Apes share a distinct set of morphological and anatomical characteristics that allow us to use our arms and hands in unique ways. Apes also have relatively larger brains with similar sulcal patterning indicating there is a distinctively hominoid brain structure. These features in great apes have consistently been linked with higher cognitive skills and are considered to be the precursors leading to the exceptional developments of humans over evolutionary time – establishing the physiological basis that allows us to make and use tools to modify our environments and build our unique cultures. This study examines the general model that orthogrady and suspensory postures were the antecedents for enhanced manipulative ability in apes, which consequently set the stage for enhanced cognitive abilities in early hominoids. The primary hypothesis is that if single-handed prehensility is enhanced by suspensory orthogrady, then we may predict ape feeding style will differ significantly from that of pronograde monkeys, allowing them to access foods in unique ways. Using sympatric white-handed gibbons, Hylobates lar, representative of orthograde apes, and pig-tailed macaques, Maccaca leonina, representative of pronograde monkeys, as models, the comparative feeding styles of primates were analyzed focusing on their positional behaviour and manual skill. Results support the hypothesis that gibbons exhibit a unique feeding style associated with their orthogrady/suspensory postures in comparison with pronograde macaques. This was demonstrated by their increased access to food in the trees with more stable postures, an expanded foraging radius, and more frequent use of the terminal branches, and was evident in their complex manipulative skills with larger manual repertoires, more variability in wrist use, and more sophisticated manual techniques. Moreover, significant differences in positional behaviour and manual skill demonstrated by gibbons and macaques were evident even when feeding on the same types of foods within their shared environment. This study proposes that the combined uniquely ape traits to forage in suspensory orthograde postures with precision dexterity have allowed apes to become highly selective feeders within their environments, leading to advance manual dexterity and cognitive prowess in apes.

The conversion of a memory from an initially fragile state to an enduring representation requires cellular, molecular, and systems-level brain network changes. This reorganization is hypothesized to involve time-dependent neuroanatomical changes that may differentially support some types of remote versus recent memory, and may also influence the latency to decide and complete responses during retrieval. To quantify the timecourse of learning and retrieval after different retention durations, a paradigm is developed to measure in humans and monkeys the retrieval speed of visuomotor associations, which require an intact hippocampus for initial acquisition but not for retrieval after days or weeks. Two components of retrieval speed, a decision time to initiate movement and a velocity-dependent movement completion time to complete a motor response, are shown to change differently relative to a pre-retention baseline. Movement completion times decrease across repetitions within single learning session, and continue to decrease from the level reached at the end of learning following retention. Decision times also decrease within the learning session, but increase on the first post-retention retrieval attempt as a function of retention interval duration. Extensive practice is required for decision times to reach a level below that obtained at the end of learning, and the transition from a long- to short-latency decision depends on the number and spacing of practice trials. The findings are discussed in a framework in which post-retention processing time is influenced by the speed of visual identification, the time to retrieve the associative relationship from long-term memory, and the time to plan and execute a motor response. The creation of sparser, long-lasting visual form representations and strengthened cortico-striatal connections predict behavioral efficiency gains in visual identification and motor responses after learning. Decision times could be fast and automatic following extensive practice when the neural representation may become stored permanently in cortico-cortical and cortico-striatal linkages, or could increase after retention because of several cognitive and neural factors, including interference and frontal inhibition of the hippocampal system to prevent new learning before choice feedback. The experimental results are discussed in the context of the existing literature on memory consolidation.

According to the International Union for Conservation of Nature and Natural Resources (IUCN), 64% of primate species are declining in the wild and 49% face a significant risk of extinction. This crisis is largely the result of human activity, including logging, ranching, and hunting. In this study I examine the impacts of the anthropogenic habitat disturbances associated with cattle ranching on a primate community. Research was conducted at the preeminent site for the study of rain forest fragmentation, the Biological Dynamics of Forest Fragments Project, Manaus, Brazil. I surveyed 8 line transects totaling 13 km that sampled: 1) secondary forest on abandoned cattle pasture,2) selectively logged primary forest, and 3) undisturbed primary forest. Specifically, I tested for edge effects, niche partitioning, and interhabitat differences in population density. Primate presence in edge habitats was negatively related to the amount of fruit consumed, a relationship that was also apparent in the densities of individual species. Four species were more abundant in edge habitats: Alouatta macconnelli (folivore-frugivore), Chiropotes chiropotes (seed predator), Saguinus midas (generalist), and Sapajus apella (generalist); one was less abundant: Ateles paniscus (frugivore); and the last showed no edge-related pattern: Pithecia chrysocephala (seed predator). Niche partitioning was evident in diet and macrohabitat use. In addition, in primary forest there was partitioning along several microhabitat variables. In secondary forest, however, microhabitat partitioning was absent, possibly due to habitat constraints or low encounter rates. Body size was positively related to use of vertical strata in both habitats, hence a combination of body size and competition may drive vertical niche partitioning. Primate characteristics were not related to their presence in selectively logged or undisturbed primary forest, though body size was inversely related to presence in secondary forest. Only the two generalists (Saguinus and Sapajus) heavily utilized secondary forest. The two largest species, Ateles (frugivore) and Alouatta (folivore-frugivore), showed an equal preference for all primary forest (logged and undisturbed) over secondary forest. Chiropotes (seed predator) also preferred undisturbed primary forest while Pithecia (seed predator) was relatively uniformly distributed. / acase@tulane.edu

abstract: Arguments of human uniqueness emphasize our complex sociality, unusual cognitive capacities, and language skills, but the timing of the origin of these abilities and their evolutionary causes remain unsolved. Though not unique to primates, kin-biased sociality was key to the success of the primate order. In contrast to ancestral solitary mammals, the earliest primates are thought to have maintained dispersed (non-group living) social networks, communicating over distances via vocalizations and scent marks. If such ancestral primates recognized kin, those networks may have facilitated the evolution of kin-biased sociality in the primate order and created selection for increased cognitive and communicative abilities. I used the gray mouse lemur (Microcebus murinus) to model whether vocalizations could have facilitated matrilineal and patrilineal kin recognition in ancestral primates. Much like mouse lemurs today, ancestral primates are thought to have been small-bodied, nocturnal creatures that captured insects and foraged for fruit in the thin, terminal ends of tree branches. Thus, the mouse lemur is an excellent model species because its ecological niche is likely to be similar to that of ancestral primates 55-90 million years ago. I conducted playback experiments in Ankarafantsika National Park, Madagascar testing whether mouse lemur agonistic calls contain matrilineal kin signatures and whether the lemurs recognize matrilineal kin. In contrast to large-brained, socially complex monkeys with frequent coalitionary behavior, mouse lemurs did not react differently to the agonistic calls of matrilineal kin and nonkin, though moderate signatures were present in the calls. I tested for patrilineal signatures and patrilineal kin recognition via mating and alarm calls in a colony with known pedigree relationships. The results are the first to demonstrate that a nocturnal, solitary foraging mammal gives mating calls with patrilineal signatures and recognizes patrilineal kin. Interestingly, alarm calls did not have signatures and did not facilitate kin recognition, suggesting that selection for kin recognition is stronger in some call types than others. As this dissertation is the first investigation of vocal kin recognition in a dispersed-living, nocturnal strepsirrhine primate, it greatly advances our knowledge of the role of vocal communication in the evolution of primate social complexity. / Dissertation/Thesis / Ph.D. Anthropology 2014

<p>To solicit the attention or determine the intentions of another, we use our eyes. While many animals appear to use eyes as an important behavioral cue, for humans, these cues are especially critical. The power of the eyes to attract and direct attention shapes human behavior from an early age and likely serves as a foundation for social skill acquisition, ranging from simple, friendly eye contact to complex, spoken language, even to our almost mystical ability to empathize and "see the world through another's eyes". Humans have transformed our environment through our economic alliances and military competitions, and our individual successes and failures depend critically on social skills built on a foundation of shared attention. When these abilities break down, as in autism, pervasive social awkwardness can challenge the close relationship of individuals with their friends, family, and community. Nonetheless, we know almost nothing about the brain mechanisms that have evolved to process social cues and convert them into a rich experience of shared attention. To investigate this process, we explored the ability of human and nonhuman primates to follow the attention of other individuals. First, we characterized natural gaze-following behavior using a novel telemetric device in socially-interacting prosimian primates, and later in monkeys and humans responding to gaze cues in the lab. Finally, we examined the neuronal responses to gaze cues in a macaque posterior parietal area implicated in attention control--the lateral intraparietal area, LIP. Our findings suggest that gaze-following abilities may be widespread in social primates, relying on conserved, homologous brain pathways; and that they may not be informationally-encapsulated reflexes, but rather are densely interwoven with diverse social processes. Indeed, we found gaze cues influenced neurons in LIP, part of the dorsal frontoparietal attention network. Finally, we report that "mirror" neurons in parietal areas may thus play a role not only in representing perceived bodily actions, but also perceived mental states such as observed attention.</p> / Dissertation

Operant conditioning using positive reinforcement techniques has been used extensively in the management of nonhuman primates in both zoological and laboratory settings. Based on a large body of previous research that demonstrates the utility of such techniques in reducing stress, abnormal behavior, and aggression, this research project was intended to develop and test the usefulness of habituation and counter-conditioning techniques in reducing the fear-responses of singly-housed male rhesus macaques living in the laboratory environment. Additionally, we investigated the variable of temperament as it relates to the reduction of fear-responsivity and overall training success. Based on a Wilcoxon Matched-Pairs Sign Test, we found that animals exposed to desensitization training were significantly likely to show a reduction in the rate at which they engaged in cringing toward humans (exact significance = .016, one-tailed, N ties = 6), cringing in general (exact significance = .016, one-tailed, N ties = 6), and in stress-related behaviors (exact significance = .016, one-tailed, N ties = 6). Animals exposed to basic husbandry training or exposed to no training at all were not significantly likely to show a reduction in the rates of these behaviors. When these same behaviors were analyzed in terms of duration of behavior, desensitization-exposed animals were significantly likely to show reduction in the amount of time spent cringing toward humans (exact significance = .016, one-tailed, N ties = 6), but not in cringing behaviors in general or in stress-related behaviors. Neither the husbandry-exposed group nor the group exposed to no training showed a significant number of subjects exhibiting a reduction in duration of any of these behaviors. Additionally, initial temperament assessments were found to significantly predict the relative ability of subjects exposed to training to acquire trained behaviors such that animals generally ranked as more inhibited in terms of temperament also ranked as slower learners based on a Wilcoxon Matched-Pairs Signed-Ranks test, z = -.316, p = .752 (two-tailed). Results of this study could enhance both laboratory animal welfare and laboratory animal research, and could be a first step in developing techniques for reducing fearful behavior in rhesus monkeys in the laboratory environment.

Pygmy tarsiers (Tarsius pumilus) of Central Sulawesi, Indonesia are the only species of tarsier known to live exclusively at high altitudes. This study was the first to locate and observe multiple groups of this elusive primate. This research tested the hypothesis that variation in pygmy tarsier behavior and morphology correlates with measurable ecological differences that occur along an altitudinal gradient. As a response to decreased resources at higher altitudes and the associated effects on foraging competition and energy intake, pygmy tarsiers were predicted to exhibit lower population density, smaller group sizes, larger home ranges, and reduced sexually selected traits compared to lowland tarsiers. Six groups containing a total of 22 individuals were observed. Pygmy tarsiers were only found between 2000 and 2300 m, indicating allopatric separation from lowland tarsiers. As expected, the observed pygmy tarsiers lived at a lower density than lowland tarsier species, in association with decreased resources at higher altitudes. The estimated population density of pygmy tarsiers was 92 individuals per 100 ha, with 25 groups per 100 ha. However, contrary to expectation, home range sizes were not significantly larger than lowland tarsier home ranges, and average NPL was smaller than those of lowland tarsiers. The average home range size for the observed pygmy tarsiers was 2.0 ha, and the average nightly path length (NPL) was 365.36 m. Pygmy tarsiers exhibited a nonrandom, clumped distribution near forest edges. While insect abundance and biomass were found to decrease as altitude increased, insect abundance and biomass was higher along anthropogenic edges. Thus, tarsiers within the study area may mitigate the decreased availability of insects at high altitudes by remaining close to forest edges, which in turn may be related to smaller than expected home range sizes. Further, estimates of pygmy tarsier abundance may be inflated because of increased insect abundance along anthropogenic edges. Contrary to the prediction for smaller group sizes as a response to feeding competition, the observed pygmy tarsiers lived in relatively large groups with multiple adult males. However, in support of the prediction for energetic constraints on body proportions, the observed pygmy tarsiers did not exhibit sexually selected traits. The pygmy tarsiers exhibited low sexual dimorphism and small relative testes mass, a trend opposite from lowland tarsier species, which may indicate a constraint on the development of those traits. Considered together, these results suggest that the observed pygmy tarsiers have adapted to life in an environment with limited resources. Future studies should explore the possible contributing effects of seasonality and topography.