Positional behavior of black-handed spider monkeys (Ateles geoffroyi), including a one-armed individual, at El Zota Biological Field Station, Costa Rica

Adaptions to arboreal habitats result in species-specific patterns of locomotion and postures in non-human primates. Having a range of positional behaviors enables spider monkeys (Ateles spp.) to manage the varying aspects of habitat structure that may hinder their access to preferred food sources, escape predators and myriad of other challenges to an arboreal primate. This study presents new data on the positional behavior and habitat use of black-handed spider monkeys (A. geoffroyi) living in lowland tropical rainforest in northeastern Costa Rica, a habitat that is common for the species but where they are not well-studied due to the challenges of this wet environment. The contexts of travel and foraging were compared to observe context-specific postural and locomotor behaviors. Comparisons of locomotor and postural behaviors between contexts approached significance when all individuals were analyzed as a whole. However, results did not reveal significant differences between sexes or age-classes within these contexts. This may be indicative of the value of certain positions when exploiting the environment, regardless of sex or age-class. This study also included data on a one-armed juvenile male spider monkey (JF) to observe his varied use of postural and locomotor modes when compared to the A. geoffroyi at the site with all functioning limbs. Overall, his positional behavior appears to mimic that of the other spider monkeys, though results reveal behaviors unique to JF, as well. JF adjusted to accommodate his missing limb in ways to improve his efficiency during daily activities, such as decreasing use of positions involving the forelimbs. Aspects of social behavior were recorded, as well, to assess JF’s social development in comparison to others in his age-class, though the sample size was small. Few encounters yielded social data on JF or other juvenile males, but in interactions with adult males, all of the immature monkeys exhibited similar behavior

Thermo-imaging bipedalism on the savanna: Chimpanzee locomotion at Fongoli, Senegal and implications for the evolution of hominin bipedalism

Pressures associated with savanna habitats, such as heat stress, are often cited to explain adaptive traits in hominins, like the evolution of bipedalism. Wheeler’s (1984) physiological model, for instance, predicts that bipedal posture reduces contact with UV radiation by lessening the total body area exposed to direct sunlight. Chimpanzees occupying a savanna mosaic environment provide a unique opportunity to assess aspects of these hypotheses, such as how thermal stresses impact furred apes in a hot, arid and open environment. This study followed chimpanzees at the Fongoli site in Senegal, as they are thus far the only habituated savanna woodland community. Chimpanzees here display more bipedal behavior than is observed at other sites and are known to soak in pools and use caves to cope with heat stress. Apes here are, therefore, good living primate models to use in assessing selective pressures associated with hot, arid savanna environments. This research tested the hypothesis that body temperature differs between the array of positional behaviors used by West African chimpanzees throughout their home range; more specifically, bipedalism was predicted to correlate with a lower chimpanzee body temperature when compared to quadrupedal positions. Using a thermo-imaging camera to record individual body temperatures, I evaluated the heat load related to various postural and locomotor behaviors, specifically that of bipedalism. Results reveal lower body temperatures associated with bipedalism when compared to positions like sit and quadrupedal stand. These data offer support to models of hominin evolution that suggest bipedalism confers a thermoregulatory advantage

Thermo-imaging bipedalism on the savanna: Chimpanzee locomotion at Fongoli, Senegal and implications for the evolution of hominin bipedalism

Pressures associated with savanna habitats, such as heat stress, are often cited to explain adaptive traits in hominins, like the evolution of bipedalism. Wheeler’s (1984) physiological model, for instance, predicts that bipedal posture reduces contact with UV radiation by lessening the total body area exposed to direct sunlight. Chimpanzees occupying a savanna mosaic environment provide a unique opportunity to assess aspects of these hypotheses, such as how thermal stresses impact furred apes in a hot, arid and open environment. This study followed chimpanzees at the Fongoli site in Senegal, as they are thus far the only habituated savanna woodland community. Chimpanzees here display more bipedal behavior than is observed at other sites and are known to soak in pools and use caves to cope with heat stress. Apes here are, therefore, good living primate models to use in assessing selective pressures associated with hot, arid savanna environments. This research tested the hypothesis that body temperature differs between the array of positional behaviors used by West African chimpanzees throughout their home range; more specifically, bipedalism was predicted to correlate with a lower chimpanzee body temperature when compared to quadrupedal positions. Using a thermo-imaging camera to record individual body temperatures, I evaluated the heat load related to various postural and locomotor behaviors, specifically that of bipedalism. Results reveal lower body temperatures associated with bipedalism when compared to positions like sit and quadrupedal stand. These data offer support to models of hominin evolution that suggest bipedalism confers a thermoregulatory advantage.</p

Positional behavior of black-handed spider monkeys (Ateles geoffroyi), including a one-armed individual, at El Zota Biological Field Station, Costa Rica

Adaptions to arboreal habitats result in species-specific patterns of locomotion and postures in non-human primates. Having a range of positional behaviors enables spider monkeys (Ateles spp.) to manage the varying aspects of habitat structure that may hinder their access to preferred food sources, escape predators and myriad of other challenges to an arboreal primate. This study presents new data on the positional behavior and habitat use of black-handed spider monkeys (A. geoffroyi) living in lowland tropical rainforest in northeastern Costa Rica, a habitat that is common for the species but where they are not well-studied due to the challenges of this wet environment. The contexts of travel and foraging were compared to observe context-specific postural and locomotor behaviors. Comparisons of locomotor and postural behaviors between contexts approached significance when all individuals were analyzed as a whole. However, results did not reveal significant differences between sexes or age-classes within these contexts. This may be indicative of the value of certain positions when exploiting the environment, regardless of sex or age-class. This study also included data on a one-armed juvenile male spider monkey (JF) to observe his varied use of postural and locomotor modes when compared to the A. geoffroyi at the site with all functioning limbs. Overall, his positional behavior appears to mimic that of the other spider monkeys, though results reveal behaviors unique to JF, as well. JF adjusted to accommodate his missing limb in ways to improve his efficiency during daily activities, such as decreasing use of positions involving the forelimbs. Aspects of social behavior were recorded, as well, to assess JF’s social development in comparison to others in his age-class, though the sample size was small. Few encounters yielded social data on JF or other juvenile males, but in interactions with adult males, all of the immature monkeys exhibited similar behavior.</p