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Predation risk sensitivity and the spatial organization of primate groups: A case study using GIS in lowland Woolly Monkeys (Lagothrix lagotricha poeppigii)
Abstract
Predation risk is thought to be a potent force influencing intragroup cohesion, and the level of risk experienced by an individual is expected to vary with both group size and spatial position within a group. Smaller-bodied and less-experienced individuals are presumed to be more vulnerable to predators, suggesting that within-group spatial organization should show size- and age-dependent patterns in predator sensitive positioning. However, such effects have been difficult to evaluate for arboreal primates living in large groups. We conducted a preliminary study using a novel, spatially explicit method of assessing group spatial organization using GIS data in two groups of wild lowland Woolly monkeys, in which one group had a membership roughly twice as large as the second. In the larger group, group spread was more diffuse and large adult males were more frequently on the outskirts of the group than other age/sex classes, while immatures and females with dependents were more often in the center. Leaf cover around an individual—presumed to index an animal's perception of risk—increased significantly with distance from the group center for all immatures, although they were typically under lower leaf cover than adults; the number of groupmates in proximity also had an effect, but nearest neighbor distance did not. These differences were not detectable in the smaller group. This preliminary study suggests that thorough studies of spatial organization and predation risk sensitivity in arboreal primates are possible and could yield valuable information on how gregarious individuals offset ecological risks through social spacing. Am J Phys Anthropol, 2014. © 2014 Wiley Periodicals, Inc.
... Age and sex influence both predation risk and intra-group spatial position (reviewed in Schmitt & Di Fiore, 2015;Teichroeb et al., 2015). The relative positioning of individuals of various sex and age in mixed groups can vary considerably between the species. ...
... However, in many primate species adult males tend to be at the front of moving groups, while females and juveniles typically stay closer to the group's centre (Teichroeb et al., 2015). The males' tendency to maintain front positions in the groups could be especially pronounced in sexually dimorphic primate species because larger males may be less vulnerable to predators and more actively participate in antipredator defence (Schmitt & Di Fiore, 2015). In primates, juveniles usually stay more central because they face the greatest risk of predation and have to rely on adults for vigilance (Teichroeb et al., 2015). ...
... Contrary to our prediction and the results of the previous studies on other mammals such as primates (e.g. Schmitt & Di Fiore, 2015;Teichroeb et al., 2015), adult males did not tend to be the first individuals in their groups. In addition, the analysis of the distribution of adult males within the mixed groups showed that they did not prefer to be in the first third of the group and were roughly equally distributed between the front, central and rear parts. ...
In group-living animals, the social structure and organisation play a significant role in survival and reproduction. Understanding the social aspects of animal lives in the wild may be crucially important for effective conservation of threatened species. The fitness costs and benefits of living in a group are related to particular spatial positions individuals take within their groups. Age and sex of the individual is a major factor determining intra-group spatial position. In the present study, we investigated the within-group spatial positioning of individuals in the Critically Endangered Saiga tatarica (hereinafter – saiga). In saigas living under natural predation pressure in the Stepnoi State Nature Sanctuary (Astrakhan Region, Russia), we investigated the sex-age category of the first individual in the group, the inter-individual distance in the front individuals and the individuals following them, and the distribution of individuals of each sex-age category between various parts of the group. Three (summer) or four (autumn) sex-age categories of the individuals in the moving groups were recognised by direct observations in the field. In summer, adult females, accompanied by their calves, were the very first individuals in most saiga groups observed. This result agrees with the previous notion that experienced females often lead the saiga groups. However, further investigation is needed to confirm whether adult females do indeed take the role of a leader during long-distance group movements. In line with the results on other mammals, the majority of adult females moved in the central third of the group. Spatial preferences of adult females seem to be based on the risk minimisation as the central positions are likely the safest in the group. In autumn, juvenile males were moving first in the majority of the investigated groups probably because they were the most active and fast-moving sex-age category during this season. In addition, juvenile males and females were significantly more often observed in the first third of the group than in the central and the rear thirds. We suggest that despite the fact that the front edge of the group could be the most dangerous spatial position, foraging benefits may outweigh the increased risk for juvenile saigas. In contrast to some other mammals, adult males did not tend to move at the front edge and were equally often observed in the front, central and rear parts of saiga groups. Finally, our results showed that saigas closer to the front edge of the group maintained shorter inter-individual distances than the individuals positioned behind them. The tighter spacing could be used by front individuals to compensate for the increased risks associated with their within-group spatial position.
... Many studies on wild primates have employed the individual identification method, thus contributing to empirical knowledge that different individuals occupy distinct positions within a group. Briefly, individuals that occupy the center of a group may be either dominant [14,15], highly sociable [16], stay longer in the group [17], or female and immature [18,19]. Males can be located in front of the group while travelling, where the risk of encountering predators is high [15,[20][21][22]. ...
In environments with multiple predators, vulnerabilities associated with the spatial positions of group-living prey are non-uniform and depend on the hunting styles of the predators. Theoretically, coursing predators follow their prey over long distances and attack open areas, exposing individuals at the edge of the group to predation risk more than those at the center (marginal predation). In contrast, ambush predators lurk unnoticed by their prey and appear randomly anywhere in the group; therefore, isolated individuals in the group would be more vulnerable to predators. These positions of vulnerability to predation are expected to be taken by larger-bodied males. Moreover, dominant males presumably occupy the center of the safe group. However, identifying individuals at higher predation risk requires both simultaneous recording of predator location and direct observation of predation events; empirical observations leave ambiguity as to who is at risk. Instead, several theoretical methods (predation risk proxies) have been proposed to assess predation risk: (1) the size of the individual ‘unlimited domain of danger’ based on Voronoi tessellation, (2) the size of the ‘limited domain of danger’ based on predator detection distance, (3) peripheral/center position in the group (minimum convex polygon), (4) the number and direction of others in the vicinity (surroundedness), and (5) dyadic distances. We explored the age-sex distribution of individuals in at-risk positions within a wild baboon group facing predation risk from leopards, lions, and hyenas, using Global Positioning System collars. Our analysis of the location data from 26 baboons revealed that adult males were consistently isolated at the edge of the group in all predation risk proxies. Empirical evidence from previous studies indicates that adult male baboons are the most frequently preyed upon, and our results highlights the importance of spatial positioning in this.
... The presence of sub-adult males/older juvenile in front of the troop with less dominant bolder males is associated with the intention of sub-adult males to learn the role of protecting the troop (Social preference hypothesis- Bon et al. 2001). In addition to that, although sub-adult males are more or less similar in size as adult females, they are considered to have less fear intensity compared to adult female, hence less nervous, therefore can retaliate to predator attack as do adult males (Schmitt and Di Fiore 2015). The non-significant different results between males (adult and sub-adult) on feeding behind and in front of the troop, indicates that sex has influence on the horizontal positioning of yellow baboons during feeding. ...
Foraging is among complex animal behaviours, which involve making decisions on what and where to forage, so as to maximize nutritional gain and reduce predation risk. In ungulates, it is known to also be influenced by sexual size dimorphism, however, this is not clear in sexually size dimorphic yellow baboon. Using focal animal sampling techniques, we collected data from habituated troops of yellow baboons to test whether body size and/or sex has influence on their use of vertical and horizontal strata when foraging. Results showed that, yellow baboons foraged more frequently on the ground up to 1 m than beyond this height. However, adult females foraged on the ground significantly more frequently than adult and subadult males. While, adult and subadult males used higher canopy beyond 2 m, more frequently than adult females. Moreover, adult females and subadult males foraged more frequently at the troop centre than adult males. This study concludes that sex and to some extent body size significantly influence foraging decisions of yellow baboon in the use of vertical and horizontal strata. Detailed understanding of spacing behaviour of baboons is recommended as it is important towards better understanding of their complex social life.
... Introduction Schmitt et al. 2015;Catano et al. 2016). The risk of predation can even drive species emigration from certain habitats (Carpenter et al. 2010;Suraci et al. 2016;Jorgensen et al. 2019). ...
Risk-induced fear effects exerted by top predators are pervasive in terrestrial and marine systems, with lasting impacts on ecosystem structure and function. The loss of top predators can disrupt ecosystems and trigger trophic cascades, but the introduction of novel apex predators into ecosystems is not well understood. We documented the emigration of white sharks Carcharodon carcharias in response to the presence of a pair of killer whales, Orcinus orca, at a large white shark aggregation site in South Africa. Between February and June in 2017, five white shark carcasses washed up on beaches in Gansbaai, Western Cape Province, four of which had their livers removed. Sightings per unit effort (sea days) and telemetry data demonstrated that white sharks emigrated from Gansbaai following these predation events, and in response to further sightings of this pair and other killer whale pods in the vicinity. Tagging data demonstrated the immediate departure of white sharks from Gansbaai, and some sharks were subsequently moving east. Contrary to expected and well-documented patterns of white shark occurrence at this site, their sightings dropped throughout the following 2.5 years; change-point analysis on both datasets confirmed these departures coincided with killer whale presence and shark carcasses washing out. These findings suggest that white sharks respond rapidly to risk from a novel predator, and that their absence triggered the emergence of another predator, the bronze whaler Carcharhinus brachyurus. Predator–prey interactions between white sharks, other coastal sharks, and killer whales are increasing in South Africa and are expected to have pronounced impacts on the ecosystem.
... If we pick food scarcity and predation pressure as two fundamental stressors and consider general arguments about the costs and benefits of sociality in gregarious primates (van Schaik 1983;Schülke and Ostner 2012;Markham and Gesquiere 2017), adaptive responses to these two stressors should yield rather different outcomes. Offspring developing in a food-impoverished environment will be faced with increased costs of sociality in terms of within-group scramble and contest feeding competition (van Schaik 1989; Schülke and Ostner 2012) promoting less gregarious and more aggressive/competitive behavior coupled with more exploration and risk taking (Miller 2002;Schmitt and Di Fiore 2015). If the source of maternal allostasis is increased predation risk though, the same prenatal maternal stress response of increased HPA activity should elicit in the offspring changes towards a less risk-prone, explorative, more socially tolerant, and gregarious yet less aggressive phenotype (Sheriff et al. 2017). ...
Prenatal developmental plasticity in response to various environmental and social adversities can affect multiple aspects of offspring phenotype including social behavior strategies with effects that can last into adulthood. Here, we (1) identify adaptive social behavior strategies and their underlying mechanisms as potential targets of developmental plasticity in primates, (2) derive predictions about social behavior outcomes of prenatal adversity from different types of evolutionary models, (3) review the primate evidence for prenatal stress effects on offspring cognitive function, social, and non-social behavior, and (4) discuss avenues for future research. The scarce evidence currently available points towards increased distress behavior, particularly in infant offspring, and reductions of activity, exploration, and affiliative behavior in response to experimental prenatal adversity. Not all effects are stable, the results do not replicate well, and, for the most part, the current data cannot be used to test predictions of evolutionary models because relevant aspects of social behavior were not quantified and not assessed in the complex social environments they evolved for. More comprehensive research in developmental plasticity needs to incorporate sex differences and the interaction of effects from different sensitive periods including adolescence. Moreover, future research needs to assess the role of social buffering in mediating intergenerational effects and trade-offs between the pace of life and social cognitive performance.
... The decision made by an individual on how to position itself relative to its group mates is an underappreciated factor that certainly modulates how different selective pressures define inclusive fitness (Schmitt & Di Fiore 2015). Here, we found that in a group of L. caissara the individual order during coordinated linear movements arriving at and departing from sleeping sites was not random. ...
... The decision made by an individual on how to position itself relative to its group mates is an underappreciated factor that certainly modulates how different selective pressures define inclusive fitness (Schmitt & Di Fiore 2015). Here, we found that in a group of L. caissara the individual order during coordinated linear movements arriving at and departing from sleeping sites was not random. ...
Monkey groups travel in line, exposing individuals to differential risks according to their position. We recorded events of arriving and departing from the sleeping site in a group of Leontopithecus caissara to investigate how the highest risk position is shared among group-mates during those events. We found the dominant male was the first to arrive and depart from the tree hole on most occasions. This finding suggests that the dominant adult male assumed higher risks and played a differential role in predator defense, possibly creating direct benefits for subordinate individuals to stay in the group.
... In primates, predation risk varies considerably among individuals and species of different body sizes (Schmitt and Di Fiore 2015). Smaller-bodied primates are more vulnerable to predation in general and to a wider range of potential predators than larger ones (Struhsaker 1986;Cheney and Wrangham 1987;Mitchell et al. 1991;Isbell 1994;Hill and Dunbar 1998;Ferrari 2009). ...
Predation has been suggested to play a major role in the evolution of primate ecology, although reports of predation events are very rare. Mammalian carnivores, raptors, and snakes are known predators of Neotropical primates, and most reported attacks by snakes are attributed to Boa constrictor (terrestrial boas). Here, we document the predation of a squirrel monkey (Saimiri sciureus) by an Amazon tree boa (Corallus hortulanus), the first record of the predation of a platyrrhine primate by this boid. The event was recorded during a nocturnal herpetological survey in the Piratuba Lake Biological Reserve, in the north-eastern Brazilian Amazon. The snake was encountered at 20:00 hours on the ground next to a stream, at the final stage of ingesting the monkey. The C. hortulanus specimen was 1620 mm in length (SVL) and weighed 650 g, while the S. sciureus was a young adult female weighing 600 g, 92 % of the body mass of the snake and the largest prey item known to have been ingested by a C. hortulanus. The evidence indicates that the predation event occurred at the end of the afternoon or early evening, and that, while capable of capturing an agile monkey like Saimiri, C. hortulanus may be limited to capturing small platyrrhines such as callitrichines.
In environments with multiple predators, the vulnerabilities attached to the spatial positions of group-living prey are not uniform and depend on the hunting styles of the predators. Coursing predators, mainly canids and hyenas, follow their prey over long distances and attack open areas, making individuals at the edge of the group more dangerous than those at the center (marginal predation). In contrast, ambush predators, mainly cats, approach their prey undetected and appear randomly anywhere in the group; therefore, isolated individuals are at a greater risk of predation. However, identifying individuals at high risk of predation requires the simultaneous recording of predator locations and direct observation of predation events, which are both difficult. Therefore, several theoretical methods have been proposed to assess predation risk (predation risk proxies). In a group of wild anubis baboons exposed to predation by leopards, lions, and hyenas, we calculated predation risk proxies using movement data collected from global positioning system (GPS) collars and found that adult males were on the edge of the group with a higher risk of predation (Hypothesis 1). In addition, adult males were more isolated within this group (Hypothesis 2). None of the predation risks differed among the other age-sex classes. The most dominant male was expected to be in the safety center of the group (Hypothesis 3) but was isolated on the periphery, like the other males. Therefore, we discussed why adult males were more peripheral and isolated.
Description Fit linear and generalized linear mixed-effects models. The models and their components are represented using S4 classes and methods. The core computational algorithms are implemented using the 'Eigen' C++ library for numerical linear algebra and 'RcppEigen' ``glue''.
Woolly monkeys have been considered vulnerable to forest fragmentation. However, we found a population of woolly monkeys that has been living in a small forest remnant in Colombian Amazonia, raising questions about which factors determine the persistence or extinction of woolly monkeys in fragmented forests. The main purpose of this investigation was to describe the behavioral ecology of woolly monkeys (Lagothrix lagothricha) in a 136-ha forest fragment in Guaviare, Colombia. We recorded activity patterns, diet, and use of space for three monkey troops by instantaneous sampling on focal animals, and we quantified interindividual distance, between January and December 2008. This group of woolly monkeys spent on average 31.7 % of their time feeding, 32.4 % resting, 34.2 % moving, and 1.8 % in social interactions. Their main feeding items were fruits (57.2 %), followed by leaves (15.5 %), arthropods (15.8 %), seeds (5.2 %), flowers (5.1 %), and others (1.2 %). The three most used plant families for fruit consumption were Moraceae (23.4 %), Fabaceae (16.3 %), and Ulmaceae (8.3 %), and the most important species was Ampelocera edentula (Ulmaceae). We estimated an average daily travel distance of 2,339 m and a home range of 126 ha. We found a negative relationship between the degree of interindividual distance and group size. Most of the studied ecological parameters were within the reported ranges for woolly monkeys in undisturbed habitats. Thus, our evidence indicates that their persistence in fragments does not require drastic behavioral changes. We suggest that fragmentation represents a threat to woolly monkeys when (1) fragments are not productive enough to sustain the population and/or (2) when it leads to a higher hunting pressure on the population.
Primate life histories are marked by remarkably long prereproductive periods, particularly in atelins. Woolly monkeys have among the longest immature phases relative to their body size, but the behavior of woolly monkey juveniles and adolescents has until now been largely unknown. This chapter establishes guide-lines for identifying developmental landmarks in immature woolly monkeys and presents data on a study of the behavioral development and life history of wild juve-nile and adolescent lowland woolly monkeys ( Lagothrix poeppigii) in Amazonian Ecuador. Despite overall low levels of sociality across all ages in this taxon, some sex-specific developmental patterns emerged. Male immatures preferentially inter-acted with adult male groupmates, presumably to gain access to important social resources. Female immatures appeared to increasingly distance themselves from groupmates up to dispersal, but showed a sharp increase in sexual interest in coresi-dent adult males immediately prior to dispersing. Although data on adolescents are limited, this phase in particular appears to be a time of critical importance to woolly monkey life histories in both males and females, and may be of particular interest for future research.
We investigated the time allocation decisions of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a terra firma forest in eastern Ecuador where they occur sympatrically with 9 other primate species. Woolly monkeys spent considerable amounts of time searching for and attempting to procure animal prey—roughly as much time as they spent consuming plant material: ripe fruits, leaves, and flowers. The amount of time spent foraging for animal prey is positively related to the habitat-wide availability of ripe fruits (the predominant component of the woolly monkey diet), and negatively related to both ambient temperature and the abundance of potential prey items in the habitat. Time spent resting showed exactly the opposite pattern with respect to these ecological variables. These results suggest that woolly monkeys follow an energy-maximizing strategy of food acquisition during times of fruit abundance—focusing on animal foods and perhaps laying down fat reserves to utilize when ecological conditions worsen—and follow an energy-minimizing strategy when fruit resources are scarce. Such a strong and seasonal commitment to animal prey foraging is unique among the ateline primates and is not ubiquitous even among lowland woolly monkeys. We suggest that this foraging strategy, and the greater intragroup cohesion that characterizes some populations of Lagothrix, are both opportunistic responses to regional differences in habitat quality. Identifying and accounting for such intraspecific variation should be a goal of any analysis of comparative socioecology.
Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. The importance of predation during evolutionary time is clear, but growing evidence suggests that animals also have the ability to assess and behaviorally influence their risk of being preyed upon in ecological time (i.e., during their lifetime). We develop an abstraction of the predation process in which several components of predation risk are identified. A review of the literature indicates that an animal's ability to assess and behaviorally control one or more of these components strongly influences decision making in feeding animals, as well as in animals deciding when and how to escape predators, when and how to be social, or even, for fishes, when and how to breathe air. This review also reveals that such decision making reflects apparent trade-offs between the risk of predation and the benefits to be gained from engaging in a given activity. Despite this body of evidence, several areas in the study of animal behavior have received little or no attention from a predation perspective. We identify several such areas, the most important of which is that dealing with animal reproduction. Much work also remains regarding the precise nature of the risk of predation and how it is actually perceived by animals, and the extent to which they can behaviorally control their risk of predation. Mathematical models will likely play a major role in future work, and we suggest that modelers strive to consider the potential complexity in behavioral responses to predation risk. Overall, since virtually every animal is potential prey for others, research that seriously considers the influence of predation risk will provide significant insight into the nature of animal behavior.
Sexually selected traits and the use of strategies to enhance male reproductive success (e.g., competition and dispersal) can yield sex differences in metabolic requirements, rates and durations of growth and maturation, and the propensity for risky behavior, which are suggested to result in age-specific sex differences in mortality and life span. We investigated age-specific sex ratios, mortality, and dispersal in Propithecus edwardsi in Ranomafana National Park, Madagascar. We predicted that, due to similarities in growth rates and body sizes, male and female juvenile mortality rates would be comparable; because both sexes disperse and have intense intersexual competition and aggression, adult mortality would be similar; given similarities in dispersal frequency and distance, the timing of dispersal would not differ. We used 80 group-years births, deaths, and dispersals (Nfemales = 41, Nmales = 34) collected over 23 years to calculate sex ratios and survival curves. Females lived longer than males (maximum 32 and 19 years, respectively). Sex ratios were male biased from sexual maturity through 17 years and female biased at birth and older ages. Infant survival probabilities were similar. Thus, differential development and maturation are unlikely explanations for longer female life span in this species. Males were more likely to survive from 2 to 18 years. However, male annual survival probability declined quickly around 13–18 years; males continued to disperse until their deaths, whereas females generally stopped dispersing after 11 years. We suggest that sex differences in the timing of dispersal and the unique challenges of risky behavior at older ages may be sufficient to yield differences in male and female life span.
How do animals use their habitat? Where do they go and what do they do? These basic questions are key not only to understanding a species' ecology and evolution, but also for addressing many of the environmental challenges we currently face, including problems posed by invasive species, the spread of zoonotic diseases and declines in wildlife populations due to anthropogenic climate and land-use changes. Monitoring the movements and activities of wild animals can be difficult, especially when the species in question are small, cryptic or move over large areas. In this paper, we describe an Automated Radio-Telemetry System (ARTS) that we designed and built on Barro Colorado Island (BCI), Panama to overcome these challenges. We describe the hardware and software we used to implement the ARTS, and discuss the scientific successes we have had using the system, as well as the logistical challenges we faced in maintaining the system in real-world, rainforest conditions. The ARTS uses automated radio-telemetry receivers mounted on 40-m towers topped with arrays of directional antennas to track the activity and location of radio-collared study animals, 24 h a day, 7 days a week. These receiving units are connected by a wireless network to a server housed in the laboratory on BCI, making these data available in real time to researchers via a web-accessible database. As long as study animals are within the range of the towers, the ARTS system collects data more frequently than typical animal-borne global positioning system collars (∼12 locations/h) with lower accuracy (approximately 50 m) but at much reduced cost per tag (∼10X less expensive). The geographic range of ARTS, like all VHF telemetry, is affected by the size of the radio-tag as well as its position in the forest (e.g. tags in the canopy transmit farther than those on the forest floor). We present a model of signal propagation based on landscape conditions, which quantifies these effects and identifies sources of interference, including weather events and human activity. ARTS has been used to track 374 individual animals from 38 species, including 17 mammal species, 12 birds, 7 reptiles or amphibians, as well as two species of plant seeds. These data elucidate the spatio-temporal dynamics of animal activity and movement at the site and have produced numerous peer-reviewed publications, student theses, magazine articles, educational programs and film documentaries. These data are also relevant to long-term population monitoring and conservation plans. Both the successes and the failures of the ARTS system are applicable to broader sensor network applications and are valuable for advancing sensor network research.
Considerable interspecific variation in female social relationships occurs in gregarious primates, particularly with regard
to agonism and cooperation between females and to the quality of female relationships with males. This variation exists alongside
variation in female philopatry and dispersal. Socioecological theories have tried to explain variation in female-female social
relationships from an evolutionary perspective focused on ecological factors, notably predation and food distribution. According
to the current “ecological model”, predation risk forces females of most diurnal primate species to live in groups; the strength
of the contest component of competition for resources within and between groups then largely determines social relationships
between females. Social relationships among gregarious females are here characterized as Dispersal-Egalitarian, Resident-Nepotistic,
Resident-Nepotistic-Tolerant, or Resident-Egalitarian. This ecological model has successfully explained differences in the
occurrence of formal submission signals, decided dominance relationships, coalitions and female philopatry. Group size and
female rank generally affect female reproduction success as the model predicts, and studies of closely related species in
different ecological circumstances underscore the importance of the model. Some cases, however, can only be explained when
we extend the model to incorporate the effects of infanticide risk and habitat saturation. We review evidence in support of
the ecological model and test the power of alternative models that invoke between-group competition, forced female philopatry,
demographic female recruitment, male interventions into female aggression, and male harassment. Not one of these models can
replace the ecological model, which already encompasses the between-group competition. Currently the best model, which explains
several phenomena that the ecological model does not, is a “socioecological model” based on the combined importance of ecological
factors, habitat saturation and infanticide avoidance. We note some points of similarity and divergence with other mammalian
taxa; these remain to be explored in detail.
I studied proximal spacing within a group of woolly monkeys (Lagothrix lagotricha) during 7 months at Parque Nacional Tinigua, Colombia. I collected a total of 1188 instantaneous samples on focal individuals, recording the number and age/sex class of individuals that were in contact with, <2 m from, <5 m from the focal animal The results indicate that proximate spacing reflects social affinities and is related to mother-infant relationship and social grooming. Subadult females and adult males are the sex/age classes with the lowest number of individuals in proximity. There are low proximity between adult females and between adult males and high frequencies of nearness between mother and offspring. Associations between males and females were usually low, but in some cases males showed preferences for a given female. There was a relatively gradual increase in spacing between mothers and their offspring as they became older. Old juvenile males were associated chiefly with other males-mostly subadults-whereas juvenile females maintained some proximity only to their mothers. There are also differences in spacing behavior according to different activity types.
I studied antipredator behavior in two species of monkeys to elucidate the role of predation in shaping the social systems of arboreal primates. I compared the responses of monkeys to auditory and visual contact with predators to response elicited by sound playback experiments using the recorded calls of predators. Changes in vigilance and aggregation persisting up to 30 min after predator encounter occurred in both cases. Measures of vigilance shed light on individual perceptions of risk, while aggregation measures—intragroup spatial cohesion and polyspecific associations—permit direct inference about the protective benefits of grouping for the monkeys. They responded to real predator encounters and simulations in similar ways. Thus, sound playbacks of predator vocalizations are effective to simulate predator proximity. Contrary to predictions, predator encounters did not lead invariably to increased cohesion within groups or to increased time spent vigilant. Moreover, behavior in polyspecific associations was no different from that in single-species groups. Only red colobus encountering chimpanzees behaved as predicted by increasing vigilance and intragroup cohesion. The red colobus social system may have developed to protect against chimpanzee attack. In contrast, red-tailed monkey encounters with raptors and chimpanzees involved no change in time spent vigilant, coupled with decreases in intragroup cohesion. I conclude that predation is not a uniform selective pressure and patterns of social behavior within groups do not predict antipredator behavior.
Vigilance behavior, predator detection abilities, and responses to real and model predators were studied in two species of capuchin monkeys (Cebus albifrons and C. apella) in a Peruvian lowland rain forest. Adult males were more vigilant than adult females in both species, mainly because the males spent less time feeding and foraging and partly because they were at the periphery more often than the females. The increased vigilance of adult males is reflected in their superior performance in the detection of (model) predators. Adult and subadult males were also far more likely to approach and mob real and model predators. Adults that were outside the center of the group increased foraging activities but cut back an feeding, much of which was done in exposed tree crowns. Current theory suggests that primate groups are multi-male when a single male is unable to defend sexual access to the group of females. In these small capuchin groups, which are multimale, the enhanced safety of females and young provided by extra adult males furnishes a more plausible explanation. A comparison of the two capuchins with the ecologically similar Southeast Asian Macaca fascicularis suggests that the high predation risk outside the group may also have caused the unusual male career profile in capuchins, which have a long tenure of dominants and a very long potential lifespan. Further predictions of this hypothesis are developed.
Seasonal patterns of group fragmentation, including the size of subgroups and percentage of time spent in subgroups, may provide
information on individual decision-making in response to resource distribution. Age-sex class composition of subgroup membership
can offer insights into the social dynamics of the group as a whole. At most field sites, capuchins (Cebus spp.) form stable groups with no evidence of group fragmentation. Here I describe seasonal subgrouping patterns, including
proportion of time spent in subgroups, subgroup size, age-sex membership, dyadic fidelity, stability of membership, and the
effect of subgrouping on individual foraging efficiency, in a group of wild Cebus apella nigritus. From September 1996 to August 1997 the study group at the Estação Biológica de Caratinga, Brazil divided into 148 different
subgroups, on 99of 194 census days. In contrast to expectations for subgrouping patterns as a response to seasonal distribution
of resources, the proportion of days spent in subgroups did not vary significantly by season. Subgroup composition was relatively
fluid, with multimale multifemale subgroups the most common throughout the year. Unimale multifemale subgroups were restricted
to the wet season; in contrast, all-male subgroups and unimale unifemale subgroups occurred in the dry season. For both males
and females, low rank predicted membership in smaller subgroups. For males, but not females, subgrouping coincided with increased
foraging efficiency, as measured by increased time spent ingesting food and decreased time spent traveling on days with subgrouping
compared to days with the group in a cohesive unit.
Individuals in foraging groups of wedge-capped capuchin monkeys, Cebus nigrivittatus, are organized in consistent and predictable configurations. This study examines how an individual's position in space, as characterized by its position relative to other animals and by its proximity to neighbours, influences its (a) capture success when foraging for invertebrates, (b) access to fruiting trees, and (c) time spent in vigilance (a measure of its vulnerability to predators). The dominant male and female and animals tolerated by this female occupy the advantageous centre-front positions. The positions of other animals depend on their respective age-sex classes, and are discussed relative to the risk of predation and foraging requirements of the different age-sex classes.
Twenty juvenile members of known genealogies in two baboon groups were studied over a 16-month period to evaluate a number of predictions about juvenile spacing behaviour based on the natural history of savannah baboons. Young juveniles (1–2·5 years old) approached more frequently and spent more time in proximity to other group members than did old juveniles (3–5·5 years old). In particular, young juveniles associated more closely with their mothers, particular adult males (possible fathers) and age-peers than did old juveniles. Approaches of young juveniles towards unrelated, high-ranking adults were more likely to occur during feeding than were those of old juveniles. Also, following such an approach, young juveniles were more likely than old juveniles to begin feeding immediately. The overall rates of feeding of old juveniles were depressed when they were in proximity to unrelated, high-ranking adults, whereas the feeding rates of young juveniles were not. Juvenile males approached adult males more often than did juvenile females. Juvenile females approached unrelated adult females more often than did juvenile males. Sex differences also existed in juveniles' choices of unrelated adult female neighbours. Juvenile females associated most often with lactating females, whereas juvenile males associated primarily with cycling females. During group resting, juvenile females approached adult females from higher-ranking matrilines more often than they approached adult females from lower-ranking matrilines. Juvenile males did not exhibit this attraction. Also, among old juveniles, females associated closely with their mothers, whereas males did not. Taken together, the results support the hypotheses that juvenile baboons associate with group members in ways that (1) enhance the probability of surviving an early period of high mortality, (2) create opportunities for social learning of sex-typical behaviours/skills, and, for females, (3) facilitate acquisition of familial dominance status.
Nineteen scientists from different disciplines collaborated in highlighting new methodological and theoretical aspects in the re-emerging study area of fission-fusion dynamics. The renewed interest in this area is due to the recognition that such dynamics may create unique challenges for social interaction and distinctive selective pressures acting on underlying communicative and cognitive abilities. In five sections, we outline new frameworks for integrating current knowledge on fission-fusion dynamics and suggest promising directions for future research using a broad comparative perspective. In the first section, we briefly review the diverse uses of the term “fission-fusion” and propose a fundamental re-thinking away from its current general use as a label for a particular modal type of social system (i.e., fission-fusion societies). Specifically, because the degree of spatial and temporal cohesion of group members varies both within and across taxa, we note that any social system can be described in terms of the extent to which it expresses fission-fusion dynamics, and we thus advocate a realignment of use of the term “fission-fusion” to reflect this perspective. The implications of this perspective are then discussed and expanded in three sections focusing on the socioecology, communication, and cognitive demands of fission-fusion dynamics. The last section explores the relevance of fission-fusion dynamics for human social evolution.
Although ecologists have long recognized that animal space use is primarily determined by the presence of predators and the distribution of resources, the effects of these
two environmental conditions have never been quantified simultaneously in a single spatial model. Here, in a novel approach, predator-specific landscapes of fear are constructed on the basis of behavioral responses of a prey species (vervet monkey; Cercopithecus aethiops), and
we show how these can be combined with data on resource distribution to account for the observed variation in intensity of space use. Results from a mixed regressive–spatial regressive analysis demonstrate that ranging behavior can indeed be largely interpreted as an adaptive
response to perceived risk of predation by some (but not all) predators and the spatial availability of resources. The theoretical framework behind the model is furthermore such that it can easily be extended to incorporate the effects of additional factors potentially shaping
animal range use and thus may be of great value to the study of animal spatial ecology.
Predator sensitive foraging represents the strategies that animals employ to balance the need to eat against the need to avoid being eaten. Ecologists working with a wide range of taxa have developed sophisticated theoretical models of these strategies, and have produced elegant data to test them. However, only recently have primatologists begun to turn their attention to this area of research. This volume brings together primary data from a variety of primate species living in both natural habitats and experimental settings, and explores the variables that may play a role in primates' behavioural strategies. Taken together, these studies demonstrate that predator sensitive foraging is relevant to many primates, of various body sizes and group sizes and living in different environments. Eat or be Eaten encourages further discussion and investigation of the subject. It will make fascinating reading for researchers and students in primatology, ecology and animal behaviour.
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes.
[Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
Spatial variation in predation risk generates a ‘landscape of fear’, with prey animals modifying their distribution and behaviour in response to this variable predation risk. In systems comprising multiple predators and prey species, a key challenge is distinguishing the independent effects of different predator guilds on prey responses. We exploited the acoustically distinct alarm calls of samango monkeys, Cercopithecus mitis erythrarchus, to create a predator-specific landscape of fear from eagles to assess its impact on space use within mixed regressive–spatial regressive models incorporating data on resource distribution and structural characteristics of the environment. The landscape of fear from eagles was the most significant determinant of samango range use, with no effect of resource availability. The monkeys also selected areas of their range with higher canopies and higher understory visibility, behaviour consistent with further minimizing risk of predation. These results contrast with those of vervet monkeys, Chlorocebus aethiops pygerythrus, at the same site for which the landscapes of fear from leopards and baboons were the most significant determinants of space use. While highlighting that predation risk is a key driver of primate behaviour in this population, the landscapes of fear experienced by samango monkeys and vervet monkeys appear to differ despite exposure to identical predator guilds. This emphasizes the importance of distinguishing between the risk effects of different predators in understanding prey ecology, but also that closely related prey species may respond to these predator-specific risks in different ways.
Glance rates, a measure of vigilance, were sampled in infant and young juvenile yellow baboons, Papio cynocephalus, in Amboseli, Kenya, to test ecological and social predictions about the ontogeny of vigilance. Glance rates of young baboons did not vary between closed and open habitats, but did vary with sex, maternal rank and age. Daughters of low-ranking mothers glanced significantly more often than daughters of high-ranking mothers, and the converse was true for males. Glance rates of females, but not males, decreased significantly between 6 and 24 months of age.
Investigates patterns of predation in Papio populations across Africa. The primary predators of baboons are the terrestrial carnivores; in order of importance leopards Panthera pardus, lions Panthera leo and hyaena. In terms of prey selection, leopards are more likely to take 1) adults than juveniles and 2) males than females. While lion attacks are strictly diurnal, leopards will attack during both the day and night. However, both predators are usually limited to conducting attacks when and/or where visibility is limited. Leopards are about twice as successful as lions at hunting baboons. Nocturnal leopard hunts were more successful than diurnal hunts when twilight cases were excluded. Leopard attacks at sleeping sites were more likely to end in prey capture than attacks at waterholes. Male baboons are more likely to retaliate than females, and such behaviour effectively deters predators. Males are paticularly aggressive towards leopards, where in 4/11 cases the leopard was killed. -from Author
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
The use of both linear and generalized linear mixed‐effects models ( LMM s and GLMM s) has become popular not only in social and medical sciences, but also in biological sciences, especially in the field of ecology and evolution. Information criteria, such as Akaike Information Criterion ( AIC ), are usually presented as model comparison tools for mixed‐effects models.
The presentation of ‘variance explained’ ( R ² ) as a relevant summarizing statistic of mixed‐effects models, however, is rare, even though R ² is routinely reported for linear models ( LM s) and also generalized linear models ( GLM s). R ² has the extremely useful property of providing an absolute value for the goodness‐of‐fit of a model, which cannot be given by the information criteria. As a summary statistic that describes the amount of variance explained, R ² can also be a quantity of biological interest.
One reason for the under‐appreciation of R ² for mixed‐effects models lies in the fact that R ² can be defined in a number of ways. Furthermore, most definitions of R ² for mixed‐effects have theoretical problems (e.g. decreased or negative R ² values in larger models) and/or their use is hindered by practical difficulties (e.g. implementation).
Here, we make a case for the importance of reporting R ² for mixed‐effects models. We first provide the common definitions of R ² for LM s and GLM s and discuss the key problems associated with calculating R ² for mixed‐effects models. We then recommend a general and simple method for calculating two types of R ² (marginal and conditional R ² ) for both LMM s and GLMM s, which are less susceptible to common problems.
This method is illustrated by examples and can be widely employed by researchers in any fields of research, regardless of software packages used for fitting mixed‐effects models. The proposed method has the potential to facilitate the presentation of R ² for a wide range of circumstances.
Establishing the importance of predation pressure in determining primate social structure has generated a great deal of discussion. However, the substantive issues in this debate have been obscured by a conflation of the respective roles of predation risk and predation rate as selective forces. In addition, the reported relationships between predation rate and both group size and body weight are likely to be confounded by the effects of reproductive rate and activity period. We propose that the level of sustainable predation rate for a species is determined by the rate at which it is able to reproduce, and that, within this constraint, a species adjusts its body weight and a population its group size so as to reduce predation rate to some tolerable level. In effect, the observed predation rate is the excess mortality from predation that animals are unable to control by adjusting their behaviour. This implies that there should be no relationship between predation rate and either group size or body weight, once the effects of reproductive rate and activity period are removed. We analyse data from the primate literature and show that reproductive rate is indeed the best predictor of a species' predation rate, and that the reported relationships with group size are entirely attributable to a combination of the inclusion of nocturnal species which do not use group size as an antipredator response and the confounding effects of reproductive rate. We discuss these findings in the light of current investigations on predation risk, and conclude that an understanding of the role of predation as a selective pressure on primates will only be achieved by attempts to study the factors that are important in determining a primate's perceived risk of predation.
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 On primate behavior requires defining the intrinsic predation risk they experience, that is the expected rate of predation they would suffer under standardized levels of anti-predator behavior (possibly none — see Hill & Dunbar, this volume). This abstract variable can be assessed qualitatively across different conditions by reference to modeling or common sense, or quantitatively by analyzing the hunting success of the predator independent of the prey's behavior (Cowlishaw, 1997). Great care must be taken in interpreting the behavioral responses of animals to different levels of predation risk when a given behavior can serve multiple functions, such as is the case with vigilance. Furthermore, most anti-predator behaviors carry fitness costs, not only from the lost opportunity to perform other fitness-enhancing activities, but even in terms of predation itself — apparently some primate species benefit from living in small groups which are very difficult for predators to detect instead of using a large-group early-warning defense as postulated in many theoretical models. Such costs will limit the extent to which primates are able to reduce their intrinsic predation risk (Fig. 1).
Dispersal is a behavioral process that shuffles genes across the physical and social landscapes. Analysis of how genetic variation is structured hierarchically and among males versus females can provide insights into underlying dispersal processes, even when direct observations of dispersal events are lacking, but application of these techniques in primate studies has been limited. We investigated dispersal patterns in two South American primates — woolly and spider monkeys — using a combination of multilocus genotype data from > 150 animals sampled at two sites in Amazonian Ecuador and opportunistic field observations that shed light on likely dispersal events. Molecular analyses revealed considerable gene flow by females, but substantial male-mediated gene flow was also detected, particularly for woolly monkeys. In both taxa, the extent of population differentiation between the two study sites was greater for males than for females, indicating that gene flow by males has been more restricted historically. Additionally, in one group of spider monkeys, the average relatedness among adult males was significantly greater than that among females, consistent with strong male philopatry, and assignment tests for that group likewise suggest female-biased dispersal. However, for another group of spider monkeys — and for all groups of woolly monkey surveyed — these patterns were not observed. Our molecular results are concordant with field observations of immigrations by female spider monkeys, disappearances (likely emigrations) involving females of both species, and multiple sightings of solitary males and small bachelor groups in woolly monkeys, as well as with the specific dispersal histories of a few woolly monkey individuals discernable through longitudinal molecular sampling. Overall, the results demonstrate the utility of molecular approaches to studying dispersal in primates as a complement to observational studies, but also suggest that further evaluation of dispersal patterns among these primates is needed.
It has long been thought that predation has had important ecological and evolutionary effects on primates as prey. Predation has been theorized to have been a major selective force in the evolution of hominids.1 In modern primates, behaviors such as active defense, concealment, vigilance, flight, and alarm calls have been attributed to the selective pressures of predation, as has group living itself. It is clear that primates, like other animals, have evolved ways to minimize their risk of predation. However, the extent to which they have been able to do so, given other constraints of living such as their own need to acquire food, has not yet been resolved. Perhaps most hotly debated is whether predation has been the primary selective force favoring the evolution of group living in primates. Part of the difficulty in resolving the debate lies in a paucity of direct evidence of predation. This is regrettable yet understandable since primatologists, by definition, focus on the study of primates, not predators of primates (unless these are also primates). Systematic direct evidence of the effects of predation can best be obtained by studying predators that are as habituated to observers as are their primate prey. Until this is done, we must continue to rely on opportunistic accounts of predation and predation attempts, and on systematically obtained indirect evidence. Such data reveal several interesting patterns: (1) although smaller primates may have greater predation rates than larger primates, even the largest primates are not invulnerable to predation; (2) the use by primates of unfamiliar areas can result in higher predation rates, which might be one pressure favoring philopatry, or site fidelity; (3) arboreal primates are at greater risk of predation when they are more exposed (at forest edges and tops of canopies) than in more concealed locations; (4) predation by mammalian carnivores may often be episodic; and (5) terrestrial primates may not experience greater predation than arboreal primates.
For species of primates in which females emigrate, we would expect males within groups to be related to one another. Kin selection theory suggests that these males should associate preferentially with one another, be more affiliative and cooperative with one another than females are, and compete less overtly with one another over reproductive opportunities than males in female philopatric taxa do. Precisely these patterns of social behavior characterize well-studied populations of 2 of the 3 atelin primate genera: spider monkeys (Ateles) and muriquis (Brachyteles). For the third atelin genus, Lagothrix, patterns of intragroup social behavior have been less well-documented. We studied the social and reproductive behavior of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in Ecuador during a one-year observational study and subsequently used molecular techniques to investigate population genetic structure and dispersal patterns for this taxon.
Among adult male woolly monkeys, both affiliative and agonistic interactions were rare, and males were seldom in close proximity to one another. Relationships among male woolly monkeys are best characterized as tolerant, especially in the context of mating wherein direct competition among males was minimal despite the fact that females mated with multiple males. Relationships among females were likewise generally tolerant but nonaffiliative, though females often directed harassment towards copulating pairs. Affiliative interactions that did occur among woolly monkeys tended to be directed either between the sexes—primarily from female to male—or from younger towards older males, and the proximity partners of females tended to be members of the opposite sex. These results suggest that bonds between the sexes may be more important than same-sex social relationships and that direct female-female competition is an important feature of woolly monkey reproductive biology. Our genetic results indicate that, as in other atelins, dispersal by females is common, but some male dispersal likely occurs as well. In some but not all groups we studied, nonjuvenile males within social groups were more closely related to one another on average than females were, which is consistent with greater male than female philopatry. However, differences in these patterns among our study groups may reflect local variation in dispersal behavior.
The spatial order of mangabey age-sex classes in progressions across canopy gaps was found to resemble strongly that of baboons.
Greater peripherality of adult males (particularly dominant males) and centrality of independent juveniles characterized intragroup
spatial structure whether the predominant group activity was feeding, social interaction, or movement. The similarities in
spacing, despite striking differences in the number and nature of predators, between arboreal, forest mangabeys and terrestrial,
open-country baboons suggest that intragroup spatial structure responds to factors other than predation.
Ecological and behavioral data from long-term field studies of known individuals in two closely related squirrel monkey species (Saimiri oerstedi and S. sciureus) were used to examine hypotheses about the source of variation in female bonding among group-living primates. Social relationships in species which live in cohesive groups are thought to depend on the nature of competition for resources. S. oerstedi and S. sciureus both live in large groups and are subject to intense predation. Direct feeding competition both between and within groups is extremely low in S. oerstedi; in this species female relationships are undifferentiated, no female dominance hierarchy is evident and females disperse from their natal group. S. sciureus also experiences very low levels of between-group competition, but within-group direct competition for resources is frequent; this species demonstrates differentiated female relationships, a female dominance hierarchy, and female philopatry. The correlated ecological and social variables found in these two congeners further minimize the minor effects of phylogenetic differences and emphasize the importance of food distribution in determining social characteristics.
Field data were collected on a free ranging population of vervet monkeys (Cercopithecus aethiops sabaeus) on St. Kitts to test four hypotheses relating cover, risk of predation, and food density to interindividual distance. The
results indicated that when food was not a factor, interindividual distance was positively related to the amount of cover
in the immediate environment, and therefore to risk of predation. When cover was held constant, distance was inversely related
to food density. When the minimum distance for optimal foraging was greater than that required for safety, a compromise distance
intermediate between the two predicted values was observed. Cover and food density also predicted the inverse relationship
found between age-sex class and interindividual distance. Implications of the above in relation to interindividual competition
are discussed.
In winter when the mountain slopes are covered with deep snow, it is easy to obtain quantitative data on the two-dimensional
deployment of members of a troop of wild Japanese monkeys. We observed the deployment of a troop on a slope from the opposite
side of a river. The deployment patterns, evaluated on the basis of the relative distance from the central point (centroid)
of the troop, were different for each sex and age category. Adult females, infants, and 1-year-olds tended to be grouped together
and were concentrated near the center of the troop. On the other hand, adult males were randomly spaced. These tendencies
suggest that the deployment reflects the social structure of the duplicate concentric-circle model originally proposed by
J. Itani (1954).
To determine whether adult males provide females with a service, in this case anti-predator behaviour, in return for inclusion in a group a free-ranging troop of vervet monkeys, Cercopithecus aethiops, was observed for 9 months. Males were more vigilant than females and the discrepancy increased as the breeding season approached. Higher levels of vigilance by males were associated with their spending a greater proportion of time either isolated or exposed at the tops of trees. Males, however, were not vigilant because they were exposed but moved into such positions in order to scan the surroundings. Despite this, males were no more efficient than females at detecting predators. The top-ranking male was the most vigilant and active against predators. It is argued from these and other data that male vigilance is directed at other males and is not a quid pro quo for inclusion. Although females benefit from this vigilance they are not capable of controlling male numbers, and troops, as a consequence, contain a number of supernumerary males who may well be the beneficiaries of the vigilance of others.
Colour pattern variation is a striking and widespread phenomenon. Differential predation risk between individuals is often invoked to explain colour variation, but empirical support for this hypothesis is equivocal. We investigated differential conspicuousness and predation risk in two species of Australian rock dragons, Ctenophorus decresii andC. vadnappa . To humans, the coloration of males of these species varies between ‘bright’ and ‘dull’. Visual modelling based on objective colour measurements and the spectral sensitivities of avian visual pigments showed that dragon colour variants are differentially conspicuous to the visual system of avian predators when viewed against the natural background. We conducted field experiments to test for differential predation risk, using plaster models of ‘bright’ and ‘dull’ males. ‘Bright’ models were attacked significantly more often than ‘dull’ models suggesting that differential conspicuousness translates to differential predation risk in the wild. We also examined the influence of natural geographical range on predation risk. Results from 22 localities suggest that predation rates vary according to whether predators are familiar with the prey species. This study is among the first to demonstrate both differential conspicuousness and differential predation risk in the wild using an experimental protocol. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.
Alarm calling is a widespread antipredator behaviour. Although the function and evolution of alarm call behaviour have long been studied in detail, only in the last decade has there been an upsurge in research into its development. Here, we review the literature on the development of alarm call production (the delivery of calls with a specific set of acoustic features), alarm call usage (the use of calls in particular contexts) and alarm call responses (the responses to calls produced by others). We detail the mechanistic processes that may underlie the development of each aspect, consider the selection pressures most likely to explain the relative importance of these processes, and discuss the substantial variation in developmental rates found both between and within species. Throughout, we interpret existing findings about age-related differences in alarm call behaviour from two major communicatory viewpoints: the idea that signals carry information from sender to receiver, with young taking time to acquire adult-like skills; and the possibility that signals are used to manage the behaviour of receivers, with young behaving adaptively for their age. We conclude that a broader use of various techniques (e.g. cross-fostering and temporary removals), the formation of stronger collaborative links with other disciplines (e.g. physiology and neurobiology) and the initiation of new research avenues (e.g. kleptoparasitism) will ensure that studies on the development of alarm call behaviour continue to enhance our understanding of such topics as the evolution of communication and language, kin selection and cognitive processing.
Abstract This paper investigates the determinants of individual spacing behaviour in a desert baboon population (Papio cynocephalus ursinus). Patterns of neighbour proximity and neighbour density were examined among adults in four groups under different ecological and social conditions (through instantaneous sampling during focal follows). Initial analysis of these data shows that (1) the use of vertical substrates (refuges such as tall trees and cliff faces) can confound patterns of spacing, and (2) individual differences in spacing can depend on the spatial scale over which it is measured. To minimise these substrate and scale effects, this analysis focuses on animals which are off refuges and examines spacing behaviour through its underlying statistical `dimensions' (identified through factor analysis). Analysis of these dimensions indicates that sex, group size, activity-habitat and female reproductive state can all have independent effects on spacing: (1) males are more dispersed than females in smaller groups, (2) male and female dispersion increases with time spent in foraging habitats, and (3) female dispersion is reduced during lactation. According to the hypotheses tested, these results indicate that feeding competition only affects spacing behaviour during foraging while predation risk plays little or no role in spacing. Most aspects of spacing behaviour are best explained by male reproductive strategies and their social repercussions.
Linear Mixed-Effects * Theory and Computational Methods for LME Models * Structure of Grouped Data * Fitting LME Models * Extending the Basic LME Model * Nonlinear Mixed-Effects * Theory and Computational Methods for NLME Models * Fitting NLME Models
Generalized linear mixed models provide a flexible framework for modeling a range of data, although with non-Gaussian response variables the likelihood cannot be obtained in closed form. Markov chain Monte Carlo methods solve this problem by sampling from a series of simpler conditional distributions that can be evaluated. The R package MCMCglmm implements such an algorithm for a range of model fitting problems. More than one response variable can be analyzed simultaneously, and these variables are allowed to follow Gaussian, Poisson, multi(bi)nominal, exponential, zero-inflated and censored distributions. A range of variance structures are permitted for the random effects, including interactions with categorical or continuous variables (i.e., random regression), and more complicated variance structures that arise through shared ancestry, either through a pedigree or through a phylogeny. Missing values are permitted in the response variable(s) and data can be known up to some level of measurement error as in meta-analysis. All simu- lation is done in C/ C++ using the CSparse library for sparse linear systems.
This paper presents an antithesis to the view that gregarious behaviour is evolved through benefits to the population or species. Following Galton (1871) and Williams (1964) gregarious behaviour is considered as a form of cover-seeking in which each animal tries to reduce its chance of being caught by a predator.It is easy to see how pruning of marginal individuals can maintain centripetal instincts in already gregarious species; some evidence that marginal pruning actually occurs is summarized. Besides this, simply defined models are used to show that even in non-gregarious species selection is likely to favour individuals who stay close to others.Although not universal or unipotent, cover-seeking is a widespread and important element in animal aggregation, as the literature shows. Neglect of the idea has probably followed from a general disbelief that evolution can be dysgenic for a species. Nevertheless, selection theory provides no support for such disbelief in the case of species with outbreeding or unsubdivided populations.The model for two dimensions involves a complex problem in geometrical probability which has relevance also in metallurgy and communication science. Some empirical data on this, gathered from random number plots, is presented as of possible heuristic value.
Evidence of nonrandom positioning among adult males is crucial for a protection theory of the spatial organization of baboon progressions. In a recent study it was suggested that systematic positioning of troop members other than mothers and infants is so slight and rare that progressions may be regarded as essentially random. This suggestion depends upon debatable methodological points presumably downgrading previous findings of nonrandom order. Reanalysis of data from this study revealed numerous analytical and statistical problems, as well as serious calculation and other errors, and showed that the findings are consistent with results of the present and previous research. Adult males tended toward the front or back of progressions, a tendency which was intensified in potentially dangerous situations. Dominant males were disproportionately more often frontward and subordinate males rearward. Nonrandom order, which was found for a variety of circumstances at high levels of statistical significance, was unusually general in that it occurred in 6 studies, 7 troops, 2 species, and 5 locations. Such generality is consistent with a protection theory postulating phylogenetic underpinnings of a sociospatial organization which allows an advanced primate to adapt to terrestrial coexistence with predators.
Vervet monkeys give different alarm calls to different predators. Recordings of the alarms played back when predators were
absent caused the monkeys to run into trees for leopard alarms, look up for eagle alarms, and look down for snake alarms.
Adults call primarily to leopards, martial eagles, and pythons, but infants give leopard alarms to various mammals, eagle
alarms to many birds, and snake alarms to various snakelike objects. Predator classification improves with age and experience.
In a year-long study, I investigated the ranging behavior of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a terra firma rainforest in Yasuní National Park, Ecuador, and examined the relationship between ranging, diet, food availability, and food patch use for this population. In Yasuní the total home range sizes for two social groups were 124 and 108 ha, which are much smaller than has been reported previously for Lagothrix elsewhere in its geographic distribution. The mean yearly day range estimates for these same groups were 1,792 m and 1,878 m, which are well within the range of variation previously reported. Ranging behavior was not correlated with the current habitat-wide abundance of ripe fruit, which comprises 76.3% of the yearly diet for this population, but was associated with one measure of likely insect prey abundance and with the availability of immature fruits, a minimal part of the diet. Specifically, one study group moved significantly greater distances during months of high likely insect prey abundance and when immature fruits were abundant. The second study group also traveled farther when likely insect prey abundance was high and when immature fruits were abundant, although the latter relationship only approached significance. This group also devoted significantly more of its daily activity budget to travel during these times. These results indicate that variation in ripe fruit abundance makes no meaningful contribution to explaining variation in ranging behavior for this population of woolly monkeys. Instead, the results raise the possibility that some aspects of the ranging behavior of frugivorous primates may be related to the availability of alternative food sources, such as animal prey, or to monitoring the phenological status of important fruit trees, rather than simply reflecting the degree of intragroup feeding competition.