Watch out or relax: conspecifics affect vigilance in wild spider monkeys (Ateles geoffroyi)

In most animal species, predation risk is considered the main factor affecting vigilance, and an individual is expected to spend less time vigilant in larger than in smaller groups. However, vigilance patterns in primates appear to differ, with no consistency in group-size effects. As individuals in highly gregarious species such as diurnal primates face frequent threats from group members, there may be increased vigilance in larger groups to monitor conspecifics rather than or in addition to predators. We tested this hypothesis in wild spider monkeys, which live in communities but fission and fuse in subgroups of variable size and membership throughout the same day. We found no overall effect of subgroup size, as traditionally measured, on vigilance. However, a possible explanation is that vigilance may be effectively shared only with individuals in close proximity, rather than with all subgroup members. We found that a larger number of neighbours (i.e., subgroup members within 5 m) was associated with a lower proportion of time individuals spent vigilant, which is similar to findings in other studies. Another social factor that may affect individuals’ vigilance is the possibility of between-community encounters. Higher levels of vigilance can be expected in areas closer to the boundary of the home range, where between-community encounters are more likely to occur compared with non-boundary areas. We found that location in terms of boundary vs. non-boundary areas had a significant effect on the time individuals spent vigilant in the expected direction. We also found that location modulated the effect of subgroup size on vigilance: only in the boundary areas did larger subgroup sizes result in less individual vigilance time. We concluded that conspecifics affect vigilance of wild spider monkeys in multiple ways

Relationship quality affects fission decisions in wild spider monkeys (Ateles geoffroyi)

Fission-fusion dynamics are thought to be mainly a response to differential availability of food resources. However, social factors may also play a role. Here, we examined whether the quality of social relationships between group members affects fission decisions. During 21 months, we collected data on social interactions and fission events of 22 spider monkeys (Ateles geoffroyi) living in a community in the protected area of Otoch Ma'ax Yetel Kooh, Yucatan, Mexico. By entering seven indexes of social interactions into a principal component analysis, we obtained three components of relationship quality, which we labelled "compatibility," "value" and "insecurity" given the relative loadings of the indexes. Our results showed that individuals were more likely to fission into the same subgroup with community members with whom they shared higher levels of compatibility and value and lower levels of insecurity. In addition, individuals preferred to fission into the same subgroup with same-sex group members, as expected based on what is known for the species. Our findings highlight the role of social factors in fission decisions. Adjustments in subgroup size are based on multifaceted social preferences, incorporating previously unexamined aspects of relationship quality, which are independent from overall levels of affiliative interactions. © 2017 Blackwell Verlag GmbH

Watch out! Insecure relationships affect vigilance in wild spider monkeys (Ateles geoffroyi)

Abstract: Vigilance is used to monitor extra-group threats as well as risky group members. We examined whether relationship quality affects vigilance patterns of spider monkeys. We used focal animal sampling to collect data on social interactions and individual vigilance of all adults and subadults (N = 22) in a community of well-habituated Geoffroy’s spider monkeys living in the protected area of Otoch Ma’ax Yetel Kooh, Yucatan, Mexico. Through a principal component analysis of seven indices of social interactions, we previously obtained three components of relationship quality, reflecting the levels of compatibility, value, and security. Such components could differentially affect vigilance depending on whether vigilance is directed to extra-group threats or risky group members. We tested whether an individual’s vigilance was affected by (1) the mean level of compatibility, the mean level of value and the mean level of security across subgroup members; (2) the lowest level of compatibility, the lowest level of value, and the lowest level of security with any subgroup member; and (3) the mean level of compatibility, the mean level of value, and the mean level of security with neighbors (i.e., subgroup members within 5 m). We did not find evidence for any effect of compatibility and value; however, security did affect vigilance, as individuals were more vigilant when they had a less secure relationship with the subgroup member with the lowest level of security or with the average neighbor. Significance statement: Vigilance for monitoring group members is common in primate species. We examined whether the quality of social relationships with subgroup members and neighbors modulates vigilance in wild spider monkeys. We used three components of relationship quality (reflecting the levels of compatibility, value, and security) and predicted each component would affect vigilance depending on whether vigilance was directed to extra-group threats or risky group members. We found no evidence that compatibility and value affected vigilance. However, an increase in vigilance occurred when spider monkeys had a less secure relationship with (1) the subgroup member with the lowest level of security and (2) the average neighbor. Our results show monitoring risky group members is an important component of vigilance, especially in species facing low predation pressure. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

Same-sex sexual behavior in brown-headed spider monkeys (Ateles fusciceps fusciceps) during grappling between two subadult males.

Sexual behavior in animals fulfills reproductive and social functions, extending beyond the traditional focus on reproduction. Same-sex sexual behavior, defined as genital contact or manipulation between individuals of the same sex, occurs in various primate species. In spider monkeys, grappling, a behavior involving prolonged mutual embraces, face greeting, tail intertwining, and genital manipulation, occurs primarily between males. Here, we report a novel incidence of same-sex sexual behavior and grappling between two subadult male brown-headed spider monkeys (Ateles fusciceps fusciceps). Our observation contributes to the understanding of the social functions of sexual behavior and to the broader appreciation of primate sexuality

Predation Attacks on Wild Spider Monkeys (Ateles geoffroyi).

We report 2 cases of predation on an adult and a subadult spider monkey (Ateles geoffroyi) by a puma (Puma concolor) and an unidentified terrestrial predator at the natural protected area of Otoch Ma'ax yetel Kooh, in the Yucatan Peninsula, Mexico. Although spider monkeys are believed to experience overall low predation pressure compared to other primate species, our observations show that predation occurs in the study area and therefore behavioral strategies are likely to be in place to reduce predation risk. Our observations are further evidence that terrestrial predators are a threat for both young and full-grown spider monkeys

The impact of the establishment of otoch ma’ax yetel kooh protected area (YucatÁn, mexico) on populations of two neotropical primates

In 2002, Otoch Ma’ax Yetel Kooh (OMYK) was decreed a federal Flora and Fauna Protected Area in the state of Yucatán, Mexico, resulting in bans on hunting, logging and slash-and-burn agriculture within its limits. Our aim was to evaluate the influence of the establishment of the protected area on local primate populations. We compared relative abundances of Geoffroy’s Spider Monkeys (Ateles geoffroyi) and Black Howler Monkeys (Alouatta pigra) in mature and secondary forest before OMYK was established (in 1998) and 13 years after (in 2015). In both years, the relative abundance of Spider Monkeys was higher in mature than in secondary forest and Howler Monkeys were found exclusively in mature forest. The overall similarity in Spider and Howler Monkey relative abundances over time when mature and secondary forests are considered together is likely because the primates were not hunted and logging was not carried out prior to the establishment of the protected area. Benefits to wildlife of banning slash-and-burn agriculture take longer to become apparent. Still, the legal status of the protected area is critical to defend this site from future land-use changes and it allows the secondary forests to age, thereby increasing habitat for the primate populations

How Survey Design Affects Monkey Counts: A Case Study on Individually Recognized Spider Monkeys (Ateles geoffroyi).

The fast movement and high degree of fission-fusion dynamics of spider monkeys (Ateles spp.) make them notoriously difficult to survey. We examined which aspects of survey design affect spider monkey sightings along transects in a group of individually recognized spider monkeys (Ateles geoffroyi) in Punta Laguna, Yucatan, Mexico. We calculated the number of monkeys and subgroups sighted per transect walk. Using generalized linear models, we found no effect of the number of observers, transect type (new vs. existing), walking speed, or time of day on individual monkey counts or subgroup counts. Recounting of individuals was relatively rare and occurred when transects were walked relatively slowly. We missed more young than adult monkeys. The group composition based on survey data was similar to the known group composition. Based on our findings we recommend that surveys performed on relatively flat terrain be conducted at speeds similar to or faster than the moving speed of spider monkeys to minimize recounting of individuals and that young:adult female ratios based on survey data be interpreted as conservative indicators of population health. The novel methods presented to determine sources of bias in population estimates are applicable to a wide range of primates that are difficult to survey

Differential impact of severe drought on infant mortality in two sympatric neotropical primates

Extreme climate events can have important consequences for the dynamics of natural populations, and severe droughts are predicted to become more common and intense due to climate change. We analysed infant mortality in relation to drought in two primate species (white-faced capuchins, Cebus capucinus imitator, and Geoffroy's spider monkeys, Ateles geoffroyi) in a tropical dry forest in northwestern Costa Rica. Our survival analyses combine several rare and valuable long-term datasets, including long-term primate life-history, landscape-scale fruit abundance, food-tree mortality, and climate conditions. Infant capuchins showed a threshold mortality response to drought, with exceptionally high mortality during a period of intense drought, but not during periods of moderate water shortage. By contrast, spider monkey females stopped reproducing during severe drought, and the mortality of infant spider monkeys peaked later during a period of low fruit abundance and high food-tree mortality linked to the drought. These divergent patterns implicate differing physiology, behaviour or associated factors in shaping species-specific drought responses. Our findings link predictions about the Earth's changing climate to environmental influences on primate mortality risk and thereby improve our understanding of how the increasing severity and frequency of droughts will affect the dynamics and conservation of wild primates

Anthropogenic habitat disturbance and food availability affect the abundance of an endangered primate: a regional approach

Anthropogenic habitat disturbances are causing large-scale declines in animal abundance. For many species, information on the drivers of decline is lacking or restricted to single sites, despite calls for regional approaches. In this study, we determined the effect of different types of habitat disturbance (natural or anthropogenic) and ecological factors on Geoffroy’s spider monkey (Ateles geoffroyi) abundance using a regional approach. We selected this study species because of its high degree of social flexibility and its endangered status. We surveyed 4 sites in the Yucatan Peninsula and recorded the number of individual monkeys encountered along 72 line-transect segments each measuring 500 m. Habitat disturbance variables were obtained from open-access databases and included distance to roads, presence and number of hurricanes, forest loss, and presence of forest fires. Ecological factors were based on data collected during vegetation surveys and included number and basal area of feeding tree species, and canopy height. We ran generalized linear mixed models and found that monkey abundance was negatively affected by forest loss but positively affected by the basal area of feeding trees. We, therefore, suggest that a combination of anthropogenic and ecological factors affects spider monkey abundance. Spider monkey’s high degree of social flexibility may be a mechanism allowing them to adjust to changes in their environment when canopy connectivity is not lost. Our results provide policy and conservation decision makers with key information to develop regional conservation plans. Additionally, our methods can be used to identify the factors that affect the abundance of other mammal species. © 2020, Deutsche Gesellschaft für Säugetierkunde

Lymphatic marker podoplanin/D2-40 in human advanced cirrhotic liver- Re-evaluations of microlymphatic abnormalities

<p>Abstract</p> <p>Background</p> <p>From the morphological appearance, it was impossible to distinguish terminal portal venules from small lymphatic vessels in the portal tract even using histochemical microscopic techniques. Recently, D2-40 was found to be expressed at a high level in lymphatic endothelial cells (LECs). This study was undertaken to elucidate hepatic lymphatic vessels during progression of cirrhosis by examining the expression of D2-40 in LECs.</p> <p>Methods</p> <p>Surgical wedge biopsy specimens were obtained from non-cirrhotic portions of human livers (normal control) and from cirrhotic livers (LC) (Child A-LC and Child C-LC). Immunohistochemical (IHC), Western blot, and immunoelectron microscopic studies were conducted using D2-40 as markers for lymphatic vessels, as well as CD34 for capillary blood vessels.</p> <p>Results</p> <p>Imunostaining of D2-40 produced a strong reaction in lymphatic vessels only, especially in Child C-LC. It was possible to distinguish the portal venules from the small lymphatic vessels using D-40. Immunoelectron microscopy revealed strong D2-40 expression along the luminal and abluminal portions of the cell membrane of LECs in Child C-LC tissue.</p> <p>Conclusion</p> <p>It is possible to distinguish portal venules from small lymphatic vessels using D2-40 as marker. D2-40- labeling in lymphatic capillary endothelial cells is related to the degree of fibrosis in cirrhotic liver.</p