Wild Hyenas Research Articles

9-Year Follow-Up on Maxillofacial Implant-Supported Framework Designed to Accommodate Childhood Growth.

This clinical report focuses on the challenges and solutions for a child subjected to craniofacial trauma from a wild hyena biting off his nose and anterior maxilla. Unique considerations in prosthodontics and biomedical engineering were required based on future craniofacial growth and development of the child. The physical requirement of a maximum retentive prosthesis for an active, athletic child required unique engineering designs and executions. The sequence of treatment and prosthesis fabrication are detailed. The patient has been followed for 9 years without physiologic complications and only minor prosthodontic complications.

Bathing Behaviour in Spotted Hyenas (Crocuta crocuta) in Laikipia, Kenya: Two Observational Cases

Homeothermic animals have regulatory mechanisms to maintain a constant body temperature in response to harsh climatic conditions. In low latitude areas near the equator, animals have adapted a coat to avoid strong UV rays, but a thick coat interferes with heat dissipation due to high daytime temperatures. Therefore, animals spend hot hours in cool shade or dens as the most common method to avoid overheating Alternatively, some animals cool themselves by bathing with sand, mud or water. Spotted hyenas (Crocuta crocuta) are medium-sized carnivorous animals weighing about 45–70 kg, and aredouble coated. Bathing is a well-known behaviour in spotted hyenas, but it is not clear from natural historical descriptions whether their bathing is a heat-resistant behaviour. Here we report on two bathing observation cases of hyena and describe them with reference to the heat resistance function of bathing based on the time and temperature at which observations occurred. A wild hyena of a four-headed clan inhabiting Laikipia, Kenya bathed in a pool at around 18:00 h and 9:00 h in the dry season. The temperature at 18:00 h showed largest difference from the highest annual mean temperature. The bathing at 9:00 h in the morning was the time when the temperature began to rise. These observations suggest that hyena bathing may be a heat-avoiding behaviour. Bathing also has other functions such as parasite extermination, play and ambush hunting, hence more observations are needed in the future.

Visual communication in social play of a hierarchical carnivore species: the case of wild spotted hyenas.

Communication relies on signals that can be produced via different sensory modalities to modify receivers’ behavior. During social interactions, the possibility to perceive subtle visual cues enhances the use of facial expressions to exchange information. One of the most appropriate fields to explore the specific design features of visual signals is play fighting. Here, we explored the production and potential role of Relaxed Open Mouth (ROM) and Head Bobbing (HB) in regulating play fighting of wild spotted hyenas Crocuta crocuta, a highly hierarchical carnivore species. In accordance with the assumptions of the signal optimization theory, wild hyenas produced ROM and HB almost exclusively when the sender was in direct visual contact with the receiver thus suggesting that senders were attentive to the playmates’ face. Contrary to HB, the sequential analysis revealed that ROM often anticipated offensive patterns such as play biting thus supporting the hypothesis that ROM, but not HB, is a metacomunicative signal. Moreover, when the offensive patterns were biased toward one of the 2 players, the session was punctuated by a higher number of ROMs. Our findings support the general hypothesis that these 2 visual signals can play different roles in the management of play fighting in this carnivore species. The complementary use of ROM and HB would suggest that spotted hyenas are highly competent and fast in processing facial displays of different nature to correctly “read others’ intentions” and respond with appropriate motor actions to avoid misunderstanding during one of the most multifaceted and risky social interaction.

Innovative problem-solving in wild hyenas is reliable across time and contexts

Individual differences in behavior are the raw material upon which natural selection acts, but despite increasing recognition of the value of considering individual differences in the behavior of wild animals to test evolutionary hypotheses, this approach has only recently become popular for testing cognitive abilities. In order for the intraspecific approach with wild animals to be useful for testing evolutionary hypotheses about cognition, researchers must provide evidence that measures of cognitive ability obtained from wild subjects reflect stable, general traits. Here, we used a multi-access box paradigm to investigate the intra-individual reliability of innovative problem-solving ability across time and contexts in wild spotted hyenas (Crocuta crocuta). We also asked whether estimates of reliability were affected by factors such as age-sex class, the length of the interval between tests, or the number of times subjects were tested. We found significant contextual and temporal reliability for problem-solving. However, problem-solving was not reliable for adult subjects, when trials were separated by more than 17 days, or when fewer than seven trials were conducted per subject. In general, the estimates of reliability for problem-solving were comparable to estimates from the literature for other animal behaviors, which suggests that problem-solving is a stable, general trait in wild spotted hyenas.

Interspecies comparison of the residue levels and profiles of persistent organic pollutants in terrestrial top predators

Serum samples from three species of living terrestrial top predators were analysed for six groups of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlordane compounds (CHLs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDEs). The study included three carnivore species: lion (Panthera leo), hyena (Hyena brunnea) and cheetah (Acinonyx jubatus). All samples were collected from healthy living animals between 2004 and 2005. Most of the samples (wild lions (n = 50) and hyenas (n = 11)) were collected from various locations within the Kruger National Park and Addo National Park (South Africa), while captive lions (n = 6) and cheetahs (n = 3) were collected from the Antwerp Zoo (Belgium). In general, relatively low levels of POPs were found in the studied species, varying widely within species and locations. Median concentrations of POPs were higher in captive lions (PCBs: 505 pg/mL; DDTs: 270 pg/mL; HCHs: 72 pg/mL; HCB: 34 pg/mL; CHLs: 24 pg/mL; PBDEs: 8 pg/mL) compared to wild lions (DDTs: 274 pg/mL; HCHs: 44 pg/mL; CHLs: 7.9 pg/mL; PCBs: 2.1 pg/mL; HCB: < LOQ; PBDEs: < LOQ). In the wild animals, POPs accumulated in the following order: DDTs > HCHs > CHLs > HCB > PCBs > PBDEs, while in the captive animals, the order was: PCBs > DDTs > CHLs > HCHs > HCB > PBDEs, suggesting differences in the diet of these animals. Furthermore, wild hyena contained significantly higher (p < 0.05) median levels of POPs compared to wild lions, possibly reflecting differences in metabolic capacity and/or feeding habits, together with an uneven distribution of POPs in the area where the animals lived. No previous data are available to compare for similar terrestrial top predators, such as lion, hyena and cheetah. To our knowledge, this is first study on POPs in these three species. The low POP levels found in this study were several orders of magnitude lower than those for other carnivore species, such as polar bears, grizzly bears, brown bears and wolves worldwide. The present study has revealed the need for expanding research and monitoring on occurrence, levels and disposition of POPs in the top predators of the terrestrial environment.

Markedly Elevated Antibody Responses in Wild versus Captive Spotted Hyenas Show that Environmental and Ecological Factors Are Important Modulators of Immunity.

Evolutionary processes have shaped the vertebrate immune system over time, but proximal mechanisms control the onset, duration, and intensity of immune responses. Based on testing of the hygiene hypothesis, it is now well known that microbial exposure is important for proper development and regulation of the immune system. However, few studies have examined the differences between wild animals in their natural environments, in which they are typically exposed to a wide array of potential pathogens, and their conspecifics living in captivity. Wild spotted hyenas (Crocuta crocuta) are regularly exposed to myriad pathogens, but there is little evidence of disease-induced mortality in wild hyena populations, suggesting that immune defenses are robust in this species. Here we assessed differences in immune defenses between wild spotted hyenas that inhabit their natural savanna environment and captive hyenas that inhabit a captive environment where pathogen control programs are implemented. Importantly, the captive population of spotted hyenas was derived directly from the wild population and has been in captivity for less than four generations. Our results show that wild hyenas have significantly higher serum antibody concentrations, including total IgG and IgM, natural antibodies, and autoantibodies than do captive hyenas; there was no difference in the bacterial killing capacity of sera collected from captive and wild hyenas. The striking differences in serum antibody concentrations observed here suggest that complementing traditional immunology studies, with comparative studies of wild animals in their natural environment may help to uncover links between environment and immune function, and facilitate progress towards answering immunological questions associated with the hygiene hypothesis.

Limited social learning of a novel technical problem by spotted hyenas

Social learning can have profound evolutionary consequences because it drives the diffusion of novel behaviours among individuals and promotes the maintenance of traditions within populations. We inquired whether spotted hyenas (Crocuta crocuta), generalist carnivores living in complex, primate-like societies, acquire information from conspecifics about a novel problem-solving task. Previously, we presented wild hyenas with a food-access puzzle and found that social learning opportunities did not affect problem-solving success among observers, but did reduce observers’ neophobia. However, we had little control over which individuals observed conspecifics solve the problem, and few wild hyenas were successful. Therefore, we conducted an experiment in captivity where we controlled observer access to two demonstration styles. Again, social learning opportunities did not affect problem-solving success, but tended to reduce neophobia among captive observers. Social learning opportunities also influenced problem-solving style. Captive hyenas showed limited evidence for directed social learning; low-ranking individuals paid closer attention to demonstrators than high-ranking individuals, although this greater attention did not result in greater success. We conclude that wild and captive hyenas exploit social learning opportunities similarly, and that the limited social learning shown by hyenas on this task is likely based on localized stimulus enhancement.

Siblicide in the spotted hyena: analysis with ultrasonic examination of wild and captive individuals

Integrated field and laboratory studies of long-lived, large-bodied mammals are rare but offer unique opportunities to elucidate the behavioral ecology of these animals. Here, we used this approach to examine whether siblicide in spotted hyenas (Crocuta crocuta) is obligate or facultative. First, we tested predictions of obligate and facultative hypotheses by using ultrasonography to compare litter size before and after parturition and identify potential causes of litter reduction. Second, we compared litter size and composition between wild and captive hyenas to assess variation in offspring sex ratios. Third, we used demographic data to compare survivorship among litters of various sizes and compositions. Fourth, we compared sex ratios within twin litters born in the wild under conditions of high population density and intense feeding competition with those born when population density and intensity of feeding competition were reduced. Our data were inconsistent with the obligate siblicide hypothesis. Litter reduction occurred during roughly one-third of pregnancies in both wild and captive hyenas, and all such reductions among captives were due to fetal resorptions or stillbirths. Litter sizes and compositions differed little between wild and captive hyenas. However, sex ratios in twin litters varied in the wild with intensity of feeding competition. In conjunction with captive data, longterm study of a wild hyena population under varying environmental conditions suggests facultative siblicide is most likely to occur when feeding competition is most intense, thus offering an ecological explanation for earlier conflicting reports on siblicide in this species. Key words: Crocuta, hyenas, siblicide, sibling rivalry, siblings. [Behav Ecol]

Non-invasive measurement of fecal estrogens in the spotted hyena ( Crocuta crocuta)

Fecal hormone analysis is a useful tool for frequent, non-invasive sampling of free-living animals. Estrogens fluctuate throughout life among reproductive states in female animals, and intensive repetitive sampling can permit accurate assessment of female reproductive condition. This type of repetitive sampling is difficult in large carnivores, including the spotted hyena ( Crocuta crocuta). Patterns of estrogen secretion in captive and free-living hyenas are virtually unknown. Here we present validation of an enzyme-immunoassay to measure fecal estrogen (fE) concentrations in wild and captive spotted hyenas. Results from high-performance liquid chromatography indicate that an antibody specific for estradiol exhibits high immunoreactivity with our extracted samples. Fecal extract displacement curves paralleled our estradiol standard curve within the range of 20–80% antibody binding. Additionally, animals treated with luteinizing hormone-releasing hormone showed a measurable rise in fE concentrations. Finally, once we controlled for effects of time of day of sample collection from wild hyenas, patterns in fE concentrations resembled those in plasma estradiol, including higher levels of fE in mature than immature females, and higher levels of fE during late than early pregnancy. Together, these results suggest that fE concentrations reflect circulating estrogens in spotted hyenas.

Non-invasive monitoring of fecal androgens in spotted hyenas ( Crocuta crocuta)

Spotted hyenas ( Crocuta crocuta) exhibit an array of behavioral and morphological characteristics that set them apart from other mammals: females are heavier and more aggressive than males, and females have external genitalia that closely resemble those of the male. Because androgenic hormones might mediate the expression of these traits, androgens are of great interest in this species. Past work on circulating androgens in wild hyenas has been limited, in part because of small sample sizes. In this study we validated a non-invasive method of monitoring variation in androgens by measuring total androgen metabolites in the feces of wild and captive spotted hyenas with an enzyme immunoassay. HPLC analysis revealed multiple immunoreactive androgen metabolites in fecal extracts from both males and females. LHRH challenge in three male and two female hyenas in captivity caused an increase in fecal androgens one to three days after LHRH injection. Furthermore, presence of bone in the diet did not affect fecal androgen concentrations in captive female hyenas. In wild spotted hyenas, time of day of fecal deposition, time elapsed between deposition and freezing of the sample, and time elapsed between freezing and extraction did not systematically affect fecal androgen concentrations. Finally, in wild hyenas, fecal androgen patterns mirrored plasma testosterone patterns in that adult immigrant males had higher concentrations than adult natal males, and pregnant females had higher concentrations than lactating females. These methods can therefore be used in future studies addressing relationships among fecal androgens, social status, reproductive state, and behavior in spotted hyenas.