Nonhuman primates use greeting behaviors as nonaggressive communicatory signals in multiple social contexts. Adult male mantled howlers (Alouatta palliata) perform a ritual greeting that has been associated with bond-strengthening functions. The aim of this study is to explore the greeting patterns of male howlers living on Agaltepec Island, Mexico. Specifically, we analyzed the relationships between greetings and several individual, relational, and contextual variables, such as the expression of affiliation and agonism, dominance rank, age, kinship relationships, spatial organization, activity patterns, and subgrouping patterns. Greetings were more frequent between males with closer dominance ranks. Among those dyads that greeted at least once, dominant males initiated greetings more frequently than less-dominant males. On the other hand, more greetings were observed when one of the participants had recently returned to a subgroup and during locomotion. On the basis of these results, we propose that on Agaltepec greetings are a conflict management mechanism used between males of similar ranks. The fission-fusion social system of this group of howlers allows males with conflicting interests to remain separated, and greetings may reduce tension during fusion events.

To develop effective conservation and management actions, it is important to examine anthropogenic disturbance patterns and their impact on wildlife. We examined variation in the behavioral and physiological stress response of the Critically Endangered Mexican mantled howler monkeys Alouatta palliata mexicana in relation to two types of anthropogenic disturbance, habitat spatial patterns and presence of humans or their livestock (noise and presence nearby primates). We studied four groups (42 individuals) in two forest fragments at the Los Tuxtlas Biosphere Reserve for a total of 1100 observation hours, during which we recorded the howler monkeys’ vocalizations, locomotion and vigilance. We additionally collected fecal samples to determine the concentrations of glucocorticoid metabolites (fGCM). Howler monkeys vocalized less and moved more when in more spatially disturbed locations and when exposed more time to nearby noise but spent less time in locomotion when humans were present. fGCM were only related to human presence, suggesting that habitat spatial patterns are less of a challenge than human presence. This may be related to the generally unpredictable nature of the latter. Although our study does not allow determining whether the behavioral and physiological responses of howler monkeys to disturbance are costly, from a conservation standpoint it may be more prudent to assume that they are and design strategies to mitigate them. In this sense, actions aimed at reducing anthropogenic noise could benefit the conservation of Mexican mantled howler monkeys.

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To date, no study has investigated how human disturbance affects the size of the behavioral repertoire of a species. The aim of the present study is to illustrate how measurement of behavioral diversity assists in documenting biodiversity loss, demonstrating that human disturbance has a negative effect on behavioral diversity. We studied the social interaction repertoire of 41 adult black howler monkeys (Alouatta pigra) belonging to 10 groups living in different habitats in Campeche (Mexico), and related repertoire size to a proxy of human-induced habitat disturbance, habitat size. The social interaction repertoire of groups living in habitats with higher human-induced disturbance included lower number of behavioral types, and in particular, fewer energy-demanding behaviors. Thus, in addition to a loss in biodiversity, measured through organismal diversity, the disturbance of black howler monkeys' habitats is accompanied by a loss in behavioral diversity. We believe that the study of behavioral diversity as an element of biodiversity will become an increasingly important research topic, as it will improve our understanding of the behavioral strategies displayed by wildlife facing anthropogenic disturbance.

Diel activity rhythms in mammals are regulated by an endogenous (circadian) timing system which is synchronized by environmental 24-hr periodicities called zeitgebers.Additional direct responses to stochastic environmental factors ensure the fine-tuning to the actual situation and may mask the circadian time course. Following an observational study on behavioral effects of visitor activities in a group of spider monkeys (Ateles geoffroyi) kept free-ranging on a small island of Lake Catemaco, Veracruz, Mexico, we analyzed the effect of weekly varying numbers of visiting tourist boats on the monkeys' diel activity rhythm. With small accelerometer-data logger devices we recorded the monkeys' locomotor activity continuously for several months each. Then we compared the data with those from spider monkeys living without tourist contact. Neither the duration of the monkeys' activity time (α) nor its phase relationship to the 24-hr solar day did change on different weekdays in either site. However, their activity level showed a clear 7-day rhythm. The monkeys of the tourist site showed highest activity on Saturday and Sunday, when the frequency of visiting tourist boats was highest, whereas those of the non-tourist site were least active on Sunday and Monday, when human activities were lowest there. While the monkeys of the nontourist site usually displayed a distinct bimodal activity pattern peaking in the morning and late afternoon, the pattern in those of the tourist site mostly lacked a morning peak and varied more over time. Based on our results, we suggest that circadian entrainment is not involved in the differences between the diel activity rhythms of the spider monkeys from the two keeping sites and the differing 7-day variation in their activity level. Rather, these differences seemingly reflect direct responses to the differing human activities and thus may correspond to circadian masking effects. K E Y W O R D Sactivity pattern, circadian rhythm, circaseptan rhythm, masking effect, zoo visitor effect