Mammal assemblages in forest fragments and landscapes occupied by black howler monkeys

Demography and life-history parameters of mantled howler monkeys at La Flor de Catemaco: 20 years post-translocation

Translocations usually aim at maintaining and enhancing wild populations. Thus, the long-term monitoring of translocated individuals is critical for assessing translocation success. In this study, we report the demographic and life-history parameters of mantled howler monkeys that were translocated to La Flor de Catemaco (Los Tuxtlas, Mexico) to determine the success of the translocation process. Nine individuals belonging to two social groups living in areas that were going to be destroyed were released into La Flor de Catemaco between 2002 and 2004. Before 2022 there were no resident monkeys at the site. From January 2012 to December 2021, we recorded births, deaths, migrations, and group formation (1535 sampling days). The population grew until reaching 35 mantled howler monkeys. Two new groups including both individuals born at the site and migrants were founded. Mean ± SD group size was 8.1 ± 1.1 individuals. We recorded 42 births and 14 deaths, mostly of young infants (< 6 months of age). We recorded emigrations and immigrations of adult and immature individuals as well as several instances of individuals that remained and reproduced in their natal groups. Mean female age at first birth was 57.8 ± 18.5 months, interbirth intervals were 23.3 ± 11.3 months, and birth rates were 0.5 ± 0.2 births per female per year. The growth and persistence of the groups at the site, as well as similarity in demographic and life-history parameters between this and unmanaged populations, suggest that mantled howler monkeys living at La Flor de Catemaco represent a stable population and thus that this was a successful translocation.

Environmental Stress and the Primate Microbiome: Glucocorticoids Contribute to Structure Gut Bacterial Communities of Black Howler Monkeys in Anthropogenically Disturbed Forest Fragments

Animals living in anthropogenically disturbed habitats are exposed to environmental stressors which can trigger physiological reactions, such as chronic elevations of glucocorticoid hormones. Physiological responses to stressors may induce changes in the gut microbiome, most likely, facilitated by the gut–brain communication. Although these effects have been observed in humans and animal models, elucidating gut bacterial changes in wild animals under natural stressful conditions is still an ongoing task. Here we analyzed the association between physiological stress related to anthropogenic forest disturbance and changes in gut bacterial communities of black howler monkeys (Alouatta pigra) living in forest fragments in Mexico. We measured individuals’ fecal glucocorticoid metabolites (fGCMs) as an index of physiological stress and created inventories of fecal bacterial communities sequencing the 16S rRNA gene to assess gut microbiome change. We evaluated environmental stress by estimating differences in food availability – feeding tree diversity and biomass – in each group’s habitat. We found that both fGCMs and food availability indices were related to gut bacterial community shifts in black howler monkeys. Furthermore, using structural equation modeling, we found that a decrease in food availability, estimated through reductions in feeding tree basal area, increased fGCMs, which in turn induced increases in bacterial richness. Our findings show that the activation of the hypothalamic–pituitary–adrenal (HPA)-axis, which is a physiological response sensitive to environmental stressors such as the ecological disturbance of a habitat, contributes to structure the gut microbiome of arboreal primates in disturbed forests.

Validation of the Calakmul–Laguna de Terminos corridor for jaguarsPanthera oncain south-eastern Mexico

The fragmentation of jaguarPanthera oncapopulations as a result of habitat loss is considered to be one of the main challenges for the conservation of the species. Corridors have been proposed as a means of maintaining connectivity and the long-term viability of jaguar populations. The corridor that connects the jaguar conservation units of Calakmul and Laguna de Terminos in Mexico has been considered to be a link for the movement of individuals between these units but its functionality had yet to be verified. During 2012–2014 we divided the corridor into four sections, where we used camera traps to verify the corridor's functionality. We obtained 106 photographs of jaguars, proving the presence of jaguars (including resident jaguars and females) in three of the corridor sections. We did not record any individuals in more than one section of the corridor. The presence of several resident jaguars and females throughout the corridor suggests that portions of the corridor should be incorporated into the Calakmul and Laguna de Terminos jaguar conservation units. Nevertheless, to confirm that the corridor is fully functional it is necessary to obtain evidence of movement of jaguars among the various sections of the corridor. Our results suggest that the area should be included in regional conservation strategies.

Are interspecific associations of primates in the Western Ghats a matter of chance? A case study of the lion-tailed macaque

When animals or groups of animals in their wild habitats come close to each other within a defined distance, it is termed as an association. Observing two groups of the lion-tailed macaque at Nelliyampathy and Andiparai forests of the Western Ghats of India, we asked whether the lion-tailed macaque associations with the sympatric Nilgiri langur and bonnet macaque were by chance or had any biological significance. Employing ‘all occurrences’ sampling, we recorded an association if a group of another primate species came within 30 m of the focal group of the lion-tailed macaque. Date, time, associating species, activity of the study species and of the associating species, type of interaction, aggressor and the recipient, species displaced and duration of the association were recorded. We used the Waser gas model to calculate the expected frequency and duration of associations and compared them with the observed associations. The lion-tailed macaque spent less time in associations than expected. The lion-tailed macaque and the Nilgiri langur initiated associations less often, and remained in association for less time, than expected by chance. Whereas the expected and observed initiation of associations between the lion-tailed macaque and the Nilgiri langur in Nelliyampathy was significantly different (expected rate = 153; observed rate = 64), in Andiparai, it was not (expected rate = 55.5; observed rate = 61). The expected and observed association duration was significantly different in Nelliyampathy (expected duration = 54 min; observed duration = 15 min) and Andiparai (expected duration = 48 min; observed duration = 19 min). In contrast, we detected few differences between observed and expected association frequency for the lion-tailed macaque and the bonnet macaque. Aggressive interactions were common in areas where density of the Nilgiri langur groups was high. This is the first study on Asian primates using the ideal gas approach to show that primates do not form active associations with each other.