Spatial partitioning by a subordinate carnivore is mediated by conspecific overlap

There are several hypotheses that could explain territory size in mammals, including the resource dispersion hypothesis (RDH), the intruder pressure hypothesis (IPH), and the intraguild predation hypothesis (IGPH). In this study, we tested predictions of these three hypotheses regarding territories of 19 packs of endangered African wild dogs (Lycaon pictus) over 2 years in the Kruger National Park, South Africa. If territory size was supported by the RDH, then we would observe (1) wild dog territories would be larger when resource patches were more dispersed, (2) pack sizes would be larger when resource patches were rich, and (3) pack size would not affect territory size. If supported by the IPH, then we would observe (4) larger territories would experience less intrusions, and (5) there would be an increase in territory overlap in areas of low resource dispersion. Finally, if supported by the IGPH, we would observe (6) territories would be larger in areas of higher lion (Panthera leo) density, as evidence of a spatial avoidance strategy. We found that the IGPH was fully supported (6), the IPH half supported (5), and the RDH partially supported (1 and 3), where we found spatial partitioning of wild dogs with lions, potentially mediated by resources and territory overlap with conspecifics. Ultimately, our results show that subordinate carnivores must balance a trade-off between dominant interspecific competitors and conspecifics to successfully coexist in areas with dominant carnivores.South African National Parks (SANParks) honorary rangers and the Endangered Wildlife Trust (EWT).http://link.springer.com/journal/4422020-09-18hj2020Mammal Research InstituteZoology and Entomolog

Reproductive endocrinology of zoo-housed aardwolves

Knowledge regarding the relationship between endocrine parameters and reproductive activity can offer important insights into how social and environmental factors influence the reproductive success of mammals. Although components of both the physical and social environment affect endocrine regulation of reproduction, less is understood about the potential role of interactions between different endocrine axes on reproductive activity. We evaluated temporal patterns of reproductive and adrenocortical steroids in two male and three female aardwolves (Proteles cristata) housed in captivity at Brookfield Zoo, Chicago, USA. We found seasonal variation in faecal androgens, estrogens, and progestagens, which provide support for previous observations of the aardwolf as a seasonal breeder. However, the timing of peak endocrine activity did not correspond to observations from wild populations. Our interpretation is that this discrepancy is caused by photoperiodic regulation of reproductive activity. We found a positive relationship between faecal androgens and faecal glucocorticoid metabolites in males and a positive relationship between faecal estrogens and faecal glucocorticoid metabolites in females when housed with conspecifics but not when housed alone. We also found a positive but asymptotic relationship between faecal progestagens and faecal glucocorticoid metabolites. We argue that these observations indicate a potential effect of reproductive endocrine activity on the hypothalamic-pituitary adrenal axis, which could result in interesting physiological trade-offs in male reproductive tactics and female prepartum maternal investment because of the negative effects of long-term glucocorticoid elevation on reproductive performance. Finally, our results suggest that social and environmental factors interact in regulating many aspects of endocrine fluctuations in this mostly solitary species.D. Marneweck, F. Dalerum and A. Ganswindt were supported by the National Research Foundation of South Africa, and F. Dalerum and A. Ganswindt were further supported by research fellowships from University of Pretoria.http://acta.zbs.bialowieza.pl/hb2013ab201

A 20-year review of the status and distribution of African wild dogs (Lycaon pictus) in South Africa

South Africa is one of only seven countries with a viable population of African wild dogs (Lycaon pictus). The national population in 2017 was 372 adults and yearlings and comprised three subpopulations: 1) Kruger National Park (Kruger), 2) an intensively managed metapopulation established through reintroductions into isolated, fenced reserves, and 3) a free-roaming population that occurs naturally outside protected areas. We assessed the long-term (four wild dog generations, ~20 years) trends in population size and growth rate within each of these three subpopulations. We found that Kruger supports a substantial population,which has declined over time.The metapopulation is the only subpopulation that has increased significantly over time (both in population size and number of packs), likely due to intensive conservation efforts and the reintroduction of wild dogs into 15 additional reserves since 1998. The free-roaming subpopulation has remained small but stable, even though the number of packs has declined due to anthropogenic threats. The overall national population has remained stable even though the number of packs has increased. Kruger has consistently supported the highest proportion of the national population over the last two decades. However, the contribution of the metapopulation has increased significantly over time. It is clear that despite differences in survey effort among the three subpopulations, South Africa has a small (~500) but stable population of wild dogs, with the metapopulation contribution becoming increasingly important. The circumstances in the country necessitate, and demonstrate the benefit of, intensive, adaptive management for the national population of wild dogs. While this assessment provides baseline information for the three subpopulations, wild dog conservation in South Africa would benefit greatly from equal survey effort and standardized methods to accurately assess long-term population trends.https://journals.co.za/journal/wild2pm2021Zoology and Entomolog

Top–down limits on prey populations may be more severe in larger prey species, despite having fewer predators

Variation in the vulnerability of herbivore prey to predation is linked to body size, yet whether this relationship is size‐nested or size‐partitioned remains debated. If size‐partitioned, predators would be focused on prey within their preferred prey size range. If size‐nested, smaller prey species should become increasingly more vulnerable because increasingly more predators are capable of catching them. Yet, whether either of these strategies manifests in top–down prey population limitation would depend both on the number of potential predator species as well as the total mortality imposed. Here we use a rare ecosystem scale ‘natural experiment’ comparing prey population dynamics between a period of intense predator persecution and hence low predator densities and a period of active predator protection and population recovery. We use three decades of data on herbivore abundance and distribution to test the role of predation as a mechanism of population limitation among prey species that vary widely in body size. Notably, we test this within one of the few remaining systems where a near‐full suite of megaherbivores occur in high density and are thus able to include a thirtyfold range in herbivore body size gradient. We test whether top–down limitation on prey species of particular body size leads to compositional shifts in the mammalian herbivore community. Our results support both size‐nested and size‐partitioning predation but suggest that the relative top–down limiting impact on prey populations may be more severe for intermediate sized species, despite having fewer predators than small species. In addition we show that the gradual recovery of predator populations shifted the herbivore community assemblage towards large‐bodied species and has led to a community that is strongly dominated by large herbivore biomass.The Earthwatch Institute, Ezemvelo KwaZulu-Natal Wildlife and a Marie Curie Grant held by JC (grant # PCIG10-GA-2011-304128). ElR was supported by the South African National Research Foundation, Nelson Mandela Univ. and the Claude Leon Foundation.http://www.ecography.org2020-06-01hj2019Centre for Wildlife Managemen

Environmental controls on African herbivore responses to landscapes of fear

Herbivores balance forage acquisition with the need to avoid predation, often leading to tradeoffs between forgoing resources to avoid areas of high predation risk, or tolerating increased risk in exchange for improved forage. The outcome of these decisions is likely to change with varying resource levels, with herbivores altering their response to predation risk across heterogeneous landscapes. Such contrasting responses will alter the strength of non-consumptive predation effects, but are poorly understood in multiple-predator/multiple-prey systems. We combined fine-scaled spatial information on two predator and 11 herbivore species with remotely-sensed measurements of forage quantity and vegetation structure to assess variation in herbivore response to predation risk with changing environmental context, herbivore body size, herbivore foraging strategy (browsers versus grazers), predator type (ambush versus coursing hunters) and group size across a South African savanna landscape. Medium-sized herbivore species were more likely to adjust their response to risk with a changing resource landscape: warthog, nyala and wildebeest tolerated increased long-term predator encounter risk in exchange for abundant (warthog and nyala) or preferred (wildebeest) forage, and nyala selected areas with higher visibility only in landscapes where food was abundant. Impala were more likely to be observed in areas of high visibility where wild dog risk was high. In addition, although buffalo did not avoid areas of high lion encounter risk, large buffalo groups were more frequently observed in open areas where lion encounter risk was high, whereas small groups did not alter their space use across varying levels of risk. Our findings suggest that risk effects are not uniform across landscapes for medium-sized herbivores and large buffalo groups, instead varying with environmental context and leading to a dynamic landscape of fear. However, responses among these and other prey species were variable and not consistent, highlighting the complexities inherent to multi-predator/multi-prey systems.Data availability statement: Data available from the Dryad Digital Repository: (Davies et al. 2020).http://www.oikosjournal.orghj2022Mammal Research InstituteZoology and Entomolog

Food, family and female age affect reproduction and pup survival of African wild dogs

Understanding factors that affect the reproductive output and growth of a population of endangered carnivores is key to providing information for their effective conservation. Here, we assessed patterns in reproduction for a small population of endangered African wild dogs (Lycaon pictus) over 90 pack years. We tested how availability of prey, pack size, pack density, rainfall, temperature and female age affected the age of first litter, litter size and pup survival. We found that females bred younger when pack density, availability of prey and pack size were large. We also found that fecundity increased significantly with age while the population was male biased only for 1-, 2- and 4-year olds. Larger litters were produced by larger packs, suggesting strong reproductive benefits of grouping related to cooperative hunting and food provisioning for helpers and alpha females. We also found an interaction between breeding female age and pack size where older females in large packs raised a high proportion of pups. Additionally, large litters and large packs were important for raising a greater number of pups to 6 and 12 months, respectively, suggesting that while litter size is important for pup survival, the benefits of a large pack are only realised when pups are older and mobile with the pack. Collectively, these results illustrate the novel finding that prey availability is critically important in initiating reproduction in wild dogs and that the number of non-breeding helpers, female age and litter size is essential to pup survival.The National Research Foundation of South Africa Scarce Skills Development Fund (grant number SFH13072423287) and The Rufford Small Grants Foundation (grant number: 14409-1).http://link.springer.com/journal/2652020-05-01hj2019Mammal Research InstituteZoology and Entomolog

A novel technique for artificial pack formation in African wild dogs using odour familiarity:

Reintroductions are recognized tools for species recovery. However, operations are costly, difficult to implement, and failures are common and not always understood. Their success for group-living species depends on the mimicry of natural processes that promote social integration. Due to fragmented landscapes, human mediated (i.e. artificial) group formation is often required