Sex-specific androgen binding in spotted hyaena (Crocuta crocuta) plasma

• 1.1. A charcoal adsorption assay demonstrated a large variance in androgen binding ability in female spotted hyaenas.
• 2.2. A positive correlation between plasma androgen binding ability and ovarian steroid concentrations was demonstrated in adult females.
• 3.3. The strong plasma binding affinity for testosterone and dihydrotestosterone (DHT) (nM) together with the lack of cortisol and weaker oestradiol-17β binding suggests that a specific androgen binding substance, possibly a protein, is present in adult females of this species.
• 4.4. The lack of high affinity binding in male spotted hyaenas is unusual and deserves further investigation.
• 5.5. Some androgen binding in all, including males and immature animals suggests that albumin may bind some plasma androgens in this species.

     

Social organization of the spotted hyaena (Crocuta crocuta). I. Demography

A 4-year field study of one group of 60–80 spotted hyaenas (Crocuta crocuta) in Kenya's Masai Mara National Reserve has revealed a form of social system undescribed among carnivores but common among primates. Male juveniles disperse from the natal group around puberty and join a population of nomadic males, wandering widely before settling in a new clan. Adult males frequently leave their adopted clan after a variable period of residence. Females remain in their natal group for life. Thus, the clan comprises several matrilines of related females, while resident adult males originate outside the group. Clans in the Mara tend to be separated by wide buffer zones where prey is scarce and boundary maintenance behaviours are relatively uncommon. Transients are subordinate to residents, but are tolerated by them, in contrast to the more territorial clan system that has been described in Ngorongoro Crater.     

Mechanisms of maternal rank 'inheritance' in the spotted hyaena, Crocuta crocuta

Maternal rank 'inheritance', the process by which juveniles attain positions in the dominance hierarchy adjacent to those of their mothers, occurs in both cercopithecine primates and spotted hyaenas. Maternal rank is acquired in primates through defensive maternal interventions, coalitionary support and unprovoked aggression ('harassment') directed by adult females towards offspring of lower-ranking individuals. Genetic heritability of rank-related traits plays a negligible role in primate rank acquisition. Because the social lives of Crocuta and cercopithecine primates share many common features, we examined whether the same mechanisms might operate in both taxa to promote maternal rank 'inheritance'. We observed a large clan of free-living spotted hyaenas in Kenya to test predictions of four mechanistic hypotheses. Hyaena rank acquisition did not appear to be directly affected by genetic heritability. Unprovoked aggression from adult female hyaenas was not directed preferentially towards low-ranking cubs. However, high-ranking mothers intervened on behalf of their cubs more frequently and more effectively than low-ranking mothers. Maternal interventions and supportive coalitions appeared to reinforce aggression directed at 'appropriate' conspecific targets, whereas coalitionary aggression directed at cubs apparently functioned to extinguish their aggressive behaviour towards 'inappropriate' targets. Young hyaenas and primates thus appear to 'inherit' their mothers' ranks by strikingly similar mechanisms. Copyright 2000 The Association for the Study of Animal Behaviour.     

A seasonal feast: long-term analysis of feeding behaviour in the spotted hyaena (Crocuta crocuta)

The feeding behaviour of the Talek clan of spotted hyaenas in the Masai Mara National Reserve, Kenya, was monitored continuously for 7 years. Talek hyaenas adapted to large temporal variations in prey abundance by being opportunistic predators. During the first half of the year, the hyaenas fed on resident ungulates, and their diet consisted mainly of topi and Thomson's gazelles. Upon arrival of the migratory herds of wildebeest and zebra from the Serengeti, Talek hyaenas switched to feeding on the wildebeest which provided them with a superabundance of food for about 3 months. After the migratory animals returned to the Serengeti, Talek hyaenas experienced a period of reduced prey abundance due to the temporary dispersion of resident ungulates. At this time hyaenas hunted the few remaining wildebeest, and also increased their use of the remaining resident animals. Although Talek hyaenas were generally opportunistic in their feeding behaviour, they did exhibit clear dietary preference for larger prey species, particularly wildebeest. Finally, carrion comprised only 5% of the biomass consumed by Talek hyaenas, the lowest proportion of carrion in the diet of any Crocuta population studied to date.     

Morphological and steroidogenic assessment of ovarian activity during lactation in the spotted hyaena (Crocuta crocuta)

Histological evidence suggests that the spotted hyaena ( Crocuta crocuta ) is polyoestrous, and that corpora lutea are persistent and are not visible after one birth interval. Multiple generations of corpora lutea therefore represent recurring 'infertile' oestrous cycles. Plasma oestradiol-17β and progesterone concentrations fluctuate concurrently, with the highest concentrations occurring during pregnancy. The reduced mean oestradiol-17β concentrations observed during lactation suggest reduced ovarian steroid secretion during this reproductive phase. However, signs of follicular activity in some lactating females indicate that endocrine activity may still occur during lactation. The presence of multiple 'infertile' cycles and some degree of follicular development during lactation explains the ability of this species to fall pregnant soon after the loss of a litter, and provides a mechanism for overcoming the low recruitment rate so characteristic of this species.     

Growth, development and parental investment in the spotted hyaena, Crocuta crocuta

In the Cervidae, sexual dimorphism in body mass, armament and structure of the breeding pelage appears to be, as in African antelope, a curvilinear function on openness of habitat. Sexes converge in characteristics towards male-like monomorphism in deer that hide in dense cover, as well as in gregarious, cursorial dwellers in open terrain. Relative antler mass correlates with weight dimorphism. The most cursorial species, the wapiti ( Cervus elaphus canadensis ) and the caribou ( Rangifer farandus ) converge towards male monomorphism, with the wapiti showing strong reduction in weight dimorphism (compared to red deer C. elaphus hippelaphus ), and structure of the breeding pelage, but not in weaponry. Male and female caribou converge strongly in the structure of the breeding pelage, less so in weaponry, and least in weight dimorphism; antlers in female caribou are thus comparable to horns in male-like females of plains bovids. In weight dimorphism, wapiti have almost reached the level of the African grazing antelopes of the tribes Alcelaphini and Orygini. Sexual dimorphism is maximal in mixed and concentrate feeders from semi-open landscapes.     

The scent-marking behaviour of the spotted hyaena Crocuta crocuta in the southern Kalahari

All hyaenas scent mark their territories by smearing grass stems with paste from their subcaudal scent glands and by depositing faeces at latrines, but they adopt different strategies in terms of how they disperse these scent marks in their territories. For example, brown hyaenas living in the southern Kalahari deposit pastes and latrines throughout the whole of their territory, while spotted hyaenas living in the Ngorongoro Crater of East Africa place their scent marks strictly along the territorial borders. We have argued elsewhere (Gorman & Mills, 1984) that these different strategies are not species-specific but are instead adaptive responses to local conditions. Here, we use data from a population of spotted hyaenas, living in small clans and large territories in the Kalahari, to test the hypothesis that hinterland marking is a response to the problem of marking a very large territory with a limited amount of scent and within a limited time budget.     

Social organization of the spotted hyaena Crocuta crocuta. II. Dominance and reproduction

A 4-year study of the social organization of spotted hyaenas in a clan of 60–80 individuals showed that there is a separate dominance hierarchy within each sex. One female and her descendants dominated all others; matrilineal rankings were stable over time because maternal rank is inherited. Cubs of higher ranking females were able to feed at kills in competition with adults more successfully than other cubs, and male offspring of the alpha female were the only males able to dominate adult females. The mating system is highly polygynous: only the behaviourally dominant male was seen to mate, though all other resident males regularly courted females. Among females, there was no correlation between reproductive success and age, size, or social rank. It is postulated that the unusually aggressive sons of the alpha female would probably be highly successful competitors in the context of a polygynous mating system. A primary consequence of female dominance over males is that females and their young have priority of access to food in a highly competitive feeding situation. This competition may have been the selective force that produced female dominance and the associated syndrome of female virilization that is characteristic of the species. Cooperation among related females may be the basis for the matrilineal system, as has been suggested for certain primate species.     

Densities of spotted hyaena (Crocuta crocuta) and African golden wolf (Canis anthus) increase with increasing anthropogenic influence

We report densities of spotted hyaena (Crocuta crocuta) and African golden wolf (Canis anthus) in Enderta district in northern Ethiopia with high human and low natural prey densities. We estimated spotted hyaena and African golden wolf abundance and characterized their spatial distribution with three methods we surveyed four road-transects for 66 nights during dry (n = 41) and wet (n = 25) seasons, we used 34 calling stations and we mapped all active spotted hyaena dens at the time of the survey. The density of spotted hyaena and African golden wolf increased with proximity to towns where human density was higher. A total of 562 spotted hyaena and 63 African golden wolf responded to calling stations, leading to estimates of 1145 spotted hyaena and 166 African golden wolf in Enderta district. This method also found a significantly higher spotted hyaena and African golden wolf abundance in high human density areas. Maximum response radius was 2.8 km for spotted hyaena and 2.5 km for African golden wolf, and response probability was 0.83 for spotted hyaena and 0.8 for African golden wolf, respectively. We found 40 active spotted hyaena dens with 1507 remnants of prey, and the majority of the dens were located close to rivers and villages. Our findings show a positive relationship between spotted hyaena, African golden wolf and human concentrations that might demonstrate a case of exceptional coexistence of humans and carnivores, both at high densities. We suggest further investigations into co-adaptations between humans and predators in the study area.     

Prey preferences of the spotted hyaena (Crocuta crocuta) and degree of dietary overlap with the lion (Panthera leo)

Spotted hyaenas Crocuta crocuta were once considered mere scavengers; however, detailed research revealed that they are very efficient predators. Information on what spotted hyaenas actually prefer to prey on and what they avoid is lacking, as well as the factors that influence prey selection. Data from 14 published and one unpublished study from six countries throughout the distribution of the spotted hyaena were used to determine which prey species were preferred and which were avoided using Jacobs' index. The mean of these values for each species was used as the dependent variable in multiple regression, with prey abundance and prey body mass as predictive variables. In stark contrast to the rest of Africa's large predator guild, spotted hyaenas do not preferentially prey on any species. Also surprisingly, only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyaena most prefer prey within a body mass range of 56–182 kg, with a mode of 102 kg. The dietary niche breadth of the spotted hyaena is similar to that of the lion Panthera leo , and the two species have a 58.6% actual prey species overlap and a 68.8% preferred prey species overlap. These results highlight the flexible and unselective nature of spotted hyaena predation and are probably a reason for the species' success throughout its range, despite a large degree of dietary overlap with lions.     

Social intelligence in the spotted hyena (Crocuta crocuta)

If the large brains and great intelligence characteristic of primates were favoured by selection pressures associated with life in complex societies, then cognitive abilities and nervous systems with primate-like attributes should have evolved convergently in non-primate mammals living in large, elaborate societies in which social dexterity enhances individual fitness. The societies of spotted hyenas are remarkably like those of cercopithecine primates with respect to size, structure and patterns of competition and cooperation. These similarities set an ideal stage for comparative analysis of social intelligence and nervous system organization. As in cercopithecine primates, spotted hyenas use multiple sensory modalities to recognize their kin and other conspecifics as individuals, they recognize third-party kin and rank relationships among their clan mates, and they use this knowledge adaptively during social decision making. However, hyenas appear to rely more intensively than primates on social facilitation and simple rules of thumb in social decision making. No evidence to date suggests that hyenas are capable of true imitation. Finally, it appears that the gross anatomy of the brain in spotted hyenas might resemble that in primates with respect to expansion of frontal cortex, presumed to be involved in the mediation of social behaviour.     

Fine‐scale movements and use of space by spotted hyaena (Crocuta crocuta) on Ongava Game Reserve,Namibia

We deployed Global Positioning System (GPS) collars on spotted hyaena, Crocuta crocuta, on Ongava Game Reserve in northern Namibia. We analysed the movement profiles recorded from three periods of fine temporal scale (15 min interval) GPS data – dry season data from a sub‐adult female (36 days) and a lactating adult female (54 days), and wet season data from the same adult female (55 days). The hyaenas both had similar daily activity patterns – at rest between 12.00 and 18.00 hours, with a peak of activity in the 2‐h period around sunrise. They exhibited one or two active periods each night, travelling up to 30 km and being active for up to 10 h. Daily rest sites were widely distributed across the reserve, typically located on elevated ground and never revisited on consecutive days. In the dry season, both hyaenas made extensive use of the reserve, plus adjacent areas in Etosha National Park (sub‐adult home range 240 km², adult home range 366 km²). The wet season data for the adult female showed a significant reduction of space used (home range 232 km²). However, their utility distributions showed a nonuniform use of space, with multiple areas of high‐density utilization located away from open terrain.