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What is an apex predator?
Abstract
Large ‘apex’ predators influence ecosystems in profound ways, by limiting the density of their prey and controlling smaller ‘mesopredators’. The loss of apex predators from much of their range has lead to a global outbreak of mesopredators, a process known as ‘mesopredator release’ that increases predation pressure and diminishes biodiversity. While the classifications apex- and meso-predator are fundamental to current ecological thinking, their definition has remained ambiguous. Trophic cascades theory has shown the importance of predation as a limit to population size for a variety of taxa (top–down control). The largest of predators however are unlikely to be limited in this fashion, and their densities are commonly assumed to be determined by the availability of their prey (bottom–up control). However, bottom–up regulation of apex predators is contradicted by many studies, particularly of non-hunted populations. We offer an alternative view that apex predators are distinguishable by a capacity to limit their own population densities (self-regulation). We tested this idea using a set of life-history traits that could contribute to self-regulation in the Carnivora, and found that an upper limit body mass of 34 kg (corresponding with an average mass of 13–16 kg) marks a transition between extrinsically- and self-regulated carnivores. Small carnivores share fast reproductive rates and development and higher densities. Large carnivores share slow reproductive rates and development, extended parental care, sparsely populated territories, and a propensity towards infanticide, reproductive suppression, alloparental care and cooperative hunting. We discuss how the expression of traits that contribute to self-regulation (e.g. reproductive suppression) depends on social stability, and highlight the importance of studying predator–prey dynamics in the absence of predator persecution. Self-regulation in large carnivores may ensure that the largest and the fiercest do not overexploit their resources.
... Apex predators support increased biodiversity by suppressing lower trophic level species via direct predation or instilling fear, aiding in the restriction of mesopredator release and limiting over-herbivory (Estes et al., 2011). Despite their importance within ecosystems, apex predators are highly sensitive to habitat modification and are confronted with considerable challenges due to their typically large spatial and resource requirements (Ripple et al., 2014;Wallach et al., 2015). For apex predators, movement is critical in delineating territories to defend essential resources from neighbouring competitors (Wallach et al., 2015). ...
... Despite their importance within ecosystems, apex predators are highly sensitive to habitat modification and are confronted with considerable challenges due to their typically large spatial and resource requirements (Ripple et al., 2014;Wallach et al., 2015). For apex predators, movement is critical in delineating territories to defend essential resources from neighbouring competitors (Wallach et al., 2015). Where habitat is reduced and fragmented, resources become limited or widely dispersed, significantly impacting the ability for multiple territorial groups to occur in a region (Rolstad, 1991;Dugger et al., 2011). ...
... Identifying how apex predators move through and utilise space within their home-range enables targeted and enhanced management of highly frequented and likely important areas (Allen and Singh, 2016). However, due to their mobile and elusive life traits (Wallach et al., 2015), determining the visitation behaviour of apex predators can be challenging. The visitation behaviour of powerful owls has been contentious, as debated by Kavanagh (1988) and Pavey (1992). ...
Effectively managing apex predators in human-modified landscapes poses considerable challenges. Habitat fragmentation disperses resources across wider expanses and undermines the ability of apex predators to reach isolated habitat patches as they traverse multi-tenured landscapes comprising unsuitable habitat. Understanding a species response to landscape configuration is key to informing effective management strategies, particularly for threatened, mobile and ecologically important species like apex predators. Here we use GPS tracking data collected from 37 powerful owls (Ninox strenua), an Australian threatened apex predator that occurs across the urban-agricultural-forest gradient, to investigate how landscape characteristics influence their spatial and movement behaviour. We demonstrate that as habitat fragmentation increases, the spatial requirements of powerful owls expand, their home-range shape becomes more intricate and individuals travel further each night, significantly adjusting their movement behaviours and spatial configurations to connect remaining habitat. Landscapes with unified and connected habitats, on the other hand, have smaller spatial requirements, likely due to greater habitat availability that minimises competition for essential resources. This facilitates the establishment of smaller home-ranges and consequently, the occurrence of more territories. Interestingly, landscape characteristics did not influence sequential nightly visitation behaviour, suggesting that powerful owls across all landscape types visit different portions of their home-range each night to exert an unpredictable hunting strategy regardless of local landscape conditions. Our research highlights the importance of integrating the influence of local landscape features and visitation behaviours into decision-making processes. This integration is crucial for informing effective conservation strategies aimed at supporting apex predator survival in disturbed landscapes.
... However, most PAs do not support minimum viable populations (MVPs; see section below) of many species represented within them, particularly medium-and large-sized mammals (Nicholls et al. 1996;Pacifici et al. 2020;Williams et al. 2022), i.e., mammals with a body mass greater than 2 kg Njoroge et al. 2009). This is because most PAs around the world tend to be small (<10 000 ha) (Naughton-Treves et al. 2005;Ripple et al. 2015) and are located in marginal or suboptimal habitats (Kerley et al. 2020;Britnell et al. 2023b). Therefore, most PAs do not effectively contribute to the conservation of many species (Naughton-Treves et al. 2005;Ripple et al. 2015). ...
... This is because most PAs around the world tend to be small (<10 000 ha) (Naughton-Treves et al. 2005;Ripple et al. 2015) and are located in marginal or suboptimal habitats (Kerley et al. 2020;Britnell et al. 2023b). Therefore, most PAs do not effectively contribute to the conservation of many species (Naughton-Treves et al. 2005;Ripple et al. 2015). This places such species at risk of extinction. ...
... For example, large herbivores, by virtue of their large size and high biomass, affect vegetation structure and composition by trampling and consumption (Ripple et al. 2015;Cromsigt et al. 2018). Megabrowsers (e.g., African elephant Loxodonta africana and black rhinoceros Diceros bicornis) reduce the woody vegetation component across landscapes (Cromsigt et al. 2018) and thereby maintain habitat heterogeneity in landscapes that would usually only support woody vegetation (Owen-Smith 2006). ...
Conservation planning has focused extensively on representation of species in protected areas (PAs), rather than achieving the persistence of these species in PAs. Consequently, most PAs do not support viable populations of many species represented within them, particularly large mammals, resulting in extinction debt risks. The challenge is therefore to identify opportunities to achieve viable populations and to develop and implement conservation plans to achieve this, e.g., expand and connect existing PAs. A recent meta-analysis provides a minimum viable population (MVP) estimate of 5 000 individuals for mammals. This value was used as the target for modelling conservation opportunities for the South African endemic Cape mountain zebra (Equus zebra zebra), blesbok (Damaliscus pygargus phillipsi), black wildebeest (Connochaetes gnou) and co-existing medium- and large-sized mammal species. This study focused on the region between the Camdeboo and Mountain Zebra national parks (ca. 736 000 ha). Within the envisaged Camdeboo Mountain Zebra (C-MZ) mega-reserve, a spreadsheet model was used to estimate potential herbivore population sizes, spatial requirement data were used to estimate potential omnivore and insectivore population sizes, and herbivore densities were used to estimate potential large carnivore population sizes. I show that 12 (the three endemic grazers and nine co-existing species) of the 28 modelled medium- and large-sized mammal species will potentially exceed 5 000 individuals, the MVP target, within the envisaged mega-reserve. The remaining 16 species show potential to reach substantial population sizes, however, will likely require ongoing metapopulation management. Using a conservation planning approach, I identify priority areas for the conservation of suitable habitat for Cape mountain zebra, blesbok, and black wildebeest within the envisaged mega-reserve, thus indirectly identifying priority areas for the conservation of these endemic species. I show that the potential incorporation of these priority areas within the envisaged mega reserve will contribute considerably to the conservation of all focal species. In addition, the potential incorporation of these priority areas will contribute to PA expansion and significantly improve connectivity between existing PAs within the envisaged C-MZ mega-reserve. The importance of adequately-sized PAs to support viable populations of focal species is thus evident, and will ensure their long-term survival and ability to persist by allowing population and evolutionary scale processes.
... For instance, wolves exhibit density dependence through territorial behavior thereby creating a carrying capacity in local density (O'Neil et al., 2017(O'Neil et al., , 2019. Among predatory mammals, large size is associated with selection for endogenous socio-behavioral controls on growth such as female reproductive suppression, female territoriality, and cooperative behaviors that regulate per capita growth and mitigate direct links between density and discrete vital rates (Wallach et al., 2015). ...
... Understanding how these mechanisms work is essential for understanding and predicting equilibrium densities (Van Deelen, 2009), the potential for prey regulation (Messier, 1994), trophic dynamics (Wallach et al., 2015) and population responses to perturbation (Stenglein et al., 2018). Recently recovered wolf (Canis lupus) populations (USA) show negative ensemble density feedback. ...
... However, Wallach et al. (2015)'s predictions of a compensatory (negative) feedback mediated by socio-behavioral effects at high-density prompt an important life history question: How do territorial animals with limited perception ranges "know" that their population's global range is beginning to saturate such that socio-behavioral mitigators of growth can operate? Do they need to know? ...
... Mesopredators generally weigh less than 25 kg (see Carbone, Teacher & Rowcliffe, 2007;Prugh et al., 2009;Wallach, Izhaki, Toms, Ripple & Shanas, 2015 for specific weight thresholds) and their populations can be regulated through top-down control by larger predators (i.e. apex predators for many mesopredators, Prugh et al., 2009;Ritchie & Johnson, 2009) as well as through bottom-up processes like food availability (López-Bao, Rodríguez & Palomares, 2010). ...
... Under these circumstances, along with maintaining their functional role as described above, mesopredators can also assume the ecological role of de facto apex predators through direct predation effects and indirect fear-driven effects at multiple trophic levels (Palomares & Caro, 1999;Ripple & Beschta, 2004). Thus, following mesopredator release, there is often an increase in predation pressure and a reduction in biodiversity (Wallach et al., 2015). One of the most studied consequences of mesopredator release is the impact that dominant mesopredators have on subordinate sympatric mesopredators. ...
... Understanding the role of black-backed jackals (10.3 kg: mean weight -taken from Wallach et al., 2015) in ecosystems in southern Africa is challenging due to their elusive nature (James, James, Scott & Overall, 2015). Despite the long-standing problem of black-backed jackal predation on livestock, our understanding of their ecology has seldom extended beyond that of cursory single species investigations of diet, activity patterns, and only recently, genetics and reproduction (See Chapter 7). ...
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/
... For some apex predators, the manner in which they influence their prey depends on the functioning and structure of their social systems (Wallach et al. 2015). Predator social structures allow for cooperation, thus facilitating hunting of large and difficult prey and for defending territory. ...
... Predator social structures allow for cooperation, thus facilitating hunting of large and difficult prey and for defending territory. Many canids form family groups ('packs') composed of a breeding pair and one or more generations of adult offspring, whom together cooperate to raise and educate young as well as cooperatively hunting prey (Wallach et al. 2015). Persecution by humans fractures these social structures with implications for their ecological effects, including the regulation of smaller canid populations (Haber 1996, Ripple et al. 2014. ...
... We examined how humans shape the responses of red foxes Vulpes vulpes to predation risk from dingoes Canis dingo. Dingoes are mainland Australia's only mammalian apex predator (Wallach et al. 2015). They structure ecosystems by suppressing populations of mesopredators and herbivores, a cascading ecological effect that is weakened when they are persecuted (Wallach et al. 2010). ...
Apex predators structure ecosystems by hunting mesopredators and herbivores. Their ecological influence is determined not only by the number of animals they kill, but also by how prey alter their behaviours to reduce risk. Predation risk is variable in space and time creating a landscape of fear. In Australia, dingoes hunt red foxes and suppress their populations. As both predators are commonly subjected to eradication programs, the question arises whether humans alter the risk dingoes pose to foxes and in turn alter the foxes' avoidance behaviours. We studied the spatio-temporal activity patterns and wariness behaviours of foxes and dingoes at sites where they were protected (predator friendly), where they were persecuted (predator persecuted), and at sites where foxes were persecuted, and dingoes had been eradicated (dingo eradicated). The landscape of fear hypothesis predicts that foxes will be the most spatiotemporally restricted and most fearful at predator friendly sites, and least restricted and fearful at dingo eradicated sites. We found that fox occupancy was highest at dingo eradicated sites; and that they avoided times of heightened dingo activity at predator friendly sites more than at predator persecuted sites. Contrary to predictions, foxes were the least fearful (lowest frequency of cautious and vigilant behaviour) and most social (highest frequency of social interactions) at predator friendly sites. Our findings suggest that in the absence of persecution, mesopredators living with socially-stable apex predators can anticipate and avoid risk, reducing the need for constant vigilance (i.e. fear). Where predators are protected, predator avoidance may be driven by knowledge rather than fear alone.
... The small carnivore is a definite concept with an upper limit body mass of 15 kg (Wallach et al. 2015) and are often considered as a mid-trophic predators (so-called meso-carnivore) in terrestrial ecosystems (Gehrt and Clark 2003). Compared to apex carnivores, small carnivores exhibit higher density, faster reproductive rates and compact populated territories (Wallach et al. 2015). ...
... The small carnivore is a definite concept with an upper limit body mass of 15 kg (Wallach et al. 2015) and are often considered as a mid-trophic predators (so-called meso-carnivore) in terrestrial ecosystems (Gehrt and Clark 2003). Compared to apex carnivores, small carnivores exhibit higher density, faster reproductive rates and compact populated territories (Wallach et al. 2015). It appears that small carnivores contribute fundamentally to ecosystem function, structure, and dynamics, and their impact can be particularly profound in the absence of apex predators (Roemer et al. 2009). ...
Context
Rapid increases in human population and the resulting apex predator defaunation are affecting the spatial and temporal dynamics of small carnivores, with uncertain consequences for the ecological community. Documenting the spatiotemporal impact of apex predators and human disturbance on small carnivores becomes crucial to managers overseeing carnivore persistence.
Objectives
Assessing the spatiotemporal responses of five small carnivores to two apex carnivores (tigers Panthera tigris, leopards P. pardus) and human disturbances in Northeast Asia.
Methods
We first applied an occupancy-modelling framework to test whether site occupancy of small carnivores depended on apex carnivore and human disturbance. Then, we calculated the overlap of activity periods between small carnivores and apex predators, as well as the overlap with human/cattle activities using kernel density functions. Finally, we used cross-wavelet analysis to determine the temporal coherence between related species.
Results
Spatially, most small carnivores were independent of tigers and leopards. Compared to apex predators, small carnivores were more likely to use areas with high human activity. Temporally, small carnivores exhibited highly heterogeneous diel overlaps and more in-phase activities with apex predators. However, we found a significant difference in the mean activity time between apex and small carnivore. Meanwhile, small carnivores exhibited low levels of temporal overlap and more out-phase temporal coherence with humans and cattle at shorter periods.
Conclusions
Apex carnivores and human disturbances don’t limit the space use or intensity of use of small carnivores. Temporal segregation and anti-phase activity are the key role for small carnivores to minimize intraguild predation and human persecution.
... More restrictive definitions only include members of the order Carnivora, weighing between 1-15 kg (Buskirk and Zielinski 2003, Gehrt and Clark 2003, Roemer et al. 2009). In addition, a mesopredator cannot self-regulate its population density, in comparison to large apex predators (Wallach et al. 2015). ...
... Because of their larger size, the severity of the conflicts, and more negative human perception (Fox 2006, Curtis et al. 2007, Bateman and Fleming 2012, Elliot et al. 2016, they require mitigation methods that are not easily transferable to the 3 selected species. Furthermore, with the range contraction of wolves (Canis lupus) and other large carnivores in North America Gese 2007, Ripple et al. 2014), coyotes are now functionally and ecologically apex predators in many ecosystems (Crooks and Soulé 1999, Roemer et al. 2009, Prugh et al. 2009, Wallach et al. 2015. ...
Conflicts between humans and mesopredators are frequent and widespread. Over the last decades, conflicts have led to the development and application of different mitigation methods to diminish the costs and damage caused by such conflicts. We conducted a systematic literature search and meta‐analysis to assess the influence of different mitigation methods on 3 common nuisance species: raccoons ( Procyon lotor ), red foxes ( Vulpes vulpes ), and striped skunks ( Mephitis mephitis ). A majority of the studies, from 1963‒2022, were conducted in North America, followed by Australia and Europe. The predation of wildlife species of conservation concern by nuisance species is the main reported source of conflict in the published literature. Lethal control is the most commonly tested method and is generally effective at reducing conflicts based on the calculated effect size. Barriers have mixed effects, with electric fences and nest exclosures both being effective, whereas conventional fences seem to be less effective. Repellents mimicking predators (e.g., guard animal, predator smell) are also effective. Conditioned taste aversion is a promising approach, but no precise product or chemical has proven to be effective. Many interventions suffered from a lack of validation through experimental approach. Research on human–mesopredator conflict mitigation would benefit from repeated studies using the same methods in similar contexts, thus reducing heterogeneity in the results, and by testing new and innovative methods.
... However, the ecological classification of apex predator is rather broad as it generally refers to the elevated trophic position of a taxon within a food web (Wallach et al., 2015). The term can even be argued as simplistic since it rarely considers the functional repertoires of predators, which can have subtly different impacts on the environments in which they live (DeVault et al., 2003;Wallach et al., 2015;Wilkenros et al., 2013). ...
... However, the ecological classification of apex predator is rather broad as it generally refers to the elevated trophic position of a taxon within a food web (Wallach et al., 2015). The term can even be argued as simplistic since it rarely considers the functional repertoires of predators, which can have subtly different impacts on the environments in which they live (DeVault et al., 2003;Wallach et al., 2015;Wilkenros et al., 2013). For example, in the African savannah lions (Panthera leo) and spotted hyenas (Crocuta crocuta) are both recognized as apex predators with overlapping prey preferences (Schubert et al., 2010;Sinclair et al., 2003;van Valkenburgh et al., 1990). ...
Pseudosuchian archosaurs, reptiles more closely related to crocodylians than to birds, exhibited high morphological diversity during the Triassic and are thus associated with hypotheses of high ecological diversity during this time. One example involves basal loricatans which are non-crocodylomorph pseudosuchians traditionally known as "rauisuchians." Their large size (5-8+ m long) and morphological similarities to post-Triassic theropod dinosaurs, including dorsoventrally deep skulls and serrated dentitions, suggest basal loricatans were apex predators. However, this hypothesis does not consider functional behaviors that can influence more refined roles of predators in their environment, for example, degree of carcass utilization. Here, we apply finite element analysis to a juvenile but three-dimensionally well-preserved cranium of the basal loricatan Saurosuchus galilei to investigate its functional morphology and to compare with stress distributions from the theropod Allosaurus fragilis to assess degrees of functional convergence between Triassic and post-Triassic carnivores. We find similar stress distributions and magnitudes between the two study taxa under the same functional simulations, indicating that Saurosuchus had a somewhat strong skull and thus exhibited some degree of functional convergence with theropods. However, Saurosuchus also had a weak bite for an animal of its size (1015-1885 N) that is broadly equivalent to the bite force of modern gharials (Gavialis gangeticus). We infer that Saurosuchus potentially avoided tooth-bone interactions and consumed the softer parts of carcasses, unlike theropods and other basal loricatans. This deduced feeding mode for Saurosuchus increases the known functional diversity of basal loricatans and highlights functional differences between Triassic and post-Triassic apex predators.
... Apex predators occupy the highest trophic positions in food webs and serve profoundly important roles in ecological and evolutionary processes, shaping and re-shaping the traits of prey and how they interact with one another and the ecosystem. Wallach et al. (2015) presented some simple traits that define apex predators among carnivora, especially size >34 kg and the capacity for self-regulation. ...
... Our perspective necessarily returns to the question of predator terminology and where humans fit. Wallach et al. (2015) described humans as a special case of mesopredator release, not an apex predator. ...
In nearly every ecosystem, human predators (hunters and fishers) exploit animals at extraordinarily high rates, as well as target different age classes and phenotypes, compared to other apex predators. Demographically decoupled from prey populations and technologically advanced, humans now impose widespread and significant ecological and evolutionary change.
In this paper, we investigate whether there is evidence that humans provide complementary services and whether ecosystem services of predators can be maintained by humans where wild predators are lost. Our objective is to contribute to two key ecological themes: the compatibility of human harvesting within ecosystems and management approaches in consideration of the intentional or unintentional loss of predators.
We reviewed evidence for five key effects of predators: natural selection of prey, disease dynamics, landscape effects, carbon cycling and human well‐being. Without carefully designed management strategies, such changes can impose harm to ecosystems and their constituents, including humankind.
Ultimately, we applied this information to consider management paradigms in which humans could better support the role of, and potentially behave more like, apex predators and discuss the challenges to such coexistence.
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... Large apex predators have self-regulation (limit the density of their populations), may limit the density of their prey, and control the mesopredators. Apex predators are considered to be keystone species (Caro 2010;Paine 1966;Wallace et al. 2015). Hypercarnivores are high protein consumers (greater than 70%) (Holliday and Steppan 2004). ...
... As an apex predator, the American lion plays a keystone role in regulating their ecosystem. Based on the terrestrial apex large carnivores today (e.g., Wallace et al. 2015), the American lion most likely has sparsely populated territories and engaged in cooperative hunting as well as exhibiting pride behavior (Wheeler and Jefferson 2009). ...
Kincaid Shelter (Uvalde County, Texas) contains a sequence of vertebrate and cultural remains spanning from the late Pleistocene to Historic. Kincaid Shelter perhaps is best known for its Paleoindian component, including a cobblestone floor interpreted as a Clovis habitation surface. Zone 3 lacustrine sediments are beneath that cobblestone floor and yielded a diverse late Pleistocene vertebrate fauna. Recovered in 1948, the assemblage has never been formally studied or described. The current analysis focuses on the composition, paleoecology, and taphonomy of the Zone 3 faunal assemblage to establish and clarify this important late Pleistocene record. Sixteen vertebrate taxa are represented. Large mammals predominate, but reptiles, including American alligator, and a bird also occur. The presence of Bison antiquus and Panthera atrox indicate a late Pleistocene (Rancholabrean Land Mammal Age) age for the faunal assemblage. The Zone 3 faunal composition is typical of latest Pleistocene faunas from the Great Plains and supports an interpretation of a grassland biome.
... Study organisms were assigned to one of four trophic levels: primary producers, herbivores, meso-predators, and top-predators, based on how they perform and function in their natural ecosystem. We note that whereas the classification of top (i.e., apex) and meso-predators are fundamental to current ecological thinking, their distinction remains ambiguous (e.g., Wallach et al., 2015). Here we classified 'top-predators' based on their ecological role and their elevated trophic position in their food web. ...
... However, it should be noted that when splitting trophic levels among developmental stages (Fig. S5A), we still find the same pattern reported for OA when developmental stages are pooled, signifying a robust result that is independent of species ontogeny. In addition, although top-predators could be pooled with meso-predators due to the ambiguity associated with these trophic distinctions (Wallach et al., 2015), doing so would provide little change to the meta-analysis resultwith consumers still showing less tolerance to OA than predators. Even so, we clearly need more studies on climate change effects on top-predators to allow for stronger inferences on the effects of OA and OW on this important trophic position. ...
Marine ecosystems are currently facing a variety of anthropogenic perturbations, including climate change. Trophic differences in response to climate change may disrupt ecological interactions and thereby threaten marine ecosystem function. Yet, we still do not have a comprehensive understanding of how different trophic levels respond to climate change stressors in marine ecosystems. By including 1278 experiments, comprising 236 different marine species from 18 different phyla in a meta-analysis of studies measuring the direct effect of ocean acidification and ocean warming on marine organisms, we found that higher trophic level species display greater tolerance to ocean acidification but greater sensitivity to warming. In contrast, marine herbivores were the most vulnerable trophic level to both acidification and warming. Such imbalances in the community and a general reduction of biodiversity and biomass in lower trophic levels can significantly disrupt the system and could drive negative bottom-up effects. In conclusion, with ocean acidification and elevated temperatures, there is an alarming risk that trophic disparity may disrupt species interactions, and thereby drive community destabilization under ocean climate change.
... Ungulate species detected were roe deer, moose, musk deer, red deer, and wild boar. Mesopredators were defined as predators or population of predators that are classified to be in the mid-size of the available predators within the given ecosystem (Groom et al., 2006;Prugh et al., 2009;Wallach et al., 2015); under this definition, we detected sable Martes zibellina and weasels Mustela nivalis in this system. Top predators (apex predators, alpha predators or mega-predators) were defined as large predators with no natural predators to feed on them within the food chain (Groom et al., 2006;Prugh et al., 2009;Sukhdeo, 2012;Wallach et al., 2015); we detected bear, lynx, and wolverine as top predators in this system. ...
... Mesopredators were defined as predators or population of predators that are classified to be in the mid-size of the available predators within the given ecosystem (Groom et al., 2006;Prugh et al., 2009;Wallach et al., 2015); under this definition, we detected sable Martes zibellina and weasels Mustela nivalis in this system. Top predators (apex predators, alpha predators or mega-predators) were defined as large predators with no natural predators to feed on them within the food chain (Groom et al., 2006;Prugh et al., 2009;Sukhdeo, 2012;Wallach et al., 2015); we detected bear, lynx, and wolverine as top predators in this system. ...
As an apex predator, the grey wolf (Canis lupus) is an ecologically important species. It is considered an ecologically important species due to its position as an apex predator. Grey wolves survive in a wide range of habitats including deserts, steppe, tundra, shrubs, coniferous and deciduous forests. Grey wolves have a cosmopolitan distribution, mostly found in the northern hemisphere. Due to historical and continued persecution; and reduced prey populations, its current range is restricted to remote areas. Thanks to conservation initiatives, grey wolves are beginning to reclaim parts of its historical distribution, currently listed as Least Concern by the IUCN. During a two year camera-trapping survey, we obtained the first photographic detection of grey wolves in Hanma National Nature Reserve, China. We deployed 113 camera traps spaced at least 1km apart, which ran for 27,607 trap nights. On October 11th 2017 at 16:40, a camera located in the coniferous forest detected two adult grey wolves. Thus, we report the first photographic detection of grey wolves in HNNR. We emphasize the need for more research to further determine the true distribution of grey wolves in China and suggest that wildlife managers can use the same conservation strategies applied in HNNR to other areas in order to assist grey wolf recovery.
... Top predators are broadly defined as species that occupy the highest trophic niches (Sergio et al., 2014). They predate on other species and are rarely predated on in their adult form (Wallach et al., 2015). ...
In many intact African savannah ecosystems, martial eagles are the top avian predator, while lions are the top terrestrial predator. Here, we report seven records of martial eagle predation or attempted predation of lion cubs in the greater Mara region, Kenya. These events resulted in the death of nine lion cubs, most of which were at least partially consumed, and are the first detailed records of this behaviour to be published. While these observations represent intraguild interactions, we suggest that they reflect neither intraguild predation nor interspecific killing. Rather, the ecology of both species coupled with the details of our records suggest that martial eagles opportunistically kill lion cubs purely to eat them. We hope that by publishing these records we will encourage others to share their observations of raptors predating on large mammalian carnivores, thus improving our understanding of a behaviour that we suspect may be more widespread than the current lack of evidence suggests.
... It might be expected, therefore, that the welfare benefits of artificially reducing fertility could be large when fierce competition among individuals for resources is prevalent but small or even negative when cooperative behavior is beneficial for resource exploitation and individual survival. In some group-living species, particularly highly social apex predators, dominant individuals often control the reproduction of conspecifics, such that population densities stay well below the point where resources become limiting (Wallach et al. 2015 ). Contraception in these cases might therefore be less likely to be beneficial to their welfare. ...
To date, research on the welfare impacts of wildlife contraceptives has mostly been focused on the potential harms of contraceptives. However, there are compelling theoretical reasons to expect direct and indirect welfare benefits of wildlife contraceptives. These positive welfare effects would be experienced by more than just the treated individuals, because per capita resource availability will increase with decreasing numbers of individuals sharing a resource. In the present article, we discuss the potential for wildlife contraceptives to alleviate resource competition and their associated negative welfare effects at different scales. These effects are expected to vary across contexts and would presumably be stronger when wildlife contraceptives are used with the explicit purpose of improving wild animal welfare. The potential for considerable welfare gains for wildlife through the targeted use of contraceptives highlights the importance of both species-specific studies on the welfare benefits of wildlife contraceptives and further research on the links between population dynamics and wild animal welfare.
... Literature on coexistence of carnivores with each other in the Neotropics suggests that jaguars are dominant over pumas (Haines, 2006;Oliveira & Pereira, 2014), whereas ocelots are subordinate to both these species due to their smaller size (Elbroch & Kusler, 2018;Wallach et al., 2015). The outcomes from theoretical and empirical studies regarding coexistence of jaguars and pumas suggest that the avoidance behavior between these species is scale dependent and is discernible only at a very fine scale (i.e., forest patch level) (Palomares et al., 2016). ...
Anthropogenic activities may alter felid assemblage structure, facilitating the persistence of tolerant species (commonly mesopredators), excluding ecologically demanding ones (top predators) and, consequently, changing coexistence rules. We aimed to determine how human activities influence intraguild relationships among top predators and their cascading effects on mesopredators, which remain poorly understood despite evidence of top carnivore decline. We used structural equation modeling at a continental scale to investigate how habitat quality and quantity, livestock density, and other human pressures modified the intraguild relations of the 3 species that are at the top of the food chain in the Neotropics: jaguars (Panthera onca), pumas (Puma concolor), and ocelots (Leopardus pardalis). We included presence–absence data derived from systematic studies compiled in Neocarnivores data set for these felid species at 0.0833° resolution. Human disturbance reduced the probability of jaguar occurrence by −0.35 standard deviations. Unexpectedly, the presence of sheep (Ovis aries) or goats (Capra aegagrus hircus) and jaguars was positively related to the presence of pumas, whereas puma presence was negatively related to the presence of ocelots. Extent of forest cover had more of an effect on jaguar (β = 0.23) and ocelot (β = 0.12) occurrences than the extent of protected area, which did not have a significant effect. The lack of effect of human activities on puma presence and the positive effect of small livestock supports the notion that pumas are more adaptable to habitat disturbance than jaguars. Our findings suggest that human disturbance has the potential to reverse the hierarchical competition dominance among large felids, leading to an unbalanced community structure. This shift disadvantages jaguars and elevates the position of pumas in the assemblage hierarchy, resulting in the exclusion of ocelots, despite their relatively lower susceptibility to anthropogenic disturbance. Our results suggest that conservation efforts should extend beyond protected areas to encompass the surrounding landscape, where complexities and potential conflicts are more pronounced.
... Apex predators are usually free from predation, and thus, the main drivers of population dynamics are the availability of trophic resources affecting productivity (bottom-up regulation; Schmidt et al., 2018), inter-and intraspecific interactions (competition and territoriality; Carrete et al., 2006), and adult survival (mainly conditioned by human-induced mortality; Whitfield et al., 2004). Indeed, apex predators show ecological and behavioral traits of population auto-regulation, and their populations can be regulated by density-dependent processes (Wallach et al., 2015), largely mediated by prey resource availability and consumption in territorial species (Cariappa et al., 2011). Trophic niche breadth (i.e., the variety and composition of food resources used by a given species) has been described in many apex predators, albeit changes in the long term are poorly known, even in species whose demographics have been widely studied (e.g., large raptors, wolves, big cats; Newton et al., 2016;Ripple et al., 2014). ...
Understanding the trophic and demographic dynamics of apex predators is of paramount importance for ecosystem conservation. Apex predators are usually free from predation, and thus, the main driver of population dynamics is the availability of trophic resources, which affects breeding performance. Albeit food habits have been described in many apex species, the effects of changes in the trophic niche on long‐term demographic dynamics are poorly known. We describe the long‐term (N = 25 years) changes in trophic niche breadth of a recovering golden eagle population in a Mediterranean landscape (northern Spain) and search for potential correlates with their productivity (i.e., number of fledged eaglets per controlled pair) as a proxy for their breeding performance (N = 290 pair‐years). We identified a total of 3475 prey items from 77 species; rabbits, hares, and red‐legged partridges were the most frequent prey consumed (overall 51%), followed by roe deer (10%), red‐billed chough, red foxes, and woodpigeons, all of them with >5%. Prey diversity in eagles' diet decreased during the study period. Consumption of rabbits and roe deer increased, while that of hares and partridges decreased; no significant trends were observed in the consumption of foxes, choughs, and woodpigeons. Prey diversity and red‐legged partridge consumption were negatively correlated with productivity at the territory level, while rabbits, corvids, and pigeons showed a strong positive relationship with productivity. The size of the territory showed the strongest positive relationship with productivity, while roughness was negatively correlated. Rabbits and ungulates showed negative and positive correlations with roughness, respectively, while predator consumption exhibited a negative relationship with the size of the territory. Our findings give insights into the potential trophic mechanisms driving the dynamics of recovering apex predator populations; a reduction in the trophic niche breadth toward specific groups of prey, which could be due to a higher availability and individual specificity toward these prey species, might enhance productivity at the territory level and, ultimately, influence population dynamics facilitating the recovery process. The remarkable increase in the consumption of wild ungulates, predators, and other apex consumers suggests that the current population recovery and reduced trophic niche breadth may facilitate this eagle population to exhibit its apex role and contribute to ecosystem functionality.
... Es decir, el oso es una especie paraguas porque confiere protección a otras especies situadas por debajo en la cadena trófica. Y es que, aunque el valor instrumental o funcional a nivel ecológico del oso pardo, como un omnívoro que destaca por su capacidad como dispersor de semillas, no casaría con su valor intrínseco o composicional como un gran carnívoro, su definición como especie paraguas permite concebirlo como un animal situado en el ápice de la pirámide trófica, como los grandes depredadores, a través del cual puede protegerse todo un ecosistema (Ritchie et al. 2012;Wallach et al. 2015). Entendiéndolo así, la presencia de osos en el Pirineo es concebida como un índice de calidad que connota la protección de los recursos naturales a través de su reverdecimiento y, por tanto, la mejora del entorno comprendido dentro de su extenso hábitat. ...
... Through exploitative competition, kleptoparasitism and direct killing, apex predators can outcompete sympatric mesopredators (Polis et al. 1989, Hamilton 2002. This may lead to suppression of mesopredator behaviour, abundance and distribution, and can thereby constrain the predation pressure that mesopredators exert onto lower trophic levels (Ripple et al. 2014, Wallach et al. 2015). An apex predator decline may relieve the mesopredators of this suppression, leading to the phenomenon that is known as mesopredator release (Prugh et al. 2009, Brashares et al. 2010). ...
1. Conservation successes in Europe have sparked the recovery of apex predators , which may affect the populations of mesopredators. The mesopredator release hypothesis (MRH) predicts that a decline in apex predators triggers a 'release' of mesopredators from suppression.
2. We expanded the MRH to include predictions of inverse responses following increases in apex predator abundance or distribution. We examined European mesopredator responses to changes in apex predator populations and evaluated the extended MRH's explanatory power.
3. We examined the results of 47 studies on European predators for supporting evidence, mixed evidence, no evidence, or contrasting evidence for the extended MRH.
4. Out of 38 apex predator-mesopredator pairings, 10 predominantly supported the extended MRH, while others provided limited or no support. In 23 instances across 17 pairings, mesopredator responses contradicted predictions. Initial findings suggest the extended MRH better predicts mesopredator responses in pairings with intermediate to large body size differences and in pairings where mesopredators primarily hunt.
5. Our results reveal non-uniform mesopredator responses to changing apex predator populations. This emphasises the complexity of predator interactions, which extends beyond suppression. We suggest the MRH's scope is more restricted than previously thought, cautioning against overreliance on the MRH as a default expectation for European mesopredator responses to apex predator population changes.
... Nowadays cetaceans' health is threatened by several natural and anthropic factors and, considering their role in the marine food chain and their longevity, their health might reflect the status of the marine ecosystem [1,2]. Despite this increasing interest and need of information, several data on their biology and medicine are still missing due to the limitation of studies conducted in their natural environment. ...
Dolphins, as apex predators, can be considered relevant sentinels of the health of marine ecosystems. The creation of 3D cell models to assess in vitro cell-to-cell and cell-to-matrix interactions in environmental-mimicking conditions, is of considerable interest. However, to date the establishment of cetacean 3D culture systems has not yet been accomplished. Thus, in this study, different 3D systems of bottlenose dolphin (Tursiops truncatus) skin fibroblasts have been analyzed. Particularly, novel scaffolds based on hyaluronic acid and ionic-complementary self-assembling peptides such as RGD-EAbuK and EAbuK-IKVAV have been compared to Matrigel. Histological and fluorescent staining, electron microscopy (TEM) analyses and viability assays have been performed and RT-PCR has been used to detect extracellular matrix (ECM) components produced by cells. Results showed that Matrigel induced cells to form aggregates with lower viability and no ECM production compared to the novel scaffolds. Moreover, scaffolds allowed dispersed cells to produce a collagenous ECM containing collagen1a1, laminin B1 and elastin. The HA-EAbuK-IKVAV scaffold resulted in the most suitable 3D model in terms of cell quantity and viability. The development of this innovative approach is the first step towards the possibility to create 3D in vitro models for this protected species.
... Numerous studies, including ours, confirmed that this trend extends to big cat species, which are studied more often than smaller felid species, owing to the endangered and/or emblematic status of big cats, as well as their history of conflict with humans (Ripple et al. 2014, Lozano et al. 2019). Additionally, their large size is often associated with their ability to shape ecosystems with far-reaching effects on lower trophic levels, a role that smaller carnivores cannot fulfil, some argue (Wallach et al. 2015, Avrin et al. 2023. In this review, the snow leopard (Panthera uncia) is the only big cat for which no result was found. ...
1. Carnivores, often identified as keystone species, can influence prey and subordinate carnivores through density- and behaviourally mediated pathways. Although the magnitude of their impacts remains debated, carnivores may trigger successional direct and indirect ecological effects on lower trophic levels in specific contexts, commonly known as trophic cascades. Felids, as ambush predators, have great potential to impact food webs. Yet, their influence on ecosystem dynamics remains understudied.
2. This global comprehensive literature review aimed to assess evidence for felids' ecological roles in trophic cascades across both natural and human-dominated ecosystems.
3. We found 61 publications that studied the influence of 18 felid species in trophic cascades. Research exhibited taxonomic and geographic biases, favouring big cats, temperate regions and biomes, as well as tropical moist forests in Central and South America. Of the studies, 23% (n = 14) were experimental, while 77% were observational or correlative. Among the latter, 60% tested at least one alternative hypothesis and 47% examined bottom-up processes.
4. Despite varying levels of inference, 80% of studies provide information consistent with trophic cascades involving felids. Their examination confirmed wild cats' ability to induce density- and behaviourally mediated trophic cascades, thereby influencing critical biotic and abiotic processes, including mesopredator control, functional diversity maintenance, and carbon storage. The magnitude of these effects may be altered in human-dominated landscapes, although current research effort remains too limited to draw conclusions.
5. In conclusion, felids may act as drivers of ecosystem change, and acknowledging their ecological roles can aid in promoting their conservation. However, we encourage more strongly inferential and comprehensive investigations into felid-mediated trophic cascades, prioritising research on small cats, felids in Asia and Africa, and the impacts of humans on trophic cascades, which can help to better inform conservation interventions and perspectives.
... The exposure to SGARs in non-target consumers is likely leading to a broader movement of these compounds through the ecosystem, and as such a wider range of predators can be secondarily exposed. This is a concern as predators fulfill vital roles in maintaining ecosystem stability through top-down regulation of primary consumers (Ritchie and Johnson, 2009;Wallach et al., 2015). Disruption of predator-prey balances because of rodenticide exposure could also lead to significant alterations to natural abundances of primary consumer populations in the absence of a key predator. ...
... Nossos resultados mostraram que os catetos podem ajustar suas atividades devido à presença de um predador de topo, mas essas alterações não são generalizadas para todos os predadores. and the apex predators occupying the highest ranking position (Wallach et al., 2015). ...
Collared peccaries ( Dicotyles tajacu , Cetartiodactyla) adjust their daily activity patterns in response to different factors, such as the presence of predators or climatic factors (temperature and rainfall), as a way of ensuring survival. The knowledge of these patterns allows us to understand the interspecific interactions of the community. This study measured daily activity of the collared peccary, and evaluated how different climatic conditions, and the presence of predators influenced their activity patterns. Data were obtained from eight camera traps over 13 months in the Municipality of Ouro Preto, Brazil. The daily activity periods of collared peccaries and their predators were evaluated and the animals classified as diurnal, nocturnal, crepuscular, or cathemeral. Camera‐trap records were used to assess whether temperature and rainfall affected daily activity patterns in peccaries. We found that neither rainfall nor temperature influence the activity pattern. Peccary activity overlapped with the activity of local predators. A low level of overlap was recorded with the activity of Puma concolor and high level of overlap with the activity of Leopardus pardalis , Canis lupus familiaris , and human activity. The low activity overlap of collared peccaries with P. concolor may be related to an attempt to decrease predation risk, while the high activity overlaps with domestic dogs and humans may be related to the low hunting pressure exerted in the region and also to the foraging opportunities for peccaries in areas closer to human settlements, where orchards are present. The high activity overlap with L. pardalis can be related to the smaller size of this predator and the aggressive group anti‐predator behaviour of the collared peccary. Our results show that collared peccaries can adjust their daily activity when an apex predator is present, but this adjustment is not generalized to all predators.
... It is common to see elasmobranchs referred to as 'apex predators', meaning that they occupy the highest trophic (i.e. feeding) level of the food web that they are part of (Wallach et al. 2015). However, this is a somewhat simplistic and misleading representation of their ecological role. ...
The waters of the United Arab Emirates (UAE) are home to a wide variety of shark and ray species, many of which are unique to the region and about which relatively little is known. Research efforts to date have focused primarily on identifying the species that occur locally and their importance to fisheries, but further research is required to understand their inherent biological and ecological traits. Decades of heavy fishing pressure and coastal development have impacted shark and ray populations to the extent that some, once common species, are now considered rare. Encouragingly, the UAE has adopted a National Plan of Action for the Conservation of Sharks to guide researchers and policy makers in their efforts to ensure that the nation’s shark and ray populations are effectively managed and conserved.
... These different trophic levels of consumers are all considered crucial for the role they play, as Ripple et al. (2014) have emphasized, in the maintenance of stability of an ecosystem through subjecting the plants and consumers of the lower trophic level to efficient predation thereby keeping their population at the appropriate number not exceeding and pressuring the ecosystem's natural carrying capacity. The primary reason why there are fewer apex predator populations than the primary and secondary consumers are due to the greatly reduced energy passed to their trophic level (Wallach et al., 2015) as demonstrated by the 2 nd law of thermodynamics (Galucci, 1973). If the number of apex predators exceeds that of their prey, it would create a deficit in the energy that they acquire to what is present, thereby resulting in an unbalanced food chain and food web. ...
Coastal ecosystems are where land and water converge creating a distinct environment hosting a rich diversity of marine organisms. This study aimed to determine the zonation pattern of mangroves and the trophic relationship among the associated macrobenthos in the local coastal ecosystem of Guang-guang, City of Mati, Davao Oriental. The establishment of the study area and gathering of field data were conducted on December 2, 2017, a period of one day during low tide. There was an absence of zonation pattern on the mangal due to Rhizophora stylosa being the only mangrove species present. The marine gastropods observed on the mangal were Monilea callifera, Pomalea canaliculata, Crassostrea iredalei, Trochus pyramis, Spisula solidissima, Zeacumantus lutulentus, Cominella glandiformis, Diloma subrostrata and Haustrum scabina. On the adjacent intertidal zone, the seagrasses and macroalgae found were Enhalus acoroides, Thalassia hemprichii, Padina gymnospora, Halophila ovalis, and Halimeda sp., and the presence of the associated macrobenthos starfish, hermit crab, Philippine sand dollar, mud crab, blue mussel, marine gastropod, shrimp, brittle star, fish and jellyfish. The area had a high macrobenthic diversity with 1.34 on the Shannon-Wiener diversity index and 0.6 on Simpson’s diversity index. On the highest trophic level of the coastal ecosystem food chain are the producers including mangroves, sea grasses and algae and the lowest on the trophic level are the tertiary consumers and apex predators are birds, turtles, and larger fishes.
... The need to hunt prey, or to avoid being killed by predators, has driven the evolutionary trajectories of organisms across the globe [1]. Predators evolve novel morphologies, behaviours, and life history traits to better hunt prey [2,3], while prey evolve traits to defend themselves, avoid detection, deter predators, and reduce the risk of a predator encounter [4,5]. Predator and prey are entangled in an ecoevolutionary arms race, as improved hunting abilities demand compensatory improvements in prey avoidance and vice versa [6]. ...
Predator-prey ecology and the study of animal cognition and culture have emerged as independent disciplines. Research combining these disciplines suggests that both animal cognition and culture can shape the outcomes of predator-prey interactions and their influence on ecosystems. We review the growing body of work that weaves animal cognition or culture into predator-prey ecology, and argue that both cognition and culture are significant but poorly understood mechanisms mediating how predators structure ecosystems. We present a framework exploring how previous experiences with the predation process creates feedback loops that alter the predation sequence. Cognitive and cultural predator-prey ecology offers ecologists new lenses through which to understand species interactions, their ecological consequences, and novel methods to conserve wildlife in a changing world.
... The most functionally distinct species identified in our analysis tend to occupy a higher trophic position in the food web to the extent that some, such as Porbeagle (Lamna nasus) that feeds mainly on teleost fish and cephalopods (Stevens, 2010), are known to be apex predators (Wallach et al., 2015). Because top predators exert topdown regulation (Barley et al., 2017a(Barley et al., , 2017bRuppert et al., 2013), their decline or disappearance may destabilize ecosystems functioning through cascade reactions (Leitão et al., 2016;Mouillot, Graham, et al., 2013;Murgier et al., 2021;Violle et al., 2017). ...
Aim
The criteria used to define the International Union for Conservation of Nature (IUCN) Red List categories are essentially based on demographic parameters at the species level, but they do not integrate species' traits or their roles in ecosystems. Consequently, current IUCN‐based protection measures may not be sufficient to conserve ecosystem functioning and services. Some species may have a singular combination of traits associated with unique functions. Such functionally distinct species are increasingly recognized as a key facet of biodiversity since they are, by definition, functionally irreplaceable. The aim of this study is to investigate whether threatened species are also functionally rare and to identify which traits determine extinction risk.
Location
European continental shelf seas.
Time period
1984–2020.
Major taxa studied
Marine fish.
Methods
Using newly compiled trait information of 425 marine fish species in European waters, and more than 30 years of scientific bottom trawl surveys, we estimated the functional distinctiveness, restrictedness and scarcity of each species and cross‐referenced it with their IUCN conservation status.
Results
In European continental shelf seas, 38% of the species threatened with extinction (9 out of 24 species) were identified as the most functionally distinct. By mapping extinction risk in the multidimensional species trait space, we showed that species with the greatest risk of extinction are long‐lived and of high trophic level. We also identified that the most functionally distinct species are sparsely distributed (4% of the total area on average) and have scarce abundances (<1% of the relative mean abundance of common species).
Main Conclusions
Because a substantial proportion of threatened species are functionally distinct and thus may play unique roles in ecosystem functioning, we stress that species traits—especially functional rarity—should become an indispensable step in the development of conservation management plans.
... Body growth is associated with the requirement for larger prey, and larger individuals within a species tend to occupy a higher TL (Al-Habsi et al., 2008;Wallach et al., 2015). In the present study, the increase in the δ 15 N values of the hairtail sampled from the water depth of 30-40 m in section F terminated at a size of~200 mm in preanal length, indicating an end to the ontogenetic diet shift, which was close to the diet shifts reported previously at the preanal length of 190 mm or the body length of 200 mm in the hairtail from the Beibu Gulf and the ECS, respectively (Chen and Zhu, 1984;Zhang, 2004;Yan et al., 2010). ...
The feeding habit of large-head hairtail (Trichiurus lepturus) in the northern South China Sea was investigated through isotopic and stomach content analyses. The isotopic features of the hairtail at the same body size differed among regions, with the fish in coastal waters presenting higher δ15N and δ13C values compared to those in the open sea, indicating different trophic levels (TL), food habits, and isotopic baselines. According to the partial correlation of water depth with δ15N values, the sampling stations were divided into three regions based on the depth of water: coastal (20-40 m), near coastal (60-80 m), and open sea (100-200 m) regions. In the coastal region, the hairtail from stations affected by the Pearl River plume exhibited lower δ15N and δ13C values. The stomach content analysis indicated different feeding habits of the hairtail from different regions. The hairtail in the coastal and near coastal waters fed more on fish and less on crustaceans compared to the hairtail in the open sea. The relationship between δ15N and fish size exhibited two contrary patterns. First, the δ15N values increased with increasing preanal length in the hairtail sampled from the water depth of 30-40 m in section F (in fish with preanal length < 200 mm) and those samples from the water depth of 100-200 m. This finding reflected an ontogenetic shift in diet and TL. However, the δ15N values tended to decrease with the increasing preanal length of the hairtail samples collected from the water depth of 30-40 m in section F (fish with a preanal length of ~200-300 mm). These findings suggested that under the conditions of insufficient availability of high-quality prey, the larger hairtail fed more on low-TL prey to compensate for the increase energy demand, arising due to growth, which led to the observed decrease in δ15N values.
... Our study sheds light on important component of endemic species conservation by assessing the habitat suitability and attributes associated with the distribution of a habitat specialist mega herbivore, the swamp deer, in an important conservation landscape of Nepal. In the recent scenarios of a drastic decline in the global population of large herbivores, owing to their relatively low population densities, unique habitat requirements, and slow life history characteristics [108,109], large-scale conservation initiatives are deemed imminent for their sustainable conservation. This implies that precise information on distribution, and various habitat parameters are necessary to ensure their future survival. ...
Over the last few years, intensifying human impact and the deterioration of natural habitats have severely restricted the global distribution of large herbivores. Rucervus duvaucelii, commonly recognized as the swamp deer, is a habitat-specialist endemic large herbivore of the Indian Subcontinent. It is classified as vulnerable by the IUCN and listed in CITES Appendix I due to a steep decline in its population, which is primarily due to anthropogenic causes. In Nepal, the last remaining population of this species is confined to limited pocket areas within the western Terai Arc Landscape. We explored potential habitat for swamp deer across this landscape using species distribution modelling through the MaxEnt algorithm by using 173 field-verified presence points alongside six anthropogenic, four topographic, and four vegetation-related variables. Our study found that out of the total study area (9207 km2), only 6% (590 km2) was suitable for swamp deer. Approximately 45% of suitable habitat was incorporated within protected areas, with Shuklaphanta National Park harboring the largest habitat patch. The suitability of habitat was discovered to be positively associated with low-elevation areas, areas near water sources, and areas far from settlements, implying the need to conserve water sources and minimize the extension of anthropogenic pressure for their long-term conservation. Additionally, we suggest the implications of a swamp deer-centric conservation strategy, with an emphasis on increasing connectivity through the corridors and landscape-level population connectivity through trans-boundary conservation initiatives between Nepal and India. Moreover, considering large herbivores' high vulnerability to extinction, similar researche incorporating anthropogenic factors is of the utmost importance to produce vital information on habitat suitability for conserving other regionally and globally endemic, habitat-specialized herbivores.
... An alternative of the functional megafauna concept would be apex megafauna: animals so large that they escape most non-anthropogenic predation as adults. This concept is related to the megaherbivore and apex predator concepts (Owen-Smith, 1988, and Wallach et al., 2015 Moleón et al. (2020) concluded that approaching the concept of megafauna from a functional perspective would render it more broadly applicable to eco-evolutionary contexts and scientific approaches. These authors encouraged the explicit definition and contextualization of the concept of megafauna in every study as a means of achieving conceptual disambiguation. ...
The Pleistocene Pampean Megafauna (PPM) may be considered as the assemblage consisting mainly of large mammals (i.e., bodymass ≥ 45 kg) that inhabited what is currently considered the Pampean Region during the Pleistocene and became extinct near the Pleistocene–Holocene transition. This contribution addresses several conceptual issues that may guide future efforts in its reconstruction and to consider potential consequences of its extinction. First, we approach the concept of megafauna by urging its explicit definition and contextualization in every investigation as a means of avoiding conceptual ambiguity. Second, we call attention to the risks of succumbing too readily to the temptation of employing a simplistic approach that assumes that extinct taxa had virtually the same biological requirements as those of their extant counterparts. We claim that within the PPM the abundance of taxa distantly related to or markedly distinct morphologically from their living counterparts poses significant challenges for understanding their paleobiology. Paleobiological interpretations need not be rigidly phylogenetically restricted, and phylogenetically based interpretations require critical assessment before their application. Third, we consider the paleoecology of the PPM from a metabolic perspective: as it was clearly dominated by allegedly hypometabolic megaherbivores (xenarthrans), there is no clear counterpart among living faunas. Fourth, we call attention to the fact that the loss of the PPM may have left in its wake an enduring but little-recognized legacy on the functioning of the contemporary ecosystem of the Pampean Region. Extinction of the PPM opened an enormous ecological chasm in the herbivore guild during the Holocene that persisted for about 6000 years, until it was filled, at least in part, by herds of cattle introduced since the sixteenth century.
... The three sites with trials in multiple years showed similar estimates of median carcass persistence between years (14 v 18 days at Altamont: Site 1, 551 v 814 at Braes of Doune: Site 4, 156 v 165 days at Wolfe Island: Site 16, Table 1). Such a result would be expected if scavenger numbers at a site are (a) not primarily limited by prey availability, as has been suggested for apex predators (e.g., Wallach et al., 2015), (b) relatively constant across years due to long life-spans or (c) both. While ecological theory and the results from these three sites suggest that carcass persistence trials at a site may not be needed over multiple years, more multi-year carcass persistence trials would be needed to confirm this is the case. ...
Bird and bat turbine collision fatalities are a principal biodiversity impact at wind energy facilities. Raptors are a group at particular risk and often the focus of post-construction fatality monitoring programs. To estimate fatalities from detected carcasses requires correction for biases, including for carcasses that are removed or decompose before the following search. This is addressed through persistence trials, where carcasses are monitored until no longer detectable or the trial ends. Sourcing sufficient raptor carcasses for trials is challenging and surrogates that are typically used often have shorter persistence times than raptors. We collated information from raptor carcass persistence trials to evaluate consistencies between trials and assess the implications of using persistence values from other studies in wind facility fatality estimates. We compiled individual raptor carcass persistence times from published sources along with information on methods and location, estimated carcass persistence using GenEst and ran full fatality estimates using the carcass persistence estimates and mock datasets for other information. We compiled results from 22 trials from 17 sites across four terrestrial biomes, with trials lasting between 7 and 365 days and involving between 11 and 115 carcasses. Median carcass persistence was estimated at 420 days (90% confidence interval (CI) of 290 to 607 days) for the full dataset. Persistence time varied significantly between trials (trial-specific persistence estimates of 14 (5–42) days to 1,586 (816–3,084) days) but not between terrestrial biomes. We also found no significant relationship between either the number of carcasses in the trial or trial duration and estimated carcass persistence. Using a mock dataset with 12 observed fatalities, we estimated annual fatalities of 25 (16–33) or 26 (17–36) individuals using a 14- or 28-day search interval respectively using global dataset. When using trial-specific carcass persistence estimates and the same mock dataset, estimated annual fatalities ranged from 22 (14–30) to 37 (21–63) individuals for a 14-day search interval, and from 22 (15–31) to 47 (26–84) individuals for a 28-day search interval. The different raptor carcass persistence rates between trials translated to small effects on fatality estimates when using recommended search frequencies, since persistence rates were generally much longer than the search interval. When threatened raptor species, or raptors of particular concern to stakeholders are present, and no site-specific carcass persistence estimates are available, projects should use the lowest median carcass persistence estimate from this study to provide precautionary estimates of fatalities. At sites without threatened species, or where the risk of collision to raptors is low, the global median carcass persistence estimate from this review could be used to provide a plausible estimate for annual raptor fatalities.
... In absence of other species preying on them (besides humans), population dynamics of apex predators at the top of the trophic chain are potentially regulated by changes in the availability of their prey species (i.e., bottom-up regulation) which have an effect on survival rates and breeding performance, both affected by environmental factors influencing habitat quality and feeding opportunities. However, there is increasing evidence that apex predators also exhibit behavioral and ecological traits of population auto-regulation (Wallach et al., 2015) and that other socially mediated mechanisms (i.e., density-dependent processes) can be important for limiting populations at specific levels (e.g., Cariappa et al., 2011). ...
Apex predators play a critical role in shaping the biological and functional diversity of ecosystems. Like in many other living groups, population dynamics of apex predators exhibit auto‐regulation traits, including density‐dependent processes, which can be important for limiting population numbers. However, the study of these processes is challenging due to their slow life history traits, especially when their populations are depressed. Our main objective is to describe mechanisms driving population dynamics in apex predators by documenting the relationship between population density and demographic parameters at population level and analyzing the influence of population density and other environmental factors on the reproductive parameters at territory level. We used as biological model a recovering population of golden eagles Aquila chrysaetos in a Mediterranean landscape (North Spain). We monitored yearly all known eagle pairs within the study area for 28 years, implying 1539 reproductive events in a total of 84 territories. The average density was 3.04 pairs/1000 km², and the reproductive success, productivity, and flight rates averaged 0.45, 0.54, and 1.20, respectively. The population increased during the study period (from 37 to 78 pairs), although we did not find any effect of density on the reproductive parameters at population level. At territory level, we found that size of territory, proportion of open habitat, and spring precipitation increased reproductive performance, while older territories performed worse than new ones. Our findings suggest that population dynamics in recovering apex‐predators are driven by a complex combination of compensatory density‐dependent processes, mainly operating at territorial level, and by environmental factors mainly related with resource availability and human pressure. For species with slow life history traits, population recovery seems to be facilitated by re‐colonization from refuge areas, wilder but less productive, to areas with higher resource availability, once they became safer after reduction of human pressures.
... A c c e p t e d M a n u s c r i p t 3 Apex predators play a fundamental role in ecosystems (Wallach et al. 2015). Operating as a top-down force, they can affect the ecology of competitors and prey (Beschta and Ripple 2009), with the potential to shape the dynamics of communities (Paine 1969). ...
Prey adjust their antipredator behavioral tactics to minimize the risk of an encounter with predators. Spatio-temporal responses of prey to predators have been reported, but antipredator response is not ubiquitous, and it is the object of increasing interest, especially considering the recent recovery of large carnivores in Europe, and the potential for behavioral antipredator responses to elicit consequences at the ecosystem level. We have tested multiple antipredator responses by fallow deer Dama dama to wolf Canis lupus, in a Mediterranean protected area recently recolonized by this apex predator. Through intensive camera trapping, we tested for temporal and spatial association between predator and prey, and we have also studied deer vigilance in forest habitats where focal observations are usually impossible. Wolf detection rates were spatially associated with those of fallow deer. Accordingly, no evidence was found for fallow deer avoiding sites with higher predator detection rates. Temporal activity patterns were significantly different between the two species, with the wolf being mainly nocturnal whereas fallow deer was active especially during daylight. A comparison with a preliminary study strongly suggests an increase in diurnal activity of fallow deer along with the stabilization of wolf presence in the area. Both the rate and the duration of vigilance of female fallow deer increased with the local frequency of wolf activity. We suggest an antipredator response based on temporal – rather than spatial – avoidance, as well as increased vigilance.
... Davis et al. (2019) found that co-occurrence probabilities were greatest for pairs of carnivores that shared ecological traits such as similar body size, diet or temporal activity pattern. However, co-occurrence decreased as compared to other species pairs when the pair included a large-bodied carnivore, confirming that large carnivores play an important top-down role (Roemer et al., 2009;Wallach et al., 2015;Ramesh et al., 2017;Zhao et al., 2020). Donadio & Buskirk (2006) found that interspecific killing among carnivores occurred with greater frequency and intensity when a larger species was 2-5.4 times the mass of the smaller victim. ...
Carnivore species are believed to exert strong competitive pressure on each other, resulting in adaptations to allow for niche separation through resource partitioning. However, factors that promote ecological separation among species in tropical forests are difficult to explain and are poorly understood because robust field studies are lacking. We examined spatial, temporal and morphological segregation between tropical carnivores in a protected forest in north‐central Thailand. Sympatric spatial overlap was calculated from radio‐telemetry data of 38 individuals from six species (5 yellow‐throated martens, Martes flavigula , 20 leopard cats, Prionailurus bengalensis , 2 Asiatic golden cats, Catopuma temminckii , 4 clouded leopards, Neofelis nebulosa , 5 binturongs, Arctictis binturong , and 2 dholes, Cuon alpinus ) in the same study area. Spatial overlap was then correlated with 14 independent variables (i.e. skull and dental morphology, body mass, habitat use and activity patterns) compared among the six species. We predicted that carnivores with differing morphology and activity patterns would exhibit more spatial overlap because these species would compete less for prey resources. Our statistical analyses indicated that lower mean carnassial length and activity patterns in closed habitat cover were significantly correlated ( p < 0.05) with species spatial overlap. Binturongs appeared to have the greatest amount of spatial overlap with other species of carnivores, whereas dholes had the least spatial overlap; also, dholes and yellow‐throated martens tended to be more active in open habitats and during diurnal time periods, whereas clouded leopards and Asiatic golden cats were more active in closed cover and were more arrhythmic in activity. Although these results provide useful information on carnivore coexistence, we recommend that future studies monitor larger sample sizes of carnivore species over the same time period to provide more robust statistical analyses. In addition, we suggest that future research on carnivore coexistence evaluates the impacts of anthropogenic activity on study results.
... The upper limit on the number of territories that can be supported effectively caps breeding by a cooperatively breeding social carnivore, limiting the influence of increased natality on population growth (Fuller et al., 2003). This limitation may be evidence of how territoriality can be a self-regulating mechanism for a population (Wallach et al., 2015). ...
As climate change accelerates in northern latitudes, there is an increasing need to understand the role of climate in influencing predator-prey systems. We investigated wolf population dynamics and numerical response in Denali National Park and Preserve in Alaska, United States from 1986 to 2016 under a long-term range of varying climatic conditions and in the context of prey vulnerability, abundance, and population structure using an integrated population modeling approach. We found that wolf natality, or the number of wolves added to packs, increased with higher caribou population size, calf:cow ratio, and hare numbers, responding to a 1-year lag. Apparent survival increased in years with higher calf:cow ratios and cumulative snowfall in the prior winter, indicators of a vulnerable prey base. Thus, indices of prey abundance and vulnerability led to responses in wolf demographics, but we did not find that the wolf population responded numerically. During recent caribou and moose population increases wolf natality increased yet wolf population size declined. The decline in wolf population size is attributed to fewer packs in recent years with a few very large packs as opposed to several packs of comparable size. Our results suggest that territoriality can play a vital role in our study area on regulating population growth. These results provide a baseline comparison of wolf responses to climatic and prey variability in an area with relatively low levels of human disturbance, a rare feature in wolf habitat worldwide.
... Entscheidend ist dabei nicht allein die finale Größe einer Art, sondern vielmehr ihre Wechselbeziehungen mit Beutetieren und konkurrierenden Kleinräubern. Demnach verfügt nur ein Gipfelräuber (Spitzenprädator, Topräuber) über weitgehende Freiheit von natürlichen Feinden und somit die Selbstregulierung seiner Populationsdichte (Wallach et al. 2015). Natürlich sind spezifische Faktoren wie etwa im zwischenartlichen Verhalten ebenbürtiger Fleischfresser denkbar (Lehman et al. 2016), aber paläontologisch kaum auflösbar. ...
Conservation management to aid in the recovery of threatened species requires an understanding of their habitat availability and preference. Species distribution modelling can help delineate critical habitats to frame conservation decisions, particularly for a habitat-specialist species. Swamp deer is a grassland-obligate species, with three subspecies identified based on physical and geographic variations. Of these, the eastern swamp deer has restricted distribution and occurs only in two protected areas in the Brahmaputra valley of Assam, India. With assisted conservation efforts, the swamp deer population has revived in Manas National Park from an erstwhile heavily reduced remnant population. Through this paper an attempt has been made to analyse the patterns of swamp deer occurrence as determined by habitat variables using random forest algorithm models. The results indicate that the optimal habitats of swamp deer are the large grassland patches with wet climatic conditions, measured by the precipitation and evapotranspiration, within the broad grassland habitat of the park. The findings have significant implications for the conservation of the threatened grassland habitat and its obligate species in the Terai grasslands of the region.
Whether gray wolf Canis lupus population density is limited intrinsically or extrinsically has occupied researchers for decades. Since 1983, prey biomass, an extrinsic factor, has been accepted as limiting, but that conclusion was recently challenged for unusually high wolf densities which were then said to be limited by behavioral, or intrinsic, factors such as intraspecific strife, dispersal, etc., below prey‐biomass constraints. That contention has been disputed, so disagreement remains. This article discusses the models involved, presents revised models that shed new light, and offers evidence that supports the conclusion that at least at densities below 79 wolves 1000 km⁻², wolf numbers per area are limited by prey biomass. As wolf density increases, behavioral factors limit the density to the number of wolves the prey biomass will support. Extra wolves disperse, and wolf range expands. Thus, while wolf density is self‐limiting, the population is not.
Motivation
Terrestrial predators play key roles in cycling nutrients, as well as limiting prey populations, and shaping the behaviour of their prey. Prehistoric, historic and ongoing declines of the world's predators have reshaped terrestrial ecosystems and are a topic of conservation concern. However, the availability of ecologically relevant predator functional traits is limited, hampering efforts to understand macroecological changes in this ecologically important functional group. Here, we present CarniTraits , a comprehensive open‐access functional trait database of all late Quaternary (~130,000 ybp) terrestrial mammalian predators (149 species, ≥1 kg body mass, ≥50% vertebrate meat consumption).
Main Types of Variables Contained
Mammalian terrestrial predator functional traits including body mass, diet, scavenging, locomotion, cooperative hunting, hunting habitat, hunting method, bone consumption, temporal activity patterns, brain mass and encephalisation quotient.
Spatial Location and Grain
Global.
Time Period and Grain
Late Quaternary (the last ~130,000 years).
Major Taxa and Level of Measurement
All late Quaternary terrestrial mammalian predators (149 species, ≥1 kg body mass, ≥50% vertebrate meat consumption).
Software Format
csv.
Sympatric species reduce competitive interactions by segregating their ecological niche as a strategy that promotes coexistence. The main dimensions in which niche differentiation occurs are spatial, trophic, and temporal axes. Thus, describing the spatiotemporal patterns of sympatric species help us better grasp how species coexist. In Mexico, coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) are sympatric and widely distributed, and information about their temporal and spatiotemporal interactions is still needed to explain their coexistence throughout their distribution. The evaluation of the ecological niche in temperate forests where both species coexist has shown high spatial and trophic overlap. Therefore, more pronounced segregation must occur in other niche dimensions, such as temporal and spatiotemporal axes, to maintain the coexistence between coyotes and gray foxes. As an approach to exploring the coexistence between these species in temperate forests, we pose the following question: Is there temporal or spatiotemporal segregation between sympatric coyotes and gray foxes? We hypothesized that both species maintain coexistence due to differences in their daily activity patterns (temporal segregation) and the presence of avoidance behaviors at the spatiotemporal level (spatiotemporal segregation), thereby reducing agonistic interactions. We aimed to evaluate indicators of niche segregation through two approaches: (i) temporal niche partitioning, measuring the overlap of the daily activity patterns and activity levels; and (ii) spatiotemporal niche partitioning, through temporal co-occurrence analysis and time to encounter analysis. In 2018, we used a camera-trap array (n = 43) to evaluate spatiotemporal interactions of coyotes and gray foxes in temperate forests of northern Mexico. We found that coyotes exhibited a diurnal daily activity pattern, whereas gray foxes were nocturnal, showing low overlap between daily activity patterns. Temporal co-occurrence and time to encounter analysis showed that coyotes and gray foxes occurred independently of each other. Therefore, we demonstrated that the spatiotemporal interactions between both species is a result of random species associations. In conclusion, here we provide evidence that ecological segregation occurred in the temporal niche and not in the spatiotemporal niche of the species. Thus, the temporal niche segregation represents one of the ecological strategies that facilitates the coexistence between coyotes and gray foxes and therefore promotes their sympatry in the temperate forests of northern Mexico.
Context Habitat loss and fragmentation are major threats to global biodiversity, especially for wide-ranging apex carnivores. The Persian leopard (Panthera pardus saxicolor) is an endangered species. Although populations of Persian leopards are declining, the species remains widely distributed across large areas of Iran. Aims This study aimed to determine habitat suitability for Persian leopards in the Khaeiz and Sorkh protected area of south-western Iran and to identify the most significant factors influencing their habitat use/selection and spatial distribution. Methods We performed species distribution modelling in two stages: First, we ran the model with three abiotic predictors: slope; aspect; and distance from water resources. In the second stage, modelling was conducted using three ecological predictors: caracal distribution; wild goat distribution; and livestock distribution. Ensemble modelling was applied based on five replicates of eight SDMs (species distribution models; GLM, CTA, FDA, GBM, ANN, MARS, RF and MaxEnt). Key results We observed only minor differences in habitat suitability between the abiotic and ecological models. Habitat suitability for Persian leopards was higher in steeper areas, close to water resources and near the distribution of caracals, livestock and wild goats. The ecological model predicted 2.03% (329 ha) more suitable habitat than the abiotic model did. Conclusions Most habitat suitability models focus on abiotic variables, but we found that ecological variables offer similar predictive power for determining the habitat suitability of Persian leopards. Implications Habitat suitability models for Persian leopards can be used to guide conservation and management decisions. They are also useful indicating where conflicts between predators and humans may occur.
In ecology, the community structure of an ecosystem is paramount to demonstrating the integrity and interrelationship of the various flora and fauna of the ecosystem. The objectives of this paper are to show the variation of community structures from a micro-ecosystem (log ecosystem) to a macro-ecosystem (mangrove forests and seagrass beds) and determine the biodiversity of these ecosystems. In this paper, class data gathered from the field were quantified to produce a coherent result showing that the ecosystem in a typical Philippine college or university can be used as a field laboratory to study biodiversity and increase the awareness of students and the academic community on understanding the various concepts of ecology. The relative abundance, rank abundance, Simpson and Shannon-Wiener biodiversity indices were measured and quantified for the various ecosystems. Furthermore, the apparent lack of concern for biodiversity is discussed, as is how these fragmented ecosystems are being neglected because of a lack of coherent policy to address these issues and protect the ecosystem landscape.
Aim
Interspecific competition plays a key role in shaping carnivore communities. Top-down effects can impact the coexistence of superordinate and subordinate competitors and prey across a shared landscape. Limited resources, their abundance and diminishing habitats can all exacerbate interspecific competition. Sometimes, behavioural mechanisms or adaptations are critical for subordinate carnivores to coexist with larger species. Here, we investigated the distribution pattern of the striped hyaena (Hyaena hyaena) population with respect to habitat features, sympatric carnivores and their prey species across a large landscape.
Location
Western and Eastern Ghats, India.
Taxon
Striped hyaena.
Methods
We collected presence–absence data for hyaenas, tigers, leopards, dholes and their prey using camera-trapping and indirect sign surveys. Using a random forest algorithm, we modelled the local distribution of hyaenas as a function of important ecological variables, including climate, domestic prey abundance and the predicted probabilities of occurrence of other large carnivores and their prey.
Results
We found that striped hyaenas were confined to relatively small, discrete areas compared to the three other predators, likely a mechanism for achieving coexistence in the landscape. Our empirical results suggested that hyaenas tend to avoid high occurrence probability areas of their co-predators at a landscape level but foothold opportunities such as, arid climatic conditions, and prey abundance primarily determined spatial incumbency. Coexistence in an area with low to medium relative abundance of co-predators offsets the interplay between carcass acquisition and risk associated. The coexistence of species was favoured by altitudinal heterogeneity probably providing denning refugia and also by their preference towards suboptimal thorn forests that sustain a low density of co-predators.
Main Conclusions
Our study showed a desisting impact of large predators on the distribution of the striped hyaena population. Furthermore, we suggest preventing habitat alteration in suboptimal habitats of large carnivores to facilitate coexistence in a shared landscape.
Sympatric species reduce competitive interactions by segregating their ecological niche as a strategy that promotes coexistence. Two main dimensions in which niche differentiation occurs are spatial and temporal axes. Thus, describing the spatiotemporal patterns of sympatric species help us better grasp how species coexist. In Mexico, coyotes ( Canis latrans ) and gray foxes ( Urocyon cinereoargenteus ) are sympatric and widely distributed, and information about their temporal and spatiotemporal interactions is needed to explain their coexistence. As an approach to exploring the coexistence between these species in a temperate forest, we pose the following question: Is there temporal or spatiotemporal segregation between sympatric coyotes and gray foxes? We aimed to evaluate indicators of ecological niche segregation through two approaches: i) temporal partitioning, measuring the levels and overlap of daily activity patterns; and ii) spatiotemporal partitioning, through temporal co-occurrence analysis and time-to-encounter analysis. In 2018, we used a camera trap network (n = 43) to measure spatiotemporal patterns of coyotes and gray foxes. We found that coyotes showed a diurnal daily activity pattern while gray foxes were nocturnal, the overlap was low (49%), and daily activity levels varied significantly as coyotes remained active during slightly higher levels of proportion of the circadian cycle (60%) compared with the gray foxes (37%). We found a temporal co-occurrence random pattern (not aggregation/segregation pattern) between species and no avoidance behavior between coyotes and gray foxes was displayed, according to the time-to-encounter analysis. In general, we did not detect segregation patterns between species at the spatiotemporal level, but we found strong evidence of important temporal activity segregation patterns between coyotes and gray foxes as a mechanism that facilitates sympatry, and which likely complements the ecological strategy of coexistence between these species in temperate forests at the southern of the Sierra Madre Occidental, Mexico.
The reproductive traits of the Talpidae remain unclear. Here, we applied microsatellite DNA markers (12 loci) to a female individual of the lesser Japanese mole (Mogera imaizumii) and its offspring to evaluate paternal elements and the utility of these markers for relatedness accuracy. We also evaluated the identification probability using genotype data of the wild population at three sites in Yamagata Prefecture from a previous study. As a result, of 12 loci, 10 loci were available for the identification of individuals and the detection of paternity. We concluded that the offspring were derived from single paternity. In addition, using a combination of the 10 loci, we could identify all individuals, i.e., the female and its offspring, indicating that these loci would be useful for elucidating the mating system in M. imaizumii.
(Chinese Title: 中国东部灵长类及其他常见兽类的分布变迁：1573~1949——基于地方志与 GIS 技术的量化分析. The final version was submitted to Sun Yat-sen University Library and The Ministry of Education of the People's Republic of China on December 22, 2022.)
Background: Primatology is an important branch of biological anthropology, and it is a cross-disciplinary area with biology, psychology, etc.. Humans are causing the 6th Mass Extinction since several hundred years ago. The long-term co-existence between people and wild animals exerted a long-term and formative influence on the distribution of animals. And mammals, especially primates and other large/medium-sized mammals, had a particularly close relationship with people and were affected severely, thus become important indicators of ecological change. The human population of China, especially in eastern China, increased rapidly from the late Ming Dynasty to the Republic of China (ROC), and the distribution of wild animals including primates was greatly affected. Numerous local gazetteers in Ming dynasty, Qing Dynasty and ROC are well preserved today, and their records of local products are valuable resources for researching the historical biodiversity. However, previous studies only focused on the records of present animal and ignored the records of absent animal, resulting in obvious biases, and there is still a lack of quantitative studies. In order to understand the changes of the distribution of mammals and the influence from the population increasing in China better, I made full use of the records in local gazetteers to reconstruct the distribution of mammals and analyzed the distribution history of large and medium-sized mammals quantitatively.
Methods: I established the Database of Wild Mammal Records in Chinese Local Gazetteers. And innovatively, I fixed the biases in previous researches, i.e. I analyzed the historical changes of biodiversity by using the data of both presence and absence records of mammals. In eastern China from 1573 to 1949 (sorted into 4 periods), I reconstructed the distribution of 14 kinds of mammals which sorted in 5 functional groups with ecological values by using ArcGIS 10.3 software. The mammals are: (1) primates: “yuan” - gibbons & Colobinae(including langur monkeys and snub-nosed monkeys, different to modern taxonomy in Chinese) and “hou” - macaque monkeys; (2)large carnivores: tigers, leopards and bears; (3)medium-sized carnivores: wolves, foxes, “li”(civets, including Felinae and Viverridae, different to modern taxonomy in Chinese), dholes and mustelids; (4)large deer: large deer as a whole (including moose); (5)medium-sized deer: “Zhang-She”(including water deer and musk deer), muntjac deer and roe deer. I used statistical software, e.g. SPSS, Fragstats and SmartPLS, to analyze the changes of distribution(area, altitude, slope gradient and fragmentation index) and the impact from the increase of human population. And analyzed the indexes of functional group richness and species(kinds) richness combined with the relevant events of human population history, to show ecological environmental changes in each provincial-level administrative regions.
Results: (1)In general in all periods, with the increase of human population, the distribution area of primates, large carnivores, large-sized deer and medium-sized deer retracted, the mean altitude and mean slope gradient increase and the distribution changed from distributed widely to be confined in mountainous areas with high altitudes and high slopes, as the “refuge effect”. (2)The distribution of medium-sized carnivores expanded in general, confirming to be a typical ecological decline phenomenon - mesopredator release. The mean altitude and mean slope gradient also increase, but meaning expand from plains to mountains. (3)The ecological environment in the research area deteriorated with the increase of human population, but some areas in some periods recovered temporarily after specific events e.g. wars in Sichuan in late Ming–early Qing, Taipingtianguo rebellion, muslin anti-Qing revolts in Tongzhi reign.
Conclusion: (1)Based on the reconstruction, I provide directive evidences of the human interference on the historical distribution of mammals, and show the specifics. Thus, quantitatively, I prove that the increase of local human population played a significant role in this process. The stereotype “wild large/medium-sized mammal live in hilly areas” is not a natural status but a man-made phenomenon in long term. The results provide a support for further researches. (2)Pioneeringly, I discovered that the environment in eastern China experienced the mesopredator release phenomenon in recent centuries, providing a base for further researches by researchers. (3)And my innovative reorganization of local gazetteers and the application of quantitative methods also provide examples for similar further researches.
Keywords: Primate; Local Gazetteer; Historical Zoogeography; Quantitative History; 6th Mass Extinction
背景：灵长类学是生物人类学的重要分支，也是人类学与生物学、心理学及其他学科的交叉领域。数百年来，人类正逐步造成第六次物种大灭绝。人类与野生动物长期相处，对动物分布格局产生了长期且塑造性的影响，而兽类（即哺乳纲动物）尤其是包括灵长类动物在内的大中型兽类与人类关系密切，受影响亦尤为明显，是生态变化的重要指示性物种。明后期至民国是中国，尤其是中国东部人口急速增长的时期，灵长类等大中型兽类分布受影响明显，且该时期地方志资源丰富，明代、清代及民国时期的地方志大量保存至今，其对各地物产的记载是研究历史上生态多样性的宝贵资源。但已有相关研究只关注动物在当地分布（Presence）的记录，而忽略了动物在当地不分布（Absence）的记录，造成明显偏差，且量化研究尚十分欠缺。为更清楚地了解灵长类等兽类分布变化及其受到中国人口剧增的影响，笔者充分利用地方志中的记载，重拟各类曾广泛分布的灵长类等大中型兽类分布情况并量化分析其分布变迁历史。
方法：笔者建立了中国地方志兽类记录数据库，创新性地修正已有研究的偏差，在新方法中同时使用兽类分布与不分布的数据插值制图重拟其分布的历史变迁。以1573年（万历元年）至1949年间（分四阶段）的中国东部大陆地区为时空范围，笔者使用地理信息系统软件ArcGIS 10.3重拟14类兽类动物的分布，并根据生态意义将这些兽类划分为5个生态功能群，即（1）灵长类功能群：猿类（长臂猿以及含叶猴与金丝猴在内的疣猴，与现代科学分类体系所指猿类不同）、猴类（猕猴属）；（2）大型食肉兽类功能群：虎、豹类、熊类；（3）中型食肉目兽类功能群：狼、狐类、狸类（猫亚科与灵猫科，与现代科学分类体系所指狸类不同）、豺、鼬类；（4）大型鹿类功能群：大型鹿类整体（含麋）；（5）中型鹿类功能群：獐麝类（獐与麝类）、麂类、狍。笔者通过SPSS、Fragstats、SmartPLS等统计软件量化分析分布的面积、海拔、坡度与破碎化程度等变化情况及分析人口剧增对动物分布的影响；并根据功能群数与大中型兽类种类数两种指标对各省区的大中型兽类多样性变化进行梳理，结合人口史资料研究当地生态变迁。
结果：（1）总体上，随着人口剧增，灵长类、大型食肉目兽类、大型鹿类及中型鹿类的分布面积均有不同程度的缩减，分布平均海拔与平均坡度均有所提升，其分布从较广泛分布缩减至主要在高海拔大坡度的山地分布，产生“避难所效应”。（2）而中型食肉目兽类的分布总体上实现了扩张，经证实为中型捕食者释放效应这一典型的生态衰退现象，其分布平均海拔与平均坡度亦有所提升，但主要为从平原地区向山地扩散。（3）量化证实研究区域的大中型兽类多样性总体上随着人口增长而恶化，但明末清初四川战乱、太平天国运动、同治年间回民反清斗争等事件后部分地区的多样性在特定阶段有所恢复。
结论：（1）基于重拟，笔者给出了历史上人类干扰灵长类等大中型兽类分布的直接证据并展示了具体变化过程，量化证实中国东部人口增长在大中型兽类分布缩减过程中起了明显的作用，“大中型兽类主要在山地分布”这一刻板印象并非自然状态，而是人类长期塑造的结果，为学界提供了进一步研究的支持。（2）笔者首次发现了近世中国东部经历了中型捕食者释放效应现象，为学界提供了进一步研究的基础。（3）同时笔者对地方志动物记载的创新性整理及量化处理，也将为将来类似研究提供范例。
关键词：灵长类，地方志，历史动物地理学，量化历史学，第六次大灭绝
The restoration of ecosystems through trophic rewilding has become increasingly common worldwide, but the effects on predator–prey and ecosystem dynamics remain poorly understood. For example, predation pressure may impose spatiotemporal behavioural adjustments in prey individuals, affecting herbivory and predation success, and therefore potentially impinging on the long-term success of trophic rewilding through apex predator reintroduction. Predation risk might have detrimental effects on prey through displacement from water or other vital resources. We investigated how five species of African ungulates responded behaviourally to changes in predation risk, following cheetah releases in the system. We grouped ungulates by body size to represent preferred prey weight ranges of the cheetah and examined changes in visitation rates, duration of stay, and activity patterns at waterholes with and without cheetah presence. During cheetah presence, visitation rates of ungulates were low for medium-sized species but high for large-sized species, suggesting that the species within the cheetah’s preferred prey weight range adjusted behaviourally to minimize waterhole visits. Visits to waterholes were longer for small- and large-sized ungulates with cheetah presence, possibly indicating increased vigilance, or a strategy to maximize water intake per visit while minimizing visits. We did not detect significant differences in circadian or seasonal activity in waterhole visits, which may be attributable to the need of ungulates to access water year-round in our semi-arid study system and where migration was impeded due to physical barriers (fencing). We recommend further research into the long-term behavioural consequences of trophic rewilding on prey populations and trophic cascades to assist the success of recovery programs and to minimize potential detrimental effects at target sites.
The decline and extirpation of large carnivore populations can lead to cascading effects in natural ecosystems. An understanding of large carnivore population densities, distribution and dynamics is therefore critical for developing effective conservation strategies across landscapes. This is particularly important in island environments where species face increased extinction risk due to genetic isolation coupled with local losses of finite habitat. The Sri Lankan leopard Panthera pardus kotiya is one of two remaining island-living leopards on Earth and the only apex predator in Sri Lanka. Despite its iconic status in Sri Lanka, robust research on the species has been limited to only a handful of scientific studies, limiting meaningful scientific recommendations for the species’ conservation and management. In this study, we conducted a single season camera trap survey in Sri Lanka’s largest protected area, Wilpattu National Park (1,317 km²), located in the country’s northwest. Our objective was to estimate key ecological state variables of interest (density, abundance, sex-specific movement and spatial distribution) of this leopard subspecies. Our results indicate that Wilpattu National Park supports a density of 18 individuals/100 km² (posterior SD=1.5; 95% HPD interval=16–21) with a mean abundance of 144 (posterior SD=15) individual leopards and a healthy sex ratio (f:m=2.03:1). The estimated activity range for male leopards >2 years old was 49.53 km² (Posterior SD=3.43; HPD interval=43.09–56.41) and for female leopards >2 years old was 22.04 km² (Posterior SD=1.82; HPD interval=18.34–25.65). This density falls at the higher end of published estimates for the species anywhere in its global range, based on similar methods. Given Sri Lanka’s limited size, this national park system should be considered as a critical stronghold that maintains a source population of leopards, contributing to the long-term population viability of leopards in the larger landscape.
Context: The spatio-temporal partitioning of large carnivores is influenced by interspecific competition and coexistence within small, enclosed reserves. Lions (Panthera leo), spotted hyaenas (Crocuta crocuta) and leopards (Panthera pardus) are the three largest African carnivores and have the greatest potential for intra-guild competition, particularly where space is limited.
Aim: To investigate the spatio-temporal partitioning between lions, spotted hyaenas and leopards in a small (~75 000 ha), enclosed nature reserve, Madikwe Game Reserve (Madikwe), South Africa.
Methods: We deployed 110 camera traps (baited n = 55 and unbaited n = 55) across Madikwe from 26 August 2019 until 6 May 2020. Von Mises kernel density plots were used to investigate daily temporal partitioning among the three species. A multiple-species, single-season occupancy model was used to investigate daily space use patterns.
Key results: We found both temporal and spatial exclusion between lions and spotted hyaenas on Madikwe. However, no evidence was found of spatio-temporal partitioning between lions and leopards, and spotted hyaenas and leopards.
Conclusions: Exploitative and interference competition on Madikwe might be high enough to warrant spatio-temporal partitioning between lions and spotted hyaenas to avoid the negative effects of intra-guild competition. Contrastingly, patterns observed between leopards and both lions and spotted hyaenas preclude the possibility of top-down control by superior carnivores.
Implication: These findings call for an adaptive management approach, where both carnivore and prey species compositions are constantly monitored. Management strategies such as these will allow for the conservation of valuable resources (i.e. prey species) to ensure the persistence of large carnivore populations across African ecosystems.
The global expansion of road networks threatens apex predator conservation and ecosystem functioning. This occurs through wildlife-vehicle collisions, habitat loss and fragmentation, reduced genetic connectivity and increased poaching. We reviewed road impacts on 36 apex predator species and assessed their risk from current roads based on road exposure and species vulnerability. Our findings reveal all apex predators are exposed to road impacts. Eight of the ten species with the highest risk occur in Asia, although other high-risk species are present in the Americas, Africa and Europe. The sloth bear suffers the highest risk of all apex predators, followed by the tiger and dhole. Based on species risk from roads, we propose a widely applicable method to assess the potential impact of future roads on apex predators. We applied this method to proposed road developments in three areas: the Brazilian Amazon, Africa, and Nepal, to locate high-impact road segments. Roughly 500 protected areas will be intersected by these roads, threatening core apex predator habitats. We advocate the need for rigorous road development planning to apply effective mitigation measures as an urgent priority and to avoid construction in wilderness areas and predator strongholds.
Four cases where large predators caused Grey Wolf (Canis lupus) mortality are recorded. We describe two incidents of Cougars (Puma concolar) killing Wolves in Montana and one incident of a Cougar killing a Wolf in Alberta. We report the first recorded incident of a Grizzly Bear (Ursus arctos) killing a Wolf in the western United States
Human‐caused harassment and mortality (e.g. hunting) affects many aspects of wildlife population dynamics and social structure. Little is known, however, about the social and physiological effects of hunting, which might provide valuable insights into the mechanisms by which wildlife respond to human‐caused mortality.
To investigate physiological consequences of hunting, we measured stress and reproductive hormones in hair, which reflect endocrine activity during hair growth. Applying this novel approach, we compared steroid hormone levels in hair of wolves ( Canis lupus ) living in Canada's tundra–taiga ( n = 103) that experience heavy rates of hunting with those in the northern boreal forest ( n = 45) where hunting pressure is substantially lower.
The hair samples revealed that progesterone was higher in tundra–taiga wolves, possibly reflecting increased reproductive effort and social disruption in response to human‐related mortality. Tundra–taiga wolves also had higher testosterone and cortisol levels, which may reflect social instability.
To control for habitat differences, we also measured cortisol in an out‐group of boreal forest wolves ( n = 30) that were killed as part of a control programme. Cortisol was higher in the boreal out‐group than in our study population from the northern boreal forest.
Overall, our findings support the social and physiological consequences of human‐caused mortality. Long‐term implications of altered physiological responses should be considered in management and conservations strategies.
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.
Large terrestrial carnivores, e.g. wolves or bears, often play a key ecological role from their position at the apex of trophic systems. Changes to their populations reverberate through ecological communities; consequently their widespread decline in numbers and shrinking distribution due to human persecution has brought about a loss and reconfiguration of biological diversity in many systems. Although many large carnivore populations are now under conservation-minded management, political and economic constraints make compromises necessary. A common compromise is to permit limited harvests, with the premise of sustainability and the objective to increase tolerance and funding for carnivore recovery and conservation. Here we question whether a large carnivore that has to “look over its shoulder” for human hunters can still fully perform its ecological role at the apex of a trophic system. We use information about carnivore behavior, ecology, trophic interactions, and the effects of human exploitation to argue that exploitation of large carnivores, even if sustainable numerically, undermines the commonly expressed rationale for their conservation, namely the restoration and preservation of ecosystem functionality. Our argument centers around (i) the necessity of behavioral adjustments in large carnivores to anthropomorphic risk, which may limit their contribution to the “landscape of fear”, and (ii) the observation that many of the same features that put large carnivores at the apex of trophic systems also make them vulnerable to human exploitation and persecution, with implicit consequences for their ecological functionality and evolution. Although hunting large carnivores can improve public acceptance, managers must be aware of the trade-offs.
How foragers balance risks during foraging is a central focus of optimal foraging studies. While diverse theoretical and empirical work has revealed how foragers should and do manage food and safety from predators, little attention has been given to the risks posed by dangerous prey. This is a potentially important oversight because risk of injury can give rise to foraging costs similar to those arising from the risk of predation, and with similar consequences. Here, we synthesize the literature on how foragers manage risks associated with dangerous prey and adapt previous theory to make the first steps towards a framework for future studies. Though rarely documented, it appears that in some systems predators are frequently injured while hunting and risk of injury can be an important foraging cost. Fitness costs of foraging injuries, which can be fatal, likely vary widely but have rarely been studied and should be the subject of future research. Like other types of risk-taking behaviour, it appears that there is individual variation in the willingness to take risks, which can be driven by social factors, experience and foraging abilities, or differences in body condition. Because of ongoing modifications to natural communities, including changes in prey availability and relative abundance as well as the introduction of potentially dangerous prey to numerous ecosystems, understanding the prevalence and consequences of hunting dangerous prey should be a priority for behavioural ecologists.
Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity.
Cooperative hunting is believed to have important implications for the evolution of sociality and advanced cogni- tive abilities. Variation in the level of hunt organisation amongst species and how their cognitive, behavioural and athletic adaptations may contribute to observed patterns of cooperative hunting behaviour, however, are poorly under- stood. We, therefore, reviewed the literature for evidence of different levels of hunt organisation and cooperation in carni- vorans and examined their social and physical adaptations for hunting. Descriptions of group hunting were scarce for many species and often of insufficient detail for us to be able to classify the level of hunt organisation involved. However, despite this, reports of behaviour fitting the description of collaboration, the most advanced level of hunt organisation, were found in over half the carnivorans reported to hunt coop- eratively. There was no evidence that this behaviour would require advanced cognitive abilities. However, there was some evidence that both social mechanisms reducing aggression between group members and information transfer amongst individuals may aid cooperative hunting. In general, the coop- erative strategies used seemed to depend partly on the species’ locomotor abilities and habitat. There was some evidence that individuals take on consistent roles during cooperative hunts in some species, but it was not clear if this reflects individuals’ physical differences, social factors or life experiences. Better understanding of the social, cognitive and physical mecha- nisms underlying cooperative hunting, and indeed establishing to what degree it exists in the first instance, will require more data for multiple individuals and species over many hunts.
The dogma that gray wolf (Canis lupus) population densities in naturally occurring systems are limited almost solely by available ungulate biomass is based upon studies that fit straight line linear regressions (Type 1 numerical response) to data collected at 32 sites across North America. We fit Type 1, 2, and 3 response functions to the data using linear and nonlinear regression as appropriate and found that the evidence supported wolf population regulation by density-dependence as much as limitation by prey availability. When we excluded 4 of 32 points from the original data set because those points represented exploited or expanding wolf populations the data suggested that wolf populations are self regulated rather than limited by prey biomass by at least a 3:1 margin. In establishing goals for sustainable wolf population levels, managers of wolf reintroductions and species recovery efforts should account for the possibility that some regulatory mechanism plays an important role in wolf population dynamics. © 2011 The Wildlife Society.
Factors affecting territory size in wolves Canis lupus were studied at 2 scales, the local population (Białowieża Primeval Forest (BPF), eastern Poland) and the geographic range of species (literature review from 14 localities in the Holarctic). Four packs of wolves were studied by radio-tracking in BPF from 1994 to 1999. The annual territories of packs (Minimum convex polygons with 95% of locations) averaged 201 km2 (SD 63, range 116–310). Core areas of territories (50% MCP) covered from 14 to 78 km2 (mean 35). Territory sizes and core areas both were negatively correlated to the encounter rates of ungulates (mean number of ungulates seen per unit time spent in the forest by human observers). Pack size (3–8 wolves) did not influence territory size. Home ranges of individual wolves from the same pack varied with season as well as the age, sex, and reproductive status of the wolf. Review of literature from North America and Europe (42–66oN), showed that latitude and prey biomass were essential factors shaping the biogeographic variation in wolf territory size. Territories increased with latitude and declined with growing biomass of prey. The analysis showed that latitude acted partly independently of the south–north gradient in prey abundance. At similar standing crop of ungulate biomass (100 kg km−2), wolf territories would average 140 km2 at 40oN, 370 km2 at 50oN, and 950 km2 at 60oN. Pack size was larger at northern latitudes, but the increase did not keep pace with enlargement of territories. Within-territory density of wolves declined from 2.5–3 wolves 100 km−2 at 40–45oN to 0.7 wolves 100 km−2 at 60oN. Our analyses documented similarities regarding the role of prey resources in shaping wolf territoriality at the different scales. Furthermore, a macroecological approach revealed additional factors affecting wolf territory size that were not emergent from knowledge of local population.
Empirical associations among co-adapted traits such as body size and patterns of reproduction, development, and behavior are unknown for most animal species, despite numerous theories suggesting otherwise. One way to study these complex relationships is first to consider closely related species and then to generalize findings to other groups. In the present study, relationships among body size, reproductive patterns, development, and sociality were examined in 17 members of the family Canidae (canids). Large canids are more social than smaller species, and offspring of large species achieve independence and tend to breed first at a later age. Large females give birth to absolutely larger young, but relative to their own body weight they allocate fewer resources to bringing a large pup to term. Overall, sexual dimorphism in size is small to moderate, and this is associated with monogamous mating habits and paternal care of young.
Legal and illegal killing of animals near park borders can significantly increase the threat of extirpation for populations living within ecological reserves, especially for wide-ranging large carnivores that regularly travel into unprotected areas. While the consequences of human-caused mortality near protected areas generally focus on numerical responses, little attention has been given to impacts on social dynamics. For wolves, pack structure typically constitutes an unrelated breeding pair, their offspring, and close relatives, but intense harvest may increase adoption of unrelated individuals into packs. Concerns that high human-caused mortality outside Algonquin Park, Canada threatened the persistence of eastern wolves, led to implementation of a harvest ban in surrounding townships. We combined ecological and genetic data to show that reducing anthropogenic causes of mortality can restore the natural social structure of kin-based groups despite the absence of a marked change in density. Since implementation of the harvest ban, human-caused mortality has decreased (P = 0.000006) but been largely offset by natural mortality, such that wolf density has remained relatively constant at approximately three wolves/100 km2. However, the number of wolf packs with unrelated adopted animals has decreased from 80% to 6% (P = 0.00003). Despite the high kinship within packs, incestuous matings were rare. Our results indicate that even in a relatively large protected area, human harvesting outside park boundaries can affect evolutionarily important social patterns within protected areas. This research demonstrates the need for conservation policy to consider effects of harvesting beyond influences on population size.
Top-order predators often have positive effects on biological diversity owing to their key functional roles in regulating trophic cascades and other ecological processes. Their loss has been identified as a major factor contributing to the decline of biodiversity in both aquatic and terrestrial systems. Consequently, restoring and maintaining the ecological function of top predators is a critical global imperative. Here we review studies of the ecological effects of the dingo Canis lupus dingo, Australia's largest land predator, using this as a case study to explore the influence of a top predator on biodiversity at a continental scale. The dingo was introduced to Australia by people at least 3500 years ago and has an ambiguous status owing to its brief history on the continent, its adverse impacts on livestock production and its role as an ecosystem architect. A large body of research now indicates that dingoes regulate ecological cascades, particularly in arid Australia, and that the removal of dingoes results in an increase in the abundances and impacts of herbivores and invasive mesopredators, most notably the red fox Vulpes vulpes. The loss of dingoes has been linked to widespread losses of small and medium-sized native mammals, the depletion of plant biomass due to the effects of irrupting herbivore populations and increased predation rates by red foxes. We outline a suite of conceptual models to describe the effects of dingoes on vertebrate populations across different Australian environments. Finally, we discuss key issues that require consideration or warrant research before the ecological effects of dingoes can be incorporated formally into biodiversity conservation programs.
Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these
animals may be humankind’s most pervasive influence on nature. Although such losses are widely viewed as an ethical and aesthetic
problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater
ecosystems worldwide. This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but
also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire,
carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary
research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.
The process of nutrient transfer through an ecosystem is an important determinant of production, food-chain length, and species diversity. The general view is that the rate and efficiency of nutrient transfer up the food chain is constrained by herbivore-specific capacity to secure N-rich compounds for survival and production. Using feeding trials with artificial food, we show, however, that physiological stress-response of grasshopper herbivores to spider predation risk alters the nature of the nutrient constraint. Grasshoppers facing predation risk had higher metabolic rates than control grasshoppers. Elevated metabolism accordingly increased requirements for dietary digestible carbohydrate-C to fuel-heightened energy demands. Moreover, digestible carbohydrate-C comprises a small fraction of total plant tissue-C content, so nutrient transfer between plants and herbivores accordingly becomes more constrained by digestible plant C than by total plant C:N. This shift in herbivore diet to meet the altered nutrient requirement increased herbivore body C:N content, the C:N content of the plant community from which grasshoppers select their diet, and grasshopper fecal C:N content. Chronic predation risk thus alters the quality of animal and plant tissue that eventually enters the detrital pool to become decomposed. Our results demonstrate that herbivore physiology causes C:N requirements and nutrient intake to become flexible, thereby providing a mechanism to explain context dependence in the nature of trophic control over nutrient transfer in ecosystems.
Plant-ants live in a mutualistic association with host plants known as "myrmecophytes" that provide them with a nesting place and sometimes with extra-floral nectar (EFN) and/or food bodies (FBs); the ants can also attend sap-sucking Hemiptera for their honeydew. In return, plant-ants, like most other arboreal ants, protect their host plants from defoliators. To satisfy their nitrogen requirements, however, some have optimized their ability to capture prey in the restricted environment represented by the crowns of trees by using elaborate hunting techniques. In this study, we investigated the predatory behavior of the ant Azteca andreae which is associated with the myrmecophyte Cecropia obtusa. We noted that up to 8350 ant workers per tree hide side-by-side beneath the leaf margins of their host plant with their mandibles open, waiting for insects to alight. The latter are immediately seized by their extremities, and then spread-eagled; nestmates are recruited to help stretch, carve up and transport prey. This group ambush hunting technique is particularly effective when the underside of the leaves is downy, as is the case for C. obtusa. In this case, the hook-shaped claws of the A. andreae workers and the velvet-like structure of the underside of the leaves combine to act like natural Velcro that is reinforced by the group ambush strategy of the workers, allowing them to capture prey of up to 13,350 times the mean weight of a single worker.
For many purposes it is often desirable to estimate animal population densities over large areas. Where total counts are not possible and sightings are relatively rare, a range of methods exists to estimate densities from indirect sign. Such methods are frequently unreliable and usually require independent calibration or confirmation. We present an analytical method for estimating population density from track counts. The method, widely known in the Russian Federation but not in the English language scientific literature, requires counts of tracks of known age, together with estimates of animal daily travel distances. We use simulations to verify the theoretical basis of the approach and to indicate potential precision that may be achieved. We illustrate application of the approach using a large data set on ungulate track counts in the Russian Far East. We suggest that under most circumstances, nonparametric bootstrapping will be the most appropriate method for deriving estimates of confidence intervals about density estimates. As with other approaches to estimating density from indirect sign, the method that we discuss is vulnerable to violations of an array of underlying assumptions. However, it is easily applied and could represent an important method by which the relationship between indices of abundance and absolute density can be understood.
Black bears (Ursus americanus) or grizzly bears (Ursus arctos) visited 8 of 55 cougar-killed (Felis concolor) ungulates in Glacier National Park (GNP), Montana, from 1992 to 1995, and 19 of 58 cougar kills in Yellowstone National Park (YNP), Wyoming, from 1990 to 1995. Bears displaced cougars from 4 of 8 carcasses they visited in GNP and 7 of 19 in YNP. Cougar predation provided an average of 1.9 kg/day (range = 0-6.8 kg/day) of biomass to bears that fed on cougar-killed ungulates. This biomass was an important percent (up to 113%) of the daily energy needs of bears when compared to their caloric requirements reported in the literature. We suggest that ungulate carrion resulting from cougar predation is important nutritionally to bears in some regions and seasons. Cougars that were displaced from their kills by bears lost an average of 0.64 kg/day of ungulate biomass, or 17-26% of their daily energy requirements. Biologists modelling or measuring cougar predation rates should be aware that losses to scavengers may be significant.
Principal component analysis has often been dealt with in textbooks as a special case of factor analysis, and this tendency has been continued by many computer packages which treat PCA as one option in a program for factor analysis—see Appendix A2. This view is misguided since PCA and factor analysis, as usually defined, are really quite distinct techniques. The confusion may have arisen, in part, because of Hotelling’s (1933) original paper, in which principal components were introduced in the context of providing a small number of ‘more fundamental’ variables which determine the values of the p original variables. This is very much in the spirit of the factor model introduced in Section 7.1, although Girschick (1936) indicates that there were soon criticisms of Hotelling’s method of PCs, as being inappropriate for factor analysis. Further confusion results from the fact that practitioners of ‘factor analysis’ do not always have the same definition of the technique (see Jackson, 1981). The definition adopted in this chapter is, however, fairly standard.
We demonstrate the use of piecewise regression as a statistical technique to
model ecological thresholds. Recommended procedures for analysis are illustrated with a
case study examining the width of edge effects in two understory plant communities. Piecewise
regression models are ‘‘broken-stick’’ models, where two or more lines are joined at
unknown points, called ‘‘breakpoints.’’ Breakpoints can be used as estimates of thresholds
and are used here to determine the width of edge effects. We compare a sharp-transition
model with three models incorporating smooth transitions: the hyperbolic-tangent, benthyperbola,
and bent-cable models. We also calculate three types of confidence intervals for
the breakpoint estimate: an interval based on the computed standard error of the estimate
from the fitting procedure, an empirical bootstrap confidence interval, and a confidence
interval derived from an inverted F test.We recommend use of the inverted F test confidence
interval when sample sizes are large, and cautious use of bootstrapped confidence intervals
when sample sizes are smaller. Our analysis demonstrates the need for a careful study of
the likelihood surface when fitting and interpreting the results from piecewise-regression
models.
Background/Question/Methods
The process of energy and materials transfer governs ecosystem production, food chain length and species diversity. Herbivores are pivotal in this process because their low plant assimilation efficiencies constrain transfer rates and ecosystem carbon: nitrogen balance. Theory suggests that physiological stress due to predation risk could be an important determinant of trophic transfer efficiency and ecosystem nutrient budget. We tested this assertion in a series of field and laboratory experiments. We reared grasshopper herbivore nymphs with or without risk of spider predation and measured their metabolic rate, nutritional requirements, and excretion and body elemental composition. We also calculated how the risk of spider predation affects elemental composition of uneaten plant material entering the soil organic matter pool.
Results/Conclusions
We show that shifting nutrient demand of herbivores facing predation risk causes carbohydrate carbon to become an important nutrient to fuel stress-heightened respiration. This had cascading effects on C:N balance of herbivore body tissue, fecal material and uneaten plant material. Fear from predation risk thus represents an endogenous mechanism regulating materials transfer via chronic exacerbation of herbivore physiological stress and shift in what becomes a limiting nutrient.
Suppose that the distribution of a random variable representing the outcome of an experiment depends on two parameters xi and theta and that one wishes to test the hypothesis xi = 0 against the alternative xi > 0. If the distribution does not depend on theta when xi = 0, standard asymptotic methods such as likelihood ratio testing or C(α) testing are not directly applicable. However, these methods may, under appropriate conditions, be used to reduce the problem to one involving inference from a Gaussian process. This simplified problem is examined and a test which may be derived as a likelihood ratio test or from the union-intersection principle is introduced. Approximate expressions for the significance level and power are obtained.
Understanding the population dynamics of top‐predators is essential to assess their impact on ecosystems and to guide their management. Key to this understanding is identifying the mechanisms regulating vital rates.
Determining the influence of density on survival is necessary to understand the extent to which human‐caused mortality is compensatory or additive. In wolves ( Canis lupus ), empirical evidence for density‐dependent survival is lacking. Dispersal is considered the principal way in which wolves adjust their numbers to prey supply or compensate for human exploitation. However, studies to date have primarily focused on exploited wolf populations, in which density‐dependent mechanisms are likely weak due to artificially low wolf densities.
Using 13 years of data on 280 collared wolves in Yellowstone National Park, we assessed the effect of wolf density, prey abundance and population structure, as well as winter severity, on age‐specific survival in two areas (prey‐rich vs. prey‐poor) of the national park. We further analysed cause‐specific mortality and explored the factors driving intraspecific aggression in the prey‐rich northern area of the park.
Overall, survival rates decreased during the study. In northern Yellowstone, density dependence regulated adult survival through an increase in intraspecific aggression, independent of prey availability. In the interior of the park, adult survival was less variable and density‐independent, despite reduced prey availability. There was no effect of prey population structure in northern Yellowstone, or of winter severity in either area. Survival was similar among yearlings and adults, but lower for adults older than 6 years.
Our results indicate that density‐dependent intraspecific aggression is a major driver of adult wolf survival in northern Yellowstone, suggesting intrinsic density‐dependent mechanisms have the potential to regulate wolf populations at high ungulate densities. When low prey availability or high removal rates maintain wolves at lower densities, limited inter‐pack interactions may prevent density‐dependent survival, consistent with our findings in the interior of the park.