I focus on the foraging efficiency (food intake per time) of a hypothetical forager that uses dis... more I focus on the foraging efficiency (food intake per time) of a hypothetical forager that uses distinct levels of information about a set of discrete renewing resources. The information may be the distance to the resource (D), both distance and maximum productivity of the resource (DP), or distance, productivity, and the elapsed time since the forager last visited each resource (DPT). The expected foraging efficiencies are based on the results of a field experiment on wild capuchin monkeys (Janson, 2016a) that documented the use of integrative memories of resource location, productivity, and elapsed time since the previous visit. Computer simulations of the choice process are used to extend the resource parameter space beyond the field experiment. The goal is to explore to what extent the use of elapsed time in choosing discrete feeding sites is a benefit under various conditions of resource and consumer characteristics. Major findings include that the use of elapsed time generally increases foraging efficiency on renewing resources by 30-35%, without much effect of resource size or variability-indeed, DPT outperforms D or DP choice even when all resources have the same productivity. The relative benefit of DPT increases when the most productive resources are only moderately common (not so rare that they contribute little to food intake, nor so common that choosing the nearest resource is likely to arrive at a highly productive one). The relative benefit of DPT decreases when the forager's gut capacity is small or gut passage time is long because it cannot ingest all of the resource accumulated after long elapsed intervals. I suggest that memory for and use of elapsed intervals since prior visits in foraging choices will prove to be a common feature of diverse foraging animals whenever the presence of a forager depresses food availability in a local area.
Large vertebrates are important elements of mutualistic interactions and provide positive impacts... more Large vertebrates are important elements of mutualistic interactions and provide positive impacts on plant population and community dynamics. Despite the increasing interest on vertebrate frugivory we are still not able to disentangle the real contribution of seed dispersal to Neotropical forest functioning. Consuming fruits does not imply effective seed dispersal and many variables, such as seed size and animal diet, may influence the outcome of plant-animal interactions. Here, we performed a comprehensive literature search on seed dispersal by Neotropical vertebrates (with a focus on primates) to closely approach their role as seed dispersers, hypothesizing frugivory degree and seed size as main drivers of fruit handling behavior and diversity of dispersed seeds. We found that the great majority of seeds manipulated by Neotropical primates, with exception to the seed predators pitheciins, were swallowed and passed intact through their gut. Larger seeds (> 12 mm) tended of being ingested exclusively by primates and other large vertebrates, such as tapirs and peccaries. Furthermore, primate feeding guild had a great influence on the richness and sizes of seeds dispersed, as primarily frugivores dispersed more species and had higher probabilities of ingesting larger seeds when compared to other feeding guilds. Organizing available knowledge and filling the main knowledge gaps allowed us to validate common sense assumptions and ultimately draw new conclusions about the role played by primates together with other major frugivores in Neotropical forests.
Seed dispersal distance (SDD) is a vital component of vertebrate-mediated seed dispersal process:... more Seed dispersal distance (SDD) is a vital component of vertebrate-mediated seed dispersal process: the average distance at which seeds are deposited away from the parent plant represents the starting template of plant regeneration. We present a simple model to explain and predict observed measures of average dispersal distance and we hypothesize that it is a consequence of how long seeds are retained in the disperser's gut, how rapidly the disperser moves per unit time and how twisted the animal travel path is relative to the straight-line distance moved away from the seed source. We retrieved data on dispersal distances from 26 published studies including nine primate species dispersing up to 112 plant species per study. We used gut transit time (TT) as a proxy for residence time inside the gut, the disperser's travel path per hour as proxy for movement rate, and the daily path length relative to the home range area as a correlate of path twisting (PT). We illustrate this model with comparative data on Neotropical primates. These three variables explained 90% of the variation in the average SDD. Path analysis indicates that additional variables exerted only indirect effects. Our model can be applied to primate populations for which detailed seed dispersal data are missing, and help evaluate conservation priorities for primate species according to the potential service they provide in terms of forest regeneration.
There is considerable controversy about the existence, extent and adaptive value of integrated mu... more There is considerable controversy about the existence, extent and adaptive value of integrated multimodal memory in non-human animals. Building on prior results showing that wild capuchin monkeys in Argentina appear to recall both the location and amount of food at patches they had previously visited, I tested whether they also track and use elapsed time as a basis for decisions about which feeding patches to visit. I presented them with an experimental array of eight feeding sites, at each of which food rewards increased with increasing elapsed time since the previous visit, similar to the pattern of ripe fruit accumulation in natural feeding trees. Over the course of 68 days, comprising two distinct renewal rate treatments, one group repeatedly visited sites in the feeding array, generating 212 valid choices between sites. Comparison of observations against simulated movements and multinomial statistical models shows that the monkeys' choices were most consistent with dynamic ...
... Charles Janson, Maria Celia Baldovino, and Mario Di Bitetti ... ornatus), jaguarundis (Puma y... more ... Charles Janson, Maria Celia Baldovino, and Mario Di Bitetti ... ornatus), jaguarundis (Puma yagouaroundi), oncillas (Leopardus tigrinus), margays (Leopardus wiedii), ocelots (Leopardus pardalis), pumas (Puma concolor), jaguars (Panthera onca), and tayras (Eira barbara). ...
This paper models the coalition formation process among primates as a sequential game. The popula... more This paper models the coalition formation process among primates as a sequential game. The population consists of individuals having distinct social ranks which is determined by the individual's resource holding potential. Each member of the population is interested in gaining access to a food resource, either individually or via a coalition. At any given stage of the game, a player can either propose a specific coalition or he can be proposed to in order to join one. Hence, the strategy of a player consists of a sequence of decisions regarding who to propose to for the formation of a coalition and which proposals to accept or reject. We derive the preferences of the players over the various coalition structures under the assumption that the probability of a coalition to obtain the resource is given by a logistic distribution as a function of relative strengths of the players. We show that, given the primates' strategic behavior, a variety of different coalition structures can emerge in equilibrium.
Evolutionary Anthropology: Issues, News, and Reviews, 2012
Attempts to explain differences in the size and structure of primate groups have argued that they... more Attempts to explain differences in the size and structure of primate groups have argued that they are a consequence of variation in the intensity of feeding competition caused by contrasts in food distribution. However, although feeding competition can limit the size of female groups, many other factors affect the costs and the benefits of sociality to females and contribute to differences in group size. Moreover, interspecific differences in social relationships between females, in female philopatry, and in kinship between group members appear to be more closely associated with variation in life-history parameters, reproductive strategies, and phylogeny than with contrasts in food distribution or feeding competition. The mismatch between predictions of socioecological theory and observed variation in primate social behavior has led to protracted arguments about the future of primate socioecology. We argue that future attempts to understand the diversity of primate societies need to be based on an approach that explores separate explanations for different components of social organization, combines ecological and phylogenetic information, and integrates research on primates with similar studies of other groups of mammals.
Evolutionary Anthropology: Issues, News, and Reviews, 2005
Evolutionary Anthropology 151 (RajasthaniIndia): Recent observations and a reconsideration of hyp... more Evolutionary Anthropology 151 (RajasthaniIndia): Recent observations and a reconsideration of hypotheses. Primates 28:163-197. 15 Dolhinow P (in press) A mystery: Explaining behavior. In Strum SC, Lindburg DG, Hamburg DA (eds) The New Plzvsical Antlzro-16 Hrdy SB (1979) Infanticide among animals: A review, classification, and examination of the implications for the reproductivc strategies of females. Ethol Sociobiol 1:1340. 17 Hrdy SB (1984) Assumptions and evidence regarding the sexual selection hypothesis: a reply to Boggess. In Hausfater G, Hrdy SB (eds) Infanticide: Comparative and Evolutionaty Perspectives, pp. 315-319. New York: Aldine. 18 Newton PN (1988) The variable social organization of Hanuman langurs (Presbytis entellus). Infanticide and the monopolization of females. Int J Primatol 9:59-77. 19 Arnold S, Wade M (1 984) On the measure-pology.
Evolutionary Anthropology: Issues, News, and Reviews, 2010
T he 23rd Congress of the International Primatological Society (IPS) was held this year from Sept... more T he 23rd Congress of the International Primatological Society (IPS) was held this year from September 12–18 in the city of Kyoto, a checkerboard of contrasting tall modern buildings, orderly gardens, ancient royal dwellings, beautiful temples, and Shinto shrines. Bounded between two rivers, Kyoto is surrounded on all sides by forested hillsides still populated by indigenous Japanese macaques. The events of the Congress were, most appropriately, held at the University of Kyoto, a birthplace of modern field primatology. For anyone interested in this history, there was an extensive display of Kinji Imanishi’s original field notebooks and other artifacts of his wide-ranging career (Fig. 1). It was Imanishi who, in 1948, first went to Koshima Island and, together with his students, Shunzo Kawamura and Jun’ichiro Itani (whose battered binoculars were also on display) (Fig. 2), worked out the elaborate matrilineal social organization of macaques and, as it turned out, almost all cercopithecine monkeys. In the ensuing years, Itani and colleagues (Toshisado Nishida, Jiro Tanaka, and Yukimaru Sugiyama) fanned out to Africa and India to study monkeys and great apes, including humans still living as foragers. The aim of these Japanese pioneers was to attain an understanding of the roots of humanity by studying the diversity of primate behaviors from multiple perspectives, including psychological, ecological, and cultural. This holistic tradition continues to flourish in Japan, as illustrated by Takeshi Furuichi’s superb plenary talk on 30 years of research among wild bonobos in the Congo, together with the many papers presented by other faculty and students from the Primate Research Institute (PRI). At the PRI, under the directorship of Tetsuro Matsuzawa, longterm African ape field research is complemented by equally ambitious research in comparative cognitive development and neuroscience, as well as by conservation programs like Support for African/Asian Great Apes (SAGA). Decades later, these state-ofthe-art programs remain true to Japanese primatology’s unique integrative vision. One memorable moment occurred during lunch, when Matsuzawa patiently explained to some of us what is meant by the Japanese concept of ‘‘kokoro,’’ a peculiarly comprehensive term for ‘‘mind’’ that incorporates knowledge, emotion, and will. The Congress allowed many non-Japanese primatologists to savor the scientific products of Japan’s active network of primatologists and meet many of them in person both as scientists and gracious hosts. The roles of culture and socialization in learning to understand and empathize with animals were vividly brought home in Alison Jolly’s historical tour through children’s books featuring animal characters, including her own recent books designed to introduce school children in Madagascar to their country’s unique natural history. The audience’s affection and reverence for this pioneer in the study of primate cognition, lemur social organization, and conservation was palpable. All members rose to give Jolly a standing ovation as President Juichi Yamagiwa presented her with the Society’s Lifetime Achievement Award (Fig. 3). In keeping with the Japanese emphasis on mechanisms that sustain social living, the Congress in Kyoto stood out because greater attention than in years past was given to ‘‘prosocial’’ aspects of primate life. In the opening session, Sarah Hrdy (University of California, Davis) set the stage by asking what happens when apes adopt cooperative breeding with alloparental care and provisioning of young. In a carefully crafted argument, Hrdy offered her answer: Apes develop to care more about the men-
Primates are in some ways excellent subjects for studying the impact of predation on prey. They a... more Primates are in some ways excellent subjects for studying the impact of predation on prey. They are generally easy to watch and identify as individuals, so that long-term tracking of both death rates and anti-predator behaviors is possible, as amply shown by many of the studies in this volume. On the flip side, their low predation rates and large group sizes require very large total sample sizes for statistically powerful tests of the direct effects of sociality on predation rates. To study the indirect effects of predation
The impact of aggressive competition on food intake at all the resources used is analysed for eve... more The impact of aggressive competition on food intake at all the resources used is analysed for every member of a group of brown capuchin monkeys (Cebus apella) in the Manu National Park, Peru, where they live in groups of 8-14 animals. An individual's food intake at a given tree was affected independently both by its dominance rank (Fig. 1) and by how much aggression it received (Table 5). Food intake was not strongly affected by body size when dominance rank was held constant by partial correlation. At food sources where high rates of fighting occurred, an individual's food intake depended more on its dominance status than on the rate of aggression it received (Fig. 2). However, food intake at resources where rates of fighting were low depended mostly on the rate of aggression received. When aggression over food was absent, the food intakes of dominants and subordinates were equal. Dominants had significantly greater total energy intake (20.5% more) than did subordinates, even though more than one third of their diet came from food sources where little or no fighting occurred (Fig. 3). Energy intake was also significantly greater for individuals that received little aggression. The only adult that emigrated from the main study group was the individual with the lowest energy intake. Competition for food within groups was more than ten times as intense as competition between brown capuchin groups.
The impact of aggressive competition on food intake at all the resources used is analysed for eve... more The impact of aggressive competition on food intake at all the resources used is analysed for every member of a group of brown capuchin monkeys (Cebus apella) in the Manu National Park, Peru, where they live in groups of 8-14 animals. An individual's food intake at a given tree was affected independently both by its dominance rank (Fig. 1) and by how much aggression it received (Table 5). Food intake was not strongly affected by body size when dominance rank was held constant by partial correlation. At food sources where high rates of fighting occurred, an individual's food intake depended more on its dominance status than on the rate of aggression it received (Fig. 2). However, food intake at resources where rates of fighting were low depended mostly on the rate of aggression received. When aggression over food was absent, the food intakes of dominants and subordinates were equal. Dominants had significantly greater total energy intake (20.5% more) than did subordinates, even though more than one third of their diet came from food sources where little or no fighting occurred (Fig. 3). Energy intake was also significantly greater for individuals that received little aggression. The only adult that emigrated from the main study group was the individual with the lowest energy intake. Competition for food within groups was more than ten times as intense as competition between brown capuchin groups.
The environment in which humans evolved is strongly and positively autocorrelated in space and ti... more The environment in which humans evolved is strongly and positively autocorrelated in space and time. Probabilistic judgments based on the assumption of independence may not yield evolutionarily adaptive behavior. A number of “faults” of human reasoning are not faulty under fuzzy arithmetic, a nonprobabilistic calculus of reasoning under uncertainty that may be closer to that underlying human decision making.
Most studies of spatial memory in primates focus on species that inhabit large home ranges and ha... more Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezuela during a period of fruit abundance. The sakis' movements were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the predicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were signiWcantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis' preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled eYciently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with 'what' and 'where' information gained from individual visits to resources. Although the sakis' foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intragroup feeding competition, maintain intergroup dominance over important resources, and monitor the state of resources throughout their home range. The sakis' foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutritional considerations.
Most studies of spatial memory in primates focus on species that inhabit large home ranges and ha... more Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezuela during a period of fruit abundance. The sakis' movements were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the predicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were signiWcantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis' preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled eYciently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with 'what' and 'where' information gained from individual visits to resources. Although the sakis' foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intragroup feeding competition, maintain intergroup dominance over important resources, and monitor the state of resources throughout their home range. The sakis' foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutritional considerations.
The papers in this special issue examine the relationship between social and ecological cognition... more The papers in this special issue examine the relationship between social and ecological cognition in primates. We refer to the intersection of these two domains as socioecological cognition. Examples of socioecological cognition include socially learned predator alarm calls and socially sensitive foraging decisions. In this review we consider how primate cognition may have been shaped by the interaction of social and ecological inXuences in their evolutionary history. The ability to remember distant, out-of-sight locations is an ancient one, shared by many mammals and widespread among primates. It seems some monkeys and apes have evolved the ability to form more complex representations of resources, integrating "what-where-how much" information. This ability allowed anthropoids to live in larger, more cohesive groups by minimizing competition for limited resources between group members. As group size increased, however, competition for resources also increased, selecting for enhanced social skills. Enhanced social skills in turn made a more sophisticated relationship to the environment possible. The interaction of social and ecological inXuences created a spiraling eVect in the evolution of primate intelligence. In contrast, lemurs may not have evolved the ability to form complex representations which would allow them to consider the size and location of resources. This lack in lemur ecological cognition may restrict the size of frugivorous lemur social groups, thereby limiting the complexity of lemur social life. In this special issue, we have brought together two review papers, Wve Weld studies, and one laboratory study to investigate the interaction of social and ecological factors in relation to foraging. Our goal is to stimulate research that considers social and ecological factors acting together on cognitive evolution, rather than in isolation. Cross fertilization of experimental and observational studies from captivity and the Weld is important for increasing our understanding of this relationship.
Several comparative studies have linked larger brain size to a fruit-eating diet in primates and ... more Several comparative studies have linked larger brain size to a fruit-eating diet in primates and other animals. The general explanation for this correlation is that fruit is a complex resource base, consisting of many discrete patches of many species, each with distinct nutritional traits, the production of which changes predictably both within and between seasons. Using this information to devise optimal spatial foraging strategies is among the most difficult problems to solve in all of mathematics, a version of the famous Traveling Salesman Problem. Several authors have suggested that primates might use their large brains and complex cognition to plan foraging strategies that approximate optimal solutions to this problem. Three empirical studies have examined how captive primates move when confronted with the simplest version of the problem: a spatial array of equally valuable goals. These studies have all concluded that the subjects remember many food source locations and show very efficient travel paths; some authors also inferred that the subjects may plan their movements based on considering combinations of three or more future goals at a time. This analysis reexamines critically the claims of planned movement sequences from the evidence presented. The efficiency of observed travel paths is largely consistent with use of the simplest of foraging rules, such as visiting the nearest unused "known" resource. Detailed movement sequences by test subjects are most consistent with a rule that mentally sums spatial information from all unused resources in a given trial into a single "gravity" measure that guides movements to one destination at a time. Am.
The frequency of anointing bouts and the materials used for self-and social anointing vary across... more The frequency of anointing bouts and the materials used for self-and social anointing vary across capuchin species in captivity, but there is little published data on capuchin anointing in the wild. Here we present previously unpublished data on anointing behaviors from capuchin monkey populations at ten different field sites and incorporate these data into a review of the anointing literature for captive and wild capuchins. Using a comparative phylogenetic framework, we test four hypotheses derived primarily from captive literature for variation in anointing between wild untufted capuchins (Cebus) and tufted capuchins (Sapajus), including that (1) the frequency of anointing is higher in Cebus, (2) Cebus uses a higher proportion of plant species to insect species for anointing compared with Sapajus, (3) anointing material diversity is higher in Cebus, and (4) social indices of anointing are higher in Cebus. We found that wild Cebus anoints more with plant parts, including fruits, whereas wild Sapajus anoints more with ants and other arthropods. Cebus capucinus in particular uses more plant species per site for anointing compared with other capuchins and may specialize in anointing as an activity independent from foraging, whereas most other capuchin species tend to eat the substances they use for anointing. In agreement with captive studies, we found evidence that wild Cebus anoints at a significantly higher frequency than Sapajus. However, contrary to the captive literature, we found no difference in the range of sociality for anointing between Cebus and Sapajus in the wild. We review anointing in the context of other Neotropical primate rubbing behaviors and consider the evidence for anointing as self-medication; as a mechanism for enhanced sociality; and as a behavioral response to
I focus on the foraging efficiency (food intake per time) of a hypothetical forager that uses dis... more I focus on the foraging efficiency (food intake per time) of a hypothetical forager that uses distinct levels of information about a set of discrete renewing resources. The information may be the distance to the resource (D), both distance and maximum productivity of the resource (DP), or distance, productivity, and the elapsed time since the forager last visited each resource (DPT). The expected foraging efficiencies are based on the results of a field experiment on wild capuchin monkeys (Janson, 2016a) that documented the use of integrative memories of resource location, productivity, and elapsed time since the previous visit. Computer simulations of the choice process are used to extend the resource parameter space beyond the field experiment. The goal is to explore to what extent the use of elapsed time in choosing discrete feeding sites is a benefit under various conditions of resource and consumer characteristics. Major findings include that the use of elapsed time generally increases foraging efficiency on renewing resources by 30-35%, without much effect of resource size or variability-indeed, DPT outperforms D or DP choice even when all resources have the same productivity. The relative benefit of DPT increases when the most productive resources are only moderately common (not so rare that they contribute little to food intake, nor so common that choosing the nearest resource is likely to arrive at a highly productive one). The relative benefit of DPT decreases when the forager's gut capacity is small or gut passage time is long because it cannot ingest all of the resource accumulated after long elapsed intervals. I suggest that memory for and use of elapsed intervals since prior visits in foraging choices will prove to be a common feature of diverse foraging animals whenever the presence of a forager depresses food availability in a local area.
Large vertebrates are important elements of mutualistic interactions and provide positive impacts... more Large vertebrates are important elements of mutualistic interactions and provide positive impacts on plant population and community dynamics. Despite the increasing interest on vertebrate frugivory we are still not able to disentangle the real contribution of seed dispersal to Neotropical forest functioning. Consuming fruits does not imply effective seed dispersal and many variables, such as seed size and animal diet, may influence the outcome of plant-animal interactions. Here, we performed a comprehensive literature search on seed dispersal by Neotropical vertebrates (with a focus on primates) to closely approach their role as seed dispersers, hypothesizing frugivory degree and seed size as main drivers of fruit handling behavior and diversity of dispersed seeds. We found that the great majority of seeds manipulated by Neotropical primates, with exception to the seed predators pitheciins, were swallowed and passed intact through their gut. Larger seeds (> 12 mm) tended of being ingested exclusively by primates and other large vertebrates, such as tapirs and peccaries. Furthermore, primate feeding guild had a great influence on the richness and sizes of seeds dispersed, as primarily frugivores dispersed more species and had higher probabilities of ingesting larger seeds when compared to other feeding guilds. Organizing available knowledge and filling the main knowledge gaps allowed us to validate common sense assumptions and ultimately draw new conclusions about the role played by primates together with other major frugivores in Neotropical forests.
Seed dispersal distance (SDD) is a vital component of vertebrate-mediated seed dispersal process:... more Seed dispersal distance (SDD) is a vital component of vertebrate-mediated seed dispersal process: the average distance at which seeds are deposited away from the parent plant represents the starting template of plant regeneration. We present a simple model to explain and predict observed measures of average dispersal distance and we hypothesize that it is a consequence of how long seeds are retained in the disperser's gut, how rapidly the disperser moves per unit time and how twisted the animal travel path is relative to the straight-line distance moved away from the seed source. We retrieved data on dispersal distances from 26 published studies including nine primate species dispersing up to 112 plant species per study. We used gut transit time (TT) as a proxy for residence time inside the gut, the disperser's travel path per hour as proxy for movement rate, and the daily path length relative to the home range area as a correlate of path twisting (PT). We illustrate this model with comparative data on Neotropical primates. These three variables explained 90% of the variation in the average SDD. Path analysis indicates that additional variables exerted only indirect effects. Our model can be applied to primate populations for which detailed seed dispersal data are missing, and help evaluate conservation priorities for primate species according to the potential service they provide in terms of forest regeneration.
There is considerable controversy about the existence, extent and adaptive value of integrated mu... more There is considerable controversy about the existence, extent and adaptive value of integrated multimodal memory in non-human animals. Building on prior results showing that wild capuchin monkeys in Argentina appear to recall both the location and amount of food at patches they had previously visited, I tested whether they also track and use elapsed time as a basis for decisions about which feeding patches to visit. I presented them with an experimental array of eight feeding sites, at each of which food rewards increased with increasing elapsed time since the previous visit, similar to the pattern of ripe fruit accumulation in natural feeding trees. Over the course of 68 days, comprising two distinct renewal rate treatments, one group repeatedly visited sites in the feeding array, generating 212 valid choices between sites. Comparison of observations against simulated movements and multinomial statistical models shows that the monkeys' choices were most consistent with dynamic ...
... Charles Janson, Maria Celia Baldovino, and Mario Di Bitetti ... ornatus), jaguarundis (Puma y... more ... Charles Janson, Maria Celia Baldovino, and Mario Di Bitetti ... ornatus), jaguarundis (Puma yagouaroundi), oncillas (Leopardus tigrinus), margays (Leopardus wiedii), ocelots (Leopardus pardalis), pumas (Puma concolor), jaguars (Panthera onca), and tayras (Eira barbara). ...
This paper models the coalition formation process among primates as a sequential game. The popula... more This paper models the coalition formation process among primates as a sequential game. The population consists of individuals having distinct social ranks which is determined by the individual's resource holding potential. Each member of the population is interested in gaining access to a food resource, either individually or via a coalition. At any given stage of the game, a player can either propose a specific coalition or he can be proposed to in order to join one. Hence, the strategy of a player consists of a sequence of decisions regarding who to propose to for the formation of a coalition and which proposals to accept or reject. We derive the preferences of the players over the various coalition structures under the assumption that the probability of a coalition to obtain the resource is given by a logistic distribution as a function of relative strengths of the players. We show that, given the primates' strategic behavior, a variety of different coalition structures can emerge in equilibrium.
Evolutionary Anthropology: Issues, News, and Reviews, 2012
Attempts to explain differences in the size and structure of primate groups have argued that they... more Attempts to explain differences in the size and structure of primate groups have argued that they are a consequence of variation in the intensity of feeding competition caused by contrasts in food distribution. However, although feeding competition can limit the size of female groups, many other factors affect the costs and the benefits of sociality to females and contribute to differences in group size. Moreover, interspecific differences in social relationships between females, in female philopatry, and in kinship between group members appear to be more closely associated with variation in life-history parameters, reproductive strategies, and phylogeny than with contrasts in food distribution or feeding competition. The mismatch between predictions of socioecological theory and observed variation in primate social behavior has led to protracted arguments about the future of primate socioecology. We argue that future attempts to understand the diversity of primate societies need to be based on an approach that explores separate explanations for different components of social organization, combines ecological and phylogenetic information, and integrates research on primates with similar studies of other groups of mammals.
Evolutionary Anthropology: Issues, News, and Reviews, 2005
Evolutionary Anthropology 151 (RajasthaniIndia): Recent observations and a reconsideration of hyp... more Evolutionary Anthropology 151 (RajasthaniIndia): Recent observations and a reconsideration of hypotheses. Primates 28:163-197. 15 Dolhinow P (in press) A mystery: Explaining behavior. In Strum SC, Lindburg DG, Hamburg DA (eds) The New Plzvsical Antlzro-16 Hrdy SB (1979) Infanticide among animals: A review, classification, and examination of the implications for the reproductivc strategies of females. Ethol Sociobiol 1:1340. 17 Hrdy SB (1984) Assumptions and evidence regarding the sexual selection hypothesis: a reply to Boggess. In Hausfater G, Hrdy SB (eds) Infanticide: Comparative and Evolutionaty Perspectives, pp. 315-319. New York: Aldine. 18 Newton PN (1988) The variable social organization of Hanuman langurs (Presbytis entellus). Infanticide and the monopolization of females. Int J Primatol 9:59-77. 19 Arnold S, Wade M (1 984) On the measure-pology.
Evolutionary Anthropology: Issues, News, and Reviews, 2010
T he 23rd Congress of the International Primatological Society (IPS) was held this year from Sept... more T he 23rd Congress of the International Primatological Society (IPS) was held this year from September 12–18 in the city of Kyoto, a checkerboard of contrasting tall modern buildings, orderly gardens, ancient royal dwellings, beautiful temples, and Shinto shrines. Bounded between two rivers, Kyoto is surrounded on all sides by forested hillsides still populated by indigenous Japanese macaques. The events of the Congress were, most appropriately, held at the University of Kyoto, a birthplace of modern field primatology. For anyone interested in this history, there was an extensive display of Kinji Imanishi’s original field notebooks and other artifacts of his wide-ranging career (Fig. 1). It was Imanishi who, in 1948, first went to Koshima Island and, together with his students, Shunzo Kawamura and Jun’ichiro Itani (whose battered binoculars were also on display) (Fig. 2), worked out the elaborate matrilineal social organization of macaques and, as it turned out, almost all cercopithecine monkeys. In the ensuing years, Itani and colleagues (Toshisado Nishida, Jiro Tanaka, and Yukimaru Sugiyama) fanned out to Africa and India to study monkeys and great apes, including humans still living as foragers. The aim of these Japanese pioneers was to attain an understanding of the roots of humanity by studying the diversity of primate behaviors from multiple perspectives, including psychological, ecological, and cultural. This holistic tradition continues to flourish in Japan, as illustrated by Takeshi Furuichi’s superb plenary talk on 30 years of research among wild bonobos in the Congo, together with the many papers presented by other faculty and students from the Primate Research Institute (PRI). At the PRI, under the directorship of Tetsuro Matsuzawa, longterm African ape field research is complemented by equally ambitious research in comparative cognitive development and neuroscience, as well as by conservation programs like Support for African/Asian Great Apes (SAGA). Decades later, these state-ofthe-art programs remain true to Japanese primatology’s unique integrative vision. One memorable moment occurred during lunch, when Matsuzawa patiently explained to some of us what is meant by the Japanese concept of ‘‘kokoro,’’ a peculiarly comprehensive term for ‘‘mind’’ that incorporates knowledge, emotion, and will. The Congress allowed many non-Japanese primatologists to savor the scientific products of Japan’s active network of primatologists and meet many of them in person both as scientists and gracious hosts. The roles of culture and socialization in learning to understand and empathize with animals were vividly brought home in Alison Jolly’s historical tour through children’s books featuring animal characters, including her own recent books designed to introduce school children in Madagascar to their country’s unique natural history. The audience’s affection and reverence for this pioneer in the study of primate cognition, lemur social organization, and conservation was palpable. All members rose to give Jolly a standing ovation as President Juichi Yamagiwa presented her with the Society’s Lifetime Achievement Award (Fig. 3). In keeping with the Japanese emphasis on mechanisms that sustain social living, the Congress in Kyoto stood out because greater attention than in years past was given to ‘‘prosocial’’ aspects of primate life. In the opening session, Sarah Hrdy (University of California, Davis) set the stage by asking what happens when apes adopt cooperative breeding with alloparental care and provisioning of young. In a carefully crafted argument, Hrdy offered her answer: Apes develop to care more about the men-
Primates are in some ways excellent subjects for studying the impact of predation on prey. They a... more Primates are in some ways excellent subjects for studying the impact of predation on prey. They are generally easy to watch and identify as individuals, so that long-term tracking of both death rates and anti-predator behaviors is possible, as amply shown by many of the studies in this volume. On the flip side, their low predation rates and large group sizes require very large total sample sizes for statistically powerful tests of the direct effects of sociality on predation rates. To study the indirect effects of predation
The impact of aggressive competition on food intake at all the resources used is analysed for eve... more The impact of aggressive competition on food intake at all the resources used is analysed for every member of a group of brown capuchin monkeys (Cebus apella) in the Manu National Park, Peru, where they live in groups of 8-14 animals. An individual's food intake at a given tree was affected independently both by its dominance rank (Fig. 1) and by how much aggression it received (Table 5). Food intake was not strongly affected by body size when dominance rank was held constant by partial correlation. At food sources where high rates of fighting occurred, an individual's food intake depended more on its dominance status than on the rate of aggression it received (Fig. 2). However, food intake at resources where rates of fighting were low depended mostly on the rate of aggression received. When aggression over food was absent, the food intakes of dominants and subordinates were equal. Dominants had significantly greater total energy intake (20.5% more) than did subordinates, even though more than one third of their diet came from food sources where little or no fighting occurred (Fig. 3). Energy intake was also significantly greater for individuals that received little aggression. The only adult that emigrated from the main study group was the individual with the lowest energy intake. Competition for food within groups was more than ten times as intense as competition between brown capuchin groups.
The impact of aggressive competition on food intake at all the resources used is analysed for eve... more The impact of aggressive competition on food intake at all the resources used is analysed for every member of a group of brown capuchin monkeys (Cebus apella) in the Manu National Park, Peru, where they live in groups of 8-14 animals. An individual's food intake at a given tree was affected independently both by its dominance rank (Fig. 1) and by how much aggression it received (Table 5). Food intake was not strongly affected by body size when dominance rank was held constant by partial correlation. At food sources where high rates of fighting occurred, an individual's food intake depended more on its dominance status than on the rate of aggression it received (Fig. 2). However, food intake at resources where rates of fighting were low depended mostly on the rate of aggression received. When aggression over food was absent, the food intakes of dominants and subordinates were equal. Dominants had significantly greater total energy intake (20.5% more) than did subordinates, even though more than one third of their diet came from food sources where little or no fighting occurred (Fig. 3). Energy intake was also significantly greater for individuals that received little aggression. The only adult that emigrated from the main study group was the individual with the lowest energy intake. Competition for food within groups was more than ten times as intense as competition between brown capuchin groups.
The environment in which humans evolved is strongly and positively autocorrelated in space and ti... more The environment in which humans evolved is strongly and positively autocorrelated in space and time. Probabilistic judgments based on the assumption of independence may not yield evolutionarily adaptive behavior. A number of “faults” of human reasoning are not faulty under fuzzy arithmetic, a nonprobabilistic calculus of reasoning under uncertainty that may be closer to that underlying human decision making.
Most studies of spatial memory in primates focus on species that inhabit large home ranges and ha... more Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezuela during a period of fruit abundance. The sakis' movements were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the predicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were signiWcantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis' preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled eYciently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with 'what' and 'where' information gained from individual visits to resources. Although the sakis' foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intragroup feeding competition, maintain intergroup dominance over important resources, and monitor the state of resources throughout their home range. The sakis' foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutritional considerations.
Most studies of spatial memory in primates focus on species that inhabit large home ranges and ha... more Most studies of spatial memory in primates focus on species that inhabit large home ranges and have dispersed, patchy resources. Researchers assume that primates use memory to minimize distances traveled between resources. We investigated the use of spatial memory in a group of six white-faced sakis (Pithecia pithecia) on 12.8-ha Round Island, Guri Lake, Venezuela during a period of fruit abundance. The sakis' movements were analyzed with logistic regressions, a predictive computer model and a computer model that simulates movements. We considered all the resources available to the sakis and compared observed distances to predicted distances from a computer model for foragers who know nothing about the location of resources. Surprisingly, the observed distances were four times greater than the predicted distances, suggesting that the sakis passed by a majority of the available fruit trees without feeding. The odds of visiting a food tree, however, were signiWcantly increased if the tree had been visited in the previous 3 days and had more than 100 fruit. The sakis' preferred resources were highly productive fruit trees, Capparis trees, and trees with water holes. They traveled eYciently to these sites. The sakis choice of feeding sites indicate that they combined knowledge acquired by repeatedly traveling through their home range with 'what' and 'where' information gained from individual visits to resources. Although the sakis' foraging choices increased the distance they traveled overall, choosing more valued sites allowed the group to minimize intragroup feeding competition, maintain intergroup dominance over important resources, and monitor the state of resources throughout their home range. The sakis' foraging decisions appear to have used spatial memory, elements of episodic-like memory and social and nutritional considerations.
The papers in this special issue examine the relationship between social and ecological cognition... more The papers in this special issue examine the relationship between social and ecological cognition in primates. We refer to the intersection of these two domains as socioecological cognition. Examples of socioecological cognition include socially learned predator alarm calls and socially sensitive foraging decisions. In this review we consider how primate cognition may have been shaped by the interaction of social and ecological inXuences in their evolutionary history. The ability to remember distant, out-of-sight locations is an ancient one, shared by many mammals and widespread among primates. It seems some monkeys and apes have evolved the ability to form more complex representations of resources, integrating "what-where-how much" information. This ability allowed anthropoids to live in larger, more cohesive groups by minimizing competition for limited resources between group members. As group size increased, however, competition for resources also increased, selecting for enhanced social skills. Enhanced social skills in turn made a more sophisticated relationship to the environment possible. The interaction of social and ecological inXuences created a spiraling eVect in the evolution of primate intelligence. In contrast, lemurs may not have evolved the ability to form complex representations which would allow them to consider the size and location of resources. This lack in lemur ecological cognition may restrict the size of frugivorous lemur social groups, thereby limiting the complexity of lemur social life. In this special issue, we have brought together two review papers, Wve Weld studies, and one laboratory study to investigate the interaction of social and ecological factors in relation to foraging. Our goal is to stimulate research that considers social and ecological factors acting together on cognitive evolution, rather than in isolation. Cross fertilization of experimental and observational studies from captivity and the Weld is important for increasing our understanding of this relationship.
Several comparative studies have linked larger brain size to a fruit-eating diet in primates and ... more Several comparative studies have linked larger brain size to a fruit-eating diet in primates and other animals. The general explanation for this correlation is that fruit is a complex resource base, consisting of many discrete patches of many species, each with distinct nutritional traits, the production of which changes predictably both within and between seasons. Using this information to devise optimal spatial foraging strategies is among the most difficult problems to solve in all of mathematics, a version of the famous Traveling Salesman Problem. Several authors have suggested that primates might use their large brains and complex cognition to plan foraging strategies that approximate optimal solutions to this problem. Three empirical studies have examined how captive primates move when confronted with the simplest version of the problem: a spatial array of equally valuable goals. These studies have all concluded that the subjects remember many food source locations and show very efficient travel paths; some authors also inferred that the subjects may plan their movements based on considering combinations of three or more future goals at a time. This analysis reexamines critically the claims of planned movement sequences from the evidence presented. The efficiency of observed travel paths is largely consistent with use of the simplest of foraging rules, such as visiting the nearest unused "known" resource. Detailed movement sequences by test subjects are most consistent with a rule that mentally sums spatial information from all unused resources in a given trial into a single "gravity" measure that guides movements to one destination at a time. Am.
The frequency of anointing bouts and the materials used for self-and social anointing vary across... more The frequency of anointing bouts and the materials used for self-and social anointing vary across capuchin species in captivity, but there is little published data on capuchin anointing in the wild. Here we present previously unpublished data on anointing behaviors from capuchin monkey populations at ten different field sites and incorporate these data into a review of the anointing literature for captive and wild capuchins. Using a comparative phylogenetic framework, we test four hypotheses derived primarily from captive literature for variation in anointing between wild untufted capuchins (Cebus) and tufted capuchins (Sapajus), including that (1) the frequency of anointing is higher in Cebus, (2) Cebus uses a higher proportion of plant species to insect species for anointing compared with Sapajus, (3) anointing material diversity is higher in Cebus, and (4) social indices of anointing are higher in Cebus. We found that wild Cebus anoints more with plant parts, including fruits, whereas wild Sapajus anoints more with ants and other arthropods. Cebus capucinus in particular uses more plant species per site for anointing compared with other capuchins and may specialize in anointing as an activity independent from foraging, whereas most other capuchin species tend to eat the substances they use for anointing. In agreement with captive studies, we found evidence that wild Cebus anoints at a significantly higher frequency than Sapajus. However, contrary to the captive literature, we found no difference in the range of sociality for anointing between Cebus and Sapajus in the wild. We review anointing in the context of other Neotropical primate rubbing behaviors and consider the evidence for anointing as self-medication; as a mechanism for enhanced sociality; and as a behavioral response to
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Papers by Charles Janson