Carrying and hand-use patterns in Panamanian white-faced capuchins (Cebus capucinus)

The aim of this project was to examine the potential influence of postural regulation on capuchin hand-use patterns by focusing on tasks that involved the carrying of objects. Two months were spent on Barro Colorado Island, Panama, collecting data on ten white-faced capuchins (Cebus capucicus) (four adult males/six adult females). Over 215 contact hours were spent with the monkeys, and a total of 213 carries were recorded. No hand preference bias at the population level was found for the carry task; and no detectable hand-use patterns for carry were correlated with the weight of the object carried (except a right-hand bias for carrying medium-sized objects), the plane of the monkey's movement, its locomotor pattern, or its height above the ground. Therefore, the results of this study do not support the hypothesis that the need for postural regulation while carrying an object influences hand-use patterns in free-ranging capuchins. Our results are especially important because they are contrary to the results of the only other free-ranging capuchin laterality study conducted to date (Panger, 1998).     

Ontogenetic changes and the stability of rhesus monkey dominance relationships

Dominance relationships were studied in a rhesus monkey group during five consecutive years. The group consisted of eight stable matriarchies and an adult male class which was replaced at the start, and again at the midpoint, of the study. Immature males were selectively harvested to maintain a sex ratio typical of natural troops. Maximum group size during the study was 77 animals.Dominance relationships were remarkably stable, with only 4.4% of dyads failing to show unidirectional relationships. Despite this stability, a linear ranking of all group members was not possible. Male dominance relationships with other males were among the most stable, following the fighting which ensued on male introductions. Male introductions did not disrupt female dominance relationships.Adult female dominance relationships were also quite stable, but immature females slowly achieved dominance over older sisters and females subordinate to their mothers. Such reversals were the result of processes lasting over many months. Many dominance assertions occurred prior to puberty but a significant number occurred following sexual maturity. Maturing females did not reverse dominance relationships according to any particular hierarchial order and, as a consequence, many were subordinate to animals that were dominated by others that they dominated.Although there was an alpha male that was dominant to all animals in the group, adult females dominated most adult males. Adult males, however, often reciprocated aggression directed at them. They almost invariably threatened or countercharged aggressive immature animals regardless of matriarchial membership. Adult males dominated some adult and most young females, even in families containing matriarchs and adult females to which the adult males always submitted.The dominance relationships of young males were similar to those of their sisters, until puberty. Young males did not necessarily bypass adult males that their mothers outranked, and often failed to win against adult females that their mothers dominated. Adolescent female aggression against females is seldom interfered with by adult males, and females may actively aid one another against males. In contrast, the aggression of young males often elicits interference by adult males, and young males often become the targets of redirected aggression in the group. As a consequence, whereas young females rise in rank to positions adjacent to their mothers, adolescent males often suffer losses to animals that they had dominated as juveniles.     

Potentially infanticidal behavior in the Amazon river dolphin (<Emphasis Type="Italic">Inia geoffrensis</Emphasis>)

Infanticide by males is a phenomenon common in species in which the reproductive output of large numbers of females can be monopolized by a small number of males. It is thought to increase a male’s fitness, at the expense of the fitness of the infant’s parents, by bringing females into season more quickly. Infanticide by males has been recorded in just three cetacean species. We report aggressive behavior suggestive of infanticide in a fourth, the Amazon river dolphin (Inia geoffrensis). We observed and photographed a series of attacks on a neonate Amazon river dolphin by a large male, with apparent protective behavior by the mother. Although infanticide was not confirmed, the forceful, aggressive behaviors were highly suggestive of infanticidal behavior and represent another important data point for comparative studies of infanticide in mammals. Amazon river dolphins may have a polygynous, polyandrous, or promiscuous mating system, the latter two of which are not the norm in species in which the reproductive output of large numbers of females are monopolized by a small number of males. However, sexual dimorphism, high rates of aggression by males, socio-sexual object-carrying displays by males, and a long interbirth interval suggest that successful male Amazon river dolphins may be able to monopolize a large proportion of mating opportunities, and it is plausible that male dolphins can improve their reproductive success by bringing females into estrous sooner by killing the offspring of other males.     

Spatial and Social Sexual Segregation Patterns in Indo-Pacific Bottlenose Dolphins (Tursiops aduncus)

Sexual segregation seems to be common in bottlenose dolphins, whereby males and females live in different pods that mix mainly for mating. Male dolphins often use aggressive behaviour to mate with females, while females with calves may have different activity and dietary requirements to males and different susceptibility to predation. We investigated the degree of spatial and social sexual segregation in Indo-Pacific bottlenose dolphins (Tursiops aduncus) in a subtropical estuary in Australia. Based on surveys completed over three years, dolphin groups were mostly mixed-sex or female. Mixed-sex groups were found in larger groups in mostly deeper water, whereas, female groups were foraging across all water depths in smaller groups. Aggressive coercive behaviour by males towards females was high, occurring mainly in deeper water, at higher tides, and outside the breeding season. Habitat use by female dolphin groups suggests that shallow tributaries may provide a sanctuary from aggressive males, access to suitable prey items and density for mothers and their calves, or a combination of these factors.     

Genetic evidence for sex-biased dispersal in resident bottlenose dolphins (Tursiops aduncus)

In most mammals males usually disperse before breeding, while females remain in their natal group or area. However, in odontocete cetaceans behavioural and/or genetic evidence from populations of four species indicate that both males and females remain in their natal group or site. For coastal resident bottlenose dolphins field data suggest that both sexes are philopatric to their natal site. Assignment tests and analyses of relatedness based on microsatellite markers were used to investigate this hypothesis in resident bottlenose dolphins, Tursiops aduncus, from two small coastal populations of southeastern Australia. Mean corrected assignment and mean relatedness were higher for resident females than for resident males. Only 8% of resident females had a lower probability than average of being born locally compared to 33% of resident males. Our genetic data contradict the hypothesis of bisexual philopatry to natal site and suggest that these bottlenose dolphins are not unusual amongst mammals, with females being the more philopatric and males the more dispersing sex.     

Captive Bottlenose Dolphins (Tursiops truncatus) Spontaneously Using Water Flow to Manipulate Objects

Several terrestrial animals and delphinids manipulate objects in a tactile manner, using parts of their bodies, such as their mouths or hands. In this paper, we report that bottlenose dolphins (Tursiops truncatus) manipulate objects not by direct bodily contact, but by spontaneous water flow. Three of four dolphins at Suma Aqualife Park performed object manipulation with food. The typical sequence of object manipulation consisted of a three step procedure. First, the dolphins released the object from the sides of their mouths while assuming a head-down posture near the floor. They then manipulated the object around their mouths and caught it. Finally, they ceased to engage in their head-down posture and started to swim. When the dolphins moved the object, they used the water current in the pool or moved their head. These results showed that dolphins manipulate objects using movements that do not directly involve contact between a body part and the object. In the event the dolphins dropped the object on the floor, they lifted it by making water flow in one of three methods: opening and closing their mouths repeatedly, moving their heads lengthwise, or making circular head motions. This result suggests that bottlenose dolphins spontaneously change their environment to manipulate objects. The reason why aquatic animals like dolphins do object manipulation by changing their environment but terrestrial animals do not may be that the viscosity of the aquatic environment is much higher than it is in terrestrial environments. This is the first report thus far of any non-human mammal engaging in object manipulation using several methods to change their environment.     

Alliance membership and kinship in wild male bottlenose dolphins (Tursiops aduncus) of southeastern Australia

Bottlenose dolphins are one of only a few mammalian taxa where the males are known to cooperate within their social group in order to maintain mating access to single females against other males. Male bonds in bottlenose dolphins have been hypothesized as evolving through kinship and associated inclusive fitness effects. In this study we tested whether individually identified male bottlenose dolphins preferentially associate and form alliances with kin in a small coastal resident population of southeastern Australia using a combination of behavioural data, genetic sexing, sequences of the mitochondrial DNA control region and nuclear microsatellite markers. Males generally associated significantly more often than expected with one to three other males, with whom they jointly herded females for mating. Associations and alliance membership were not associated with either maternal kinship or genetic relatedness. The majority of male pairs within alliances were randomly related, although high relatedness values were found between males of different alliances in the resident population. These findings indicate that mechanisms other than kin selection may be foremost in the development and maintenance of cooperation between male bottlenose dolphins.     

Social behaviour and infant carrying in a group of moustached tamarins,Saguinus mystax (primates: Platyrrhini: Callitrichidae), on Padre Isla,Peruvian Amazonia

The social behaviour of a group of eight moustached tamarins,Saguinus mystax, (five males, three females) was studied on Padre Isla in northeastern Peru. About 60% of all allogrooming was done by the two adult males in the group, and about 11% by a young adult female. All other group members groomed very little. The adult breeding female received more grooming than any other group member. After the death of the adult female (preyed upon by an anaconda) the amount of active allogrooming remained constant for all group members except for the young adult female, who increased her contribution to about 30%. Her preferred grooming partner was the subadult female, which generally screamed when being groomed by the young adult female and terminated grooming by going away. This kind of grooming relation is termed “forced grooming” and is interpreted as a possible social control mechanism. The young adult female groomed the adult males more often after the death of the adult female than before. This might have had the function of strengthening the social bond with the adult males and in obtaining the breeding position in the group. After the death of the adult female, the vulva of the young adult female grew to full adult size. Agonistic behaviour was less frequent than allogrooming. Most aggressive interactions (50%) originated from the subadult male of the group. The young adult female was the target of most of these aggressions. Extremely little aggression occurred between the three females. The young adult female was the only individual who tried to emigrate from the group during the study period. Her attempt to join a neighbour group failed due to rejection by all four members of this group. All group members participated in carrying an infant, but the adult males and the young adult female carried most frequently. Contribution to infant carrying varied with the infant's age.     

Sex bias in biopsy samples collected from free-ranging dolphins

Biological samples of free-ranging dolphins are increasingly used to gain information on population structure and ecology. In small cetaceans, the gender of individuals usually cannot be determined at sea, and population sex ratio has to be inferred indirectly. We used molecular sexing to determine the gender of 340 biopsy samples of bottlenose dolphins, Tursiops truncatus, spotted dolphins, Stenella frontalis, and common dolphins, Delphinus delphis, collected around the Azores and Madeira. Sex ratio was globally skewed in favor of males, and differed between species and archipelagos. Skew was probably influenced by the selectivity of biopsy collectors and seasonal or year-round predominance of males in natural populations. Skew was also influenced by sampling duration and intensity. In the Azores, when several samples were successively collected within the same group, the proportion of female samples decreased as a function of sample order. This trend indicated a tendency for females to increasingly avoid the boat while samples were being collected. It showed that males and females reacted differently to the perturbation caused by the biopsy sampling process (i.e., sample collection and driving style).     

Manipulation of objects in a captive group of lion-tailed macaques (Macaca silenus)

The purpose of this study was to investigate the manipulative propensities of a captive group of lion-tailed macaques (Macaca silenus). Simple natural objects (browse and bamboo poles) were provided regularly in the home cage. Findings indicate richness in the frequency and form of manipulative activities, with juvenile males manipulating the test objects more frequently and exhibiting more goal-directed manipulative activity than adult females. A variety of goal-directed manipulative activities (use of objects to act as ladders, to apply leverage, and to create perches) occurred spontaneously, with some instances involving joint action or social use. These data are consistent with the hypotheses that macaques possess extensive capacities for object exploration and social facilitation, and that an evolutionary history of omnivorous foraging habits correlates positively with the expression of anomalous sensorimotor skills.     

Maternal aggression and intermale social aggression: a behavioral comparison

The aggressive behavior of alpha male rats and lactating females were each examined toward an intact adult male rat, a castrated adult male rat, an anesthetized adult male rat, a nonlactating adult female rat, an adult albino guinea pig (male or female), or an albino mouse (male or female). When in their living colony, females displayed high levels of aggressiveness toward all stimulus objects except a mouse. The aggression toward the intruding males occurred whether the female's pups were present or not. Alpha males were aggressive toward the same stimuli except an intruding female rat and a mouse. When tested in an unfamiliar colony, the males but not the females (with or without pups present) were aggressive toward an adult male rat. Half of the females but none of the males displayed defensive burying toward an anesthetized intruder. It is suggested that the attack on an adult female, the absence of attack outside of the resident colony, and the tendency to display defensive burying are features of the aggressiveness of lactating females that are fundamentally different from the aggressiveness of alpha males. The form of the aggression (lateral attack vs. lunge attack) was only quantitatively different in males and females.     

Paternity and kinship patterns in polyandrous moustached tamarins (Saguinus mystax)

We studied patterns of genetic relatedness and paternity in moustached tamarins, small Neotropical primates living in groups of 1–4 adult males and 1–4 adult females. Generally only one female per group breeds, mating with more than one male. Twin birth are the norm. In order to examine the genetic consequences of this mating pattern, DNA was extracted from fecal samples collected from two principal and six neighboring groups. DNA was characterized at twelve microsatellite loci (average: seven alleles/locus). We addressed the following questions: Do all adult males have mating access to the reproductive female of the group? How is paternity distributed across males in a group? Can polyandrous mating lead to multiple paternity? Are nonparental animals more closely related to the breeders than to the population mean? And, are mating partners unrelated? Breeding females mated with all nonrelated males. In at least one group the father of the older offspring did not sire the youngest infant although he was still resident in the group. We also found evidence for multiple paternity in a supposed twin pair. Yet, within each group the majority (67–100%) of infants had the same father, suggesting reproductive skew. Relatedness within groups was generally high (average R = 0.31), although both nonrelated males and females occurred, i.e., immigrations of both sexes are possible. Mating partners were never found to be related, hence inbreeding seems to be uncommon. The results suggest that while the social mating system is polyandry, paternity is often monopolized by a single male per group. Am J Phys Anthropol, 2005. © 2004 Wiley-Liss, Inc.     

Generalization of 'same-different' classification abilities in bottlenosed dolphins

Two bottlenosed dolphins taught to classify pairs of three-dimensional objects as either same or different were tested with novel stimulus sets to determine how well their classification abilities would generalize. Both dolphins were immediately able to classify novel pairs of planar objects, differing only in shape, as same or different. When tested on sets of three objects consisting of either all different objects or of two identical objects and one different object, both dolphins proved to be able to classify 'all different' sets as different and 'not all different' sets as same, at levels significantly above chance. These data suggest that dolphins can use knowledge about similarity-based classification strategies gained from previous training to perform successfully in a variety of novel same-different classification tasks. Visual classificatory abilities of dolphins appear to be comparable to those that have been demonstrated in primates.     

A QUANTITATIVE ASSESSMENT OF DOMINANCE RELATIONS AMONG BOTTLENOSE DOLPHINS

Agonistic behavior of bottlenose dolphins was studied at Brookfield Zoo for nearly 4.5 yr, and dominance relationships were determined using a quantitative technique adapted from primate behavioral research. Dominance relations among dolphins were influenced by the gender of participants. Male dolphins were clearly and consistently dominant to females, and intersexual agonism occurred at moderate rates with seasonal peaks in spring and fall. Dominance relationships among female dolphins were age-ordered and stable, even though agonism among females did occur at uniformly low rates. In contrast, the two males had a changeable dominance relationship in which periods of stability and low-level agonism were interspersed with episodes of intense competition. Zoo-based research revealed patterns of behavior that conformed to current knowledge about bottlenose dolphin social structure. Moreover, research in a zoo setting facilitated development of a quantitative technique that can be used to assess cetacean dominance relationships in field research.     

Sex differences in leadership during group movement in mantled howler monkeys (Alouatta palliata)

Benefits of group life depend in large part on whether animals remain cohesive, which often requires collective decisions about where and when to move. During a group movement, the leader may be considered as the individual occupying the vanguard position of the group progression, when its movement evokes following by other group members. In nondespotic societies, individuals with greater incentives to move frequently are leaders. During 15 months of observations (1,712 contact hours), we investigated two mantled howler monkey (Alouatta palliata) groups at La Flor de Catemaco (Los Tuxtlas, Mexico) to examine whether sex and female reproductive state influenced leadership likelihood in two contexts: movements toward feeding trees; movements associated with loud calls, a group-defense behavior used by males of this genus. Females led and occupied forward positions during group movements toward feeding trees more often than adult males. Adult females led these movements more frequently when they were gestating than when they were lactating or cycling. There were no differences between sexes in the leadership of group movements associated with loud calls. Leadership by gestating females is perhaps the result of their higher nutritional/energetic needs when compared with cycling females, and of their greater mobility when compared with lactating females carrying dependent offspring. Female leadership during movements toward feeding trees may be a mechanism to optimize access to food resources in mantled howler monkeys.     

Lactation and care for unrelated infants in forest-living ringtailed Lemurs

An adult female ringtailed lemur (Lemur catta) known not to have been pregnant showed spontaneous lactation in response to twin infants born to an unrelated female. The females had met only 7 months earlier, when they and two other unrelated adult females were released from separate locations in a forest enclosure to form a new social group. Three months after release, an adult male from an adjacent enclosure gained access to the new group for 1 day, the day of one female's estrus. No males had access to the females throughout the remainder of the breeding season. Within 2 weeks of the birth of the twins, one of the other adult females began carrying the infants frequently, typically one at a time. All three females were checked for lactation when the infants were two months old. Both their mother and the unrelated adult who had been carrying the infants were producing milk. The third adult female, who never carried either infant, had no milk. The third adult female, who never carried either infant, had no milk. This female, however, like the two maternal females, frequently attacked unfamiliar immigrating adult males when the males approached the infants. Potential implications of these observations concerning the social organization of ringtailed lemurs are discussed.     

Effect of Dominance,Reproductive State,and Group Size on Body Mass in Macaca radiata

Body mass can impact reproductive performance in males and females. In nonhuman primates the relationship is often mediated by dominance. We measured body mass monthly in a provisioned group of bonnet macaques (Macaca radiata) living at a Hindu temple. We also measured body mass on 3 occasions in a wild population of bonnet macaques. In the temple group, females that reproduced lost body mass, while females that did not reproduce gained body mass. Mass loss among females occurred primarily while they were nursing. Adult males from the temple group lost mass during the mating season and gained it during the non-mating season. Subadult males experienced less seasonal variation in body mass. Body mass and changes in mass were not related to dominance rank in either the temple or the forest group. Furthermore, maternal dominance rank did not affect infant mass. Females from the smallest forest group weighed significantly less than females from the two larger forest groups, which suggests intergroup competition in the population. Body mass was not related to dominance rank in a straightforward manner but may indirectly affect reproductive performance. The pattern of body mass change suggests that the period of lactation is critical for females and endurance rivalry is an important form of competition among males.     

Female transfer between one-male groups of proboscis monkey (<Emphasis Type="Italic">Nasalis larvatus</Emphasis>)

Successful or unsuccessful female transfers were observed seven times during a 32-month field study of proboscis monkeys (Nasalis larvatus) inhabiting a riverine forest along a tributary of the Kinabatangan River, Sabah, Malaysia. In all cases, the females voluntarily left their own groups and immediately joined with another one. When adult females tried to shift to other groups, adult males called them back to their own groups, but appeared to be indifferent to subadult females. When the adult females returned, the males never attacked the females physically, but instead often emitted herding sounds to them. One subadult female was repelled by a resident adult female. When one adult female transferred into a new one-male group, she left her behind son in an all-male group. The number of females often fluctuated in most study groups, with this fluctuation being more prominent among subadult females than adult females. It is likely that female transfer in proboscis monkeys is not a rare occurrence and that it is especially common among sub-adult females.