Kin recognition in white-footed deermice (Peromyscus leucopus)

The degree of relatedness between individuals can influence subsequent social behaviour. Peromyscus leucopus populations may consist, in part, of related individuals. Kin recognition could benefit individuals in establishing sub-populations and inbreeding avoidance. White-footed deermice were tested in pairs according to one of the following categories: littermate sibling, cagemate (1s-c), littermate sibling, non-cagemate (1s-nc), non-littermate sibling, non-cagemate (nls-nc), non-sibling, cagemate (ns-c), and non-sibling, non-cagemate (ns-nc). Differences between n1s-nc and ns-nc encounters indicate kin recognition that cannot be due to prior contact. Both sexes Investigated related strangers (nls-nc) of the opposite sex more than unrelated strangers (ns-nc). Males Avoided related stranger males and Chased unrelated stranger males. Females Warded unrelated strangers longest. This is the first study to demonstrate kin recognition that is not based on prior contact in a small rodent.     

EVOLUTIONARY RELATIONSHIPS AMONG COLONIES OF COLUMBIAN GROUND SQUIRRELS AS SHOWN BY MITOCHONDRIAL DNA

Mitochondrial DNA (mtDNA) from 71 Columbian ground squirrels (Spermophilus columbianus) collected in 12 locations in western Canada were assayed for restriction-site variation with 10 endonucleases. Five of these endonucleases revealed variant patterns, and the composite genotypes were used to develop a linear transformation series among the mtDNA genotypes. Two of the four clones had a wide distribution, while the remaining two clones were geographically restricted. The mtDNA of Columbian ground squirrels was also compared to two other species of Sciuridae: Richardson's ground squirrels (S. richardsonii) and Arctic ground squirrels (S. parryii). Calculation of divergences from fragment length and restriction-site data indicated that Arctic ground squirrels and Richardson's ground squirrels were more closely related to each other than either was to Columbian ground squirrels. The transformation series among clones within the Columbian ground squirrels was rooted using Richardson's and Arctic ground squirrels as out-groups. From these data, we conclude that the colonization by female founders of Columbian ground squirrel populations occurred after deglaciation along the eastern ranges of the Rocky Mountains, while colonies on the western ranges may have been present before extensive deglaciation occurred, having existed in refugia in northwestern Alberta.     

Managing anabolic steroids in pre-hibernating Arctic ground squirrels: obtaining their benefits and avoiding their costs

Androgens have benefits, such as promoting muscle growth, but also significant costs, including suppression of immune function. In many species, these trade-offs in androgen action are reflected in regulated androgen production, which is typically highest only in reproductive males. However, all non-reproductive Arctic ground squirrels, irrespective of age and sex, have high levels of androgens prior to hibernating at sub-zero temperatures. Androgens appear to be required to make muscle in summer, which, together with lipid, is then catabolized during overwinter. By contrast, most hibernating mammals catabolize only lipid. We tested the hypothesis that androgen action is selectively enhanced in Arctic ground squirrel muscle because of an upregulation of androgen receptors (ARs). Using Western blot analysis, we found that Arctic ground squirrels have AR in skeletal muscle more than four times that of Columbian ground squirrels, a related southern species that overwinters at approximately 0°C and has low pre-hibernation androgen levels. By contrast, AR in lymph nodes was equivalent in both species. Brain AR was also modestly but significantly increased in Arctic ground squirrel relative to Columbian ground squirrel. These results are consistent with the hypothesis that tissue-specific AR regulation prior to hibernation provides a mechanism whereby Arctic ground squirrels obtain the life-history benefits and mitigate the costs associated with high androgen production.     

Male-biased Adult Sex Ratios and their Significance for Cooperative Breeding in Dhole,Cuon alpinus,Packs

Two free-ranging packs of dholes (Asiatic wild dog, Cuon alpinus) were monitored for a period of 6 yr (Sep. 1990-Sep. 1996) in the Mudumalai sanctuary, southern India. Demographic data on age structure, litter-size, sex ratio and age and sex specific dispersal were collected. Behavioural data on social interactions and reproductive behaviour among pack members were obtained to determine the frequencies of dominant and subordinate behaviours shown by male and female pack members and a measure of each male's reproductive access to females. Behaviours displayed by pack members at dens were recorded to determine whether any age- or sex-specific role specialization existed during pup care. Tenures for dominant males and females within the pack were calculated to ascertain the rate of breeding vacancies occurring within packs. Approximate levels of genetic relatedness within packs were determined by studying pedigrees. In most years one study pack had a male-biased adult sex ratio. This was caused by almost two-fold higher dispersal of adult females over adult males. A considerable variance existed in the percentage of sub-adults dispersing from the two packs. Differences existed in the frequencies of dominant and subordinate behaviours shown by males. For males, dominance ranks and ranks based on submissive behaviours were not correlated with frequencies of reproductive behaviours. Subordinate males also displayed reproductive behaviours. In packs, dominant males had lower tenures than dominant females indicating that among males breeding vacancies arose more quickly. The litter size was found to be negatively correlated with the age of the breeding female. There were no significant differences across individuals of varying age or sex classes in the display of pup care behaviours. Significant differences did exist among individual adults. Genetic relatedness among packs tended to vary temporally as a consequence of possible mating by subordinate animals and immigration of new males into the pack. In conclusion, it appears that males delay dispersal and cooperate within their natal packs because of the variety of reproductive strategies they could pursue within. A combination of ecological constraints and the difficulties of achieving breeding status within non-natal packs may make early dispersal and independent breeding less beneficial.     

Play behaviour and its effects on social development of common chimpanzees (Pan troglodytes)

The aim of the study was to monitor the social development of infant and juvenile common chimpanzees (Pan troglodytes) through their play behaviour at Taronga Zoo in Sydney in order to examine the possible effects of captivity (such as limited opportunities to play) on social development. Play behaviour was observed by focal animal sampling to determine individual differences, and their relationship to age, sex, and relatedness of the subjects. Analysis revealed marked individual variations in social, solitary, and object play behaviours indicative of a relatively well-balanced social and physical environment. Subjects showed a marked preference for play-partners of a different age compared to their own, and initiated interactions with similar frequency with members of both sexes. Many social-play dyads consisted of related individuals, and familiarity with prospective play-mates was the most decisive factor in social interactions.     

Ground squirrel sociality and the quest for the 'holy grail': does kinship influence behavioral discrimination by juvenile Columbian ground squirrels?

Research on social discrimination by ground-dwelling squirrelshas focused on die ability of squirrels to discriminate kinfrom nonkin. The predominant mechanism underlying that abilityis social familiarization. Although familiarity-based mechanismsmay result in kin discrimination where kin are associated reliablyin space and time, past investigations have largely ignoredadditional levels of social discrimination that may result fromongoing familiarization in the natural context Here we presentdata from a cross-fostering experiment that examines the relativecontributions of rearing association and relatedness to subsequentbehavioral discrimination among juvenile Columbian ground squirrels(Spermophilus columbianus). Rearing association significantlyinfluenced recognitive and agonistic behavior among juvenileswhile relatedness proved insignificant in affecting behavioralinteractions. Thus, direct familiarization in the natal burrowis both sufficient and necessary to account for the transitiveappearance of kin-differential behavior among newly emergedjuveniles documented in previous studies. Reanalyses of datafrom field experiments on S. columbianus social discriminationfail to detect any evidence of kin-biased behavior, and evidencefrom studies purporting to document kinship effects is equivocalat best Taken together with more recent findings, the scantdata suggestive of kin discrimination by Columbian ground squirrelsare best viewed as an artifact of selection promoting the discriminationof familiar from unfamiliar individuals at the level of localizedgroups. Fitness payoffs of such discrimination may accrue viareciprocal altruism, or ‘dear-enemy’ recognition,and would promote the evolution and maintenance of socialitywithout recourse to indirect components of inclusive fitnesscommonly invoked to explain ground squirrel sociality. Finally,our data call into doubt the notion that mechanisms allowingthe direct assessment of kinship should be common among themore social sciurids.     

Social play in wild brown bears of varying age-sex class

Social play behaviour is a well-described phenomenon, almost ubiquitous among mammals. Despite its prevalence, social play takes several forms and may vary in function across species. For solitary species, the function of play outside of the family group remains unclear. Here, we describe the motor patterns of play among non-littermate wild brown bears Ursus arctos of different age-sex class. Play was documented during a time of abundant food availability in three different scenarios: play among non-littermate subadults, play among non-littermate cubs, and play among a ‘group’ of bears of different age and sex class. We used a previously described behavioural ethogram to recognise play. Play followed typical motor patterns and postures expressed by bears during play-fighting: relaxed face, puckered-lip, ears partially flattened to crescent, wrestling, jaw gaping, play-biting, paw-swatting, and lunging. No vocalisations were conducted during play bouts. Older bears displayed ‘self-handicapping’ and ‘role-reversal’ in the play postures they selected when playing with younger bears, suggesting that tactics vary according to age class and dominance ranking. Playing likely allows for the evaluation of conspecifics in a non-aggressive way during times of reduced competition and could also relieve stress in complex social situations.     

Social behavior of infant and mother Japanese Macaques (Macaca fuscata): Effects of kinship,partner sex,and infant sex

The behavioral interactions of 22 infant and mother Japanese macaques with other group members were studied. Focal-animal observations were made from the time of each infant’s birth until 1 year of age. Infants and mothers both displayed exceedingly strong preferences for associating with matrilineal kin and, specifically, for female kin. The degree of genetic relatedness was positively correlated with levels of spatial proximity, contact, grooming, aggression, and play. Overall frequencies of interactions with nonkin were very low, and partner sex was not an important factor in interactions with nonkin. There were no significant differences between male and female infants in interactions with kin versus nonkin. There was only one significant difference between male and female infants in interactions with males versus females: female infants showed stronger preferences for initiating proximity with females over males than did male infants. Because mothers provide the focal point for infant interactions during the first year of life, we compared the behavior of infants and mothers. Mothers were the recipients of more social interactions than were infants, mothers engaged in more grooming than did infants, and infants engaged in more social play than did mothers. These findings are only partially consistent with kin-selection theory, and the inadequacies of studying matrilineal kin discrimination to test kin selection are reviewed. The near-absence of infant sex differences in associations with social partners suggests that although maternal kin other than the mother are important to infant socialization, they probably do not contribute to the development of behavioral sex differences until after the first year of life.     

Kinetics of the sodium pump in red cells of different temperature sensitivity

Ouabain-sensitive K influx into ground squirrel and guinea pig red cells was measured at 5 and 37 degrees C as a function of external K and internal Na. In both species the external K affinity increases on cooling, being three- and fivefold higher in guinea pig and ground squirrel, respectively, at 5 than at 37 degrees C. Internal Na affinity also increased on cooling, by about the same extent. The effect of internal Na on ouabain-sensitive K influx in guinea pig cells fits a cubic Michaelis-Menten-type equation, but in ground squirrel cells this was true only at high [Na]i. There was still significant ouabain-sensitive K influx at low [Na]i. Ouabain-binding experiments indicated around 800 sites/cell for guinea pig and Columbian ground squirrel erythrocytes, and 280 sites/cell for thirteen-lined ground squirrel cells. There was no significant difference in ouabain bound per cell at 37 and 5 degrees C. Calculated turnover numbers for Columbian and thirteen-lined ground squirrel and guinea pig red cell sodium pumps at 37 degrees C were about equal, being 77-100 and 100-129 s-1, respectively. At 5 degrees C red cells from ground squirrels performed significantly better, the turnover numbers being 1.0-2.3 s-1 compared with 0.42-0.47 s-1 for erythrocytes of guinea pig. The results do not accord with a hypothesis that cold-sensitive Na pumps are blocked in one predominant form.     

Choice of companions in social play in piglets

Play activity differences between sexes have been predicted in sexually dimorphic species. A non-random composition of pairs of players in social play has also been suggested. In order to test these proposals in piglets, two experiments were set up on a focal-animal basis.In the first trial, social play as observed in two sets of 16 weaned piglets, from 4 litters of 8 piglets, each with an equal number of males and females. A total of 133 and 101 plays, respectively, were recorded and analysed using a log-linear model including the sex and litter of each player and their interactions. The main results show: (a) a greater play activity in males than in females; (b) more play between partners of the same sex than expected assuming statistical independence; (c) more play between partners born in the same litter than expected assuming statistical independence.The role of the pheromones segregated by submaxillary salivary glands in the sexual recognition evidenced in the first experiment was tested in the second trial. Two sets of 16 piglets, coming from 16 different litters, were observed; one of them as control and the other with 8 males whose glands had been removed and 8 normal females. The analysis of 230 plays recorded confirms the results of the first trial concerning sex and does not show significant differences either in the total number of observed plays or in the preference for partners of the same sex between sets, implying a recognition mechanism other than that of these pheromones.The observed sexual dimorphism in play activity as well as the sex and littermate preferences are in agreement with the hypothesis which assigns adaptive values to these social plays.     

Effects of Social Environment on Play in Squirrel Monkeys: Resolving Harlequin's Dilemma

Yearling-male squirrel monkeys (Saimiri sciureus) were paired with play partners either matched or different from them in age and/or sex. The frequency of play was maintained at equally high levels with both matched and mismatched partners. However, play between mismatched partners was marked by an unusually high incidence of nondirectional wrestling, a less threatening form of playfighting, and an increase in role reversal, suggesting that youngsters had considerable flexibility in the use of alternate strategies to sustain play activity with partners who were atypical for them. These results also attest to the robustness of play and its importance in the behavioral repertoire. The technique of restricting youngsters to atypical play companions is suggested as an effective means of manipulating play, with minimal disruption of other social experiences, for long-term studies of the developmental impact of social play.     

Effects of housing conditions on the development of wet skin lesions in the NOA mouse.

The effects of housing on the onset time and prevalence of wet skin lesions were investigated in NOA mice, which spontaneously develop these lesions at a high rate. Wet skin lesions developed earliest in mice that were housed individually. For mice that were housed in groups, the lesions developed earlier in mice with non-littermate group housing than in mice with littermate group housing. The prevalence of lesions was in the following order: individual housing > non-littermate group housing > littermate group housing. These results suggest that socio-psychological factors are involved in the etiology of wet skin lesions in the NOA mouse. Under individual housing conditions, two other novel characters of the NOA mouse were also observed, specifically, development of dry skin and wet skin lesions at the tail root. These characteristics developed early and with high prevalence and were easily observed on external examination. Therefore, these novel characteristics observed in NOA mice are potential markers of the psychological state of the animals.     

Littermate Influences on Behavioral Development in Acomys cahirinus and Mus musculus

To assess the influence of “littermate” characteristics on early social interactions, preweaning spiny mice (Acomys cahirinus) were raised in pairs consisting of pups differing in age by 15 days, or with a Mus musculus agemate. Whereas the older pups appeared to be relatively unaffected by the replacement of their original littermate with a younger pup, the frequencies of suckling and social contact by the younger pups differed as a function of the age of littermates with whom they were raised. Likewise, although the behaviour of Acomys pups raised with conspecifics vs. Mus agemates did not vary, Mus pups housed with a Mus littermate displayed more frequent interactions with their littermate and less contact with the foster mother than did Mus pups raised with an Acomys littermate. It was concluded that the effective preweaning social environment of Mus and A. cahirinus consists of more than the mother. In particular, littermate characteristics appear to influence interactions between the pups themselves as well as with other social partners.     

The ontogeny of sex differences in the behavior of patas monkeys

Many studies of sex differences in primates have been based on small experimental groups of peers in which only a limited range of social behavior could be expressed. In addition, the first few months of life are often the focus of such studies, with relatively little attention paid to older juveniles. In this study, 11 male and 9 female juvenile patas monkeys, living in a captive social group with all age-sex classes available, were observed between 1 and 4 years of age. A subset of seven patas monkeys was also observed between birth and 1 year of age. Here, we report the development of sex differences in independence, play, grooming, positioning behavior, and aggression over the juvenile period. Juvenile male patas monkeys played more and in longer bouts than females, but wrestling (rough-and-tumble play) was not more common among males. There were few differences in behaviors directed to male and female juveniles by other group members. Distinct differences emerged only in the behaviors of the juveniles themselves, with females being more active participants in social and aggressive interactions than males. In general, sex differences in patas monkeys show a mixture of patterns, some of which are predictive of adult sex differences and some of which appear to be specific to the particular demands of the juvenile period in this species     

The role of play in social organization: Comparative observations on squirrel monkeys (Saimiri)

Various functional theories of play stress that social play is essential for the practice and learning of sex roles, dominance relationships, troop culture, integration of individuals into the troop structure, the control of aggression, etc. Data on squirrel monkeys (Saimiri) in natural environments indicate that social interaction and troop integration can develop in various manners in the absence of social play.Comparative observations were made on squirrel monkeys in a seminatural environment in Florida and 43 natural environments in Panama, Colombia, Peru, and Brazil. There was a broad range of variance in the data on ecology, troop size, troop cohesiveness, average individual distances, frequency of play, etc. In some environments, individuals in the infant and juvenile age classes engaged in social play for approximately 1.5 to 3 hours a day. However, in one environment, not a single incidence of social play occurred during 261 hours of close range observation. The troops in which no play occurred were very cohesive (i.e., they seldom fragmented), and the animals traveled at close individual distances. Agonistic interactions were not uncontrolled. Copulations were observed; and 85 percent of the adult females were accompanied by infants, which indicates a normal rate of reproductive success for the species.Data are presented on friendly, aggressive, sexual, and spacing behavior in squirrel monkeys. These data indicate that (1) social play is not necessary for the development and/or learning of an adaptive modicum of social interaction patterns and troop cohesion, but (2) the opportunity to play provides learning experiences in which young animals can develop more complex, varied social interaction patterns and stronger habits for engaging in frequent social exchanges.     

Sex Differences in Object Manipulation in Wild Immature Chimpanzees (Pan troglodytes schweinfurthii) and Bonobos (Pan paniscus): Preparation for Tool Use?

Sex differences in immatures predict behavioural differences in adulthood in many mammal species. Because most studies have focused on sex differences in social interactions, little is known about possible sex differences in ‘preparation’ for adult life with regards to tool use skills. We investigated sex and age differences in object manipulation in immature apes. Chimpanzees use a variety of tools across numerous contexts, whereas bonobos use few tools and none in foraging. In both species, a female bias in adult tool use has been reported. We studied object manipulation in immature chimpanzees at Kalinzu (Uganda) and bonobos at Wamba (Democratic Republic of Congo). We tested predictions of the ‘preparation for tool use’ hypothesis. We confirmed that chimpanzees showed higher rates and more diverse types of object manipulation than bonobos. Against expectation, male chimpanzees showed higher object manipulation rates than females, whereas in bonobos no sex difference was found. However, object manipulation by male chimpanzees was play-dominated, whereas manipulation types of female chimpanzees were more diverse (e.g., bite, break, carry). Manipulation by young immatures of both species was similarly dominated by play, but only in chimpanzees did it become more diverse with age. Moreover, in chimpanzees, object types became more tool-like (i.e., sticks) with age, further suggesting preparation for tool use in adulthood. The male bias in object manipulation in immature chimpanzees, along with the late onset of tool-like object manipulation, indicates that not all (early) object manipulation (i.e., object play) in immatures prepares for subsistence tool use. Instead, given the similarity with gender differences in human children, object play may also function in motor skill practice for male-specific behaviours (e.g., dominance displays). In conclusion, even though immature behaviours almost certainly reflect preparation for adult roles, more detailed future work is needed to disentangle possible functions of object manipulation during development.     

A descriptive study of social development in the rat (Rattus norvegicus)

The social interactions between juvenile rat pups (Rattus norvegicus) were observed daily between 21 and 55 days of age. The data were analysed for developmental changes, sex differences, play-partner preferences, and dominance relations. The results revealed clear patterns in the development of sexual and agonistic behaviours in the rat. This development refers to changes in either the manner in which animals interact or the behaviours involved in social play, but not to the topography of specific behaviours. Development toward the adult pattern of social behaviour was temporally associated with the period of sexual maturation (i.e. between days 36 and 50).     

Individual- and Sex-related Strategies of Wrestling Play in Captive Squirrel Monkeys

The play behavior of 10 juvenile squirrel monkeys (Saimiri sciureus) was observed for 7 months in both mixed-sex and same-sex laboratory social groupings to identify strategies by which individuals may derive maximum benefit from play. Two types of play wrestling were identified: directional if one partner was on top of and dominating the other, and nondirectional if both partners hung from a perch and clasped each other equally. Males (N=5) wrestled more often, had longer bouts, and used proportionately more directional wrestling than did females (N = 5). Initiation Behaviors, leading predictably to play, were performed preferentially to certain partners, independent of affiliative (huddling) preferences. Both sexes performed more Initiation Behaviors to same-sex partners. Individuals, regardless of sex, preferred play partners whom they could dominate during directional wrestling; with partners whom they could not dominate, they preferred nondirectional wrestling, where partners were equal. The observed preferences are interpreted as evidence for individual strategies maximizing winning at directional wrestling. Role reversal is discussed as a strategy encouraging play between youngsters of diverse abilities, and as a means of providing needed experience in a variety of social roles.     

A study of postnatal appendicular skeletal maturation in captive-born squirrel monkeys (Saimiri boliviensis)

This study is based on a mixed longitudinal radiographic sampling of appendicular bones in 82 captive-born squirrel monkeys (Saimiri boliviensis). All appendicular ossification centers had appeared radiographically by 17 weeks of age, and epiphyseal fusion was complete by 47-53 months of age. No statistically significant differences were found between the sexes in comparisons carried out at birth and at 6 and 8 months of age. Valid sex comparisons could not be made at other ages owing to the small size of the sample. The sequence of appearance of the ossification centers (Spearman correlation coefficient of Saimiri vs. Callithrix = 0.68) shows greater interspecies differences than the sequence of fusion (Saimiri vs. Callithrix = 0.88).     

Hibernating patterns of free-ranging Columbian ground squirrels

Summary The patterns of torpor and euthermy during hibernation was documented for 28 free-ranging Columbian ground squirrels (Spermophilus columbianus) fitted with temperature-sensitive radio transmitter collars. Adult males began hibernation earlier, were euthermic for a greater proportion of the hibernating season and emerged earlier than other age and sex classes. The patterns of hibernation of adult females did not differ significantly from those of juveniles. Emergence from the hibernaculum was preceded by a long (3–12 d) euthermic interval in adult males but not in adult females or juveniles. Changes in soil temperature did not appear to initiate emergence. The greater time spent euthermic by adult males is interpreted as a significantly greater energy cost of hibernation for adult males than for other age and sex classes. The benefits offsetting these costs may be increased reproductive potential in spring and avoidance of predation in late summer.