ABSTRACT
Interactions among species, which range from competition to facilitation, have profound effects on ecosystem functioning. Large carnivores are of particular importance in shaping community ...structure since they are at the top of the food chain, and many efforts are made to conserve such keystone species. Despite this, the mechanisms of carnivore interactions are far from understood, yet they are key to enabling or hindering their coexistence and hence are highly relevant for their conservation. The goal of this review is thus to provide detailed information on the extents of competition and facilitation between large carnivores and their impact in shaping their life histories. Here, we use the example of spotted hyaenas (Crocuta crocuta) and lions (Panthera leo) and provide a comprehensive knowledge of their interactions based on meta‐analyses from available literature (148 publications). Despite their strong potential for both exploitation and interference competition (range and diet overlap, intraguild predation and kleptoparasitism), we underline some mechanisms facilitating their coexistence (different prey‐age selection and scavenging opportunities). We stress the fact that prey abundance is key to their coexistence and that hyaenas forming very large groups in rich ecosystems could have a negative impact on lions. We show that the coexistence of spotted hyaenas and lions is a complex balance between competition and facilitation, and that prey availability within the ecosystem determines which predator is dominant. However, there are still many gaps in our knowledge such as the spatio‐temporal dynamics of their interactions. As both species' survival becomes increasingly dependent on protected areas, where their densities can be high, it is critical to understand their interactions to inform both reintroduction programs and protected area management.
Foraging animals must contend with fluctuating environmental variables that affect foraging success, including conditions like wind noise, which could diminish the usefulness of particular sensory ...modes. Although the documented impact of anthropogenic noise on animal behavior has become clear, there is limited research on natural noise and its potential influence on mammalian behavior. We investigated foraging behavior in the myrmecophagous bat-eared fox (
Otocyon megalotis
), a species known to rely predominantly on hearing for prey detection. For a year, we monitored the foraging behavior of 18 bat-eared foxes from a habituated population in South Africa, amidst varying wind speeds (0–15.5 km/h). In contrast to expectations, foraging rates did not generally decline with increasing wind speed, except for foraging rate outside termite patches in fall. Furthermore, wind speed had little correlation with time spent in patches. In winter, however, we observed an increase in foraging rate with increasing wind speed both within and outside patches. At the observed wind speeds, these acoustically driven insectivores continue to forage effectively despite potentially distracting or masking noises. With anthropogenic noise producing sound across a broader frequency range, it is important to examine the responses of these canids to artificial sources of acoustic disturbance as well.
Estimating the size and dynamics of populations is of paramount importance in ecology. In species with uniquely marked individuals, capture–recapture methods can be used to establish population size ...and to explore associations between individuals. However, very few studies have used cameras traps to focus on group composition in social carnivores, despite being of particular interest in species characterised by “fission–fusion” formation of sub‐groups. Here, we provide estimates of (a) population size, (b) density, (c) clan size, (d) association patterns and (e) social network structure in spotted hyaenas (Crocuta crocuta) based on images from camera traps deployed at waterholes on Ongava Game Reserve (northern Namibia). In a 15 week study period, we identified 32 individuals. Dyadic associations and the resulting social network showed that all but two hyaenas associated directly or indirectly with each other, indicating the presence of one clan of at least 30 individuals, resulting in a density of 8.1 hyaenas/100 km2. We found a very high variability in the tendency of individuals to associate with others. This study confirms a highly dynamic fission–fusion society in spotted hyaenas. We argue that camera traps can provide relevant insights into large carnivore social network structure where associations between individuals are difficult to observe directly.
Résumé
L'estimation de la taille et de la dynamique des populations est d'une importance primordiale en écologie. Chez les espèces avec des individus marqués de façon unique, les méthodes de capture‐recapture peuvent être utilisées pour établir la taille de la population et explorer les associations entre individus. Cependant, très peu d'études ont utilisé des pièges à caméras pour se concentrer sur la composition du groupe chez les carnivores sociaux, en dépit d'un intérêt particulier pour les espèces caractérisées par la formation de « fission‐fusion » de sous‐groupes. Nous fournissons ici des estimations de 1) la taille de la population, 2) de la densité, 3) de la taille du clan, 4) des modes d'associations et 5) de la structure du réseau social chez les hyènes tachetées (Crocuta crocuta) à partir d'images de pièges à caméras déployés au point d'eau dans la Réserve animalière d'Ongava (au nord de la Namibie). Au cours d'une période d'étude de 15 semaines, nous avons identifié 32 individus. Les associations dyadiques et le réseau social qui en a résulté ont montré que tous les hyènes sauf deux s'associaient directement ou indirectement l'un à l'autre, indiquant la présence d'un clan d'au moins 30 individus, ce qui a donné une densité de 8,1 hyènes / 100 km2. Nous avons constaté une très grande variabilité dans la tendance des individus à s'associer aux autres. Cette étude confirme l'existence d'une société hautement dynamique de fission‐fusion chez les hyènes tachetées. Nous soutenons que les pièges à caméras peuvent fournir des informations pertinentes sur la structure du réseau social des grands carnivores où les associations entre individus sont difficiles à observer directement.
Roads impact wildlife through a range of mechanisms from habitat loss and decreased landscape connectivity to direct mortality through wildlife-vehicle collisions (roadkill). These collisions have ...been rated amongst the highest modern risks to wildlife. With the development of “citizen science” projects, in which members of the public participate in data collection, it is now possible to monitor the impacts of roads over scales far beyond the limit of traditional studies. However, the reliability of data provided by citizen scientists for roadkill studies remains largely untested. This study used a dataset of 2,666 roadkill reports on national and regional roads in South Africa (total length ~170,000 km) over 3 years. We first compared roadkill data collected from trained road patrols operating on a major highway with data submitted by citizen scientists on the same road section (431 km). We found that despite minor differences, the broad spatial and taxonomic patterns were similar between trained reporters and untrained citizen scientists. We then compared data provided by two groups of citizen scientists across South Africa: (1) those working in the zoology/conservation sector (that we have termed “regular observers,” whose reports were considered to be more accurate due to their knowledge and experience), and (2) occasional observers, whose reports required verification by an expert. Again, there were few differences between the type of roadkill report provided by regular and occasional reporters; both types identified the same area (or cluster) where roadkill was reported most frequently. However, occasional observers tended to report charismatic and easily identifiable species more often than road patrols or regular observers. We conclude that citizen scientists can provide reliable data for roadkill studies when it comes to identifying general patterns and high-risk areas. Thus, citizen science has the potential to be a valuable tool for identifying potential roadkill hotspots and at-risk species across large spatial and temporal scales that are otherwise impractical and expensive when using standard data collection methodologies. This tool allows researchers to extract data and focus their efforts on potential areas and species of concern, with the ultimate goal of implementing effective roadkill-reduction measures.
The erection of peripheral fences around protected areas has been shown to adversely affect the movement behavior, genetic connectivity and long-term viability of animal populations. However, fencing ...is also used extensively to reduce human encroachment, limit poaching activities, and mitigate human–wildlife conflicts. Limited information on the movement behavior of carnivores is available along the periphery of protected areas, particularly in semi-arid environments. To quantify the potential effects of the 824 km perimeter fence surrounding the Etosha National Park (Etosha, Namibia) on the movement and space use of carnivores, we collected GPS movement data from 36 lions (
Panthera leo
) and seven spotted hyenas (
Crocuta crocuta
) over a 14-year period. For these two apex carnivores, we measured the impact of the Etosha fence on their movements (step lengths and path straightness), calculated the likelihood of fence crossings, and evaluated the spatial–temporal characteristics of these crossings. Our results indicated that lions and hyenas moved faster (longer step lengths) when closer to the fence. Lions showed no variation in path straightness with respect to the fence but hyenas had straighter movement paths when closer to the fence. When moving within the vicinity of the fence, lions had a 9% likelihood of crossing the fence, while hyenas were much more likely (18%) to do so, which suggests that the Etosha fence was more permeable for hyenas than for lions. Fence crossings predominantly occurred at night for both species. Lions were more likely to cross the fence during the cold dry season (May–August) whereas hyenas crossed more often during the warm wet season (December–April). Female and adult lions had a higher probability of crossing the fence than males and subadults. These findings could be useful in the development of appropriate strategies to mitigate human–carnivore conflicts and thus promote the conservation of carnivores in multiple-use areas along the periphery of the park. Further research is needed to better elucidate the impact of perimeter fences on a broader suite of carnivores and other large mammals, including species-specific variation in the response to fences, as well as the economic benefits of fencing provided to local communities.
In Africa's pastoral conservation landscapes, apex predators frequently kill livestock. Retaliatory persecution such as poisoning threatens predators, but also non-target biota. Several factors ...influence conflict severity, including livestock husbandry, overlap in seasonal habitat use, and the degree to which livestock perceive and are able to respond to a landscape of fear. We investigated these factors by GPS-tracking 42 Tswana beef cattle (Bos taurus) from 29 herds in 2017 and six lions (Panthera leo) from different prides (May 2016–Dec. 2017) in the northern Okavango Delta, Botswana, where cattle depredation significantly impacts the livelihoods of rural agro-pastoralists. Cattle exhibited seasonal habitat selection patterns similar to wild ungulates in the region. They preferred woodland habitats, with more digestible grasses, during the wet season. During the dry season, they preferred wetland habitats with reliable forage and water availability. Cattle also preferred areas close to human settlements, but the necessity to forage in wetlands during the dry season exposed them to significant depredation risk, especially >4 km from settlements. Lions killed most cattle in wetlands during the late dry season but the intensity of recent lion presence (previous 14 days) only had a weak negative effect on cattle habitat selection patterns. Cattle used rangelands according to nutritional requirements, irrelevant of the associated predation risk, suggesting that socio-ecologically acceptable conflict solutions cannot rely on the exclusion of livestock from seasonal wetlands. Curbing depredation by lions will best be achieved by a combination of resource- and predation-cognisant seasonal herding strategies with adequate livestock protection. Understanding the ecological constraints that intensify conflict is pertinent to any livestock production landscape with predator presence. It is also a central prerequisite for future land use planning and devolution of legal, controlled resource access rights through policy. Coexistence strategies must account for the strong reliance of people, their livestock, and wildlife on shared key resources. This is particularly important in large trans-frontier conservation areas where the successful merging of biodiversity conservation and rural development is a strategic goal. Omission will foster resentment and resistance to coexistence with apex predators, particularly if livestock productivity and human livelihoods are negatively affected.
Barrier effect is a road‐related impact affecting several animal populations. It can be caused by behavioural responses towards roads (surface and/or gap avoidance), associated emissions ...(traffic‐emissions avoidance) and/or circulating vehicles (vehicle avoidance). Most studies so far have described road‐effect zones along major roads, without determining the actual factor inducing the behavioural response. The purpose of the present study was to assess the factors potentially causing road‐effect zones in a heterogeneous road network (with variations in road width, road surface and traffic volume) and eventually to estimate the reduction of habitat quality imposed by roads within a protected area (Doñana Biosphere Reserve, Spain). As model species, we used two ungulates, red deer Cervus elaphus and wild boar Sus scrofa. We surveyed the presence of both species along 200‐m transects. All transects started and were perpendicular to reference roads (those with a traffic volume above 10 cars per day), often intersecting unpaved minor roads with virtually no traffic. The presence probability of both species was mainly affected by the distance to the nearest road (in most cases unpaved roads without traffic), but also by the proximity to reference roads. Red deer presence was also affected by the traffic volume of the nearest reference road. At a regional scale, the overall road network within the protected area imposes a reduction in presence probability of 40% for red deer and 55% for wild boar. A road network optimization, decommissioning unused and unpaved roads, would re‐establish almost entirely the potential habitat quality (91% for both species). Synthesis and applications. We found that both study species avoided roads regardless of their surface or traffic volume, suggesting a response due to gap avoidance which may be based on the association between linear infrastructures and the possibility of vehicles occurring along them. The overall behavioural response can substantially decrease habitat quality over large scales, including the conservation value of protected areas. For this reason, we recommend road network optimization by road decommissioning to mitigate the impact of roads at a regional scale, with potential positive effects at ecosystem level.
Apex predators directly and indirectly influence prey and predators at lower trophic positions (mesopredators). The lethal effect of apex predators on mesopredators is well documented, but they also ...could affect mesopredators in non-lethal ways. We investigated foraging decisions and perceived risk in the bat-eared fox (Otocyon megalotis), a small canid that is often killed by larger terrestrial carnivores and birds of prey. We used giving-up-density (GUD) experiments and observations of vigilance behavior to assess the influence of temporal, spatial, and anthropogenic factors on perceived risk in a population of bat-eared foxes at the Kuruman River Reserve, Northern Cape, South Africa. GUDs were higher during periods around the new moon and lower in the presence of researchers, suggesting that foxes are warier in darker conditions, but perceive an increase in relative safety in the presence of humans. Vigilance, however, did not vary with these same factors. Observational data revealed foraging success outside the experimental context did not differ with lunar period, implying that higher GUDs associated with new moons were not due to higher missed opportunity costs associated with foraging at patches. These results suggest that GUDs may be capable of detecting more subtle differences in perceived risk when compared to vigilance rates. We highlight the important considerations of using GUDs to examine perceived risk for a predatory species and emphasize that future studies using GUDs should quantify predators’ risk-related decisions by documenting missed opportunity costs to determine the implications behind patch-use behavior.
De Araujo et al. (Methods in Ecology and Evolution, 2021, https://doi.org/10.1111/2041‐210X.13516) described the development and application of a wire foot snare trap for the capture of jaguars ...Panthera onca and cougars Puma concolor. Snares are a commonly used and effective means of studying large carnivores. However, the article presented insufficient information to replicate the work and inadequate consideration and description of animal welfare considerations, thereby risking the perpetuation of poor standards of reporting.
Appropriate animal welfare assessments are essential in studies that collect data from animals, especially those that use invasive techniques, and are key in assisting researchers to choose the most appropriate capture method. It is critical that authors detail all possible associated harms and benefits to support thorough review, including equipment composition, intervention processes, general body assessments, injuries (i.e. cause, type, severity) and post‐release behaviour. We offer a detailed discussion of these shortcomings.
We also discuss broader but highly relevant issues, including the capture of non‐target animals and the omission of key methodological details. The level of detail provided by authors should allow the method to be properly assessed and replicated, including those that improve trap selectivity and minimize or eliminate the capture of non‐target animals.
Finally, we discuss the central role that journals must play in ensuring that published research conforms to ethical, animal welfare and reporting standards. Scientific studies are subject to ever‐increasing scrutiny by peers and the public, making it more important than ever that standards are upheld and reviewed.
We conclude that the proposal of a new or refined method must be supported by substantial contextual discussion, a robust rationale and analyses and comprehensive documentation.
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