Uakari monkeys from the Amazon River basin are the most specialized primates in the Neotropical region. Their short tails, peculiar dentition and external morphology are strikingly divergent from most other platyrrhines. Furthermore, their geographical range is small and restricted to the forests in the floodplains of Amazonian Rivers. It is the only frugivorous primate able to live within the young várzeas (white-water river floodplain) of the Amazon. A 20-month study of the ecology of the white uakaris (Cacajao calvus calvus) was carried out in the floodplain located between the Japurá and Amazon Rivers in Brazilian Amazonia. The vegetation is unique in the way that it is able to cope with a 12-metre annual change in water level. This annual variation in water level is probably the most important overall ecological mechanism in várzea, influencing the temporal and spatial patterns of distribution of fruits. Several aspects of the ecology and ranging behaviour of the uakaris are associated with the temporal and spatial patterns of distribution of potential food sources: the seeds of immature fruits. Subdividing fruits into separate morphological classes is of fundamental importance for understanding this variation, which is largely influenced by the changes in water level. Foods of high quality, high energetic value and low in secondary compounds, are extremely important at most times of the year due to the Uakari's gut structure, metabolic requirements, use of space and, especially the topography of their habitat. Comparisons are made with another pithecine of similar morphology and diet, but which lives in the dry terra firrne forests. Based on their present distribution and ecological preferences, an attempt is made to trace the evolutionary history of these two largest pithecines. Furthermore, the role of riverine habitats in the zoogeographic and speciation patterns of primates within Amazonia is discussed.

No description available.

The energy frugality hypothesis states that in response to Madagascar’s unpredictable habitat, lemurs should adopt strategies of energy optimization. I have applied this hypothesis to lemur behavioural ecology in response to forest edges. I compared two groups of Propithecus coquereli living less than 1-km from a forest edge with two groups living greater than 1-km from the edge in Ampijoroa forest station, Ankarafantsika National Park, NW Madagascar. Edge effects in Ampijoroa penetrated up to 625-m into the forest. Propithecus coquereli were edge avoiders, with 94.54% of sightings of Propithecus coquereli found outside of the area of edge influence. There was no difference between group ranges for density of food trees, however tree diameter at breast height (dbh) and tree height did differ between groups. These habitat differences did not neatly divide edge versus interior groups, but appeared to be more nuanced. I found no differences between groups for activity budgets, food quality, or spatial patterns of plant species/ parts consumed. However, groups nearer to the edge had home ranges that were more than double in size to interior groups. Groups in the interior had higher group-specific densities and more frequent intergroup encounters which may have led groups to adopt smaller ranges to avoid expending energy in intergroup encounters. More evidence of human impact was found in the edge, therefore groups near the edge might also range further to avoid humans. Groups showed differences in the spatial pattern of behaviours, activity by age-sex category, substrate size and vertical location used while traveling, and dietary overlap. However, these differences may not be reflective of distance to the forest edge - all groups avoided the edge - but instead may reflect subtle differences in habitat structure between the four groups.

The energy frugality hypothesis states that in response to Madagascar’s unpredictable habitat, lemurs should adopt strategies of energy optimization. I have applied this hypothesis to lemur behavioural ecology in response to forest edges. I compared two groups of Propithecus coquereli living less than 1-km from a forest edge with two groups living greater than 1-km from the edge in Ampijoroa forest station, Ankarafantsika National Park, NW Madagascar. Edge effects in Ampijoroa penetrated up to 625-m into the forest. Propithecus coquereli were edge avoiders, with 94.54% of sightings of Propithecus coquereli found outside of the area of edge influence. There was no difference between group ranges for density of food trees, however tree diameter at breast height (dbh) and tree height did differ between groups. These habitat differences did not neatly divide edge versus interior groups, but appeared to be more nuanced. I found no differences between groups for activity budgets, food quality, or spatial patterns of plant species/ parts consumed. However, groups nearer to the edge had home ranges that were more than double in size to interior groups. Groups in the interior had higher group-specific densities and more frequent intergroup encounters which may have led groups to adopt smaller ranges to avoid expending energy in intergroup encounters. More evidence of human impact was found in the edge, therefore groups near the edge might also range further to avoid humans. Groups showed differences in the spatial pattern of behaviours, activity by age-sex category, substrate size and vertical location used while traveling, and dietary overlap. However, these differences may not be reflective of distance to the forest edge - all groups avoided the edge - but instead may reflect subtle differences in habitat structure between the four groups.

Primates have important ecological roles as seed dispersers and seed predators in tropical forests. Orangutans are large-bodied frugivores that consume a high diversity of plant species, however, relatively little is known about their ecological roles. Ecological interactions are critical processes for ecosystem dynamics, structures, and functions. This dissertation investigated Bornean orangutans’ (Pongo pygmaeus wurmbii) ecological roles by studying orangutan patterns of frugivory, seed dispersal, and seed predation, dispersed seed spatial patterns, and seed fate outcomes. This research was conducted at the Cabang Panti Research Station in Gunung Palung National Park, Borneo, Indonesia. Chapter 2 analyzes orangutan seed dispersal behavior using the seed dispersal effectiveness framework to identify which fruits orangutans are most effectively dispersing. Orangutans predated seeds more frequently than they spat or swallowed seeds. Additionally, the fruits preferred most by orangutans were highly predated. Despite the prevalence of seed predation, orangutans also frequently dispersed seeds, 71.8% of fecal samples contained seeds with a mean of 28 seeds (>2mm) per fecal sample. Chapter 3 models orangutan seed dispersal distances to understand how far orangutans are dispersing seeds across the landscape and if seeds are dispersed across habitat types. This study found orangutans dispersed seeds, on average, 400-650m. There were occasional long distance seed dispersal events, and the maximum dispersal distance was 2.2km. Both male and female orangutans dispersed seeds long distances (>1km). Unflanged male orangutans dispersed seeds the longest mean distances of the age-sex classes with the farthest mean maximum distances at the 80-hour gut retention time. In Chapter 4, the fate of seeds dispersed by orangutans is investigated along with the variation underlying the fate of dispersed seeds. Camera traps and seed tracking studies revealed the orangutan primary seed shadow was heavily reshaped post-dispersal. By 6-months post dispersal, most orangutan dispersed seeds (86-87%) had been removed, mostly by seed predators, and almost all of the remaining seeds (11-14%) had died. This dissertation reveals orangutans are involved in important ecological interactions. Orangutans disperse and predate high quantities of seeds from many plant genera, and the loss of the orangutan would likely negatively affect their natural ecosystems. / 2026-10-31T00:00:00Z

Cognitive research is the study of mental processes that guide behaviors and decision making in animals and humans. By studying the cognitive attributes of species within a taxon, as in the case of the order Primates, one can identify behavioral and cognitive components characteristic of certain taxa, such as families, species, or perhaps individuals. This allows us to estimate when and where these cognitive abilities arose in evolutionary history and to hypothesize about their cause and evolutionary origins. Episodic memory or episodic cognition gives an organism the ability to recall declarative forms of memories, which allows one to recall past experiences/histories and can then be used to teach, learn, or even promote socialization in many species (Dunbar, 2011). Additionally, it involves how that organism applies such memories to the past and future, thus allowing the organism to project “oneself” into time and space (Clayton, 2017). This is known as mental time travel or future-oriented memory. Scholars maintain that Homo sapiens (e.g. humans) have the most advanced degree of episodic memory (Suddendorf & Corballis, 2007; Tulving, 1985). However, when and how episodic and future-oriented memory evolved in the primate lineage, and if nonhuman and human episodic memory are comparable, is still unknown. Studying the foundation of this complex form of cognitive memory in a basal group of extant hominoids (apes), allows us to hypothesize about the phylogenetic, social, and perhaps objective mechanisms that were necessary for this complex cognitive system to evolve and persist throughout the primate lineage. Our current understanding of episodic memory is ambiguous, concerning what parts of the brain are truly utilized in this system and to what degree of episodic/future-oriented memory abilities are found throughout the animal kingdom. The current understanding is that very few taxa genuinely exhibit episodic memory capabilities (Allen & Fortin, 2013; Crystal & Suddendorf, 2019). The purpose of this research was to examine episodic/future-oriented memory in nonhuman primates, specifically in hylobatids (Family Hylobatidae), also known as small Asian apes, the gibbons, and siamangs. Hylobatids are small bodied, arboreal apes native to the tropical forests of Southeast Asia (Fleagle, 1976). Although apes, hylobatids have very different social, physical, and ecological distinctions from their larger-bodied cousins, the great apes (Reichard et al., 2016). These differences have often been used as a justification as to why hylobatid behavior and cognition have been postulated by some as “inferior” to the larger bodied great apes (Russon, 2004b; Tomasello & Call, 1997). However, without scientific evidence to back up this claim, we are still very unaware of the actual cognitive capabilities of these very cryptic small apes. In total, 12 hylobatid subjects were included in this study. Hylobates, Hoolock, Nomascus, and Symphalangus were used as representatives to investigate the episodic/future-oriented memory system of hylobatids by participating in a series of noninvasive, interactive, digital cognitive tasks presented on touchscreen technology and digital testing software. Subjects varied in age, sex, and life-histories and consisted of five different species, Symphalangus syndactylus, Hylobates pileatus, Hylobates mooloch, Hoolock leuconedys, and Nomascus leucongenys, within the four genera that make up the family Hylobatidae. To date, this is one of the largest and extensive cognitive studies done with hylobatids, and to my knowledge the only study investigating components of their episodic/future-oriented memory. The cognitive tasks employed in this study were a digitally based Paired Associates Learning Task (PAL) and Future-Oriented Memory Task (FOM). The PAL task was created by Cambridge Cognition, designed to assess acute visual episodic memory, and was employed using their Monkey CANTAB software (Cambridge Cognition). The FOM task was chosen to evaluate multiple aspects of episodic/future-oriented memory, including the “what, when, and where” paradigm, and assessment of executive function and anticipatory behavior of future-oriented memory associated with the episodic memory system. The digital portion of the FOM task was commissioned and designed by an independent software developer and was created using Python and Tkinter tool kit. Only one of the subjects (Jagger) chose to participate and complete the training procedure of the PAL task but did not meet the testing threshold to move on to the data collection portion of the task. All the other subjects attempted to participate in the PAL task but lost interest and failed to participate (not interacting with the touchscreen when PAL task was presented) after approximately ~<4 training sessions. Conversely, all subjects chose to participate in the FOM task in which three of the twelve participants performed above chance (>50%) in the task. With three subjects performing well above the predetermined threshold of >50% in the FOM task, which utilizes higher cognitive control including components of episodic/future-oriented memory, it can be established that hylobatids most likely possess the same cognitive hardware regarding complex cognitive memory as those of other extant apes. Thus, this study provides further evidence that complex cognition, including advanced episode-like/future-oriented memory capabilities, were present in the last common ancestor of all apes. Furthermore, subjects’ performances were statistically analyzed to see if age, sex, species, and or life history (LH) had an impact on task performance. There was no statistical significance between age, sex, species and/or LH for the individuals in this study, but this is most likely due to the smaller sample size and/or “uneven” number of individuals occupying each category. This is common in nonhuman primate cognition studies with ape subjects due to their endangered species status and scarcity in captive settings supporting cognitive research. The knowledge obtained by this research is significant to many different biological realms. In one aspect, this information strengthens our understanding of the cognitive traits the basal ancestor of all apes may have exhibited, therefore contributing to our understating of human cognitive origin. Furthermore, by understanding the cognitive attributes of a different species, we can further investigate their behavior and “species-specific” intelligence. For example, in-situ animal rehabilitation and reintroduction programs can use the results of this research to help maintain semi-captive populations while promoting educational programs, which can prevent human-wildlife conflicts. Additionally, both in-situ and ex-situ organizations/programs such as zoos, sanctuaries, laboratories, and rehabilitation centers can use the same information to design educational programs to promote animal welfare and conservation to the public, while simultaneously establishing new husbandry and enrichment protocols, which will promote progressive animal welfare (Cronin et al., 2017; Whitehouse et al., 2013). Note: The term hylobatid(s), gibbon(s), siamang(s), and small ape(s) are used in unanimity throughout this dissertation. All usage of such terms refers to an animal(s) that belongs to primate the family Hylobatidae.

No description available.

The Tropical Andes Biodiversity Hotspot holds a remarkable amount of species at risk of extinction due to climate change and human activities. One of these species, the Critically Endangered yellow-tailed woolly monkey (Lagothrix flavicauda), has experienced alterations in its known geographical range, along with a recent sighting in the region Junín, 206 kilometers south of previous observations, calling for a re-evaluation of potential suitable habitat. In this thesis, I fit, evaluate, and apply predictions of a habitat suitability model within the country of Peru. I used a generalized linear modeling approach across various range constraints, incorporating bioclimatic variables, forest cover, distance to cities and elevation as predictor variables. Precipitation features most strongly influencing observations of species presence in my model and evaluation measures showed the elevation-constrained model accuracy to be around 95%. Habitat suitability maps illustrate novel areas of potentially suitable habitat in central Huánuco, Pasco, and limited areas in Junín. The newly discovered population was found to be in an area of low suitability, calling for further investigation of the species in this area. Areas of suitable habitat should be surveyed to decrease bias in occurrence data, increasing the accuracy of habitat modeling for this species. Surveying these areas may also reveal corridors of gene flow between these populations, and could facilitate landscape genetics studies to characterize the viability of this taxon. Better characterization of the true distribution of the species will provide information to conservation stakeholders in priority areas, helping to protect this species and associated threatened wildlife.

Primates are the closest living relatives of Homo sapiens and are an important model for understanding human origins. From studying primates and making comparisons to what we know from the hominid fossil record, we can elucidate and make inferences into human physical and social evolution. My research focuses on the social aspects of primate life and attempts to find significant correlations between primate biology and social structure. Specifically, I am interested in how dominance hierarchies and power relationships between male and female primates are established and maintained in primate communities. This study contains a comprehensive dataset on a large sample of known primate species, predominantly from previously published sources and studies. For each primate species, the variables included are body mass, level of sexual dimorphism, brain size, habitat type, diet, life span, age at sexual maturity, gestation length, birth interval, locomotion type, social structure, terrestrial or arboreal locomotion, group size, home range, nocturnal or diurnal, philopatric sex, and dominant sex. Pearson's correlation coefficients between the above variables were calculated. The goal of this research is to determine what factors of primate life, both social and biological, have the largest influence on the formation and maintenance of dominance hierarchies. Certain biological variables related to body mass were found to be correlated with dominance. However, the correlation with sexual dimorphism was not found to be statistically significant and it is presumed that other ecological variables should be studied to better understand primate power relations.

A sobrevivência e o sucesso reprodutivo de um indivíduo estão diretamente relacionados à sua capacidade de atender à demanda por nutrientes e energia. Estudos em Ecologia Nutricional, que adotam o Modelo Geométrico para nutrição, evidenciam que, mais do que maximizar a ingestão de energia, os animais procuram regular a ingestão de múltiplos nutrientes de maneira independente, almejando um balanço específico entre esses nutrientes. Neste trabalho, empregamos análises de conteúdo nutricional e o Modelo Geométrico para investigar os parâmetros nutricionais da dieta de duas populações de macacos-prego (Sapajus spp.), em dois biomas distintos: Sapajus libidinosus, numa área de ecótono Cerrado/Caatinga, a Fazenda Boa Vista (FBV), no Estado do Piauí; e Sapajus nigritus, numa área de Mata Atlântica, o Parque Estadual Carlos Botelho (PECB), no Estado de São Paulo. Estudos anteriores sugeriram que a qualidade e a disponibilidade dos alimentos explorados por S. libidinosus no semi-árido são superiores aos dos explorados por S. nigritus na Mata Atlântica. Porém, afirmações sobre a qualidade de dieta dependem de investigações sobre o balanço nutricional obtido pelo organismo e quais as estratégias nutricionais adotadas para atingir esse balanço. Assim, os objetivos desta tese foram (1) analisar as estratégias nutricionais de um grupo de Sapajus libidinosus na FBV e (2) comparar a qualidade nutricional da dieta dessa população com a da população de Sapajus nigritus do PECB. Foram analisadas amostras de 176 itens alimentares. Para estimar o consumo de nutrientes, foram realizados 134 focais contínuos diários em que foram registrados os itens alimentares consumidos pelo indivíduo e a quantidade ingerida. Os macacos da FBV regulam a ingestão de um balanço específico entre energia proteica e energia não proteica (advinda de lipídeos e/ou carboidratos), priorizando a ingestão de energia não proteica quando a disponibilidade desse nutriente nos itens alimentares diminui. Assumindo que o objetivo nutricional de S. nigritus é o mesmo de S. libidinosus, os resultados confirmaram a hipótese de que a qualidade da dieta na FBV é superior à do PECB, área em que os alimentos dos macacos apresentam menores concentrações de energia não proteica. O Modelo Geométrico para nutrição permitiu rever afirmações feitas em estudos anteriores de que na FBV a sazonalidade dos recursos mais consumidos não é um fator limitante para esses animais. Neste estudo, mostramos que há variações sazonais na qualidade nutricional dos alimentos, o que tem um impacto na ingestão de nutrientes pelos macacos da FBV / The survival and reproductive success of an individual are directly related to its ability to meet the demand for nutrients and energy. Studies in Nutritional Ecology, adopting the Geometric Framework for Nutrition, show that more than maximize energy intake, the animals seek to regulate the intake of multiple nutrients independently, targeting a specific balance between these nutrients. In this study, we used nutritional content analysis and the Geometric Framework to investigate the diet nutritional parameters of two populations of capuchin monkeys (Sapajus spp.) in two different biomes: Sapajus libidinosus in the ecotone Cerrado/Caatinga, at Fazenda Boa Vista (FBV) in Piauí state; and Sapajus nigritus in an Atlantic Forest area, at Parque Estadual Carlos Botelho (PECB), in São Paulo state. Previous studies suggest that the quality and availability of food exploited by S. libidinosus in the semi-arid region are higher than those of the exploited by S. nigritus in the Atlantic Forest. However, statements about diet quality depend on investigating the nutrient balance obtained by individuals and which nutrition strategies are adopted to achieve this balance. Therefore, the aims of this thesis were (1) to analyze the nutritional strategies of a group of Sapajus libidinosus in the FBV and (2) to compare the nutritional quality of the diet of this population with that of Sapajus nigritus in PECB. We analyzed samples of 176 food items eaten by the animals. To estimate nutrient daily intake, we conducted 134 continuous focal follows recording the item consumed and the amount ingested by individuals. The monkeys in FBV regulate the intake of a specific balance between protein energy and non-protein energy (lipids and / or carbohydrates), and prioritize non-protein energy intake when the availability of this nutrient in food items decreases. Assuming that the nutritional goal of S. nigritus is the same as S. libidinosus, the results confirmed the hypothesis that diet quality in FBV is superior than in PECB, where foods contain lower non-protein energy concentrations. The Geometric Framework allowed to review previous studies claims that in FBV seasonality of resources availability is not a limiting factor for these animals. In this study we have shown seasonal variations in the nutritional quality of foods, which impact nutrient intake by monkeys in FBV