Michael G. L. Mills

High hunting costs make African wild dogs vulnerable to kleptoparasitism by hyaenas

The African wild dog Lycaon pictus is critically endangered, with only about 5,000 animals remaining in the wild. Across a range of habitats, there is a negative relationship between the densities of wild dogs and of the spotted hyaena Crocuta crocuta. It has been suggested that this is because hyaenas act as ‘kleptoparasites’ and steal food from dogs. We have now measured the daily energy expenditure of free-ranging dogs to model the impact of kleptoparasitism on energy balance. The daily energy expenditures of six dogs, measured by the doubly labelled water technique, averaged 15.3 megajoules per day. We estimated that the instantaneous cost of hunting was twenty-five times basal metabolic rate. As hunting is energetically costly, a small loss of food to kleptoparasites has a large impact on the amount of time that dogs must hunt to achieve energy balance. They normally hunt for around 3.5 hours per day but need to increase this to 12 hours if they lose 25% of their food. This would increase their sustained metabolic scope to a physiologically unfeasible twelve times the basal metabolic rate. This may explain why there are low populations of wild dogs in regions where the risk of kleptoparasitism is high.

The scent marking behaviour of the brown hyaena Hyaena brunnea

The deposition onto grass stalks of two distinct, strong-smelling substances produced in the anal scent pouch, is the most common form of scent marking in the brown hyaena (Hyaena brunnea). It is called pasting. The behaviour associated with pasting is described, as is the related functional anatomy of the scent pouch. The dispersion pattern of pastings within a group territory and the rate of marking in different parts of the territory were ascertained by direct observations on radio collared hyaenas. The data were analysed by the computer programs SYMAP and SYMVU which graphically display the data as a three dimensional map. Brown hyaenas leave most pastings in those areas in which they spend most time. This is in the central part of the territory. When they visit the boundaries, however, the frequency of pasting increases. GLC analyses of the pastings from two known individuals show distinct differences in the relative concentrations of the many compounds in the pastings of each. Behavioural observatio...

Handling-Induced Stress and Mortalities in African Wild Dogs (Lycaon pictus)

Recently it was suggested that the handling of wild dogs (Lycaon pictus) by researchers in the Serengeti ecosystem created stress, resulting in the reactivation of latent rabies viruses in carrier animals. We present data from ongoing studies on free-ranging and captive wild dogs elsewhere in Africa which do not support this hypothesis. Cortisol profiles suggest that immobilization of wild dogs does not cause the chronic stress required for stress-reactivation of latent viruses. Furthermore, there is no evidence of handling-related mortalities in wild dogs : the survivorship of unhandled and handled free-ranging wild dogs did not differ and no captive animals died within a year of handling (immobilization and/or vaccination against rabies). We suggest that the mortalities observed in Tanzania were due to an outbreak of a disease which rabies vaccination was unable to prevent. Intensive monitoring and active management research programmes on wild dogs are essential as without these, critically endangered wild dog populations have little hope of survival.

Cheetahs, Acinonyx jubatus, balance turn capacity with pace when chasing prey

Predator–prey interactions are fundamental in the evolution and structure of ecological communities. Our understanding, however, of the strategies used in pursuit and evasion remains limited. Here, we report on the hunting dynamics of the worlds fastest land animal, the cheetah, Acinonyx jubatus. Using miniaturized data loggers, we recorded fine-scale movement, speed and acceleration of free-ranging cheetahs to measure how hunting dynamics relate to chasing different sized prey. Cheetahs attained hunting speeds of up to 18.94 m s−1 and accelerated up to 7.5 m s−2 with greatest angular velocities achieved during the terminal phase of the hunt. The interplay between forward and lateral acceleration during chases showed that the total forces involved in speed changes and turning were approximately constant over time but varied with prey type. Thus, rather than a simple maximum speed chase, cheetahs first accelerate to decrease the distance to their prey, before reducing speed 5–8 s from the end of the hunt, so as to facilitate rapid turns to match prey escape tactics, varying the precise strategy according to prey species. Predator and prey thus pit a fine balance of speed against manoeuvring capability in a race for survival.

Mass enhances speed but diminishes turn capacity in terrestrial pursuit predators

The dynamics of predator-prey pursuit appears complex, making the development of a framework explaining predator and prey strategies problematic. We develop a model for terrestrial, cursorial predators to examine how animal mass modulates predator and prey trajectories and affects best strategies for both parties. We incorporated the maximum speed-mass relationship with an explanation of why larger animals should have greater turn radii; the forces needed to turn scale linearly with mass whereas the maximum forces an animal can exert scale to a 2/3 power law. This clarifies why in a meta-analysis, we found a preponderance of predator/prey mass ratios that minimized the turn radii of predators compared to their prey. It also explained why acceleration data from wild cheetahs pursuing different prey showed different cornering behaviour with prey type. The outcome of predator prey pursuits thus depends critically on mass effects and the ability of animals to time turns precisely. DOI: http://dx.doi.org/10.7554/eLife.06487.001

The demography and dynamics of an expanding, managed African wild dog metapopulation

Long-term demographic data are central for the evaluation of endangered species recovery plans. We present the demography and dynamics of a managed African wild dog (Lycaon pictus) metapopulation in South Africa, based on life histories of 553 individually known animals collected between 1998 and 2006. This metapopulation, distributed across nine sites (and not including Kruger National Park), was established through reintroductions (n = 9 events) and maintained by periodic augmentation (n = 10 events) and translocation (n = 20 events). In total, 66 founders were used to establish subpopulations and mean founder group size was 9.6 animals. The metapopulation grew from 17 individuals in 1998 to a peak of 202 in 2005. Mean annual population density was 3.3 (S.E. 0.44) wild dogs/100 km2, approaching the upper limit of densities reported from unmanaged populations. Mean size of breeding packs was 11.0 (S.E. 0.76), comparable to pack sizes in Kruger National Park (Kruger), the only viable unmanaged population in South Africa. Fecundity was lower than in Kruger — particularly in the older age classes. Pup survival to adulthood was 45% — nearly three times the survival rate for pups in Kruger. Mean annual population growth rate (&lgr; = 1.08, S.E. 0.13) was higher than in unmanaged populations (range 1.000–1.038), with implications for population viability and management.