachten Ökosystemleistungen mehr Beachtung finden (Jiguet 2020). ...
Zusammenfassung
Der Rotfuchs Vulpes vulpes wird in Europa intensiv bejagt. Als Begründung für die Jagd wird aufgeführt, dass Füchse gefährdete Tierarten sowie Nutztiere erbeuten, Krankheiten auf den Menschen und auf Haustiere übertragen und für Konflikte mit den Menschen im Siedlungsraum sorgen. Allerdings gibt es zunehmend Belege, dass die vorherrschenden Methoden der Fuchsjagd, trotz grossem Aufwand durch die Jägerschaft, weder die Bestände noch die verursachten Schäden wirksam und nachhaltig reduzieren. Die Jagd auf Füchse basiert aktuell nicht auf wissenschaftlichen Grundlagen, denn es fehlen Bestandszahlen sowie klar definierte und messbare Ziele. Hinzu kommt, dass nicht evaluiert wird, wie sich die jagdlichen Eingriffe auf die Fuchsbestände auswirken. Zudem werfen verschiedene Jagdmethoden wie die Baujagd mit Hunden oder der Einsatz von Schrot grundsätzliche ethische und tierschützerische Fragen auf. Daher ist ein neues Managementkonzept für den Fuchs gefordert, das ökologische, ökonomische und ethische Kriterien beinhaltet und neben Abschüssen auch nicht-letale Massnahmen einbezieht. Dies unter anderem auch, weil die wachsenden Fuchsbestände im Siedlungsraum angepasste Lösungen erfordern. Im vorliegenden Kapitel zeigen wir auf, welche Grundlagen für ein evidenzbasiertes Fuchsmanagement notwendig sind.
Summary
The red fox Vulpes vulpes is intensively hunted in Europe. The reason given for the hunting are that foxes prey on endangered species and livestock, transmit zoonoses, transmit diseases to domestic animals, and cause conflicts with humans in urban areas. However, there is increasing evidence that the prevailing hunting methods are unlikely to effectively and sustainably reduce either populations or the damage caused, despite the large investment of time by hunters. The hunting of foxes is generally not based on scientific principles, there is a lack of population figures, clearly defined and measurable objectives, and there is no evaluation how hunting interventions impact fox populations. Furthermore, various hunting methods, such as den hunting with dogs or the use of shotgun pellets, raise profound ethical and animal welfare questions. Therefore, a new management concept for the red fox is required that takes ecological, economic and ethical criteria into account and includes non-lethal measures in addition to culling. Moreover, the growing urban fox populations require adapted solutions. In this chapter, we outline which basics are necessary for an evidence-based fox management.
... To reduce predation on livestock, farmers often resort to lethal management (Thorn et al., 2013;Treves & Karanth, 2003), which may disrupt social structures resulting in predators compensating reproductively by having higher proportions of young breeders and larger litter sizes (Haber, 1996;Minnie, Gaylard et al., 2016). Disrupting social structures in territorial species may also create vacant spaces which facilitates compensatory immigration (Minnie, Zalewski, et al., 2018;Pulliam, 1988). ...
... latrans;Knowlton et al., 1999) and red foxes (Vulpes vulpes; Kierepka et al., 2017)], jackals show physiological and behavioural flexibility to local conditions (e.g. compensatory reproduction and immigration (Minnie, Gaylard et al., 2016;Minnie, Zalewski, et al., 2018)), resulting in lethal management having little effect on jackal densities (Thorn et al., 2013). ...
... Our study is consistent with Tensen et al. (2018) that lethal management thus far does not have a negative effect on genetic diversity of jackals in the study area. Genetic diversity may be maintained through compensatory migration within and from outside the study area, as it is not a closed system, whereas social/family structure may be maintained by compensatory reproduction (Minnie, Gaylard et al., 2016). Similar suggestions are reported for lethally managed coyote (Kierepka et al., 2017), red fox, (Cavallini & Santini, 1996;Marlow et al., 2016), wolverine, Gulo gulo (Gervasi et al., 2015) and cougar, Pumo concolor (Robinson et al., 2008). ...
Globally, levels of human–wildlife conflict are increasing as a direct consequence of the expansion of people into natural areas resulting in competition with wildlife for food and other resources. By being forced into increasingly smaller pockets of suitable habitat, many animal species are at risk of becoming susceptible to loss of genetic diversity, inbreeding depression and the associated inability to adapt to environmental changes. Predators are often lethally controlled due to their threat to livestock. Predators such as jackals (black backed, golden and side striped; Canis mesomelas, C. aureus and C. adustus, respectively), red foxes (Vulpes vulpes) and coyotes (C. latrans) are highly adaptable and may respond to ongoing persecution through compensatory reproduction such as reproducing at a younger age, producing larger litters and/or compensatory immigration including dispersal into vacant territories. Despite decades of lethal management, jackals are problematic predators of livestock in South Africa and, although considered a temporary measure, culling of jackals is still common. Culling may affect social groups, kinship structure, reproductive strategies and sex‐biased dispersal in this species. Here, we investigated genetic structure, variation and relatedness of 178 culled jackals on private small‐livestock farms in the central Karoo of South Africa using 13 microsatellites. Genetic variation was moderate to high and was similar per year and per farm. An absence of genetic differentiation was observed based on STRUCTURE, principal component analysis and AMOVA. Relatedness was significantly higher within farms (r = 0.189) than between farms (r = 0.077), a result corroborated by spatial autocorrelation analysis. We documented 18 occurrences of dispersal events where full siblings were detected on different farms (range: 0.78–42.93 km). Distance between identified parent–offspring varied from 0 to 36.49 km. No evidence for sex‐biased dispersal was found. Our results suggest that in response to ongoing lethal management, this population is most likely able to maintain genetic diversity through physiological and behavioural compensation mechanisms.
... South African farmers' perception is that predator numbers are increasing (Avenant and Du Plessis 2008, Du Plessis 2013. Factors causing the possible increase in predator numbers include poor fencing, limited human presence, and the possibility that continuous predator removal operations over large parts in South Africa, especially over the last three decades, has led to compensatory immigration and breeding (Avenant and Du Plessis 2008, Minnie et al. 2016, 2018b. These perceptions are in accord with the decline in government support for commercial sheep farmers, including for fencing and predator control operations (Bergman et al. 2013, Natrass and Conradie 2018; the expansion of protected areas; the increase in game; weekend and hobby farms (Reed andKleynhans 2009, Du Plessis 2013); and an increase in farmer unemployment (Western Cape Department of Agriculture 2017). ...
... Many producers believe that mesocarnivores have to decrease drastically to reduce depredation to acceptable levels (Du Plessis et al. 2015). However, livestock predation by mesocarnivores is rooted in their ethological and ecological plasticity, which allows them to persist despite centuries of population reduction efforts (Bergman et al. 2013, Minnie et al. 2016, 2018a. ...
... Caracal and black-backed jackal occur throughout South Africa (Avenant et al. 2016, Minnie et al. 2016. They are the most important native predators that cause livestock losses (Blaum et al. 2009, Strauss 2009, Van Niekerk 2010, Thorn et al. 2012, Bergman et al. 2013, Badenhorst 2014, Kerley et al. 2017, and are increasingly responsible for losses in the game ranching industry (De Waal 2009, Bergman et al. 2013, Schepers 2016. ...
South Africa has approximately 8,000 commercial small livestock farms and 5,800 communal/subsistence farmers throughout the country. Reported rates of small livestock loss to predation range from 3-13% and 0.5-19% from communal farming areas. A range of predators exist on the African continent, but in southern Africa major livestock losses are primarily due to black-backed jackal and caracal. South Africans have been managing caracals and jackals for over 300 years with no elimination of predation. During the aforementioned time frame, producers have used and/or developed a number of techniques including lethal, nonlethal, and integrated predator damage management to address predation losses. In the Karoo area of South Africa, one producer decided that a new way needs to be developed after losing over 60 lambs in a month, while practicing continuous removal of caracal and black-backed jackal. His integrated predator damage management system includes using a prototype nonlethal collar system for sheep and lambs. The collars are used to train dominant pairs of predators to avoid predation while maintaining their territories and keeping transient predators out of the area. The system has now gone into production in South Africa and is being distributed by its inventor.
... Migration in response to culling has also been shown in the red fox (Gentle et al., 2007;Lieury et al., 2015), resulting in source-sink dynamics where animals in source populations, outside of the control area, migrate to areas of higher mortality, known as sinks, created by culling. Other predators have demonstrated similar responses; for example, culling of black-backed jackals (Canis mesomelas) has been shown to lead to compensatory birth effects, and increased migration into the control areas (Minnie, Gaylard, & Kerley, 2016). Some preliminary evidence suggests that the most effective control measures can select for animals that avoid that measure (Allsop et al., 2017;Minnie et al., 2016); although the response can be expected to be context-specific. ...
... Other predators have demonstrated similar responses; for example, culling of black-backed jackals (Canis mesomelas) has been shown to lead to compensatory birth effects, and increased migration into the control areas (Minnie, Gaylard, & Kerley, 2016). Some preliminary evidence suggests that the most effective control measures can select for animals that avoid that measure (Allsop et al., 2017;Minnie et al., 2016); although the response can be expected to be context-specific. Modeling has shown that undesirable "education" of invasive predators can "create and maintain an uncatchable segment in the population with respect to a given control tool" (p.1234; [Bischof & Zedrosser, 2009]). ...
... This would make them less lethal to the native mammals that they have been "conditioned" not to attack. Another advantage of keeping "less lethal" foxes in a given landscape, is that they could prevent compensatory increases in female fox fecundity that has been observed in situations where fox (Berry & Kirkwood, 2010;Marlow et al., 2016) and black-backed jackal (Minnie et al., 2016) numbers have been artificially reduced. ...
Abstract Predation of threatened fauna by native and introduced predators can drive extinction and prevent population recovery. Most predator management involves exclusion or culling. Evidence suggests that exclusion may have detrimental effects on a prey species' predator awareness. At the same time, culling can cause selection of control‐resistant predators. There is increasing interest in harnessing evolutionary processes to drive adaptation of threatened fauna to cope, but there is limited attention on trying this from the predator direction. We need to shift the survival advantage away from predators that avoid lethal control, and go on to kill, towards those that demonstrate behaviors that reduce impact on threatened fauna. Instead of driving undesirable predator selection, could we select through management actions desirable traits to make them “less lethal” to threatened fauna? We draw on experimental research on predator aversion that suggests there may be an alternative way to mitigate the impacts of predators, while maintaining the learning opportunities of prey species. Using the case study of the invasive red fox in Australia, we propose a conceptual framework within which future research and management could occur to select for these desirable traits in predators and develop practical regimes for predator impact mitigation.
... Because of extirpations of large carnivores, black-backed jackals are the dominant predator over most of South Africa, including on small livestock farms where domestic sheep are often their main prey (Kamler et al. 2012a;Drouilly et al. 2018;Minnie et al. 2016Minnie et al. , 2018. Consequently, jackals are heavily persecuted on small livestock farms because of their real or perceived predation on livestock (Du Plessis et al. 2015;Minnie et al. 2016, Drouilly et al. 2018. ...
... Because of extirpations of large carnivores, black-backed jackals are the dominant predator over most of South Africa, including on small livestock farms where domestic sheep are often their main prey (Kamler et al. 2012a;Drouilly et al. 2018;Minnie et al. 2016Minnie et al. , 2018. Consequently, jackals are heavily persecuted on small livestock farms because of their real or perceived predation on livestock (Du Plessis et al. 2015;Minnie et al. 2016, Drouilly et al. 2018. In contrast, on many nature reserves, jackals are not hunted, or are hunted at a much lower intensity compared to livestock farms (Kamler et al. 2013b, Drouilly et al. 2018, Minnie et al. 2018. ...
... This was surprising given that betas made numerous forays to surrounding livestock farms, yet none attempted to establish territories there. Although the rate of philopatry by betas was higher than that observed in East Africa (24%; Moehlman 1986), our results were consistent with those reported by Minnie et al. (2016) in South Africa, who reported that on reserves with low human-caused mortality, only about 50% of female black-backed jackals that were 3-4 year old had become pregnant, suggesting a relatively high proportion of older jackals were betas. Beta females staying in their natal ranges for 2 subsequent litters to help their parents was reported previously for black-backed jackals (Moehlman 1979, Ferguson et al. 1983) and coyotes (Andelt 1985, Gese et al. 1996, Kamler and Gipson 2000, so it may not be unusual behavior for medium-sized canids. ...
We used radiocollars and GPS collars to determine the movements and habitat selection of golden jackals (Canis aureus) in a seasonally dry deciduous forest with no human settlements in eastern Cambodia. We also collected and analyzed 147 scats from jackals to determine their seasonal diet and prey selection. The mean (± SE) annual size of home-range ranges (47.1 ± 2.5 km 2 ; n = 4), which were mutually exclusive between mated pairs, was considerably larger than that previously reported for this species, resulting in an extremely low density (0.01 jackal/km 2). The unusually large home ranges and low density probably were due to the harsh dry season when most understory vegetation is burned and nearly all waterholes dry up, thereby causing a large seasonal decline in the availability of small vertebrate prey. Resident groups consisted of an alpha pair, but no betas, and were situated only in areas not occupied by leopards (Panthera pardus) and dholes (Cuon alpinus). Jackals avoided dense forests and streams, and had a strong selection for dirt roads, possibly to avoid larger predators. Overall the jackal diet was diverse, with at least 16 prey items identified, and there was no significant difference in diet composition between the cool-dry and hot-dry seasons. Scat analysis showed that the main food items consumed by jackals were processional termites (Hospitalitermes spp.; 26% biomass consumed), followed by wild pig (Sus scrofa; 20%), muntjac (Muntiacus vaginalis; 20%), and civets (17%). Compared to available biomass, jackals were not random in their consumption of ungulates because muntjac were selectively consumed over larger ungulate species. Dietary overlap with dholes and leopards was relatively low, and consumption patterns indicated jackals were preying on ungulates rather than scavenging from kills of larger carnivores. Our results showed that the jackal is an extremely adaptable and opportunistic species that exhibits unique behaviors to survive in an extreme environment near the edge of its distribution.
... South African farmers' perception is that predator numbers are increasing (Avenant and Du Plessis 2008, Du Plessis 2013. Factors causing the possible increase in predator numbers include poor fencing, limited human presence, and the possibility that continuous predator removal operations over large parts in South Africa, especially over the last three decades, has led to compensatory immigration and breeding (Avenant and Du Plessis 2008, Minnie et al. 2016, 2018b. These perceptions are in accord with the decline in government support for commercial sheep farmers, including for fencing and predator control operations (Bergman et al. 2013, Natrass and Conradie 2018; the expansion of protected areas; the increase in game; weekend and hobby farms (Reed andKleynhans 2009, Du Plessis 2013); and an increase in farmer unemployment (Western Cape Department of Agriculture 2017). ...
... Many producers believe that mesocarnivores have to decrease drastically to reduce depredation to acceptable levels (Du Plessis et al. 2015). However, livestock predation by mesocarnivores is rooted in their ethological and ecological plasticity, which allows them to persist despite centuries of population reduction efforts (Bergman et al. 2013, Minnie et al. 2016, 2018a. ...
... Caracal and black-backed jackal occur throughout South Africa (Avenant et al. 2016, Minnie et al. 2016. They are the most important native predators that cause livestock losses (Blaum et al. 2009, Strauss 2009, Van Niekerk 2010, Thorn et al. 2012, Bergman et al. 2013, Badenhorst 2014, Kerley et al. 2017, and are increasingly responsible for losses in the game ranching industry (De Waal 2009, Bergman et al. 2013, Schepers 2016. ...
South Africa has approximately 8,000 commercial small livestock farms and 5,800 communal/subsistence farmers throughout the country. Reported rates of small livestock loss to predation range from 3-13% and 0.5-19% from communal farming areas. A range of predators exist on the African continent, but in southern Africa major livestock losses are primarily due to black-backed jackal and caracal. South Africans have been managing caracals and jackals for over 300 years with no elimination of predation. During the aforementioned time frame, producers have used and/or developed a number of techniques including lethal, nonlethal, and integrated predator damage management to address predation losses. In the Karoo area of South Africa, one producer decided that a new way needs to be developed after losing over 60 lambs in a month, while practicing continuous removal of caracal and black-backed jackal. His integrated predator damage management system includes using a prototype nonlethal collar system for sheep and lambs. The collars are used to train dominant pairs of predators to avoid predation while maintaining their territories and keeping transient predators out of the area. The system has now gone into production in South Africa and is being distributed by its inventor.
... The high level of persecution of jackals in South Africa is controversial (Nattrass, Drouilly, & O'Riain, 2019). Although intensive jackal control can significantly reduce jackal densities on livestock farms compared to nearby reserves (Kamler et al., 2013), others believe persecution does not affect jackal densities due to compensatory mechanisms and immigration (Minnie, Gaylard, & Kerley, 2016;Minnie, Zalewski, et al., 2018). Nonetheless, under natural condition with large carnivores present, jackals might experience high mortality levels similar to those in human-hunted populations. ...
... pardus; Schaller, 1972;Estes, 1991), cheetahs (Acinonyx jubatus; and African wild dogs (Lycaon pictus; Kamler, Davies-Mostert, Hunter, & Macdonald, 2007), yet the effects of these natural mortalities on jackal populations have never been quantified. Similarly, although the effects of human-caused mortalities on the genetic and population structure of jackals have been reported (Minnie, Gaylard, et al., 2016;Minnie, Zalewski, et al., 2018;Tensen, Drouilly, & van Vuuren, 2018), the effects of human-caused mortalities on the annual survival of a jackal population have never been determined. ...
... On HWE, despite the lack of human hunters, jackals had survival that was similar to BNR, primarily because of 4 deaths to leopard predation. Jackals are likely to have evolved in ecosystems with high levels of mortalities from large carnivores and apparently compensate for increased mortality by having high reproductive rates, helping to explain why jackals can persist on private farmlands in South Africa despite high rates of human-caused mortalities (Minnie, Gaylard, et al., 2016). Major limitations of our research were that our two study sites occurred in different habitats with presumably different food resources, at different times, and in different countries. ...
... The most likely explanation for this phenomenon in jackal populations is immigration from neighbouring areas with lower hunting pressure or even without hunting (Minnie et al. 2016), as has been described also for red foxes in the UK (Baker and Harris 2006). This claim can also be supported by the fact that golden jackal populations are spreading rapidly across Europe and have nowadays high population densities in a very great spectrum of ecosystem conditions (Potočnik et al. 2019;Cunze and Klimpel 2022). ...
... Although based on our results we cannot confirm that hunting affects jackal abundance/density, it is obvious that such a specific hunting approach can affect the population demographic (age) structure as also found previously related to general hunting (Stoyanov 2018). However, at the moment we cannot predict the consequence of such change in demographic structure on population abundance, i.e., either its decrease due to intensive cull of reproductive individuals or increase due to higher reproduction success of subadults and/or immigration of individuals from neighbouring areas (see also Minnie et al. 2016). Therefore, studies of the effect of (different methods) of hunting on the population structure as well as on life history traits of golden jackal should be encouraged in the future. ...
In recent decades, the golden jackal Canis aureus has experienced a population increase in many European countries, including Croatia. As a result, human-jackal conflicts (e.g., damage to livestock and wildlife, general nuisance in (sub)urban areas) have increased dramatically, and there is an urgent need to develop and use a range of mitigation tools that also aim to control population growth. Hunting is one of the well-known tools for population control, therefore the aim of this study was to determine the effects of habitat type and weather conditions on jackal hunting success. From 2019 to 2023, a total of 217 jackals were culled during 106 hunting events in an approximately 10,500 ha lowland habitat along the Sava River in central Croatia. All jackals (56% males and 44% females) were culled using small calibre rifle (222 Remington) with night vision scope. Based on age structure, 16% juveniles and 84% adults were shot, and the average catch per unit effort (CPUE) was 2.0 animals/day. The best hunting success was obtained by attracting jackals with a calling method, i.e., by playing the sound of a wounded hare. Regarding the type of habitat, 56% of the culls were in cultivated, non-forested areas. It was confirmed that weather conditions, i.e., daily temperature and precipitation, influence hunting success, especially for males. Hunting success of adult males was lower on days with higher temperatures and on days with more precipitation. We can state that individual hunting with using calling method is an effective tool for successful golden jackals harvesting; moreover, jackal hunting can minimize the conflict with gamekeepers and farmers, and would help to improve public perception of jackals.
... However, despite >350 years of persecution, jackals and caracals have been relatively resilient to lethal management. In response to high population turnover, compensatory immigration was observed in both species (Minnie et al., 2016;Tensen et al., 2018) and compensatory reproduction was reported in jackals (Minnie et al., 2016). Non-lethal techniques, such as selective exclusion fences, may potentially be more efficient as a management tool for predator control, but more research should be conducted to address these issues. ...
... However, despite >350 years of persecution, jackals and caracals have been relatively resilient to lethal management. In response to high population turnover, compensatory immigration was observed in both species (Minnie et al., 2016;Tensen et al., 2018) and compensatory reproduction was reported in jackals (Minnie et al., 2016). Non-lethal techniques, such as selective exclusion fences, may potentially be more efficient as a management tool for predator control, but more research should be conducted to address these issues. ...
The black-footed cat (Felis nigripes) is the smallest felid species
in Africa and is endemic to the arid regions of southern Africa. It
is currently listed as “Vulnerable” in the International Union for
the Conservation of Nature (IUCN) red list of threatened species,
with a population decline suspected over the general range. Since 2005, the Black-footed Cat Working Group has been conducting long-term monitoring of black-footed cats in two study areas in South Africa. In this study, we used data from radio�collared animals to evaluate the relative importance of the different causes of mortality in this population.
... The overall adaptability of jackals is also evident from their widespread occupation of areas under human settlement (livestock farms and wildlife farms; Humphries et al. 2015) and their recolonization of areas where they were historically eradicated (Stuart and Stuart 2015;Minnie et al. 2016). Anthropogenically altered landscapes, such as livestock and wildlife farms, often reduce the availability of natural resources but provide easily obtainable prey in the form of livestock and privately owned wildlife. ...
... Furthermore, the distinct δ 13 C seen in cattle samples (strong C 4 ) is seldom seen in jackal scat samples from the livestock farm (< 10%) and given the size of cattle and limited reports of cattle predation by jackals (personal communication A. Lombaard 2019), cattle predation by jackals is extremely unlikely, confirming prediction 5. However, given the behavioral flexibility often reported in this species and their known cross-boundary movement (Minnie et al. 2016(Minnie et al. , 2018Nattrass et al. 2019Nattrass et al. , 2020 which could lead to different isotopic signatures between the controlled and protected populations.), it is possible that jackals are moving onto bordering farms and preying upon livestock that exhibit different isotopic signals due to supplemented livestock feeding regimes seen on neighboring farms during winter. ...
Wildlife and livestock farms around the world have eradicated large predators, leaving an empty niche for mesopredators to occupy. In South Africa, black-backed jackals (Canis mesomelas) are a widely distributed mesopredator that actively prey on wildlife and livestock. Despite the documented economic losses often associated with livestock predation in South Africa and abroad, research in many areas of canid ecology has received little attention. Using standard isotopic analysis (SIA), we conducted inter-population and jackal–prey isotopic comparisons by analyzing the δ13C and δ15N signals of jackal scat and prey hair samples (livestock and rodents) collected in sites of varied human exposure across multiple seasons. C3 signals dominated our results despite the C4 grasslands that are characteristic of the study sites. Our results indicated inter-population variation with a C3/C4 mixed diet in reserve and livestock farm samples, and a C3 orientated diet in wildlife farm samples. There were significant differences in the δ13C between seasons in the livestock and wildlife farm populations but not in the reserve population. δ15N had strong support for inter-population differences and no support for seasonal variation. Jackal isotopic niche breadths differed between populations, overlapped moderately with rodent prey and indicated almost no overlap with livestock. Our results highlight the feeding plasticity of jackals and the impact of human activities on resource availability and the subsequent feeding choices in canids. Using SIA, we accurately determined that livestock form a limited, if not completely absent, constituent of certain jackal populations. We strongly encourage the complementary use of SIA in dietary studies and wildlife management practices.
... For example, where Black-backed jackals have been culled in areas where food is not limiting, conspecifics are known to emigrate from areas of relatively high density to areas of low density, i.e., into those areas where individuals have been removed. Furthermore, Black-backed jackals are known to increase their rate of reproduction in areas where they are actively persecuted (Minnie, Gaylard & Kerley 2016). ...
... Accurate and robust estimates of Black-backed jackal population density are lacking in the scientific literature (Minnie et al. 2018;Minnie, Gaylard & Kerley 2016). We aimed to determine whether it would be possible to use REM and gREM estimators, in conjunction with commercially available cameras, to develop a repeatable method for monitoring of Black-backed jackal population densities on wildlife reserves, with the intention of possibly using such a method, once validated, on a wide variety of landscapes and land management regimes (potentially including stock farming enterprises). ...
... High population densities of black-backed jackals are a direct consequence of agriculture (concentration of food and poor disposal of carcases) (Humphries, Hill & Downs, 2015). Lethal control may be an ineffective measure of population control for black-backed jackals because removed individuals are simply replaced by others (Humphries, Hill & Downs, 2015;Minnie, Gaylard & Kerley, 2016). Deliberate control of problematic species may additionally result in 'compensatory reproduction' which has been shown to be present in several carnivore species, including blackbacked jackals, Canadian lynxes (Lynx canadensis), Eurasian lynxes (Lynx lynx), red foxes and side-striped jackals (Canis adustus) (Parker et al., 1983;Harris & Smith, 1987;Bingham & Purchase, 2002;Bagrade et al., 2016;Minnie, Gaylard & Kerley, 2016). ...
... Lethal control may be an ineffective measure of population control for black-backed jackals because removed individuals are simply replaced by others (Humphries, Hill & Downs, 2015;Minnie, Gaylard & Kerley, 2016). Deliberate control of problematic species may additionally result in 'compensatory reproduction' which has been shown to be present in several carnivore species, including blackbacked jackals, Canadian lynxes (Lynx canadensis), Eurasian lynxes (Lynx lynx), red foxes and side-striped jackals (Canis adustus) (Parker et al., 1983;Harris & Smith, 1987;Bingham & Purchase, 2002;Bagrade et al., 2016;Minnie, Gaylard & Kerley, 2016). Large scale compensatory reproduction further manifests in increased fecundity, larger proportion of breeding females, increased reproductive lifespan, and a decrease in age at first reproduction of the targeted species (Kerley, Wilson & Balfour, 2018). ...
Globally, anthropogenic land conversion has resulted in reduced natural land available for free-roaming wildlife, and a shift in species composition. Certain mesocarnivores exhibit an ability to adapt and expand distribution ranges under differing anthropogenic pressures. Our study addressed the socio-ecological attitudes and general perspectives towards mammalian mesocarnivores across a land-use gradient (rural-urban) from the uMgungundlovu to eThekwini municipalities of KwaZulu-Natal, South Africa. We determined threats, conflicts and attitudes towards mammalian mesocarnivores using an online questionnaire survey. The public held a range of opinions on mesocarnivores. Participants from both land-use types generally regarded mesocarnivores as non-threatening and vital for the environment. However, not all mesocarnivores were regarded with equal benevolence. Black-backed jackals, Canis mesomelas, were consistently singled out as a problematic species by rural inhabitants and this intensified reactions when a confrontation occurred. Smaller and more behaviourally flexible mesocarnivores (mongoose spp. and Cape genets, Genetta tigrina) were the most observed species in both land-use types, indicating potential population increases. Vehicle collision was the leading cause of mesocarnivore fatalities. Overall, perceived impacts and threats of mesocarnivores differed across the land-use gradients. Our study illustrates the importance of citizen science and community engagement across a land-use gradient in wildlife conservation efforts. © 2021 Southern African Wildlife Management Association. All rights reserved.
... Research on coyotes (Canis latrans) and black-backed jackals (C. mesomelas) indicates that human-caused mortality can generate compensatory reproduction that might augment the number of breeding packs and elevate the predator density, both of which might raise the risk for domestic animals (Knowlton et al., 1999;Minnie et al., 2016). ...
... Ecologists have long understood that release from competition leads to prey switches, range shifts, and other flexible, behavioral responses by surviving predators. For a particularly relevant example in our context, mesopredator release has been substantiated repeatedly after the removal of a larger, dominant competitor (Prugh et al., 2009;Allen et al., 2016;Minnie et al., 2016;Krofel et al., 2017;Newsome et al., 2017). ...
Rapid, global changes, such as extinction and climate change, put a premium on evidence-based, environmental policies and interventions, including predator control efforts. Lack of solid scientific evidence precludes strong inference about responses of predators, people, and prey of both, to various types of predator control. Here we formulate two opposing hypotheses with possible underlying mechanisms and propose experiments to test four pairs of opposed predictions about responses of predators, domestic animals, and people in a coupled, dynamic system. We outline the design of a platinum-standard experiment, namely randomized, controlled experiment with cross-over design and multiple steps to blind measurement, analysis, and peer review to avoid pervasive biases. The gold-standard has been proven feasible in field experiments with predators and livestock, so we call for replicating that across the world on different methods of predator control, in addition to striving for an even higher standard that can improve reproducibility and reliability of the science of predator control.
... Recent research from the Karoo using satellite-tagged jackals to identify feeding sites on farmland indicates that > 80% of livestock feeding events were the result of a kill rather than a scavenging event 1971a, b, Hall-Martin & Botha 1980, Moehlman 1987, Bernard & Stuart 1992, Bingham & Purchase 2002. Litter size varies from one to eight pups with a mean of about four (Bothma 1971b, Bingham & Purchase 2002 and is associated with food availability and the mother's age (Moehlman 1979, 1987, Minnie et al. 2016). Pups typically disperse after about six months but may stay and help protect and provision subsequent litters ( Moehlman 1979, Ferguson et al. 1983). ...
... Such a plastic behavioural repertoire has implications also for research methodologies seeking to pin down the ecological impact of lethal management of jackals. For example, Minnie et al. (2016) found that jackals culled in national parks were older than those culled on surrounding farmlands and concluded that this provided supportive evidence for 'source-sink' dynamics (juvenile jackals dispersing from protected areas onto farms). Yet the differing age structure of culled jackals may also reflect the fact that older jackals on farms, with greater experience of hunting and a repertoire of adaptive behaviour, were more difficult to cull than the juveniles. ...
The black‐backed jackal Canis mesomelas, henceforth jackal, has re‐emerged as a threat to South African sheep farmers. This sparked contestation between farmers and conservationists over the reasons for their return and the relative merits of lethal and non‐lethal approaches to protecting livestock. Three separate reviews of the scientific literature converged on the same broad conclusion that lethal control of jackals is probably ineffective, but that more scientific research is necessary, especially on farms. We draw on historic evidence and recent research across a range of disciplines to show that jackal diet and behaviour varies regionally and alter in response to changing threats and opportunities. More data will not support generalisable conclusions and have already been eclipsed by broad‐scale changes in the political, economic and ecological landscapes of South Africa. Reduced government support for farmers, rising production costs and falling product prices, together with an increasing frequency of droughts, have conspired to weaken the collective management hand of farmers and, ultimately, contributed to a decline in the sheep farming industry. Many sheep farmers have sold their land to non‐commercial ‘lifestyle' farmers or expanding nature reserves, creating a growing network of safer spaces for jackals to persist, from which their offspring can sink into neighbouring commercial farmland. When these landscape‐level changes are combined with the wide phenotypic plasticity and catholic diet of the jackal, we should be neither surprised at their resurgence nor contented with suggestions that more ecological research is likely to facilitate any sustainable solutions. Black‐backed jackal (Canis mesomelas) diet and behaviour varies regionally and alters in response to changing threats and opportunities. Universalisable or sustainable solutions to the conflict between jackals and sheep farmers in South Africa are unlikely.
... We compared two study sites in central South Africa, a nature reserve where carnivore populations are not managed, and a sheep and game farm where jackal and caracal populations are controlled. Lethal management of mesopredators does not necessarily result in their lower densities (Minnie, Gaylard, and Kerley 2016). However, evidence from observations during annual blackfooted cat capture sessions indicated a difference in predator density between the two sites. ...
The black-footed cat, a small felid endemic to southern Africa, is particularly vulnerable to killing by larger carnivores while also being prone to developing renal diseases. Here, we investigated the effect of predator control on black-footed cat populations by comparing adult annual survival between two sites, a nature reserve with little predator management and a sheep and game farm where jackals and caracals were lethally controlled. Although relatively low, survival rates were similar for both sites, suggesting that intraguild killing did not have an additive effect on black-footed cat mortality. Disease was however prevalent and weakened individuals might have a reduced ability to evade predators.
... Social and behavioural interactions also mediate potential changes in generation time. For example, culling of adult jackals disrupted the population's social structure, leading to earlier maturation times and dispersal into the managed area by young from source populations [65]. Hunting of adults similarly disrupted the structure of breeding groups in pumas, but in this case, frequent male turnover and increased rates of infanticide, combined with declines in female survival, led to overall population declines, and changes in generation time have not yet been observed [66]. ...
Populations declining toward extinction can persist via genetic adaptation in a process called evolutionary rescue. Predicting evolutionary rescue has applications ranging from conservation biology to medicine, but requires understanding and integrating the multiple effects of a stressful environmental change on population processes. Here we derive a simple expression for how generation time, a key determinant of the rate of evolution, varies with population size during evolutionary rescue. Change in generation time is quantitatively predicted by comparing how intraspecific competition and the source of maladaptation each affect the rates of births and deaths in the population. Depending on the difference between two parameters quantifying these effects, the model predicts that populations may experience substantial changes in their rate of adaptation in both positive and negative directions, or adapt consistently despite severe stress. These predictions were then tested by comparison to the results of individual-based simulations of evolutionary rescue, which validated that the tolerable rate of environmental change varied considerably as described by analytical results. We discuss how these results inform efforts to understand wildlife disease and adaptation to climate change, evolution in managed populations and treatment resistance in pathogens.
... vulnerable prey, often livestock; see review by(Elbroch and Treves 2023). Removing apex carnivores may also result in higher abundances of subordinate carnivores of the same species or other species(Newby and Brown 1958; Crooks and Soulé 1999; Elbroch and Treves 2023).Therefore, killing large predators like grey wolves may have varied effects on other animals including domestic ones(Krofel et al. 2007;Prugh et al. 2009; Allen et al. 2016;Minnie, Gaylard, and Kerley 2016;Newsome et al. 2017;Nattrass et al. 2019; Elbroch et al. 2020). For example, the eradication of the Tasmanian thylacine (Thylacinus cynocephalus) seems to have left niche vacancies for the smaller dingoes (Canis familiaris dingo) and red foxes (Vulpes vulpes) to become the dominant livestock predators of Australia and Tasmania ...
... Given the extent of human-wildlife conflict in agricultural and peri-urban areas, PAs are often presumed to provide an essential refuge for wildlife including mesocarnivores. Yet this may not be the case, as PAs face a wide variety of threats and include a range of management practices that can reduce their conservation potential (Balme, Slotow and Hunter, 2010;Watson et al., 2014;Santini et al., 2016) and even actively persecute mesocarnivores such as black-backed jackal (Nattrass and Conradie, 2015;Minnie, Gaylard and Kerley, 2016 ...
Protected areas (PAs) form the cornerstone for most carnivore conservation strategies. However, climate change, increased isolation and human pressure along PA boundaries are together reducing the effectiveness of PAs to conserve carnivores. Mesocarnivores, in particular, frequently move beyond the boundaries of PAs where they threaten human livelihoods, and as a result, are often subject to chronic persecution. In South Africa, we know little about the conservation status of mesocarnivores both within and outside of PAs, as most research focuses on large, charismatic apex predators. The goal of my study was to leverage data collected from large carnivore studies to understand variation in mesocarnivore species richness within PAs. Camera trap surveys were conducted as part of Panthera’s 2015 national leopard monitoring programme in seven PAs across northern KwaZulu-Natal (KZN), South Africa. Using a multi-species extension of the Royle-Nichols occupancy model, my study explored environmental, interspecific and anthropogenic drivers of mesocarnivore habitat use and species richness. I found a surprisingly low number of detections (N = 356) for all five mesocarnivore species and considerable variation across PAs. Small PAs with a recent history of human disturbance supported more mesocarnivore species and at higher relative abundance. Mesocarnivore species richness was found to decline with increased vegetation and leopard abundance but increased towards the edge of PAs. Variation in species richness estimates decreased significantly with vegetation productivity and domestic dog abundance. Together these results suggest that (1) the edges may provide a refuge for mesocarnivores from more dominant species, (2) mesocarnivores exhibited resilience/adaptability to human disturbance, and (3) primary productivity and domestic dog abundance could mediate mesocarnivore distributions within PAs. My study showed that camera trap data derived from a single-species survey can be used to make inferences about non-target species to great success. Current PAs in KZN may not adequately conserve mesocarnivores, and as a result, emphasis should be placed on coexistence with mesocarnivores in marginal habitat outside of PAs.
... Thus, recovery of large carnivores in anthropogenic landscapes could lead to unsustainably high levels of persecution and threaten some mesopredator populations with local extirpation. Although mesopredators such as coyotes and jackals (Canis spp.) have proven to be notably resilient when faced with intense persecution, this resilience is driven by a high capacity for compensatory reproduction and immigration that might not be possible for some other species (35)(36)(37). Urban-wildland gradients, where the paradox of the lethal human shield should be most influential, should thus be priority regions for monitoring trends of species that are subject to mortality from both humans and large carnivores. ...
The challenge that large carnivores face in coexisting with humans calls into question their ability to carry out critical ecosystem functions such as mesopredator suppression outside protected areas. In this study, we examined the movements and fates of mesopredators and large carnivores across rural landscapes characterized by substantial human influences. Mesopredators shifted their movements toward areas with twofold-greater human influence in regions occupied by large carnivores, indicating that they perceived humans to be less of a threat. However, rather than shielding mesopredators, human-caused mortality was more than three times higher than large carnivore-caused mortality. Mesopredator suppression by apex predators may thus be amplified, rather than dampened, outside protected areas, because fear of large carnivores drives mesopredators into areas of even greater risk from human super predators.
... A caveat of this model is that estimates of caracal growth rates for Southern Namibian individuals on farmlands were used (see Appendix 1) and are therefore not necessarily indicative of population growth rates in South Africa. The low growth rates are nonetheless surprising, since small-to medium-sized predators normally exhibit high intrinsic growth rates (Minnie, Gaylard, & Kerley, 2016). Therefore, this requires further research and investigation. ...
Anecdotal evidence suggests that there is interspecific competition between black‐backed jackal ( Canis mesomelas ) and caracal ( Caracal caracal ) on farmland in South Africa. Home range data were used across both years (1983–2016) and provinces, as well as polynomial interpolation, to quantitatively assess changes in the population of caracal and black‐backed jackal over time. The jackal abundance estimates had low uncertainty, while the caracal data had high uncertainty. A Gaussian model of interspecific competition was developed, using the properties of the Gaussian model and the more reliable jackal abundance data to reduce the uncertainty associated with the caracal data. It was found that caracals have actually declined in South Africa over the past few decades. Caracals are both beneficial to society in terms of trade and other uses and a threat to farmers in terms of livestock predation. To explore the drivers for hunting further, a predator–prey model was developed. The model found that killing for trade is not the main driver for declines in caracal numbers. However, reducing the persecution of caracal on farmland actually stabilises the number of black‐backed jackal, resulting in ‘win–win’ outcomes for both farmers and caracal. A concerted Africa‐wide response to caracal declines is needed.
... Introduced predators are highly mobile and have good dispersal abilities, which means that they can quickly invade areas where previously resident individuals have been removed through lethal control (Lieury et al. 2015, Minnie et al. 2016, Palmas et al. 2020. In some instances, this has been shown to result in an increase in activity and pressure on threatened species as multiple subordinate individuals from surrounding areas compete for the vacated territory (e.g. ...
We investigated the efficacy of baiting with the cat bait Eradicat ® as a control tool to temporarily reduce feral cat (Felis catus) activity while vegetation within harvested areas was re-establishing. In particular we were interested in whether Eradicat® baits would be taken by feral cats in karri forest areas that had been disturbed by harvesting operations;
whether baiting could be used to reduce feral cat activity; and whether Eradicat ® baits pose a risk to nontarget species in the karri forest. We assessed bait uptake patterns and relative activity levels for feral cats, foxes, potential prey (critical weight range mammals and small birds) and other native species. We used remote cameras to collect data at 30 baited sites and 30 unbaited sites for 12 months prior to and 12 months following commencement of a 2-weekly baiting program. We also identified factors likely to influence bait uptake and activity levels, and simultaneously measured these to inform predictive models.
... The home ranges of jackals in our study were, however, substantially smaller and across a narrower range than those in farmlands with a similar grassland habitat (MCP 95% varying from 5.02 km 2 to 1 300 km 2 , Humphries et al. 2016) although this broad range seems to have resulted from the transient behaviour of four of the five jackals in their study. Similarly, F-A-80438 conducted an atypical long-distance foray, which was possibly because of a search for a vacant territory in the bordering farmlands (Minnie et al. 2016b(Minnie et al. , 2018. Large variations in space use occurs between jackals of different ages (Humphries et al. 2016) and although our sample size was small, home ranges and space use were larger in subadults than adults, aligning with prediction 1 (subadult jackals would have larger annual home ranges than adults) and previous studies on jackal home ranges ( Table A for mean and error values of three jackals in our study suggest that M-SA-80435 and F-SA-80439 belong to the same social group (family group) with an annual home range overlap of greater than 50% (Ferguson et al. 1983;Loveridge and Macdonald 2001;Kamler et al. 2019). ...
An animal’s ability to traverse a landscape and utilise available resources is vital for its survival. The movement patterns of an animal provide insight into space use, activity patterns and ecological requirements that are imperative for successful farming and wildlife management practices. Home ranges are often used as a measurement of space use, which provides a quantitative value of an animal’s movement patterns in relation to various biological factors. A factor that is often overlooked in the analysis of movement patterns is the effect of moon phase, despite its known impact on the activity and hunting success of nocturnal predators. We live-trapped, radio-collared and monitored five black-backed jackals (Canis mesomelas) in the Golden Gate Highlands National Park, South Africa, between 2018 and 2019 to determine the impact of various environmental factors on movement patterns. Annual home ranges varied between individuals, were larger in subadults and overlapped between three jackals. Space use and travel velocity suggested a crepuscular activity pattern with a reliance on nocturnal activity and limited diurnal activity. Individual space use suggested variation between moon phases, although overall variation was negligible. Jackals travelled farther during new moon, compared with full moon, with the most notable difference between 23:00 and 04:00. Our results suggest that jackal behaviour does not align with the predation risk hypothesis. Space use and travel velocities varied between seasons, possibly because of differences in activity during mating and pupping periods. Our study confirms the flexibility in jackal space use and suggests a possible relationship with moon phase. To properly understand movement patterns at an individual and population level, we encourage additional research about jackals and various environmental factors via multidisciplinary collaborations.
... This home range estimate of 45.47 km 2 is consistent with those from previous studies, with territory sizes ranging from 2.1 km 2 to 91.5 km 2 (Ferguson et al. 1983;Kaunda 2001;Kalmer et al. 2012). Although studies on farmlands are limited, Humphries et al. (2016) found that the home range of a male jackal in the more mesic KwaZulu-Natal was 11.4 ± 4.3 km 2. This is considerably smaller than the home range estimated for this study in the Free State and may be explained by differences in hunting pressure, prey availability, and varying environmental conditions (Kaunda 2001;Minnie et al. 2015). ...
... Numerous control programs in open landscapes have documented little subsequent change in the number of cats detected despite high levels of cat mortality [42,[50][51][52][53]. One plausible explanation for these observations is that there is rapid reinvasion of individuals from surrounding areas, as reported from studies of similar meso-predators [54][55][56], including cats [11,42]. Considering the distances travelled and areas traversed by the cats in this study (Table 1), and other previously recorded long-distance displacements (Table 2), it is obvious that even the extensive areas covered by aerial baiting of cats in our study (650 km 2 of aerial Eradicat ® baiting in the IFRNP and ARKC) are likely to be too small to prevent rapid reinvasion into areas where cat control is undertaken. ...
Movements that extend beyond the usual space use of an animal have been documented in a range of species and are particularly prevalent in arid areas. We present long-distance movement data on five feral cats (Felis catus) GPS/VHF-collared during two different research projects in arid and semi-arid Australia. We compare these movements with data from other feral cat studies. Over a study period of three months in the Ikara-Flinders Ranges National Park, 4 out of 19 collared cats moved to sites that were 31, 41, 53 and 86 km away. Three of the cats were males, one female; their weight was between 2.1 and 4.1 kg. Two of the cats returned to the area of capture after three and six weeks. During the other study at Arid Recovery, one collared male cat (2.5 kg) was relocated after two years at a distance of 369 km from the area of collar deployment to the relocation area. The movements occurred following three years of record low rainfall. Our results build on the knowledge base of long-distance movements of feral cats reported at arid study sites and support the assertion that landscape-scale cat control programs in arid and semi-arid areas need to be of a sufficiently large scale to avoid rapid reinvasion and to effectively reduce cat density. Locally, cat control strategies need to be adjusted to improve coverage of areas highly used by cats to increase the efficiency of control operations.
... For example, and claimed that in the different Argentinean regions the culpeo has not disappeared due to the existence of a source-sink dynamics. This type of dynamics is common to other canine species populations, such as the European red fox (Vulpes vulpes) in Europe (Rushton et al., 2006), or the black-backed jackal (Canis mesomelas) in South Africa (Minnie et al., 2016), which often renders lethal control efforts useless (Treves et al., 2016;Lozano et al., 2019). ...
We conducted an extensive review of the existing literature on the culpeo to improve our understanding of its ecology, natural history and conservation, and to identify gaps in current knowledge. For resources published before 1988, we used the synthesis made by Medel and Jaksic (1988). For studies published from 1988 onwards, we carried out a literature searching in the Scopus, Web of Knowledge and Google Scholar databases, considering all of the generic names used to define the species. We found 96 scientific articles. Most of the studies focused on diet, conflicts with the species in livestock areas, and on the use of space and habitat. We found that the description of subspecies is incomplete and that subspecies’ geographic distribution is not well known. There are also few published studies on genetic issues, population dynamics and conservation concerns. It is remarkable that vast regions in South America where culpeos live still lack basic information on the species. Diet studies describe a marked trend towards resource selection at the local level, which supports the view of the culpeo as a facultative trophic specialist. In addition, it has been confirmed that in the high Andes, the culpeo can behave as a top predator and that it is an important seed disperser in arid environments. There is no sufficient information to precisely assess the species’ conservation status in most regions. The species has been listed as "Vulnerable" in Ecuador and Colombia. Direct persecution and habitat transformation are the most critical threats that the species faces in many countries, although other threats such as climate change could also have severe consequences for the culpeo on a global scale.
... Recent population expansions of coyotes and golden jackals [6,87] have increased the potential for interactions among these carnivores, including interspecific killing by wolves. This will likely increase the value of ecosystem services provided by wolves in controlling mesopredator populations, especially since traditional approaches of limiting mesopredator abundance by shooting and other forms of lethal control suffer from low effectiveness and low social acceptance [88,89]. Improved appreciation of interspecific killing of carnivores as an important ecological role and service provided by wolves could benefit their conservation if used to raise awareness and to promote greater tolerance towards this top predator. ...
The occurrence of carnivore species in wolf diet has been overlooked and poorly studied despite the potential implications for wolf ecology and wildlife management. We conducted an extensive literature review, focusing on 120 wolf diet studies worldwide to assess global patterns of carnivore consumption by wolves and their ecological and human-related determinants. We used a total of 143 sampling sites with data on the consumption of carnivores by wolves. In total, 35 carnivore species were reported to be consumed by wolves, comprising members of all taxonomic carnivore families represented within the gray wolf range. The carnivores were mostly limited to occasional consumption (<5% of wolf diet) but could account for as much as 25% in some study areas. The most frequently consumed carnivore species were those with reported scavenging behavior, belonging to medium-sized generalist canids. Generalized linear model (GLM) analysis revealed that higher magnitudes of carnivore consumption were related to nonprotected areas as well as lower occurrences of wild ungulates, domestic ungulates, and small mammals in wolf diet, while higher numbers of consumed carnivore species were related to nonprotected areas with low vegetation productivity and lower occurrences of domestic ungulates and small mammals in wolf diet. Our results suggest that carnivore consumption by wolves is driven by altered ecosystems and human-dominated landscapes, where mesopredator densities are often increased and prey densities decreased, which intensify competition and the need for alternative food sources.
... Whilst commonly used to protect livestock, lethal predator control is often expensive and not always successful (McManus et al. 2015, Moreira-Arce et al. 2018, Bruns et al. 2020, unless targeting "problem animals" (Swan et al. 2017). For some species, particularly mesopredators, the efforts of lethal control are sometimes offset by compensatory processes such as increased reproduction and immigration (Minnie et al. 2016), and can even result in an increase in livestock The ecological effects of livestock guarding dogs (LGDs) on target and non-target wildlife Bethany R. SMITH * , Richard W. YARNELL, Antonio UZAL and Katherine WHITEHOUSE-TEDD depredation (Nattrass et al. 2020). Several forms of lethal control, such as poisoning and some forms of trapping, are also indiscriminate (Ogada 2014). ...
Livestock guarding dogs (LGDs) are used across the world to reduce livestock depredation by free-ranging predatory wildlife. In doing so, they reduce the need for lethal predator control and are considered
beneficial for conservation. However, LGDs might be perceived as predators by wildlife and induce a multitude of both positive and negative ecological effects. We conducted a literature review to evaluate the ecological effects of LGDs and found 56 publications reporting LGDs interacting with or affecting wildlife. Featuring
in 77% of the publications, LGDs were widely reported to chase and kill wildlife, leading to species-specific behavioural responses. A total of 80 species were affected by LGDs, 11 of which are listed as Near Threatened or higher on the IUCN Red List. Of the affected species, 78% were non-target species, suggesting that any benefits arising from the use of LGDs likely occur simultaneously with unintended ecological effects. However, the frequency of LGD-wildlife interactions and the magnitude of any resulting ecological effects have rarely been
quantified. Therefore, more empirical studies are needed to determine the net ecological outcome of LGD use, thereby ensuring that negative outcomes are minimised, while benefiting both farmers and wildlife.
... These blanket taxonomic-based rules ignore the individual ecology of species and geographic variability, for example assuming all tropical bats are as longlived and reproductively limited as temperate species makes little ecological sense (Russo et al. 2017). Although equating all mammals to rodents is equally fallible, data indicate that even species considered taboo for collecting, such as small carnivores, can handle substantial individual losses and still persist at the population and landscape scale (Minnie et al. 2016, Barychka et al. 2019. ...
The global environment is faced with growing threats from anthropogenic disturbance, propelling the Earth into a 6th mass extinction. For the world’s mammals, this is reflected in the fact that 25% of species are threatened with some risk of extinction. During this time of species loss and environmental alteration, the world’s natural history museums (NHMs) are uniquely poised to provide novel insight into many aspects of conservation. This review seeks to provide evidence of the importance of NHMs to mammal conservation, how arguments against continued collecting of physical voucher specimens is counterproductive to these efforts, and to identify additional threats to collecting with a particular focus on small mammals across Africa. NHMs contribute unique data for assessing mammal species conservation status through the International Union for Conservation of Nature’s (IUCN) Red List of Threatened species. However, NHMs’ contributions to mammal conservation go well beyond supporting the IUCN Red List, with studies addressing topics such as human impacts, climate change, genetic diversity, disease, physiology, and biodiversity education. Increasing and diverse challenges, both domestic and international, highlight the growing threats facing NHMs, especially in regards to the issue of lethally sampling individuals for the purpose of creating voucher specimens. Such arguments are counterproductive to conservation efforts and tend to reflect the moral opposition of individual researchers than a true threat to conservation. The need for continued collecting of holistic specimens of all taxa across space and time could not be more urgent, especially for underexplored biodiversity hotspots facing extreme threats such as the Afrotropics.
... This ancient conflict is one of the leading causes of mammalian carnivore declines worldwide and predator control is one of the oldest forms of wildlife management (Berger 2006). While traditionally considered the most economical and effective method, increasing evidence suggests that lethal control can fail to mitigate depredation in the longterm, and at times may even be counterproductive (Minnie et al. 2016, Teichman et al. 2016, Treves et al. 2016, Nattrass et al. 2019. Unselective lethal control methods are also considered by some as inhumane because they can cause suffering, as well as injury and mortality to non-target animals including domestic animals, protected species, and other wildlife (Naughton- Treves & Treves 2005, Rochlitz et al. 2010. ...
The use of livestock guarding dogs (LGDs) has been widely advocated as a responsible tool for reducing livestock predation and conserving wildlife. However, their hidden ecological costs have rarely been investigated. We analysed scats (n = 183) from six LGDs and visited Global Positioning System (GPS) location clusters (n = 352) from nine GPS-collared LGDs to reconstruct their diet and assess impacts on wildlife and livestock in Namaqualand, South Africa. Wild mammals, including 10 native species, and small-livestock were the main secondary foods (i.e. besides dog food pellets). A total of 90% of scats and one third of GPS clusters investigated had associated animal remains. When accompanied by a human attendant, fewer LGD scats contained animal matter (39.9%; of which 32.3% wild mammals and 4.6% livestock), in contrast to scats of LGDs on their own (93.2%; 14.4% wild mammals, 75.4% livestock). Similarly, few clusters of accompanied LGDs included animal remains (5.7%; of which 43.8% wild mammals and 31.3% livestock), whereas unaccompanied dogs clustered frequently at carcasses (92.4%; 16% wild mammals, 74% livestock). While sample sizes were relatively small and some dogs might have scavenged, we emphasize the importance of rigorous training and intensive monitoring of LGDs to correct unwanted predation behaviour and to maximize their ecological and protective benefits.
... The parklands are more complex in habitat structure than prairie ecosystems and effective predator removal is challenging when conducted at small, widely distributed plots across a productive landscape that supports many predator species [89]. The Alberta parklands may be more vulnerable to the creation of a source-sink system where non-managed areas provide source populations for immigration into predator-removal areas [36,90]. Lieury et al. [91] suggested that immigration would quickly negate the effects of reducing red foxes at scales less than 10 km 2 , and that spring culling is more conducive to compensatory immigration than post-dispersal culling. ...
Nest survival is most limited by nest predation, which often is increased by anthropogenic causes including habitat fragmentation, mesopredator release and predator subsidies. In mallards and other upland-nesting duck species in the North American prairies, the rate of nest survival is the vital rate most influential to population dynamics, with 15%-20% survival required for maintenance of stable populations. Predator removal during the nesting season has increased duck nest survival on township-sized (9324 ha) areas of agricultural ecosystems in eastern locations of the prairie pothole region (PPR). However, predator removal has not been evaluated in western parkland habitats of the PPR where three-dimensional structure of vegetation is considerably greater. During 2015-2017, we evaluated nest survival on control and predator-removal plots at two study areas in the parklands of central Alberta, Canada. In the second year of the study, we transposed predator removal to control for habitat effects. Estimates of 34-day nest survival did not significantly differ between trapped (x = 20.9%, 95% CI = 13.2%-33.7%) and control (x = 17.8%, 95% CI = 10.5%-30.0%) plots in any year. We do not recommend predator removal be continued in Alberta parklands due to its ineffectiveness at improving duck nest survival at the local scale.
... The integrated approach elucidated caracal use of smaller prey items that were likely to be missed by GPS cluster investigations and overestimated using scat analysis alone. Caracals are frequent sources of human-wildlife conflict (Inskip and Zimmermann 2009;Minnie et al. 2016;Drouilly et al. 2017Drouilly et al. , 2019. In our urban system, they are persecuted for predating pets and domestic fowl. ...
Urbanisation radically changes habitats and alters available resources. Populations of large, highly mobile species are often extirpated at the urban-wildland interface, while species like mesocarnivores may thrive by capitalising on changes in prey abundance. We investigated the diet of the caracal (Caracal caracal), a medium-sized felid inhabiting patchy natural habitat isolated within the dense urban matrix of South Africa’s second largest city, Cape Town. We systematically integrated two classic dietary methods (scat and GPS clusters) by accounting for gut transit times. As part of a larger caracal ecology study, we GPS-collared 26 individuals over a two-year period (2014–2016) to generate coarse (3-hour) and fine-scale (20-minute) GPS movement data. Using the movement data, we investigated 677 GPS-clusters for prey remains. We collected 654 scats, half of which were found at GPS-clusters and were linked with the individual sampled. By systematically correcting for a range of gut transit times, we determined whether scat at cluster sites was from the same or an earlier feeding event, thereby increasing the overall detection of feeding events by > 50%. Avian prey dominated GPS cluster findings while micromammals were overwhelmingly represented in scat. Although > 40% of feeding events occurred within 200 meters of the urban edge, caracals largely preyed on native species. Our findings have implications for understanding the ability of some species to persist in the face of rapid environmental change, human-wildlife conflict, pathogen transmission, and bioaccumulation of pesticides. Further, this approach could be incorporated into studies that estimate foraging-explicit resource selection and habitat preference.
... Harris and Smith (1987) documented that foxes maintained productivity by reducing the proportion of non-breeding vixens in response to London fox control operations, rather than by altering litter size. Likewise, it was found in a more recent study of black-backed jackals C. mesomelas that the average litter size of females did not increase to compensate for higher mortality, but that it was compensated for by increasing the pregnancy rate and litter size of young individuals, thereby increasing the reproductive output (Minnie et al. 2016). ...
A decline in the Danish population of red foxes Vulpes vulpes due to an outbreak of canine distemper (CDV) in 2012 gave us the opportunity to test the hypothesis that the reproductive performance of foxes increases when the population density declines. The reproductive performance of 280 female foxes from two periods (mainly shot or road killed) in 1997-2000 and 2012-16, were compared. Game Bag Records of Jutland (GBRJ) were used as an estimate of population density. After a drop in GBRJ in 2013 due to the CDV epidemic, the mean litter size (based on dark placental scars from partum to oestrus) became significantly larger than in previous years; F=4.3, p>0.03, Hc=8.1, p<0.02. In 2015-2016, after population decline the mean litter size was 8.2 (±2.5 SD) and in the breeding seasons before population decline in 1997-1999 and 2012-2013 the mean litter size was 5.6 (±2.1 SD) and 5.7 (±2.0 SD), respectively. During the period 1997-1999, barrenness was relatively high especially in yearlings, and the reproducing yearling foxes made up only 6% of the breeding females compared to 2012-13 and 2015-16 where breeding yearling females made up 53% and 61%, respectively. Age related differences in litter size and productivity were found in years with a relatively high population density, when older females in their third and fourth breeding seasons had the largest litter sizes and highest productivity. This was in contrast to the years with low population size, when no age-related reproduction was found, and when young females had relatively large litter sizes and high productivity. Rump fat thickness (RFT) of the breeding females was significantly higher in breeding females than in barren females, and the RFT was positively correlated to the number of embryos (R2=41%). This study confirms that the number of barren females drops, and the proportion of yearling females and litter size increase with reduced population density. Hence, culling or epidemics in fox populations increase production, most probably due to reduced competition among foxes, but will not change population size permanently. The present level of culling and traditional hunting in Denmark has no long-term effect on population size.
... One of the components likely to vary among different situations with different operators is the impact of predator culling on local predator density [5]. A common perception is that culled predators are rapidly replaced through immigration, and this is used to argue both the futility of predator control, and its difficulty and importance [6][7][8][9]. With few exceptions (e.g. ...
Lethal control is widely employed to suppress the numbers of target wildlife species within restricted management areas. The success of such measures is expected to vary with local circumstances affecting rates of removal and replacement. There is a need both to evaluate success in individual cases and to understand variability and its causes. In Britain, red fox (Vulpes vulpes) populations are culled within the confines of shooting estates to benefit game and wildlife prey species. We developed a Bayesian state-space model for within-year fox population dynamics within such restricted areas and fitted it to data on culling effort and success obtained from gamekeepers on 22 shooting estates of 2 to 36 km². We used informative priors for key population processes—immigration, cub recruitment and non-culling mortality–that could not be quantified in the field. Using simulated datasets we showed that the model reliably estimated fox density and demographic parameters, and we showed that conclusions drawn from real data were robust to alternative model assumptions. All estates achieved suppression of the fox population, with pre-breeding fox density on average 47% (range 20%–90%) of estimated carrying capacity. As expected, the number of foxes killed was a poor indicator of effectiveness. Estimated rates of immigration were variable among estates, but in most cases indicated rapid replacement of culled foxes so that intensive culling efforts were required to maintain low fox densities. Due to this short-term impact, control effort focussed on the spring and summer period may be essential to achieve management goals for prey species. During the critical March-July breeding period, mean fox densities on all estates were suppressed below carrying capacity, and some maintained consistently low fox densities throughout this period. A similar model will be useful in other situations to quantify the effectiveness of lethal control on restricted areas.
... The ecological narrative drew on predator ecology to warn that killing territorial predators can make problems worse for farmers by releasing wild herbivore populations (thereby creating competition for grazing), disrupting predator social systems (thereby enabling younger females to breed) and facilitating compensatory immigration, potentially worsening the level of livestock depredation (Doherty and Ritchie 2017). This view has been supported by South African biological evidence suggesting that jackals are younger and have larger litters on farms, where they are heavily persecuted, than in nature reserves (Minnie et al. 2016), and that heterogeneous anthropogenic mortality induced source-sink dynamics via compensatory immigration (Minnie et al. 2018). Farmers, however, pointed out that lethal control worked in the past and that as predator numbers are a positive function of food supply, co-existing with predators on extensive livestock farms is not a stable or sustainable solution Conradie 2015, Nattrass et al. 2017, in press). ...
Populations of adaptable mesopredators are expanding globally where passive rewilding and natural recolonization are taking place, increasing the risk of conflict with remaining livestock farmers. We analysed data from two social surveys of farmers in the Karoo, South Africa, where black-backed jackals (Canis mesomelas) and caracals (Caracal caracal) have re-emerged as a threat to sheep farms in the context of falling agricultural employment and the expansion of natural areas. We show that irrespective of measurement approach, lethal control of mesopredators in this fragmented socio-economic landscape was associated with increased livestock losses the following year. Terrain ruggedness was positively, and number of farmworkers negatively, associated with livestock losses. Our study provides further evidence that lethal control of mesopredators in this context is probably counter-productive and supports calls to develop, share and financially support a range of non-lethal methods to protect livestock, especially where natural recolonization of mesopredators is occurring. A graphical abstract can be found in Electronic supplementary material.
... Similarly to other mesopredators worldwide (Gompper, 2002;Arnold et al., 2012), jackal and caracal have re-established populations in former ranges after being extirpated. Signs of their expansion are reported more frequently (Marker & Dickman, 2005;Drouilly et al., 2018c) despite sustained lethal management that seeks to reduce their numbers both on farmland (Tensen, Drouilly & van Vuuren, 2018) and even in PAs (Minnie, Gaylard & Kerley, 2016). Although our results remain preliminary due to the relatively low number of GLCs we were able to investigate, we provide clear evidence that mesopredators kill and consume livestock (presence of typical bite marks notably) but are also able to scavenge, albeit to a lesser extent. ...
Studying the feeding ecology of mesopredators living on or adjacent to farmland is important as livestock predation fuels conflict between farmers and predators and between diverse stakeholders on how to best manage this conflict. Most dietary studies on elusive and heavily persecuted predators rely on indirect methods such as scat analysis, because direct observations of predation events are rare. Consequently, the proportion of livestock and other prey that was actively hunted vs. scavenged remains largely unknown. We used data from global positioning system collars affixed to black‐backed jackal (Canis mesomelas) and caracal (Caracal caracal) to locate potential feeding sites on farmland and a protected area and to attempt to determine whether prey had been killed or scavenged. We compared dietary estimates from prey items found at global positioning system location clusters (GLCs) with those obtained from scat analysis and investigated whether GLC analysis is a suitable method to determine mesocarnivore diet. The success rate of finding a kill site when investigating GLCs was significantly higher for caracal than for jackal. Only 16.2% and 4.7% of jackal and caracal GLCs, respectively, were classified as scavenging events. Livestock was the most frequently detected prey in both scats and GLCs on farmland but GLCs provided a higher estimate of sheep biomass than scats. Caracal GLCs revealed prey ranging in size from small to large, whereas jackal GLCs were only for medium and large prey categories. Adult male caracals predated significantly more on livestock than females and younger individuals. Collared jackals residing in the protected area never formed GLCs containing livestock remains on neighbouring farms. Together, GLCs and scat analyses provide a more complete understanding of mesopredators feeding ecology on farmland. We recommend that both methods are applied, particularly in regions where livestock predation and lethal management of predators are driving conflict between stakeholders.
The primary focus of rice breeding research is now on developing high-yielding rice varieties with early maturing and physio-chemical features, such as improved cooking quality, aroma, and extra-long grain. This shift in focus is driven by the growing global demand for high-quality rice. Using traditional breeding methods to trait pyramid these extremely important traits while maintaining yield and quality is a challenging task. Good grain quality(aromatic), fertilizer responsiveness, and high-yielding varieties can help the farmers in Pakistan to increase their revenue despite global population growth and changing international market patterns. At the Rice Research Institute, Kala Shah Kaku (RRI KSK), new, improved, high-yielding, extra-long grain lines with the qualities of early maturity, small stature, and good cooking with aroma are being developed through traditional breeding methods. The present study aimed to assess the genetic variability of these lines in terms of paddy yield and to discover superior high-yielding cultivars suitable for widespread cultivation. There were notable variations in paddy yield among the different entries in the pooled analysis. The highest average paddy yield (5010 Kg/ha) was seen in entry 10640-10-1-1-1, followed by entry 10684-3-1-2 (4990 Kg/ha) and PK 10434-6-2-1 (4550 Kg/ha) and suggested for general cultivation based on their mean paddy yield. A strong positive correlation was seen between the grain thickness grading of over 2.2 mm and the number of panicles per plant. The overall quality of the Uniform Yield Trials of Fine rice samples can be reported as excellent for PK 10306-15-5, PK PB-8 and PK 10678-2-1-1 over check Basmati-515. There will be a simultaneous increase in grain yield with improvements in these qualities.
Human‐caused mortality can be pervasive and even highly selective for individuals in groups of cooperative breeders. Many studies of cooperative breeders, however, do not address human‐caused mortality. Similarly, studies focused on the effects of human‐caused mortality on wildlife populations often do not consider the ecology of cooperative breeders. We searched the literature and identified 58 studies where human‐caused mortality affected a group characteristic, vital rate, or population state of a cooperative breeder. Of studies reporting population growth or decline, 80% reported a link between human‐caused mortality and population declines in cooperative breeders. Such studies often did not identify the mechanism behind population declines, but 28% identified concurrent declines in adult survival and another 21% reported concurrent declines in recruitment or reproduction. There was little overlap between the cooperative breeding and human‐caused mortality literatures, limiting our ability to accrue knowledge. Future work would be beneficial if it ( i ) identified the vital rate(s) causing population declines, ( ii ) leveraged management actions such as lethal removal to ask questions about the ecology of group‐living in cooperative breeders, and ( iii ) used insights from cooperative breeding theory to inform management actions and conservation of group‐living species.
Expanding populations of mesopredators threaten biodiversity and human health in many ecosystems across the world. Lethal control through harvest is commonly implemented as a mitigation measure, yet the effects of harvest and its interaction with environmental conditions on mesopredator population dynamics have rarely been assessed quantitatively due to data constraints. Recent advances involving integrated populations models (IPMs) have enabled promising alternative approaches for quantitative assessments. Efficient use of multiple datasets, together with the ability to account for bias and uncertainty, make IPMs ideal tools for studying impacts of management actions and environmental conditions on harvested populations for which limited data is available. Here we developed a versatile IPM workflow for studying mesopredator population dynamics under different harvest regimes and applied it to an expanding population of red foxes in Arctic Norway. Our model combined routinely collected data on age, reproductive status, and genetic variation from >3600 harvested red foxes with opportunistic field observations and information published on red foxes elsewhere. This allowed us to quantify population dynamics over a period of 18 years, and to identify the drivers of changes in population growth rates using retrospective (Life Table Response Experiments, LTREs) and prospective (population viability analyses, PVAs) perturbation analyses. We found no long-term trends in population size over the course of our study period, not least due to intense harvest limiting the growth potential of the population. On shorter, year-to-year timescales, however, the numbers of red foxes could change dramatically due to responses of natural mortality and immigration to fluctuations in the availability of rodent prey. Our study highlights the potential of integrated modelling approaches for studying population dynamics even when no structured surveys of living animals are available and illustrates the value of extracting and curating information from harvested animals. Our semi-automated and reproducible modelling workflow is ready to be re-run periodically when new data becomes available for our study population and can easily be transferred and adapted to other harvested species, contributing to the development of cost-effective population analyses that are of high relevance for informing management strategies and mitigating biodiversity loss in practice.
Predation threatens the viability of livestock farming, while lethal predator management can negatively influence wildlife ecology. There is renewed interest in non-lethal vs lethal methods of livestock protection, but a systematic comparison is lacking. Using multivariate models, we explored how predator management (shepherd, no shepherd), land tenure, flock characteristics, and environmental factors drive losses of small livestock across the Northern Cape, South Africa. Black-backed jackal and caracal were the dominant livestock predators in both management groups. Predation of small livestock was five-fold lower in the shepherd (1.29% ± 0.38) compared to the non-shepherd group (6.09% ± 0.51; p < 0.0001), with a seven-fold lower-level of lamb predation (1.67% ± 0.51 vs. 11.52% ± 0.99; p < 0.0001). Predator management, livestock type, and flock size (but not land tenure or environmental factors) were predictor variables in a best-fit linear mixed effects model describing small livestock losses (p < 0.0001). We interpret our findings with caution because we could not control for predator and prey abundances, and the non-herder group could have inflated their predation estimates. While the efficacy of shepherding requires more research, we suggest that it is a viable predation management approach in South Africa and beyond.
The dynamics of an ecological system are closely related to the processes that occur in the adjacent environments. Consumers living in terrestrial habitats can take advantage of allochthonous resources that originate in highly productive aquatic environments and that may enable their populations to reach higher densities than those supported by land resources only. In turn, these subsidized consumers may influence the dynamics of other consumers’ populations. The terrestrial landscape that surrounds the estuary of Bahía Blanca is very diverse given its location at the intersection between the Espinal and Pampa ecoregions, but also because of the modifications related to human activities, and the presence of the coastal environments increases the complexity of its ecosystems. The ecology of the continental mammalian communities living around the estuary and coastline beyond the estuarial limits have been poorly investigated, but it is known that many species, mainly carnivores, make use of coastal environments, and the presence of populations of endemic rodents was reported. In this chapter, we review the effect of the coastal environment on the ecology of large- and medium-sized mammals. Additionally, we discuss the importance of the anthropic modifications of these coastal areas on the conservation of the coastal mammal community.
Various species of wild, adaptable, medium-sized carnivores occur outside of protected areas, often coming into contact with people and their domestic animals. Negative human-carnivore interactions can lead to antagonistic attitudes and behavior directed at such species. In the South African Karoo, a semi-arid rangeland, the predation of small-livestock by mesopredators is common and farmers typically use a combination of non-lethal and lethal methods to try and prevent livestock losses. We used ethnographic field observations and semi-structured interviews as part of a mixed methods approach, including the quantitative and qualitative analysis of farmers’ narratives to illustrate the nuanced ways in which sheep farmers relate to the two mesopredators that consume the most livestock on their farms; black-backed jackal and caracal. Overall, farmers attributed negative characteristics to jackal and caracal but farmers’ narratives provided evidence of complex perceptions in that the animals were admired as well as disliked. Both species were seen as charismatic due to traits such as their physical appearance, their “cunning” nature and their remarkable adaptability to human activities, including lethal control. Aesthetic appreciation was an important predictor of tolerance towards both species whereas negative attitudes were associated with the perception that mesopredators should only occur within protected areas. Attitudes towards jackals also appeared to have been affected by cultural representations of them as “thieves”. We showed that perceiving mesopredators as beautiful increased the average marginal probability of a farmer tolerating them, and that this strong relationship held when controlling for other covariates such as livestock predation. We advocate the importance of understanding the cultural and aesthetic aspects of predators and considering existing positive dimensions of human-wildlife relationships that may encourage increased farmers’ tolerance, which might promote coexistence.
The establishment of non‐native predator fish is a worldwide phenomenon often having adverse effects on native species. Trophic interactions are complex, and uncertainty is a common theme in discussions of non‐native predator management. Several fishes of the San Francisco Estuary have experienced significant declines in recent decades due to multiple factors, including habitat alteration and predation. The role of predation as a direct cause of mortality remains an open question, as does whether habitat conditions play a role in promoting predation on species of concern. Recent studies using visual identification of prey have found little to no evidence of predation on ESA‐listed species such as Delta Smelt Hypomesus transpacificus and juvenile Chinook Salmon Oncorhynchus tshawytscha. To increase the likelihood of detecting predation, this study employed a genetic approach. We combined this technique with habitat and water quality data to investigate the role habitat may be playing on incidence of predation. This study focused on detection of predation on Chinook Salmon and Delta Smelt, as well as 6 other native fishes, and 6 non‐native fishes by Striped Bass Morone saxatilis, and other piscivores. Unlike previous studies in the region, the proportion of predators with no prey detected in their gut contents was high (47‐81%). The study detected Delta Smelt in 1.3% of Striped Bass—considerably higher than other contemporary predation studies in the Delta. In the month of April 2014, 6.6% of Striped Bass were positive for Chinook Salmon—substantially higher than recent visual diet studies in the Delta. Interestingly, native species comprised a relatively high proportion of Striped Bass prey (60%). Water temperature and conductivity were identified as significant predictors of Chinook Salmon presence in Striped Bass gut contents. This research also suggests that predation on soft‐bodied prey may be an overlooked segment of the diets of piscivores.
Attempts to control predator numbers through spatially restricted culling typically faces a compensation process via immigration from surrounding source populations. To extend control effort to avoid this issue is in most instances impractical, both logistically and financially. Evidence-based strategy is therefore required to improve management practices. In close collaboration with local managers and hunters, we manipulated culling effort on red fox (Vulpes vulpes) over 5–6 years in 5 areas measuring 246 ± 53 km2. We estimated fox density in late February each year by spotlight counts with distance sampling and estimated reproductive performance by post-mortem examination of culled foxes. We then used mixed modeling to assess how culling rate (defined as foxes killed/foxes available) affected fox population growth from year to year, accounting for compensatory feedbacks. We found a strong compensatory density feedback acting through immigration, allowing red fox populations to resist high culling rates. Culling appeared ineffective at reducing late winter densities to below 25–32% of the estimated carrying capacity. On average, an annual culling rate equivalent to about 45% of the pre-breeding population was required to maintain density at 1 fox/km2, given a carrying capacity of 1.5 foxes/km2, although there was considerable variation among sites. The required culling rate dropped to 25% if the culling could be performed during winter, after the fox dispersal period. In contrast, culling during the pre-dispersal breeding period was totally compensated for through immigration by the following February. Concentrating culling during the winter could improve the ability of practitioners to control year-to-year trends in fox numbers, taking into account site-specific carrying capacity. A winter strategy would also reduce the number of animals killed and hence the ethical and logistical costs of fox control, given limited financial and human resources. Our study illustrates how collaboration between local practitioners and scientists can make large-scale replicated management experiments achievable, leading to mutually approved guidelines. © 2015 The Wildlife Society.
Few studies have examined the effect of interactions between predation and hunting on the rate of game bird mortality throughout the year. We monitored 134 radiotagged willow grouse (Lagopus lagopus lagopus) on 3 contiguous areas, 2 nonhunted and 1 hunted, in central Sweden between 1992 and 1995. We recorded 100 known mortalities: 22 from hunting, 40 from raptors, 19 from mammalian predators, and 19 from other causes. Excluding hunting, cause of death was similar on hunted and nonhunted areas (P > 0.5), with raptors the most important cause of death in all seasons. We did not record any deaths due to mammalian predators in winter or spring, and deaths through collision with power lines only affected winter, but not annual, survival rates. Cox proportional hazard modeling revealed season (autumn, winter-spring, summer) and area (hunted, nonhunted) as the only variables to affect risk of death (P < 0.001). The greatest rates of hunting mortality (0.24) and natural predation (0.32) occurred on the hunted area during autumn. Autumn survival on the hunted area (0.49) was lower (P = 0.029) than on the nonhunted areas (0.71). Survival increased in winter-spring to 0.69 on the hunted area and 0.81 on the nonhunted areas, and remained high (>0.78) through the summer period. We believe hunting mortality was mostly, if not totally, additive to natural mortality in our study. The population density on the hunted area did not decline as expected from the results, and we suggest that immigration from beyond the neighboring nonhunted areas was sustaining the population. We conclude that a harvest model for willow grouse must take account of dispersal and predation rates at a landscape scale.
Lethal control of wild dogs – that is Dingo (Canis lupus dingo) and Dingo/Dog (Canis lupus familiaris) hybrids – to reduce livestock predation in Australian rangelands is claimed to cause continental-scale impacts on biodiversity. Although top predator populations may recover numerically after baiting, they are predicted to be functionally different and incapable of fulfilling critical ecological roles. This study reports the impact of baiting programmes on wild dog abundance, age structures and the prey of wild dogs during large-scale manipulative experiments. Wild dog relative abundance almost always decreased after baiting, but reductions were variable and short-lived unless the prior baiting programme was particularly effective or there were follow-up baiting programmes within a few months. However, age structures of wild dogs in baited and nil-treatment areas were demonstrably different, and prey populations did diverge relative to nil-treatment areas. Re-analysed observations of wild dogs preying on kangaroos from a separate study show that successful chases that result in attacks of kangaroos by wild dogs occurred when mean wild dog ages were higher and mean group size was larger. It is likely that the impact of lethal control on wild dog numbers, group sizes and age structures compromise their ability to handle large difficult-to-catch prey. Under certain circumstances, these changes sometimes lead to increased calf loss (Bos indicus/B. taurus genotypes) and kangaroo numbers. Rangeland beef producers could consider controlling wild dogs in high-risk periods when predation is more likely and avoid baiting at other times.
Refugia from trapping are believed to be important to support a long-term sustainable harvest of Canada lynx (Lynx lynx), but long-term studies in unharvested areas are lacking. We studied lynx population characteristics in relation to snowshoe hare (Lepus americanus) densities in a 301 km(2) refugium in the Yukon Territory between 1986 adn 1994. Lynx carcasses were collected from adjacent trapping concessions for analysis of attributes of the harvested population. Hare density peaked in summer 1990 and began to decline in the winter of 1990-91. Lynx density in March varied with hare density from 2.7/100 km(2) in 1987 to 44.9/100 km(2) in 1991-92. The lynx population doubled annually for 4 years when reproduction and kit and adult survival were high, and immigration balanced or exceeded emigration. High mortality and emigration characterized the lynx decline. Proportions of breeding adults were 100% most years, including the first year of declining hare densities, but zero in the following 2 years. Yearling females reproduced only in the 2 years of highest hare numbers. Kit survival, which was 0% in 1986-87, peaked at 75% for kits of adult females and 26% for kits of yearlings in 1990-91. Emigration peaked annually from March-June, was lowest Sept.-Oct., and was not sex-biased. At least 16% (n=22) of emigrants were trapped or shot. Seventeen lynx (14M, 3F) emigrated 100-1100 km. Annual natural mortality rates were under 11% for the first 6 years of study, including 2 years of hare decline, 60% in 1992-93 and 25% in 1993-94. The carcass sample contained 36% fewer kits, 40% more yearlings, and 4% fewer adults than were present on the study area, reflecting the lower birth and survival rates of kits of yearling females and trapping bias. Mean annual lynx home range size did not vary with hare density, until 1992-93 when male ranges increased markedly, and 1993-94 when female ranges increased. We recommend a network of permanently assigned untrapped areas to facilitate normal lynx population responses to changing snowshoe hare densities, to prevent local extinctions, and to maximize lynx harvests over a complete population cycle.
Predation by coyotes (Canis latrans) on livestock continues to plague producers in the United States. Agricultural interests are concerned about coyote predation because sheep inventories in the U.S. have declined >85% in the past 60 years, with a 25% decline between 1991 and 1996, This decline in sheep numbers has been attributed to low economic returns among producers, with coyote predation cited as a major causative factor. Generalizations about the magnitude and nature of depredations can be misleading because of the varied nature of sheep operations, including size of operations, differences in management, and environmental circumstances surrounding individual operations. Coyote depredation rates appear to be influenced by sheep management practices, coyote biology and behavior, environmental factors, and depredation management programs, Most nonlethal depredation control techniques fall within the operational purview of the producers. The major controversy regarding depredation management focuses on programs that remove coyotes to prevent or curtail predation on domestic stock, especially on public lands. Differences in the magnitude, nature, and history of problems caused by coyotes, as well as the circumstances in which they occur, dictates a need for a variety of techniques and programs to resolve problems. The resolution of coyote depredation upon livestock remains controversial for producers, resource managers, and the general public. Because various segments of society attach different values to coyotes, resolution of depredations should use management programs that integrate the social, legal, economic, and biological aspects of the animals and the problem. Preferred solutions should involve procedures that solve problems as effectively, efficiently, and economically as possible in the least intrusive and most benign ways. Predation management requires a partnership among producers and wildlife managers to tailor programs to specific damage situations so the most appropriate techniques can be selected. This paper attempts to clarify the issues surrounding depredation management, synthesize past and current research, and provide information to resource managers associated with coyote depredation management. This synthesis integrates current understandings of coyote biology and behavior, the nature of depredations upon sheep producing enterprises, and the merits of various depredation control strategies and techniques.
For many carnivores, variation and long-term change in prey abundance and availability are major natural forces that shape the potential for a population to increase, but the understanding of the nature of this relationship varies by species. Relevant demographic data for carnivores are available for some species in areas where food resources vary in time (i.e., cyclic species; temporal variation) or space (geographic variation). Here we qualitatively review examples for numerous species for which changes in food abundance have been related to their demography, including density, reproduction, survival, and behaviour. We also discuss several factors that confound the understanding of these relationships.
For at least 6 carnivore species, densities are positively correlated with prey densities or biomass. This is because relatively higher food resources result in carnivores in better physical condition, and thus affect carnivore reproduction by lowering the average age of first reproduction, increasing litter size, and lowering mortality rates of juveniles. In combination, these changes increase net reproduction and thus carnivore density. Relatively poor food resources often increase mortality of adults due to starvation or intra-specific strife, cause carnivores to use larger home ranges, and result in increased rates of movements, including dispersal and transient behavior; these result in lower densities. Poor density estimates of carnivores or their food supply, time lags in demographic responses, competition with other carnivores, and mortality due to disease and humans can confound this relationship. Because predicting is important, assessment of carnivore food resources and their demographic effects clearly are important because they allow one to more confidently predict the potential of an area to support a carnivore population. These are essential components of carnivore conservation planning.
Uncoordinated and isolated control programs are often used by land managers, property owners and recreation-al hunters to control numbers and reduce the impacts of European red foxes (Vulpes vulpes). However, decades of such attempts to eradicate this significant agricultural and biodiversity pest in many countries have failed. We investi-gated the effectiveness of an uncoordinated and isolated shooting program to determine if it caused any change in red fox population density. We also determined whether shooting is more cost effective than poison baiting for fox control. First, we estimated the density of foxes on an agricultural study property using distance sampling and rates of bait uptake before and after a control program. Second, we estimated the costs associated with undertaking the control program and compared it to the estimated costs of undertaking poison baiting. Prior to control, we estimated a density of 4.18 foxes per square kilometre. After the control exercise, which re-moved 47 individuals in 12 nights, we estimated a density of 3.26 foxes per square kilometre. Our results provide evidence that one-off control programs are not effective in greatly reducing red fox density, even if the control effort is intensive. Where large-scale control programs cannot be coordinated, isolated programs should therefore involve follow-up cam-paigns to reduce population recovery. On a local scale, com-binations of shooting and baiting may also provide maximum control impact at minimal cost.
This study examines the effect of a clumped, non‐defendable and abundant year‐round food resource (Cape fur seals) for black‐backed jackal Canis mesomelas social structure and spatial organization at Cape Cross Seal Reserve and the National West Coast Recreation Area in Namibia during the jackals' denning period in 2004 and 2005. Geo‐referenced observations of behaviour and space‐use were used to test for territoriality, and to assess commuting distances, territory size, group size and within‐territory density on the Namibian coast. Jackals displayed behaviour indicative of territoriality to within 50 m of the fur seal colony. In accordance with optimal foraging theory, jackals commuted between 0.45 and 20.03 km from their territory (low prey availability) to the seal colony (high prey availability). The observed within‐population variation in group size (two to eight adults), territory size (0.20–11.11 km2) and within‐territory density (0.31–9.80 jackals km−2) was unprecedented and strongly associated with distance from the food resource. Group and territory size increased, while within‐territory density declined with increasing distance from the fur seal colony. We discuss the relative importance of the food resource and other factors in determining jackal social and spatial organization.
Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive succes fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capit deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats as by the resources and other conditions at the site. -Author
African lion populations have declined dramatically due to various anthropogenic factors. As a consequence, the majority of extant lion populations are of small size, further compromising their persistence. Lion populations in unfenced areas are more exposed to illegal hunting, snaring and poisoning, while managers of small fenced lions populations often have to limit population growth. Removal of selected individuals in fenced reserves, as opposed to indiscriminate illegal activities, does not necessarily remove the same proportion of individuals from the various age and sex classes. This may therefore affect lion social organization and population demographics differently. From 2000 - 2011, 19 lions from the predominantly unfenced Northern Tuli Game Reserve (NTGR) were shot, snared or poisoned. Just 10km away, only one lioness was shot outside the fenced Venetia Limpopo Nature Reserve (VLNR) where 29 lions were trophy hunted or culled. We found that average population size, sex ratio and litter size were the same for both reserves, but that population density, pride size and cub survival were significantly larger in VLNR. High rates of indiscriminate anthropogenic mortality constrained population size in the NTGR where 94.7% of adult mortality occurred outside the reserve. The two alternate forms of anthropogenic suppression consequently resulted in different population-level responses, ultimately affecting population viability. Lion populations are declining precipitously in Africa, and while current conservation strategies are attempting to remove fences and establish larger conservation areas, this study indicates how fences can influence population dynamics in areas where people threaten large carnivores.
Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around
the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest
mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial
effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their
prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected
effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna
abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology;
and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately
determine the fate of Earth’s largest carnivores and all that depends upon them, including humans.
Cooperative breeding refers to a social system in which individuals other than the parents provide care for the offspring. Since individuals delay breeding and invest in the offspring of others, cooperative breeding poses a challenge to a Darwinian explanation of the evolution of social behaviour. The contributors to this book explore the evolutionary, ecological, behavioural and physiological basis of cooperative breeding in mammals. The book contains a collection of chapters by the leading researchers in the field, and it is dedicated exclusively to the study of mammalian cooperative breeding. It will appeal to zoologists, ecologists, evolutionary biologists, and to those interested in animal behaviour.
The source-sink model of population dynamics predicts that density drives emigration of subordinate animals to habitats offering lower competition for resources. Several authors have suggested use of this model as a potential framework for conservation of exploited carnivores when precise enumeration is unfeasible. Dispersal is a critical behavioural mechanism for management based on this model, yet there is a lack of knowledge on the habitat and social conditions that motivate carnivore emigration and settlement. The cougar Puma concolor is a widely distributed and heavily exploited carnivore, indigenous to the western hemisphere. We evaluated patterns in cougar dispersal behaviour from two sites in Utah, differing in terms of management and the level of natural and anthropogenic habitat fragmentation. We used our results to evaluate three predictions with respect to cougar dispersal behaviour: 1) natal population density and maternal reproductive status prompt emigration, 2) movement of dispersing cougars is shaped by habitat configuration and permeability, and 3) dispersers preferentially settle in areas of high habitat quality and low conspecific density. We documented the emigration of 62 individuals and measured movement variables, including sex and site-specific frequency, distance, seasonality, direction and the habitat quality and harvest rates characterizing areas where immigrants settled. Although males and females exhibited pronounced differences in dispersal frequency, we found few differences in distance traveled, season of departure and direction moved. Dispersal occurred most frequently during spring, coinciding with the estrus pulse. Natural and anthropogenic obstacles modified landscape permeability, and therefore dispersal distances were shorter in fragmented habitats than in contiguous ones. Relative to males, females dispersed into habitats of lower productivity with higher mean annual harvest rates. Patterns in male settlement suggested habitat selection based on mating opportunities, whereas female settlement was predicated on avoiding conspecifics. Cougars in this Great Basin ecosystem largely conformed to source-sink predictions. Results can be used to parameterize source-sink models based on animal behaviour and landscape permeability to conserve exploited carnivores, under conditions of population expansion or recolonization of habitats where Allee effects are a limiting factor.
Little is known about the sublethal effects of mesocarnivores on small carnivores, which can have important implications regarding the ecology and behavior of the latter. We investigated the ecology of cape foxes (Vulpes chama) and bat-eared foxes (Otocyon megalotis) in the absence of black-backed jackals (Canis mesomelas), a dominant mesocarnivore and predator of both fox species. Results were compared with a concurrent study that investigated the ecology of both fox species in the presence of jackals, at a site <5 km away. In the absence of jackals, densities of cape foxes increased 64% despite similar food and habitat resources between sites, indicating that jackals suppressed cape fox populations. In contrast, jackals did not suppress populations of bat-eared foxes. For both fox species, the absence of jackals resulted in smaller home-range sizes and nonselective use of habitats for den sites, indicating that jackals had sublethal effects on the ecology and behavior of both fox species. Additionally, in the absence of jackals, cape foxes were marginally more active during daytime, whereas bat-eared foxes exhibited smaller group sizes. The 2 fox species became more segregated in the absence of jackals, indicating that jackals also had sublethal effects on the interspecific relationships of fox species. Our results showed that the effects of a mesocarnivore can extend well beyond population suppression of small carnivores, although sublethal effects varied in intensity and often were species specific. Sublethal effects on small carnivores can occur even if population suppression by a mesocarnivore is not occurring.
Lethal control for reducing carnivore populations is a contentious issue throughout the world. While computer simulations have been developed modeling the effects of population reduction on coyote (Canis latrans) population parameters, testing these hypotheses with empirical data from the field is lacking. We documented the demographic and spatial responses of coyotes to changes in the levels of food resources and human exploitation on the Piñon Canyon Maneuver Site, southeastern Colorado. We captured, radio-collared, and tracked 92 (53 M: 39 F) coyotes from March 1983 to April 1989. Of these, 74 animals were residents from 32 packs, plus 12 transients; 6 animals were captured while making dispersal movements. We collected 14,147 telemetry locations of the radioed coyotes spanning 7 years of study. We compared coyote pack size and density, survival rates, reproduction (litter size, litter sex ratio, % yearlings reproducing), and home range size between years receiving exploitation (1987-88) versus years receiving no exploitation (1983-86) and post-removal (1989), as well as, comparisons of these parameters between removal and non-removal areas within years. Changes in estimates of pack size and coyote density, plus the number of animals removed, indicated the coyote population was reduced 44-61% and 51-75% in the removal area during 1987 and 1988, respectively. As expected, annual survival rates declined significantly for coyotes in the removal area compared to coyotes in the non-removal area. Removals brought about a drastic reduction in pack size and a corresponding decrease in density. However, both pack size and density rebounded to pre-removal levels within 8 months post-removal. Home range size did not change in response to changes in exploitation. Coyotes in the removal area appeared to maintain their normal (i.e., pre-removal) home ranges after coyotes were removed from neighboring territories. Following removals, the population shifted to a younger age structure (i.e., more yearlings). Litter size significantly increased in the removal area 2 years after the beginning of exploitation. However, changes in litter size were confounded by changes in the prey base. Litter size was significantly related to rabbit abundance, while rodent abundance was less of a factor influencing reproductive effort. Accounting for both changes in prey abundance and coyote density, litter size was significantly related to total prey abundance/coyote. With increasing prey and reduced coyote density, mean litter size doubled in the removal area compared to pre-removal levels; females in the non-removal area also increased litter size in response to increased rabbit abundance. Litter sex ratio favored males during years of no exploitation, changing to a preponderance of females during the 2 years of exploitation. Reproduction by yearlings increased from 0 % in years prior to exploitation, to 20% following 2 years of coyote removal.
Anthropogenic changes in land use and the extirpation of apex predators have facilitated explosive growth of mesopredator populations. Consequently, many species have been subjected to extensive control throughout portions of their range due to their integral role as generalist predators and reservoirs of zoonotic disease. Yet, few studies have monitored the effects of landscape composition or configuration on the demographic or behavioral response of mesopredators to population manipulation. During 2007 we removed 382 raccoons (Procyon lotor) from 30 forest patches throughout a fragmented agricultural ecosystem to test hypotheses regarding the effects of habitat isolation on population recovery and role of range expansion and dispersal in patch colonization of mesopredators in heterogeneous landscapes. Patches were allowed to recolonize naturally and demographic restructuring of patches was monitored from 2008-2010 using mark-recapture. An additional 25 control patches were monitored as a baseline measure of demography. After 3 years only 40% of experimental patches had returned to pre-removal densities. This stagnant recovery was driven by low colonization rates of females, resulting in little to no within-patch recruitment. Colonizing raccoons were predominantly young males, suggesting that dispersal, rather than range expansion, was the primary mechanism driving population recovery. Contrary to our prediction, neither landscape connectivity nor measured local habitat attributes influenced colonization rates, likely due to the high dispersal capability of raccoons and limited role of range expansion in patch colonization. Although culling is commonly used to control local populations of many mesopredators, we demonstrate that such practices create severe disruptions in population demography that may be counterproductive to disease management in fragmented landscapes due to an influx of dispersing males into depopulated areas. However, given the slow repopulation rates observed in our study, localized depopulation may be effective at reducing negative ecological impacts of mesopredators in fragmented landscapes at limited spatial and temporal scales.
Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive success fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capita deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats a...
Population dynamics and life-history evolution depend heavily on fecundity, which, in the coyote (Canis latrans), can vary substantially according to environmental conditions. Although well studied in the central part of its range, little is known about coyote reproduction in the Mediterranean climates associated with Pacific-coastal North America. I used postmortem examinations of 441 coyotes collected throughout central California to investigate reproduction, including age-specific fecundity, breeding synchrony and seasonality, and relationship to nutritional condition. Reproductive parameters did not vary significantly among sampling locations. Overall, numbers of corpora lutea averaged 6.9 (range ¼ 4–11) and litter size (based on fetuses or placental scars) averaged 6.6 (range ¼ 1–12) among postpartum females. The number of corpora lutea increased with maternal age, and litter size also increased with age to 6 years but decreased in older females. Most (77%) adult females became pregnant and 13% of 1st-year females became pregnant. During January–March, 96% of adult males and 68% of 1st-year males had reproductive testes. Reproductive signs in both sexes occurred 3–4 weeks later in 1st-year coyotes than in adults. Parturition dates, which decreased with increasing maternal age, ranged from 9 March to 7 May, indicating that estrus occurred from early January to late March. Of 1st-year coyotes, reproductive individuals were larger during the breeding season and had higher marrow fat indexes than nonreproductive ones (both sexes). After the breeding season, 1st-year females that did not breed (become pregnant) had similar body mass to 1st-year and adult coyotes that did breed, and adult females that did not breed were larger than the others but similar to the weight of breeders during the breeding season. Thus, whether yearlings attained breeding condition apparently depended on their nutritional condition. Adult fecundity estimates were among the highest reported for coyotes. Population dynamics and life-history evolution depend heavily on fecundity. Fecundity of coyotes (Canis latrans) is highly variable, even relative to most other canids, depending on exploitation (Knowlton 1972), food resources (Clark 1972; Todd and Keith 1983; Todd et al. 1981; Windberg 1995), and possibly ambient stress levels (Hartley et al. 1994). The ability to compensate via reproduction for increased mortality is a widely recognized implication for population dynamics (Connolly and Longhurst 1975; Knowlton 1972). The high variability in fecundity also results in an unusually wide range of life-history strategies for coyotes, which resemble r-strategists (high productivity and short life span) in some situations and K-strategists (low productivity and long life span) in others (Pianka 1970). Although numerous studies have recorded reproductive data on coyotes from the central part of their range (e.g., Clark 1972; Todd and Keith 1983; Todd et al. 1981; Windberg 1995), there is a paucity of such information from coyotes in the Mediterranean climate zone associated with Pacific-coastal North America. Examination of available data suggests that, relative to inland regions of North America, coyotes in Pacific-coastal regions breed earlier in the year and less synchronously (Atkinson and Shackleton 1991; Hamlett 1938; Sacks 1996). These geographic differences likely are environmentally mediated (e.g., by seasonal temperature differences). Because Pacific-coastal North America is itself an environmentally diverse area, regional differences in the timing of coyote reproduction might be expected to occur within this area as well. For this study, I took advantage of the relatively long breeding period of coyotes in California to investigate age-specific differences in seasonal reproduction of females and males and fecundity as well as regional variation of such patterns. I also investigated relationships between reproduction and body condition to explore trade-offs between these parameters.
IntroductionMethods
Results and discussionGeneral discussionAcknowledgementsReferences
We tested a staining method on uteri for counting placental scars on red fox. We estimated reproduction parameters on 358
females collected in three study areas in western France from 1st February 2002 to 31st January 2005. Placental scars (n = 103) were described by macroscopic examinations using the following variables: (1) the width and (2) the aspect of placental
scars, (3) the abundance of macrophages or the presence of blood, (4) the presence of swellings, (5) the presence and colour
of a central band and (6) the presence and colour of lateral bands. A factorial correspondence analysis showed strong associations
between the month when scars were examined and categories of variables. Staining on placental scars made macrophages more
visible, facilitating identification of ‘active’ placental scars, i.e. related to the last pregnancy. However, distinction
between placental scars due to earlier pregnancies and resorptions was not possible. The staining method used provides a standard
that could be useful for obtaining comparable and repeatable results. The mean number of placental scars was 4.85 ± 1.46 (n = 103) per vixen. The mean number of embryos per vixen was 4.66 ± 1.35 (n = 68) for yearlings and 5.53 ± 1.50 (n = 96) for older females. Including percentages of barren vixens, the total population productivity was significantly smaller
for yearlings (3.62 ± 1.86, n = 158) than for older females (4.28 ± 1.75, n = 186). We discuss these results in relation to fox densities, culling and food availability.
Keywords
Vulpes vulpes
–Placental scar counts–Litter size–Embryos counts–Productivity–Reproductive performance
Using records from archives detailing bounties for wolves killed in northern Spain during the eighteenth and nineteenth centuries,
we investigated demographic and spatial distribution parameters of the population to determine whether direct persecution
or prey availability was responsible for the observed population decline. Captures of adult, subadult, and young individuals,
including those of litters, showed a downward trend. Progressive decreases in age ratio and litter size, and the increase
in the proportion of males, were compatible with a population under food stress, driven by the extinction of wild ungulates,
the sharp reduction in livestock numbers, and the lack of alternative prey. The immigration and dispersal process does not
seem to have functioned under such conditions. In the study area, where strychnine was not used until the end of the nineteenth
century, the broadly accepted idea of human persecution having an exclusive or primary role in wolf decline does not necessarily
apply.
Keywords
Canis lupus
-Wolf-Persecution-Prey-Spain-Mortality
During 1970-75 both snowshoe hare Lepus americanus and coyote Canis latrans populations declined from cyclic peaks to low levels. Use of hares by coyotes decreased 62-71%; use of such alternative foods as mice, voles and carrion increased with declining hare population levels. Indices of total food consumption per coyote decreased with hare abundance because of the low availability of alternative foods in the boreal forest. Decreases in body-fat indices during late winter suggested that coyotes experienced a negative energy balance during hare scarcity. Coyote pregnancy rates and litter sizes declined with the hare population and annual finite rates of reproduction decreased 33%. Sex ratios of coyotes favored males when hares were at intermediate levels, but were balanced at abundant and scarce levels. The proportion of juveniles decreased from 64% during 1970-71 (year of hare peak) to 41-44% during 1973- 75 (years of hare scarcity). Important demographic changes generally did not occur until hares became scarce. -from Authors
Aspects of reproduction in two species of jackals (Canis adustus and Canis mesomelas) from Zimbabwe were studied using reproductive organs of jackal carcasses submitted for rabies testing or collected during culls. In C. adustus, parturition took place from early September to early October and in C. mesomelas during September and October. The female reproductive cycle was synchronized in both species. Eighty percent of females bred in any particular year and 20% of those that bred lost their litters soon after birth. The average litter size at birth of C. adustus was 5.8 (n = 16, range 3-8) and of C. mesomelas 4.6 (n = 30, range 1-8). The productivity of the two species was estimated at 1.8 and 1.5 pups per adult per year for C. adustus and C. mesomelas, respectively. These data suggest that jackal populations are capable of very rapid recovery following population crashes and that populations will fluctuate seasonally, with peak densities of independent, mobile jackals (capable of participating in rabies cycles) occurring around December and January.
The reproductive output (ovulation rate, fertility, barrenness, productivity, pre-natal mortality) of the red fox Vulpes vulpes (n = 317) has been studied in a Mediterranean region (Pisa province, Central Italy) in 1992 by post-mortem analysis. On average, female foxes shed 5.03 ± 1.27 ova, had 3.95 ± 1.25 placental scars and 3.88 ± 1.55 live embryos. Twenty percent of foxes were barren, and intra-uterine mortality was common: 47% of females lost at least one ovum before implantation; 43.5% of yearlings (≤ 1 year old) lost at least one foetus, whereas only 16.7% of adults did so. Male yearlings had lower testis mass than adults. The reproductive output was higher for heavier females, but marginally so for those with greater head and body length. Barrenness and intra-uterine mortality were not related to body size. Amount of body fat and age were unrelated to reproductive output, with the exception of post-implantation mortality (higher for yearlings). All these results suggest that the reproduction of the red fox was not limited directly by food availability, but rather by social modulation. The reproductive output in this population was low in comparison with other populations, in spite of faster physical development. A review of the literature suggests compensatory reproduction in the red fox, litter size being larger in areas of higher mortality.
The impact of deliberate culling of fox populations has been much debated. Although a local (< 10 km2) impact has been accepted, previous authors have denied that culling has any impact on a larger scale because local losses are compensated through immigration. Rather, it has been claimed that at this scale fox density is determined by resources, mediated through social behaviour and breeding suppression. We determined the impact of culling on a regional scale (> 1000 km2), using data on culling (Heydon and Reynolds, 2000), fox density (Heydon, Reynolds and Short, 2000) and productivity. The three U.K. study regions (size 1238-2322 km2) were in mid-Wales (A), the east Midlands (B) and East Anglia (C). High productivity in regions A and C was associated with low density, high culling mortality and high overall mortality (all relative to region B), indicating that density was suppressed by culling. In region B (moderate) breeding suppression was associated with a higher density and lower cull than in regions A and C, implying that fox density was closer to the maximum sustainable by resources. We conclude that the impact of culling in different regions of Britain is variable, dependent on the regional prevalence, methods, and history of culling. However, it is clear that in a range of circumstances culling can substantially depress fox numbers, and that current fox densities reflect a history of culling. This conclusion is fundamental in considering the management of fox predation in farming and conservation contexts.
The arctic fox population in Iceland has undergone long-term fluctuations in size in recent decades, the causes of which are poorly known. Returns of ear-tagged foxes suggest that fox hunting is the main cause of mortality among adult foxes. A life table analysis shows that the mean expectancy of life of vixens in western Iceland (where the population has been increasing), is longer than in eastern Iceland (where the population has been reasonably stable). Over 90% of vixens appear to mate and become pregnant, with a mean of 5.44 ± 1.64 placental scars. Survival of cubs found at successful breeding dens in each area did not differ. Fecundity schedules suggest that, either the proportion of vixens that lose entire litters during pregnancy or shortly after birth is high, or natural mortality is higher in the first year of life than in later years, or both.
Six indices of body and physiological condition were determined for 330 red foxes (Vulpes vulpes) collected in Central Italy from January to May 1992: (1) subcutaneous fat; (2) perivisceral fat; (3) perirenal fat: (4) residual of the regression of body mass on body length: (5) spleen mass; (6) adrenal mass. During this season, females had more fat than males, whereas yearlings (9-13 months old) had the same fat as the adults. All the nutritional indices (1 through 4) were highly related, suggesting that they could be used at least for relative comparisons. Correcting for gut content mass marginally strengthened the relationship, and reproductive status of females had no effect on it. The two stress indices (5 and 6) were little significance, at least during late winter and spring. The index based on body mass residuals may allow an approximate estimation of fat level of live foxes. It is also applicable retrospectively to museum collections and historical data, where body mass and body length were known, but no measure of fatness was taken.