The response of lions and spotted hyaenas to sound playbacks as a technique for estimating population size

Overall, 217 lions (>1 year) Panthera leo (Linnaeus) and 2069 spotted hyaenas (>8 mo) Crocuta crocuta (Erxleben) responded to broadcast vocalizations, call‐ins, during six surveys in the Masai Mara National Reserve, Kenya.
Carnivore response varied seasonally and was significantly higher and more uniform when migratory prey were absent. Variation in wildebeest abundance, by affecting food availability, was the only significant predictor of response. Variability in response with overall prey abundance was higher for lions than hyaenas. Lion response occurred within a radius of 2·5 km, was independent of age and sex but dropped virtually to zero whenever lions possessed a carcass at the time of broadcasting.
An independent total census recorded 547 lions (all ages) in the Reserve, 9·96% of which were nomads. This proportion increased by 7·94% following the influx of migrants and raised lion (>1 year) density from 0·292 to 0·320 lions/km². The call‐in estimate of 0·294±0·009 (95% c.l.) lions/km² practically equalled the total count. The high precision and low bias (−0·224%) of this estimate imply that call‐in surveys are reliable and may be employed to effectively monitor carnivore populations in the long term. Under simple random sampling, covering about 20% of an area would seem adequate to produce reliable density estimates.     

Evolutionary ecology meets wildlife management: artificial group augmentation in the re-introduction of endangered African wild dogs (Lycaon pictus)

As an alternative to kin selection, group augmentation theory provides a framework for evolutionary mechanisms maintaining cooperative breeding when individual fitness is positively related to group size. It is expected that a cooperator group would accept or adopt unrelated foreigners when it is below a critical threshold size and group members could thus benefit from recruiting additional helpers. In re-introduction attempts, this would allow for a group to be augmented artificially before release, which would enhance its chance to establish itself successfully in the release area. This possibility was tested using endangered African wild dogs Lycaon pictus studied in Hluhluwe-iMfolozi Park, South Africa. Here, we report on the first successful artificial integration of an unrelated adult female with her three male pups into an existing pack. In addition, post-release monitoring data are presented, including how a yearling male displaced the dominant male that adopted him as a pup, adding to the controversy over the evolutionary stability of group augmentation as a route to cooperative breeding. This study thus demonstrates how theory from evolutionary ecology can be applied to practical wildlife management, and vice versa.     

Small pack size imposes a trade-off between hunting and pup-guarding in the painted hunting dog Lycaon pictus

The painted hunting dog or African wild dog, Lycaon pictus,is one of the most endangered large carnivores in Africa, withextinction predicted within a few decades if their dramaticdecline is not stopped. It has recently been hypothesized thatbecause of their constraining need for helpers, group sizewas of major importance in obligate cooperative breeding species,and that the resulting likely existence of a threshold numberof adults could create an Allee effect, increasing the groupextinction risk. One example where the importance for a criticalnumber of adults may have major repercussions for painted huntingdogs concerns baby-sitting, or pup-guarding, a behavior typicalof obligate cooperative breeders. We propose that, as forgoingthis behavior is costly because pup guards have the potentialto decrease pup mortality, its use is costly too, especiallyin small packs, because helpers are strongly needed for theircooperative foraging (hunting, protecting the kill and bringingback food to the pups). We present a simple model showing howpup-guarding imposes a cost because it implies that less foodper hunt is brought back to more individuals at the den. Wecomplete these analyses with empirical tests of the effectof pack size on the probability of pup-guarding, from fielddata from the Hwange population in Zimbabwe. Our model, aswell as our 5 years of empirical data, both suggest a criticalthreshold at a size of about five individuals.     

Profitability, encounter rates, and prey choice of African lions

The prey preferences of African lions (Panthera leo) in SerengetiNational Park, Tanzania, were examined in three ways. First,lion encounter rates with prey types were measured and comparedwith a random sample of the prey population. Lions encounteredmore wart hogs (Phacochoerus aethiopicus), Grant's gazelles(Gazella granti), wildebeests (ConnochaeUs taurinus), and zebras(Equus burchelli) than expected. Second, preferred prey typesof lions were identified using conditional logit analysis. Lionspreferred to hunt small prey groups, groups that were closerthan 200 m, and groups that contained wart hogs, wildebeests,or zebras. Third, a risk-minimization optimal foraging modeland a rate-maximization model were used to predict lion preferences.The foraging theory models predict that preferences should changewith season and with lion group size. Qualitative support wasfound for most of these predictions.     

Non-offspring nursing in social carnivores: minimizing the costs

We compare the nursing behavior of two species, African lions(PanfheraLeo) and spotted hyenas(Crocuta Craig Packer crocuta), and showthat non-offspring nursing is much less common in hyenas thanlions. Hyenas spend less time with their cubs, are more alertduring the suckling attempts of cubs, and more frequently resistthe attempts of non-offspring. Vigilance against milk theftmay therefore influence the distribution of non-offspring nursingacross species. Our detailed study of non-offspring nursingin lions shows that females preferentially nurse their own offspringand that cubs are more surreptitious when attempting to sucklefrom other females. Non-offspring nursing in lions is most commonwhen the costs are lowest. First, non-offspring nursing is morecommon among close kin. Second, females with small litters,and presumably more milk to spare, give a higher proportionof their nursing to non-offspring. Third, females give a higherproportion of their nursing to non-offspring as their own cubsgrow older and need less milk. Cubs reared in créchesdo not appear to gain more milk that cubs raised alone, andfemales do not show any evidence of reciprocity in nursing oneanother's offspring. We suggest that non-offspring nursing inlions occurs as a by-product of the females' communal defenseof their cubs against infanticide.