Risk and Ethical Concerns of Hunting Male Elephant: Behavioural and Physiological Assays of the Remaining Elephants

BACKGROUND: Hunting of male African elephants may pose ethical and risk concerns, particularly given their status as a charismatic species of high touristic value, yet which are capable of both killing people and damaging infrastructure. METHODOLOGY/PRINCIPAL FINDINGS: We quantified the effect of hunts of male elephants on (1) risk of attack or damage (11 hunts), and (2) behavioural (movement dynamics) and physiological (stress hormone metabolite concentrations) responses (4 hunts) in Pilanesberg National Park. For eleven hunts, there were no subsequent attacks on people or infrastructure, and elephants did not break out of the fenced reserve. For three focal hunts, there was an initial flight response by bulls present at the hunting site, but their movements stabilised the day after the hunt event. Animals not present at the hunt (both bulls and herds) did not show movement responses. Physiologically, hunting elephant bulls increased faecal stress hormone levels (corticosterone metabolites) in both those bulls that were present at the hunts (for up to four days post-hunt) and in the broader bull and breeding herd population (for up to one month post-hunt). CONCLUSIONS/SIGNIFICANCE: As all responses were relatively minor, hunting male elephants is ethically acceptable when considering effects on the remaining elephant population; however bulls should be hunted when alone. Hunting is feasible in relatively small enclosed reserves without major risk of attack, damage, or breakout. Physiological stress assays were more effective than behavioural responses in detecting effects of human intervention. Similar studies should evaluate intervention consequences, inform and improve best practice, and should be widely applied by management agencies

Female sexual preferences toward conspecific and hybrid male mating calls in two species of polygynous deer, Cervus elaphus and C. nippon

The behavioral processes at the basis of hybridization and introgression are understudied in terrestrial mammals. We use a unique model to test the role of sexual signals as a reproductive barrier to introgression by investigating behavioral responses to male sexual calls in estrous females of two naturally allopatric but reproductively compatible deer species, red deer and sika deer. Previous studies demonstrated asymmetries in acoustic species discrimination between these species: most but not all female red deer prefer conspecific over sika deer male calls while female sika deer exhibit no preference differences. Here, we extend this examination of acoustic species discrimination to the role of male sexual calls in introgression between parent species and hybrids. Using two-speaker playback experiments, we compared the preference responses of estrous female red and sika deer to male sexual calls from conspecifics versus red × sika hybrids. These playbacks simulate early secondary contact between previously allopatric species after hybridization has occurred. Based on previous conspecific versus heterospecific playbacks, we predicted that most female red deer would prefer conspecific calls while female sika deer would show no difference in their preference behaviors toward conspecific and hybrid calls. However, results show that previous asymmetries did not persist as neither species exhibited more preferences for conspecific over hybrid calls. Thus, vocal behavior is not likely to deter introgression between these species during the early stages of sympatry. On a wider scale, weak discrimination against hybrid sexual signals could substantially contribute to this important evolutionary process in mammals and other taxa

The relationship between testosterone and long-distance calling in wild male chimpanzees

Abstract: Long-distance calling is a common behaviour in animals, which has various important social functions. At a physiological level, calling is often mediated by gonadal hormones such as testosterone (T), particularly when its function is linked to intra-sexual competition for mates or territory. T also plays an important role in the development of vocal characteristics associated with dominance in humans. However, the few available studies of T and vocal behaviour in non-human primates suggest that in primates, T has less influence on call production than in other animals. We tested this hypothesis by studying the relationship between T concentrations and pant-hooting in wild male chimpanzees (Pan troglodytes schweinfurthii) of the Kanyawara community in the Kibale National Park, Uganda. We found three kinds of correlation. Hourly T averages were positively associated with hourly rates of pant-hooting. Monthly T levels were likewise correlated with monthly rates of pant-hooting after controlling for other influences such as fission-fusion rates. Finally, males with high T levels had higher peak frequency at the start of the call climax. These results suggest that T affects the production of pant-hoots in chimpanzees. This implies that the pant-hoot call plays a role in male-male competition. We propose that even in cognitively sophisticated species, endocrine mechanisms can contribute to regulating vocal production. Significance statement: Many animals produce long-distance calls. The production of these calls is often modulated by gonadal hormones such as testosterone, especially if the calls are involved in competition between males for mates or territory. However, comparatively little is known about the influence of testosterone over the vocal behaviour of non-human primates, especially among great apes. In this study, we examined the relationship between testosterone and pant-hooting in wild male chimpanzees. We found that testosterone levels were associated with pant-hoot rates and one acoustic feature of the call. More specifically, males pant-hooted more often and produced pant-hoots with higher peak frequencies during periods of elevated testosterone levels. These results imply that gonadal hormones are involved in regulating vocal behaviour in chimpanzees and support the view that pant-hoots play a role in male-male competition

Vocal communication in social groups

Vocal communication plays a particularly important role in the regulation of social interactions and in the coordination of activities in many mammals and birds that are organised into social groups. Previous research on the function and evolution of vocal signals has mainly considered dyadic interactions of a signaller and its addressed receiver. However, in social groups it is likely that additional individuals attend to dyadic communication and that they use this information to their own benefit, sometimes with severe costs to the signaller. To improve existing communication models, benefits and costs of vocal communication caused by bystanders must therefore also be considered. Here we discuss vocal communication in social groups and identify the effect of additional individuals on signalling interactions, concentrating on audience effects, eavesdropping and group coordination. First, review of the existing literature reveals that the presence of an audience, i.e., additional individuals within the signalling range, clearly affects the outcome of communicative interactions, and that individuals modulate their signalling behaviour according to the presence of bystanders or a particular category of bystanders in a variety of contexts. Second, social knowledge acquired by eavesdropping on the communicative network within a group influences not only future actions, but can also provide individual benefits for eavesdroppers, whereas mutual eavesdropping can structure cooperation and alliance formation, and, hence, contribute to long-term group stability. Third, communicative networks also provide a means to facilitate the maintenance of group cohosion and decision-making processes. In conclusion, cost-benefit analyses at the level of dyadic interactions reveal clear differences with communication networks, where repeated interactions with multiple partners are considered. Future communication models and empirical studies should therefore consider the composition of the entire communication network as well as the effects of repeated interactions to fully understand signalling interactions in social groups