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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.
... 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.
... age at first conception, birth interval and gestation time [24]). Also in terrestrial mammals, there is a functional transition associated with a number of life-history traits between carnivores exceeding an average mass of 13-16 kg and those carnivores of smaller size [72]. In other, less-studied cases, the key question is, of course, to define the subset of functional traits to be explored. ...
... A feasible variant of the functional megafauna concept would be 'apex megafauna': animals so large that they have escaped most non-anthropogenic predation as adults. This concept is related to the megaherbivore and apex predator concepts [24,25,72] and can be applied to humans too. In Africa, herbivores larger than 150 kg are subject to reduced predation rates than smaller mammalian prey in some areas [73], but only for herbivores exceeding 1000 kg predation is a consistently negligible cause of adult mortality [24,73,74]. ...
... In Africa, herbivores larger than 150 kg are subject to reduced predation rates than smaller mammalian prey in some areas [73], but only for herbivores exceeding 1000 kg predation is a consistently negligible cause of adult mortality [24,73,74]. Within the order Carnivora, an average mass of ca 15 kg corresponds to the transition between extrinsic-and self-regulation [72]. ...
Concern for megafauna is increasing among scientists and non-scientists. Many studies have emphasized that megafauna play prominent ecological roles and provide important ecosystem services to humanity. But, what precisely are ‘megafauna’? Here, we critically assess the concept of megafauna and propose a goal-oriented framework for megafaunal research. First, we review definitions of megafauna and analyse associated terminology in the scientific literature. Second, we conduct a survey among ecologists and palaeontologists to assess the species traits used to identify and define megafauna. Our review indicates that definitions are highly dependent on the study ecosystem and research question, and primarily rely on ad hoc size-related criteria. Our survey suggests that body size is crucial, but not necessarily sufficient, for addressing the different applications of the term megafauna. Thus, after discussing the pros and cons of existing definitions, we propose an additional approach by defining two function-oriented megafaunal concepts: ‘keystone megafauna’ and ‘functional megafauna’, with its variant ‘apex megafauna’. Assessing megafauna from a functional perspective could challenge the perception that there may not be a unifying definition of megafauna that can be applied to all eco-evolutionary narratives. In addition, using functional definitions of megafauna could be especially conducive to cross-disciplinary understanding and cooperation, improvement of conservation policy and practice, and strengthening of public perception. As megafaunal research advances, we encourage scientists to unambiguously define how they use the term ‘megafauna’ and to present the logic underpinning their definition.
... 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.
... self-regulating processes (Wallach et al., 2015). Populations of apex predators across ecosystems have been under substantial declines, pushing several to the verge of functional extinction or pass it (Pauly et al., 1998;Ripple et al., 2014). ...
... As we overfish authorized stocks, we extend our diet portfolio and move farther offshore, searching for new, yet unfished taxa (Pauly, 2020). The increased technological development has facilitated us to easily shift our ecological niche, quickly find prey, effectively avoid predators and, arguably, obviate top-down, bottom-up and density-dependent control (Darimont et al., 2015;Wallach et al., 2015). These features distinguish us from apex predators and revolve us into sort of an»Anthropo-predator«, as our impact on the ecosystems has notably amplified during Anthropocene, the epoch of human-induced changes (Moll et al., 2021;Waters et al., 2016). ...
Fisheries exploitation can cause genetic changes in heritable traits of targeted stocks. The direction of selective pressure forced by harvest acts typically in reverse to natural selection and selects for explicit life‐histories, usually for younger and smaller spawners with deprived spawning potential. While the consequences that such selection might have on the populational dynamics of a single species are well emphasised, we are just beginning to perceive the variety and severity of its propagating effects within the entire marine food webs and ecosystems. Here, we highlight the potential pathways in which fishing‐induced evolution, driven by size‐selective fishing, might resonate through globally connected systems. We look at: i) how a size‐truncation may induce shifts in ecological niches of harvested species, ii) how a changed maturation schedule might affect the spawning potential and biomass flow, iii) how changes in life‐histories can initiate trophic cascades, iv) how the role of apex predators may be shifting, and v) whether fishing‐induced evolution could co‐drive species to depletion and biodiversity loss. Globally increasing effective fishing effort and the uncertain reversibility of eco‐evolutionary change induced by fishing necessitate further research, discussion, and precautionary action considering the impacts of fishing‐induced evolution within marine food webs.
... 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.
... 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. Density‐dependence, resource availability and human pressure at territorial level drive population dynamics in a recovering apex‐predator population.
... 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. ...
... focuses on ecological values, as indicated by the presence of "Environmental Science Ecology", "Zoology" and "Biodiversity Conservation" in the top three list of the WOS research areas (Fig. 3). Several studies link conservation of biodiversity and mesopredator release (Courchamp et al., 1999;Nimmo et al., 2015;Ritchie and Johnson, 2009), focusing on the ecological roles of apex predators in the stabilization of ecosystems (Wysong et al., 2020), food webs (Ripple et al., 2014;Scoleri et al., 2020), and prey species (Wallach et al., 2015;Wysong et al., 2020). ...
Human activities severely impact the distribution and behaviour of apex predators in numerous terrestrial and aquatic ecosystems, with cascading effects on several species. Mesopredator outbreaks attributable to the removal of an apex predator have often been recorded and described in the literature as “mesopredator release”. During recent decades several examples of the phenomenon have been observed and studied in many different parts of the world. In this paper, we quantitatively reviewed the existing literature on mesopredator release using two software packages (VOSviewer and CiteSpace) to investigate patterns and trends in author keywords through occurrences and temporal analyses, and creating relative network maps. The results showed that even though the general scientific interest in mesopredator release has increased in recent decades, the vast majority of studies focus on canid species, leaving many other species or entire taxa (e.g., reptiles) understudied and under-described. The connection between invasive species and mesopredator release has only recently been more extensively explored and also the effects of apex predators declining in aquatic ecosystems are still only partially investigated. Due to the increasing effect of biological invasions, overfishing, and either the decline or the rise of apex predators in different parts of the world, we expect an even higher increase in interest and number of published documents on the subject. We also encourage widening the research focus beyond canids to include other important taxa.
... They find that the cyclic dynamics described by the Lotka-Volterra model emerge. Further, Wallach et al. (2015) propose that apex predators self-regulate their own population to make sure that there is no over-exploitation, i.e. keep their own population at a certain level, which limits the pressure on the prey population. ...
... Asterisks denote significance (P < 0.05). (Wallach et al. 2015b); interspecific cooperative hunting between carnivores (coyotes and badgers -Taxidea taxus) (Minta et al. 1992); and that human persecution alters the development of personalities in juvenile hyenas (C. crocuta) (Greenberg and Holekamp 2017). ...
Apex predators structure ecosystems by hunting mesopredators and herbivores. These trophic cascades are driven not only by the number of animals they kill, but also by how prey alter their behaviors to reduce risk. The different levels of risk navigated by prey has been likened to a “landscape of fear.” In Australia, dingoes are known to suppress red fox populations, driving a trophic cascade. However, most of what we know of this relationship comes from circumstances where predators are persecuted, which can affect their social and trophic interactions. Utilizing camera traps, we monitored fox behavior when accessing key resource points used by territorial dingoes, in a region where both predators are protected. We predicted that foxes would avoid and be more cautious in areas of high dingo activity. Indeed, foxes avoided directly encountering dingoes. However, contrary to our expectations, foxes were not more cautious or vigilant where dingo activity was high. In fact, fox activity and scent-marking rates increased where dingo scent-marking was concentrated. Further, foxes were increasingly confident with increasing levels of conspecific activity. Our results suggest that responses to the threat of predation are more complex than fear alone. In socially stable conditions, it is possible that prey may develop knowledge of their predators, facilitating avoidance, and reducing fear.
... Several species are apex predators that maintain trophic structures. Furthermore, many raptor species are associated with specific cultures, regions or nations through their use in symbols and emblems [17,30,35,38,39]. We examined case studies to demonstrate how cultural beliefs affect the perspectives of conservation stakeholders in the light of available knowledge to better appreciate or condemn raptors and thereby determine conservation outcomes. ...
The Millennium Ecosystem Assessment proposed four categories of ecosystem services as regulating, provisioning, supporting and cultural. Of these, cultural services have been the most difficult to quantify despite playing a key role in developing society’s supporting services to ecosystems. By reviewing a series of case studies related to the cultural services derived from raptors, we examine relations between tangible ecosystem services and ‘knowledge’ and ‘beliefs’ as part of supporting services from human societies to ecosystems. We identified types of raptor regulating and provisioning services and patterns in service--knowledge-beliefs that defined positive or negative outcomes for raptor conservation. We also demonstrate how possible interactions between physical, experiential, physical-symbolic and representative-symbolic cultural services and between different stakeholders can create incentives or obstacles for conservation. Predictable patterns in service-knowledge-beliefs provide a framework upon which socio-cultural and ethnobiological aspects of raptor conservation may be combined with ecological research to support conservation initiatives. Based on these patterns we present examples of how cultural services might be employed to better promote raptor conservation while respecting the beliefs and traditions of stakeholders.
... They are generally large-sized, long-living animals that are commonly characterized by late sexual maturity and their populations are relatively stable (Sergio et al. 2008). They play a key role as ecosystem regulators by inhibiting the population irruptions of prey and other smaller predators (Wallach et al. 2015). Today, it is known that top predators also promote species richness and they are spatiotemporally associated with it for a couple of reasons, such as their dependence on ecosystem productivity and sensitivity to dysfunctions (Sergio et al. 2008). ...
Marine top predators, such as sharks, teleosts and cetaceans, are great indicators of a healthy ecosystem. The primary goal of this paper is to fill the knowledge gaps on top predators in Gökçeada Island located in the North Aegean Sea. Data on marine top predators were collected through Local Ecological Knowledge. Besides, visual and acoustic field surveys were carried out in the summer and autumn of 2019 and winter of 2020. According to the results of the current study, a total of 464 individuals were reported via social media platforms and questionnaires applied to stakeholders as fishermen, divers and harpooners. Delphinus delphis Linnaeus, 1758, Tursiops truncatus (Montagu, 1821) and Physeter macrocephalus Linnaeus, 1758 were detected during approximately 15 hours of acoustic recording. The records of Carcharodon carcharias (Linnaeus,
... Wild dogs historically occurred across much of sub-Saharan Africa [26,27] evolving as an integral component of ecosystems over the past 3.9 million years [28]. Ecologically unique, wild dogs are classified as large carnivores [2,29], are the only true coursing predator in sub-Saharan Africa [30], are critically important to healthy ecosystems, and fulfill important topdown roles in regulating prey populations [31]. Despite this, wild dog populations have undergone sustained declines over the past half-century driven largely by rapid and severe habitat loss and fragmentation [27,32], direct persecution by ranchers and pastoralists [27,33], and as bycatch in a pervasive, illegal bushmeat trade [34]. ...
Large carnivores have experienced widespread extirpation and species are now threatened globally. The ecological impact of the loss of large carnivores has been prominent in Goron-gosa National Park, Mozambique, after most were extirpated during the 1977-92 civil war. To remedy this, reintroductions are now being implemented in Gorongosa, initiating with endangered African wild dogs (Lycaon pictus), hereafter 'wild dogs'. We describe the first transboundary translocation and reintroduction of founding packs of wild dogs to Gorongosa over a 28-month study period and evaluate the success of the reintroduction based on five key indicator categories. We also assess how wild dog space use and diet influenced their success. We found that pre-release, artificial pack formation in holding enclosures aided group cohesion and alpha pair establishment. Post-release, we also observed natural pack formations as a result of multiple dispersal events. Founder and naturally formed packs produced pups in two of the three breeding seasons and packs successfully recruited pups. Survival rate for all wild dogs was 73% and all mortality events were from natural causes. Consequently, the population grew significantly over the study period. All indicators of success were fully achieved and this study documents the first successful reintroduction of wild dogs into a large, unfenced landscape in Mozambique and only the second on the continent. Potential mechanisms underlying these early successes were the avoidance of habitats intensively used by lions, dietary partitioning with lion, avoidance of human settlements, and Gorongosa's management strategy. We predict further population expansion in Gorongosa given that 68% of the park is still unused by wild dogs. This expansion could be stimulated by continued reintroductions over the short-to medium-term. Recovery of wild dogs in Gor-ongosa could aid in the re-establishment of a larger, connected population across the greater Gorongosa-Marromeu landscape.
... Furthermore, we also received a high number of reports of dogs persecuting native meso-predators (foxes and Geoffroy's cats), and also an apex predator (puma, Puma concolor). It is likely that the domestic dog is playing both roles, as meso-predator and also as apex-predator harassing the top predators and destabilizing the subtle trophic balance (Wallach et al., 2015). It is also worrying that a wide range of taxonomic groups with different ecological roles are affected. ...
Exotic predators constitute an increasingly important conservation threat worldwide. Domestic dogs are considered one of the most commonly-introduced predators, and one of the causes of decline in wildlife on a global scale. Nevertheless, few studies report specific cases of interaction between dogs and the affected species; rather, the possible effect of dogs is inferred, or some cases of interaction are mentioned in studies whose focus is on a different topic. In Argentina, a large, biodiverse country with 18 ecoregions providing habitat for numerous threatened species, scientific research addressing dog-wildlife interaction is lacking. We performed a study at a national level, using an online survey to obtain concrete records of dog attacks on wildlife, focusing mainly on natural areas, as they host several vulnerable species. We categorized the species records according to conservation status and assessed the data obtained by ecoregion. Of the total number of respondents (N = 1006), 68.4% had witnessed a dog chasing or preying on wildlife at least once. At least 80 recognized species had been chased or preyed on by dogs, 6.5% of these species being categorized as Endangered or Vulnerable in national and global Red Lists. Most persecution events corresponded to birds (48%) and mammals (47%). Dog persecution of wildlife was reported throughout every Argentine ecoregion, highlighting the widespread prevalence of this problem. This information will help in the development of initial dog management plans and define priority areas for action, as well as raise social concern regarding this threat, and promote responsible pet ownership.
... We excluded pinnipeds based on our taxonomic selection criteria because they are highly adapted to life at sea, but retained the sea otter because of its taxonomic link to other semi-terrestrial otters (Estes and Bodkin, 2002). In a review of the life-history traits of 121 terrestrial and semi-terrestrial species from twelve carnivore families, Wallach et al. (2015) suggest that an apex carnivore is one that is able to self-regulate its population density, and found that an average mass of 13-16 kg marked the threshold between extrinsically-regulated and self-regulated carnivores. This weight criterion is similar to the threshold identified in previous global reviews that differentiated large from small carnivores for subsequent analysis (Prugh et al., 2009;Ritchie and Johnson, 2009;Ripple et al., 2014;Prugh and Sivy, 2020). ...
Small mammalian carnivores (Carnivora <16 kg) carry out important roles in ecosystems, such as influencing ecosystem structure and providing numerous ecosystem services. Despite their importance, there are contrasting views on the required conservation and management needs for species within this group. In a review of the IUCN Red List species-level assessments, we found that 53 small carnivore species were threatened (CR, EN, or VU) compared to 15 large. However, there were similar proportions of large (4%, 9%) and small (1%, 9%) carnivores endangered with extinction (CR or EN, respectively). We did not find support for small carnivores benefiting from mesopredator release in a global context; more than half of both large and small carnivore species decreasing, suggesting parallel declines. On average, large carnivores received their first IUCN assessment 10 years before small and, since their first assessment, small carnivores have received fewer assessments than large, highlighting the disparity in conservation attention within the guild. The leading threats for all carnivores include biological resource use and land use change. We review the major threats to threatened small carnivores and suggest areas for priority research and conservation. Collectively, we show that small carnivores are as endangered with extinction as are large carnivores, and that small carnivores should be of conservation concern globally, but particularly in species-rich regions of Southeast Asia, sub-Saharan Africa, and Madagascar. To inform conservation, we encourage more research into the basic ecology and demography of small carnivores, particularly regarding current and future threats in the face of global change.
... In recent time habitat destruction, resource depletion, hunting and human-animal conflict have resulted in massive declines of the world's large herbivores (Ceballos et al., 2017;Lindsey et al., 2017;Ripple et al., 2015) such that about 60% of them are threatened with extinction Trouwborst, 2019). The effects of such anthropogenic factors towards their extinction are further exacerbated by their relatively low population densities, unique habitat requirements and slow life history characteristics (Ripple et al., 2016;Wallach et al., 2015). While significant global conservation efforts helped in population recovery of some of the charismatic large herbivores (African rhinoceros-Emsile and Brooks, 1999; Asian elephant, gaur and sambar -Madhusudan, 2004;black rhinoceros-Brodie et al., 2011; Asian elephant and one-horned rhinoceros- Williams, 2011; elk, European bison and red deer- Sylven et al., 2012), it has mostly been targeted within protected areas, that represents only~13% of the total land surface area (Chape et al., 2005;UNEP-WCMC, 2012). ...
Recent declines in large herbivores have led to significant conservation efforts globally. However, the niche-specific megaherbivores residing outside protected areas face more imminent extinction threats. Swamp deer, the obligate grassland-dwelling endemic cervid is the most extinction-prone megaherbivore in the Indian subcontinent. Limited information on distribution and habitat status pose significant conservation and management challenges for the remaining fragmented populations in north, north-east and central India. To this end, we combined exhaustive field surveys and Maximum Entropy (MaxEnt) modeling to generate the most detailed distribution map for the northern swamp deer subspecies. We used primary data from more than 6000 km² field surveys and eight ecologically relevant covariates for model predictions. Grassland cover, annual mean temperature and distance from water were the major factors that predicted the species distribution. Models predicted swamp deer distribution in only ~3% of the entire landscape, covering both protected (~1.4%) as well as non-protected (~1.6%) areas. Our validation surveys in some of these predicted areas confirmed swamp deer presence and indicated ~85% model accuracy. Finally, we identified four ‘‘Priority Conservation Areas’’ still retaining adequate grassland habitat and species presence that require immediate attention to ensure landscape-level population connectivity. These results highlight the importance of the marginalized grassland ecosystems of northern India that still retain high biodiversity. We suggest a swamp deer-centric conservation approach to protect these human-dominated habitats and emphasize in generating such information for other endemic, habitat-specialist species across the globe.
... To close this section we briefly mention an independent way of model extension when the so-called apex predator is introduced into the traditional cyclically dominant loop [86]. From the ecological viewpoint the presence of such predator influences the stability of an ecosystem greatly and the related model study revealed that it 68001-p3 spreads uniformly in space, and contributes to destroy the traditional spiral patterns [87]. ...
Lotka's seminal work (Lotka A. J., Proc. Natl. Acad. Sci. U.S.A., 6 (1920) 410) “on certain rhythmic relations” is already one hundred years old, but the research activity about pattern formations due to cyclical dominance is more vibrant than ever. It is because non-transitive interactions have a paramount role on maintaining biodiversity and adequate human intervention into ecological systems requires a deeper understanding of the related dynamical processes. In this Perspective we overview different aspects of biodiversity, with focus on how it can be maintained based on mathematical modeling of the last years. We also briefly discuss the potential links to evolutionary game models of social systems, and finally, give an overview about potential prospects for future research.
... On the one hand, the significant increase in puma population observed during our study suggests a population recovery similar to that described in other Patagonian regions where livestock activity and predator persecution has ceased [35]. In the absence of human persecution, large carnivores self-regulate their populations through social mechanisms and density dependence [83]. Accordingly, a significant increase in abundance would not be expected in a medium-high-density puma population, in which case most of the territories would be occupied [84,85]. ...
Protected areas recently created in Argentina often include previously degraded lands, such as sheep ranches in the Patagonian deserts. We show the results of a 14-year monitoring program of three formerly persecuted carnivores, the culpeo fox (Lycalopex culpaeus), the South American grey fox (Lycalopex griseus) and the puma (Puma concolor), in two abandoned sheep ranches that were incorporated into a Patagonian national park approximately 25 years ago. The culpeo fox population underwent an average annual decline of 10–23%, whereas the grey fox and puma populations increased at an average annual rate of 7% and 19%, respectively. The grey fox’s increasing trends were strongly correlated with the decline of the culpeo fox, whereas the correlations between the fox and puma trends were weaker. Culpeo fox decline was stronger in the ranch where sheep and predator controls had been removed earlier. These relationships between species trends support the competitive release hypothesis, assuming that puma competition with the culpeo fox for trophic resources is stronger than competition with the grey fox, and that the puma can exclude culpeo foxes through interference. Species trends suggest a competitive hierarchy between fox species, with grey fox being the inferior competitor. However, mechanisms other than competition could not be discounted. Our study illustrates how long-term monitoring of interacting species allows a better understanding of ecological processes and wildlife ecology.
... In recent time, habitat destruction, resource depletion, hunting and human-animal conflict have resulted in massive declines of the world's large herbivores (Ceballos et al., 2017;Lindsey et al., 2017; such that about 60% of them are threatened with extinction Trouwborst, 2019). The effects of such anthropogenic factors towards their extinction are further exacerbated by their relatively low population densities, unique habitat requirements and slow life history characteristics (Ripple et al., 2016;Wallach et al., 2015). While significant global conservation efforts helped in population recovery of some of the charismatic large herbivores (African rhinoceros-Emsile and Brooks, 1999; Asian elephant, gaur and sambar -Madhusudan, 2004;black rhinoceros-Brodie et al., 2011; Asian elephant and one-horned rhinoceros- Williams, 2011; elk, European bison and red deer- Sylven et al., 2012), it has mostly been targeted within protected areas, that represents only ~13% of the total land surface area (Chape et al., 2005;UNEP-WCMC, 2012). ...
Recent declines in large herbivores have led to significant conservation efforts globally. However, the niche-specific megaherbivores residing outside protected areas face more imminent extinction threats. Swamp deer, the obligate grassland-dwelling endemic cervid is the most extinction-prone megaherbivore in the Indian subcontinent. Limited information on distribution and habitat status pose significant conservation and management challenges for the remaining fragmented populations in north, north-east and central India. To this end, we combined exhaustive field surveys and Maximum Entropy (MaxEnt) modeling to generate the most detailed distribution map for the northern swamp deer subspecies. We used primary data from more than 6000 km2 field surveys and eight ecologically relevant covariates for model predictions. Grassland cover, annual mean temperature and distance from water were the major factors that predicted the species distribution. Models predicted swamp deer distribution in only ~3% of the entire landscape, covering both protected (~1.4%) as well as non-protected (~1.6%) areas. Our validation surveys in some of these predicted areas confirmed swamp deer presence and indicated ~85% model accuracy. Finally, we identified four ‘Priority Conservation Area’ still retaining adequate grassland habitat and species presence that require immediate attention to ensure population connectivity across this landscape. These results highlight the importance of the marginalized grassland ecosystems of northern India that still retains high biodiversity. We suggest a swamp deer-centric conservation approach to protect these human-dominated habitats and emphasize in generating such information for other endemic, habitat-specialist species across the globe.
... Target species consisted of all mesocarnivore species (n = 7, Table 1) defined as carnivore species with mean body mass between one and 15 kg, whose populations are regulated extrinsically (Prugh et al. 2009, Wallach et al. 2015. We also included the Iberian lynx, an apex predator in Iberian ecosystems, because of its relatively small body mass, potential prey sharing, and reported competitive interactions with several Iberian mesocarnivores (Palomares and Caro 1999, Monterroso et al. 2016a). ...
Competition is a widespread interaction among carnivores, ultimately manifested through one or more dimensions of the species' ecological niche. One of the most explicit manifestations of competitive interactions regards spatial displacement. Its interpretation under a theoretical context provides an important tool to deepen our understanding of biological systems and communities, but also for wildlife management and conservation. We used Bayesian multi-species occupancy models on camera trapping data from multiple sites in Southwestern Europe (SWE) to investigate competitive interactions within a carnivore guild, and to evaluate how species' ecological traits are shaping coexistence patterns. Seventeen out of 26 pairwise interactions departed from a hypothesis of independent occurrence, with spatial association being twice as frequent as avoidance. Association behaviours were only detected among mesocarnivores, while avoidance mainly involved mesocarnivores avoiding the apex predator (n=4) and mesocarnivore-only interactions (n=2). Body mass ratios, defined as the dominant over the subordinate species body mass, revealed an important negative effect (
β
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=
-
0.38
[
CI
95
=
-
0.81
,
-
0.06
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) on co-occurrence probability, and support that spatially-explicit competitive interactions are mostly expressed by larger species able to dominate over smaller ones, with a threshold in body mass ratios of ca. 4, above which local-scale intraguild coexistence is unlikely. We found a weak relationship between pairwise trophic niche overlap and the probability of coexistence (
β
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=
-
0.19
[
CI
95
=
-
0.58
,
0.21
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), suggesting that competition for feeding resources may not be a key driver of competition, at least at the scale of our analysis. Despite local-scale avoidance, regional-scale coexistence appears to be maintained by the spatial structuring of the competitive environment. We provide evidence that SWE ecosystems consist of spatially-structured competitive environments, and propose that coexistence among near-sized species is likely achieved through the interplay of "facultative" and "behavioral" character displacements. Factors influencing carnivore coexistence likely include context-dependent density and trait mediated-effects, which should be carefully considered for a sound understanding of the mechanisms regulating these communities.
... Globally, a broad range of values have been applied to sharks. These include; apex predators [1] with a critical role in maintaining healthy marine ecosystems; fisheries target species; tourism drawcards; important indigenous cultural symbols; and species implicated in fatal attacks on humans ( Table 1). The status of 'shark' stocks is highly varied, ranging from collapsed to sustainable. ...
Sharks are high-profile taxa and often polarise communities and stakeholders. However, constructive debate around shark issues has been stymied by the many stakeholders with conflicting or unclear objectives: Government Agencies with multiple objectives (sustainable management, conservation, public safety); fishers (commercial and recreational) that target certain species of sharks, or try to avoid interactions; tourism operators; indigenous peoples with cultural links; conservation groups; other ocean-users and members of the general public who may be shark-conservationists or shark-cull advocates. The confusion appears partly due to various stakeholder groups using the collective noun ‘sharks’ when discussing issues. The use of ‘sharks’ confuses debates in a way similar to other totemic taxa (e.g. whales) where unique attributes of multiple species have been combined. In the case of ‘sharks’ the situation is exacerbated by the large number of species (globally >500), the diversity of values attributed to species and the ability of stakeholders to have multiple values (e.g. fishers who regard sharks as desirable target species and as depredators of target species). We argue that ‘sharks’ extend the super-species concept, reducing clarity and hindering the development of more broadly acceptable policies. To improve this discourse we suggest that stakeholders define ‘sharks’ in discussions and reports with species-by-area descriptors (e.g. white-sharks in Western Australia); or as a minimum, on a defined group-by-area basis (e.g. sharks that support eco-tourism in South Africa; commercially important species of sharks in southern Australia), so the species in focus is (are) clearly defined, allowing future debates to be more constructive and support the development of more widely-acceptable policies.
... A significant ecological role of large-bodied carnivores in general is implied by their being grouped as apex predators (Ordiz, Bischof & Swenson, 2013;Wallach et al., 2015). They consume many prey over a lifetime, thereby influencing populations of other animals, and are rarely eaten themselves after reaching adult size (Sergio et al., 2014). ...
Large‐bodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosystems are poorly understood, constraining the design and implementation of optimal conservation strategies for freshwater ecosystems. Conservationists and environmentalists frequently promulgate ecological roles that crocodylians are assumed to fulfil, but often with limited evidence supporting those claims.
Here, we review the available information on the ecological importance of crocodylians, a widely distributed group of predominantly freshwater‐dwelling, large‐bodied predators. We synthesise information regarding the role of crocodylians under five criteria within the context of modern ecological concepts: as indicators of ecological health, as ecosystem engineers, apex predators, keystone species, and as contributors to nutrient and energy translocation across ecosystems. Some crocodylians play a role as indicators of ecosystem health, but this is largely untested across the order Crocodylia. By contrast, the role of crocodylian activities in ecosystem engineering is largely anecdotal, and information supporting their assumed role as apex predators is currently limited to only a few species. Whether crocodylians contribute significantly to nutrient and energy translocation through cross‐ecosystem movements is unknown.
We conclude that most claims regarding the importance of crocodylians as apex predators, keystone species, ecosystem engineers, and as contributors to nutrient and energy translocation across ecosystems are mostly unsubstantiated speculation, drawn from anecdotal observations made during research carried out primarily for other purposes. There is a paucity of biological research targeted directly at: understanding population dynamics; trophic interactions within their ecological communities; and quantifying the short‐ and long‐term ecological impacts of crocodylian population declines, extirpations, and recoveries. Conservation practices ideally need evidence‐based planning, decision making and justification. Addressing the knowledge gaps identified here will be important for achieving effective conservation of crocodylians.
... This may alter their abundance, ecological roles, and importance in the corresponding food webs, and sometimes destabilize communities, drive local extinctions, and reduce overall biodiversity (e.g. Trewby et al., 2008;Prugh et al., 2009;Colman et al., 2014;Wallach et al., 2015a;Alston et al., ...
Small carnivores – here defined as members of the mammalian Order Carnivora with a body mass < 21.5 kg – occur worldwide, including in Oceania, following introductions. They are represented by 210 to 282 species, which corresponds to around 90% of terrestrial carnivores globally. Some species are endemic to one or two countries (sometimes only islands), while others, like the red fox, Vulpes vulpes, are present in nearly 90 countries over five continents. Small carnivores inhabit virtually all of the Earth’s ecosystems, adopting terrestrial, semi-fossorial, (semi-)arboreal or (semi-)aquatic lifestyles. They occupy multiple trophic levels, being primary consumers when feeding on fruits, seeds, and other plant matter, secondary consumers when preying on frugivorous, granivorous, and herbivorous animals, or tertiary consumers when killing and devouring meat-eating animals. Therefore, they play important roles in the regulation of ecosystems, e.g. natural pest control, seed dispersal and nutrient cycling. In areas where humans have extirpated large carnivores, small carnivores may become the dominant predators, which may increase their abundance (‘mesopredator release’) to the point that they can sometimes destabilize communities, drive local extirpations, and reduce overall biodiversity. On the other hand, one-third of the world’s small carnivores are Threatened or Near Threatened with extinction (sensu IUCN). This results from regionally burgeoning human populations’ industrial and agricultural activities, causing habitat reduction, destruction, fragmentation, and pollution. Overexploitation, persecution, and the impacts of introduced predators, competitors, and pathogens have also negatively affected many small carnivore species. Although small carnivores have been intensively studied over the past decades, bibliometric studies showed that they have not received the same attention given to large carnivores. Furthermore, there is a huge disparity in how research efforts on small carnivores have been distributed, with some species intensively studied, and others superficially or not at all. Regionally, North American and European small carnivores have been the focus of numerous studies, and more research is being progressively conducted in Asia. However, there is a need to increase the research effort in Africa and Central and South America. Encouragingly, the recognition of the importance of the mesopredator release effect and the exponential deployment of camera-traps have started to boost the research effort and scientific knowledge on small carnivores around the world. This book aims at filling a gap in the scientific literature by elucidating the important roles of, and documenting the latest knowledge on, the world’s small carnivores. It is divided into four main sections: (i) Evolution, Systematics, and Distribution; (ii) Ecology, Behaviour, and Diseases; (iii) Interspecific Interactions and Community Ecology; and (iv) Interactions with People and Conservation. We hope that the book will appeal to a wide audience and, considering that the field of small carnivore science remains wide open, stimulate much-needed research globally.
... Populations of highly mobile carnivores with large resource requirements are often the first to be extirpated due to habitat loss and fragmentation (Crooks 2002;Ordeñana et al. 2010;Lowry et al. 2013). In contrast, generalist mesocarnivores (defined as predators with body mass < 34 kg and an average of 13-16 kg, Roemer et al. 2009;Wallach et al. 2015) may find more abundant smaller prey (Moss et al. 2016;Smith et al. 2016) and thus thrive at the urban edge (Prugh et al. 2009;Bateman and Fleming 2012). Consequently, these smaller predators may be more vulnerable to the spill-over of pathogens and the bioaccumulation of pesticides (Bradley and Altizer 2007;Riley et al. 2007;, making them valuable sentinels of ecosystem health (Jooste et al. 2013). ...
Urbanisation radically changes habitats and alters available resources. Populations of large, highly mobile species are often extirpated at the urban-wildland interface, while species like mesocarnivores may thrive by capitalising on changes in prey abundance. We investigated the diet of the caracal (Caracal caracal), a medium-sized felid inhabiting patchy natural habitat isolated within the dense urban matrix of South Africa’s second largest city, Cape Town. We systematically integrated two classic dietary methods (scat and GPS clusters) by accounting for gut transit times. As part of a larger caracal ecology study, we GPS-collared 26 individuals over a two-year period (2014–2016) to generate coarse (3-hour) and fine-scale (20-minute) GPS movement data. Using the movement data, we investigated 677 GPS-clusters for prey remains. We collected 654 scats, half of which were found at GPS-clusters and were linked with the individual sampled. By systematically correcting for a range of gut transit times, we determined whether scat at cluster sites was from the same or an earlier feeding event, thereby increasing the overall detection of feeding events by > 50%. Avian prey dominated GPS cluster findings while micromammals were overwhelmingly represented in scat. Although > 40% of feeding events occurred within 200 meters of the urban edge, caracals largely preyed on native species. Our findings have implications for understanding the ability of some species to persist in the face of rapid environmental change, human-wildlife conflict, pathogen transmission, and bioaccumulation of pesticides. Further, this approach could be incorporated into studies that estimate foraging-explicit resource selection and habitat preference.
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.
(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 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.
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.
Per-and poly-fluorinated alkyl substances (PFAS) are a group of chemicals used in a wide variety of commercial products and industrial applications. These chemicals are persistent, can accumulate in humans' and animals' tissues and in the environment, representing an increasing concern due to their moderate to highly toxicity. Their global distribution, persistence and toxicity led to an urgent need to investigate bioaccumulation also in marine species. In 2013 PFAS contamination was detected in a vast area in Veneto region, mainly in Adige and Brenta rivers. In order to investigate any relevant presence of these substances in marine vertebrates constantly living in the area, PFAS were measured in hepatic tissue samples of 20 bottlenose dolphins (Tursiops truncatus) stranded along the northern Adriatic Sea coastline between 2008 and 2020. Using high performance liquid chromatography-mass spectrometry, 17 target PFAS (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnA, PFDoA, PFTrDA, PFTeDA, PFBS, PFHxS, PFOS, PFDS, PFHpS, PFPeS), were quantified in the samples. PFAS profiles were generally composed of the same five dominant PFAS (PFOS > PFUnA > PFDA ≈ PFDoA ≈ PFTrDA). The greatest PFOS concentration found was 629,73 ng/g wet weight, and PFOS accounted until 71% in the PFAS profiles. No significant differences between sexes were found, while calves showing higher mean values than adults, possibly indicating an increasing ability in the elimination of PFAS with age. Finally, a temporal analysis was carried out considering three different periods of time, but no temporal differences in concentrations were found. The results suggest that long-chain PFAS are widespread in bottlenose dolphins along the North Adriatic Sea. Furthermore, they represent a baseline to investigate the impact of PFAS on marine mammals' conservation and health. Filling an important gap in the knowledge of PFAS accumulation in bottlenose dolphins, this study highlights the relevant role of Environmental and Tissue Banks for retrospective analyses on emergent contaminants.
Global change is severely affecting ecosystem functioning and biodiversity globally. Remotely sensed ecosystem functional attributes (EFAs) are integrative descriptors of the environmental change —being closely related to the processes directly affecting food chains via trophic cascades. Here we tested if EFAs can explain the species fitness at upper trophic levels. We took advantage of a long-term time series database of the reproductive success of the Golden Eagle (Aquila chrysaetos) – an apex predator at the upper trophic level – over a 17-year period across a bioclimatic gradient (NW Spain; c. 29,575 km²). We computed a comprehensive database of EFAs from three MODIS satellite-products related to the carbon cycle, heat dynamics and radiative balance. We also assessed possible time-lag in the response of the Golden Eagle to fire, a critical disruptor of the surface energy budget in our region. We explored the role of EFAs on the fitness of the Golden Eagle with logistic-exposure nest survival models. Our models showed that the reproductive performance of the Golden Eagle is influenced by spatiotemporal variations in land surface temperature, albedo and vegetation productivity (AUC values from 0.71 to 0.8; ΣWi EFAs from 0.66 to 1). Fire disturbance also affected ecological fitness of this apex predator—with a limited effect at 3 years after fire (a time-lagged response to surface energy budget disruptions; ΣWi Fire= 0.62). Our study provides evidence for the influence of the matter and energy fluxes between land surface and atmosphere on the reproductive success of species at upper trophic levels.
Background & Aim: Carnivores play an important role in maintaining the structural and functional stability of ecosystems. Increasing anthropogenic pressure has resulted in dramatic population decline and habitat degradation of carnivores worldwide. Exploring regional coexistence mechanisms of carnivore populations is important to understand how mammal communities assemble, along with protecting and managing endangered species. This review summarizes the interactions of terrestrial carnivores along three dimensions (i.e., spatial, temporal and dietary), of their ecological niches, analyzing the influence of factors such as body size, prey composition, environmental difference, human disturbance and climate change on the coexistence of carnivores based on more than 100 related studies. Review Results: We put forward the problems to be addressed for current study of carnivore coexistence. This study demonstrates that there is no single theoretical explanation for carnivore coexistence through niche separation. Prey,
Mammals embody the apex of ecosystems processes, and their majestic diversity is overwhelmingly threatened in the Neotropical realm. Mammal population declines erode not only several levels of biological diversity, but may also impoverish critical ecosystem services (ES). Based on 2,427 putative baseline mammal assemblages derived from IUCN ranges polygons, we sought to understand, for the first time, the effects of mammal defaunation on natural ecosystem services throughout the entire Neotropical realm. At the assemblage-level, we simulated both stochastic and deterministic regimes of mammal defaunation, examining both diversity indices and classic metrics of ecological networks (e.g. modularity and nestedness). Our results show that ES losses are induced by declines in both taxonomic and functional diversity. Given any defaunation regime, Neotropical provinces undergo levels of ES erosion typically reaching less than a third of all potential network links. Geographic patterns of lost ecosystem services—resulting from simulated and real-world mammal extinctions—indicate that this will detrimentally affect human livelihoods across all major Neotropical provinces. We conclude that the ongoing defaunation process will promote irreversible failures of several mammal-mediated ecosystem processes at varying timescales.
We thank the SANR managers and Associação Caatinga for logistical support during fieldwork. Abstract The feeding behaviour of the puma (Puma concolor) is a fundamental characteristic that guarantees its evolutionary success. It is one of the primary factors associated with its widespread distribution, including hostile regions like the Brazilian Caatinga, a semi-arid biome. We investigate the feeding ecology of the puma in a protected area located in the Caatinga by describing its diet and evaluating patterns of prey selection mediated by energetic trade-off and meeting probability. We found ten prey species consumed by pumas, with the collared peccary (Pecari tajacu) representing almost half of consumed prey items. Prey selection by puma was correlated with an overlap of activity patterns between predator and prey, suggesting that meeting probability is an important topic in its foraging ecology. Due to the predominance of a single prey species, the puma showed a narrow niche breadth (standardised Levins' index = 0.113), positing the collared peccary as a critical element in the persistence of puma in the area. The puma is commonly described as a generalist predator since it feeds on a broad range of species across its distribution area; however, our results and recent literature suggest a more specialised diet at a local scale. This apparent contradiction could indicate that the puma diet is subject to a hierarchical organisation on a spatial scale, in which different local specialisations and adaptive strategies would lead to a generalist feeding behaviour at the distributional scale. It is important to highlight that we did not find any evidence of livestock depredation, which is a significant result from a conservation perspective, which favours puma conservation in the study area.
This study verifies the food assimilation of a carnivorous teleost in different timescales (weeks vs months) and evaluates how it uses the food sources. The target species is the adult ribbonfish, Trichiurus lepturus , a voracious teleost caught in commercial fisheries off south-east Brazil (21°S–22°S). The isotope models indicated Chirocentrodon bleekerianus as the main food in the ribbonfish diet in the last weeks (liver: 38.5%; 95% credible intervals: 3.4–73.9%) and last months (muscle: 36.2%; 95% credible intervals: 3.4–68.7%). The contribution of other food sources ranges from 10–16% (liver) and from 10–20% (muscle). Food assimilation remains similar at different timescales. The isotope models suggested a strong and long-lasting association of the adult females of ribbonfish with coastal waters along the study area.
The following study tested the viability of managing wolf populations via the presence of managed "wolf restaurants". Wolf restaurants in this context refers to supplementary feeding of wolves in close proximity to their den or areas where wolves frequent within their territory. An individual based model was built using the Netlogo software. The model was used to computationally test this theory as it has not yet been attempted in the field. This form of management was tested in two simulated wilderness areas; a large area (3000km 2 ) and a smaller area (312km 2 ). This study found that in a large wilderness area with a stable wolf population and medium densities of wild prey, nutrition management was effective in reducing dispersion by 33% and livestock depredation by 55%. The model was then tested for a smaller wilderness area. It was discovered that when prey density was high and wolf restaurants were present, livestock depredation was reduced by 450% and movement ecology was reduced by as much as 300% compared to unmanaged wolves in the same environment. The results of this model suggest that wolf nutrition management is possible to mitigate instances of wolf-human conflicts in large wild communities, but that smaller ecological islands of wilderness with high prey density is where it has the potential to work best. The smaller simulated wilderness area emulates that which wolves are moving into throughout Europe. Wolf nutrition management can be used as a tool to enhance the success of future wolf reintroductions and re-establishments.
The following study tested the viability of managing wolf populations via the presence of managed "wolf restaurants". Wolf restaurants in this context refers to supplementary feeding of wolves in close proximity to their den or areas where wolves frequent within their territory. An individual based model was built using the Netlogo software. The model was used to computationally test this theory as it has not yet been attempted in the field. This form of management was tested in two simulated wilderness areas; a large area (3000km 2 ) and a smaller area (312km 2 ). This study found that in a large wilderness area with a stable wolf population and medium densities of wild prey, nutrition management was effective in reducing dispersion by 33% and livestock depredation by 55%. The model was then tested for a smaller wilderness area. It was discovered that when prey density was high and wolf restaurants were present, livestock depredation was reduced by 450% and movement ecology was reduced by as much as 300% compared to unmanaged wolves in the same environment. The results of this model suggest that wolf nutrition management is possible to mitigate instances of wolf-human conflicts in large wild communities, but that smaller ecological islands of wilderness with high prey density is where it has the potential to work best. The smaller simulated wilderness area emulates that which wolves are moving into throughout Europe. Wolf nutrition management can be used as a tool to enhance the success of future wolf reintroductions and re-establishments.
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.
Large mammalian carnivores are ecologically important because relatively few individuals can cause strong predation-driven direct effects or fear-driven indirect effects that can ripple through communities and, ultimately, influence ecosystem structure and function. Most mammalian carnivores are not large, however, but are small to midsized species collectively termed “mesocarnivores.” Mesocarnivores are more numerous and more diverse than larger carnivores, and often reside in closer proximity to humans, yet we know little about how they influence communities and ecosystems. In this article we review the ecological role of the mesocarnivore and present examples where mesocarnivores drive community structure and function in roles similar to, or altogether different from, their larger brethren. Together, these examples substantiate the need for an assessment of the ecological role of mammalian carnivores beyond an examination of only the largest species. In particular, we emphasize the need to study the trophic penetrance of mesocarnivores and examine how ecological context modulates their functional role.
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.