Increasing population density can increase infectious disease risk and thus reduce population growth and size. Host-parasite interactions of threatened animals that remain in small protected forest fragments therefore need to be monitored carefully. Due to extreme conservation efforts, the mountain gorilla (Gorilla beringei beringei) population in the 450-km2 Virunga Massif has more than doubled since 1973, reaching 604 individuals in 2016. To better understand changes in the transmission risks of soil-borne and other enteric pathogens for mountain gorillas, we determined defecation outputs of different age-sex classes and the diurnal variation in feces deposition. We weighed 399 wet fecal samples deposited at nest sites and on trails between nest sites by gorillas of varying age and sex, determined by lobe diameter, from five social groups (n = 58 gorillas) that range in the Volcanoes National Park, Rwanda. We found increasing daily average defecation outputs with increasing age-sex class (infants, 435 g; juveniles, 1346 g; medium-sized gorillas, 2446 g; silverbacks, 3609 g). Gorillas deposited two- to threefold the amount of feces at nest sites compared to on trails, suggesting that nest sites may function as hotspots for enteric pathogen infections through direct contact or when gorillas ingest foods contaminated with infectious larvae during site revisits in intervals matching the maturation period of environmentally transmitted gastrointestinal parasites. In combination with ranging and demographic data, these findings will enable the modeling of spatiotemporal variation in soil contamination and infectious disease risk for Virunga gorillas as their population density continues to increase.
- MeSH
- defekace fyziologie MeSH
- feces * MeSH
- Gorilla gorilla fyziologie MeSH
- hnízdění MeSH
- věkové faktory MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Rwanda MeSH
The effects of social separation, including vocalization, have been studied for a very long time in non-human primates under laboratory conditions. As part of the long-term research on the vocal behaviour of Nomascus gibbons in zoos, this study provides the first record of calls of the southern yellow-cheeked gibbon (Nomascus gabriellae) in response to involuntary separation. Our study revealed that calls were also emitted by an infant (aged 1 year 8 months), and that the acoustic structure of the infant's calls was similar to that of older individuals' calls. Separation-induced calls seem to have a shorter developmental convergence than vocalizations with a stable pattern (which are specific for species and sex). The acoustic structure of the calls reported here comprised simple syllables, and differed from the sex- and species-specific vocal patterns of this species. Our findings demonstrate a novel paradigm in this genus, and provide evidence of the ability of gibbons to express distress when socially separated.
- MeSH
- Hylobatidae fyziologie MeSH
- sociální chování * MeSH
- věkové faktory MeSH
- vokalizace zvířat * MeSH
- zvířata v ZOO fyziologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Functional explanations for loud calling in nocturnal primates include territorial or sexual advertisement, maintenance of cohesiveness, and group coordination. It is generally accepted that loud calls of lesser galagos (genus Galago) are used for territorial advertisement and long-distance spacing. Field studies suggest that they are uttered at dusk and dawn, when the animals leave and reunite at their sleeping sites. However, empirical validation of these inferences is lacking. We conducted 16-night-long acoustic monitoring of a northern lesser galago (G. senegalensis) population in Senegal and quantified the occurrence of loud calls throughout the night. We hypothesized that significantly more of these calls would be emitted at dusk and dawn if they were used for territorial advertisement and long-distance spacing. This hypothesis was only partially supported, as we found an asymmetrical distribution of loud calls, which significantly increased only before and at dawn. The finding that the relatively early increase in vocal activity was not directly related to approaching and entering sleeping sites suggests that the northern lesser galagos' loud calls differ in function from reassembly calls described for other species of nocturnal primates. Furthermore, the early onset cannot be explained by changes in the intensity of sunlight, moonlight or starlight, which suggests that a different stimulus, most likely internal, elicits early-morning calling behavior in northern lesser galagos.
- MeSH
- akustika MeSH
- cirkadiánní rytmus MeSH
- Galago fyziologie MeSH
- světlo MeSH
- vokalizace zvířat * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Senegal MeSH
Animals' reactions to novel objects vary not only with zoological taxa and their ecology but also in the types of presented stimuli, the context, and individual characteristics. Behavioral reactions can vary from extremely neophobic (avoiding novel objects) to extremely neophilic (intense exploration of novel objects); most often, a mixture of these behavioral patterns appears. In primates, reactions toward novel objects vary according to species, age, sex, population, and the types of objects. Most experiments in this field have used a free exploration design with food or non-food objects. Here, we tested the reactions of captive male rhesus macaques using various stimuli, motivation levels, rewards, and time limits. We found that the monkeys explored and manipulated novel objects in various contexts, with little evidence of a neophobic response; however, environment, types of stimuli, and other parameters of the test can significantly affect monkeys' reactions.
- MeSH
- chování zvířat * MeSH
- Macaca mulatta fyziologie MeSH
- odměna MeSH
- pátrací chování * MeSH
- zvířata v ZOO MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Production of species- and sex-specific vocalisation is a trait characteristic of all gibbons. However, the mechanisms of gibbon vocalisation ontogeny and the manner of developing sex-specific vocal patterns are not yet known. We recorded vocal behaviour of a juvenile male northern white-cheeked gibbon (Nomascus leucogenys). The male produced female-specific great calls. Out of 163 great-call sequences recorded during six sessions, the juvenile son joined in 157 cases with its own great call. In addition, we observed that the juvenile male improved the structure of great calls during the study by including the twitter part. Our results indicate an interesting pattern of vocal ontogeny in Nomascus and suggest a certain degree of plasticity in the vocal signalling in gibbons.
- MeSH
- Hylobates fyziologie MeSH
- vokalizace zvířat * MeSH
- zvířata v ZOO fyziologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
Primates have been predated on by snakes throughout their evolution and as a result, antipredator responses accompanied by signs of fear are often witnessed in the wild. In captivity, however, the fear of snakes is less clear, as experiments with naïve nonhuman primates have given inconsistent results. In this study, we present evidence that naïve mouse lemurs (Microcebus murinus) and putatively naïve pig-tailed macaques (Macaca nemestrina) do exhibit fear of snakes, even though the apparent reactions are mild. In an experiment with control- or snake-odoured boxes, mouse lemurs clearly avoided feeding in the latter. When the latency of touching rubber models was measured, pig-tailed macaques took longer to touch a toy snake compared with a toy lizard. Our findings that fear of snakes is shown by naïve individuals support the hypothesis that it is innate in primates.
