Unrelated Juveniles Research Articles

Analysing age structure, residency and relatedness uncovers social network structure in aggregations of young birds

Animal sociality arises from the cumulative effects of both individual social decisions and environmental factors. While juveniles' social interactions with parents prior to independence shape later life sociality, in most bird and mammal species at least one sex undergoes an early life dispersal before first-year reproduction. The social associations from this period could also have implications for later life yet are rarely characterized. Here, we derived predictions from available examples of juvenile groups in the literature (mobile ‘flocks’, spatially stable ‘gangs’ or adult-associated ‘crèches’) and then used three cohorts of juvenile hihi, Notiomystis cincta , a threatened New Zealand passerine, to demonstrate how multistate modelling and social network analysis approaches can be used to characterize group type based on residency, movement, relatedness and social associations. At sites where hihi congregated, we found that juveniles were resighted at a higher frequency than adults and associated predominantly with unrelated juveniles rather than siblings or parents. Movement between group sites occurred, but associations developed predominantly within the sites. We suggest therefore that juvenile hihi social structure is most similar to a ‘gang’, a group structure in which juveniles congregate without adults at predictable sites. Such gangs have previously only been described formally in ravens, Corvus corax . By combining spatial and social network analyses, our study demonstrates how social group structures can be described and therefore facilitate broader comparisons and discussion about the form and function of juvenile groups across taxa. • Early life social behaviour once young leave parents is poorly understood. • We characterize group structure and social associations in a passerine bird. • Juveniles associated with unrelated juvenile peers rather than siblings or parents. • Social structure resembled ‘gangs’ which have few empirical examples. • Describing social structure can help us understand early life social environment.

Behavioral responses to changes in group size and composition: a case study on grooming behavior of female Japanese macaques (Macaca fuscata yakui)

Primates flexibly change their grooming behavior depending on group size and composition to maintain social relationships among group members. However, how drastic social changes influence their grooming behavior remains unclear. We observed the grooming behavior of adult female Japanese macaques in two groups temporarily formed as one-female groups from multi-female groups and compared their behaviors between the multi-female and one-female periods. Adult females more frequently performed grooming with both their relatives and unrelated juveniles during the one-female period when other adult females were unavailable as alternatives to their absent familiar partners. The increased grooming time and diversity of grooming partners might alleviate the short-term stress caused by the loss of grooming partners and reduce social instability or mitigate the long-term stress due to disadvantages in intergroup conflicts. Our study provides rare evidence on the flexibility in grooming behavior of primates and encourages accumulating case reports for understanding behavioral responses of primates to drastic social changes.

Kinship modulates the attention of naïve individuals to the mobbing behaviour of role models

The social acquisition of life skills is essential in a wide range of species. Field experiments have demonstrated that naive young learn particularly from their parents how to deal with predators or how to find suitable food. However, it remains unclear whether the response of young differs in a novel situation when together with related (i.e. parents) or unrelated role models. We addressed this question in a group-living bird species, the Siberian jay, Perisoreus infaustus, groups of which can contain both related and unrelated juveniles. Groups are formed around a breeding pair which engages in prolonged parental care, facilitating delayed dispersal of offspring for up to 5 years. About 25% of juveniles are killed by predators during their first year of life, suggesting that predator avoidance is a crucial life skill for juveniles. Exposing groups to perched predator models showed that kinship influenced how juveniles responded to the mobbing behaviour of breeders. Upon exposure to a predator model, related juveniles immediately paid attention to the behaviour of breeders and copied most of their movements. In contrast, unrelated juveniles copied the behaviour of breeders less frequently, but regularly foraged in the presence of a predator model. These results show that juveniles respond differently to parents and unrelated role models, potentially affecting the acquisition of vital life skills. Parental care creates a close social bond, predisposing juveniles to pay attention especially to novel behaviours shown by their care-givers. Furthermore, parents have a fitness benefit from facilitating the skill acquisition of their offspring. Thus, a prolonged parent-offspring association is likely to enhance skill acquisition and influence cognitive evolution across species.

Pair-bond formation and mate fidelity among juvenile Willow Tits

Willow Tits Poecile montanus maintain yearlong defence of their territories, and outside the breeding season the territorial pair lives in a with one or two pairs of unrelated juveniles that have settled after post-natal dispersal. Although the pair formation of juveniles involves the process of winter flock formation, it has been suggested that pairing may occur before flock formation. Here I report on 5 – 6 week old juveniles that form pair-bonds 1 – 2 weeks after dispersal. This is the first description of mate choice and pair formation of Willow Tits before establishment in a winter flock.

Intraspecific Behavior of Heather Voles (Phenacomys intermedius)

Very little is known about the social behavior of Heather Voles (Phenacomys intermedius), mainly because they are difficult to trap and maintain in captivity. We were able to maintain individuals in the laboratory and observe dyadic interactions among adult males and females, as well as related and unrelated juveniles, in a neutral arena. Overall, Heather Voles were very docile compared to other microtine species observed in captivity. There were no amicable behaviors observed, and the majority of encounters consisted of neutral egocentric actions. Males and females showed very similar levels of aggression in intrasexual encounters, although encounters between males contained more overt fighting behaviors. Male-female encounters contained the most aggressive behaviors (especially chasing), with a large proportion of those behaviors likely being the male attempting to copulate with the female, and the female resisting. No differences in aggressive behaviors were observed between related and unrelated juveniles.

Parent–offspring recognition in Brandt's voles, Lasiopodomys brandti

We investigated social interaction behaviour (amicable versus agonistic) to evaluate parent–offspring recognition in male and female Brandt's voles. We first examined whether the parents were able to distinguish their own familiar related offspring at the age of weaning from unfamiliar unrelated offspring. Both male and female parents, when encountering unfamiliar unrelated juveniles in a neutral arena, showed significantly more agonistic behaviour than when encountering their own familiar offspring, which suggested that adult Brandt's voles might be able to discriminate their own familiar descendants from unfamiliar unrelated ones. Second, we used cross-fostering to investigate the underlying parent–offspring recognition mechanism. Both males and females showed more amicable behaviour and less agonistic behaviour to familiar related offspring than to unfamiliar related offspring. Males showed significantly more amicable behaviour to familiar related offspring than to unfamiliar related offspring, and significantly less agonistic behaviour to familiar unrelated offspring than to unfamiliar unrelated offspring. Remarkably, females showed less agonistic behaviour to familiar related offspring than to unfamiliar related offspring. Furthermore, males and females did not show a significant difference in amicable or agonistic behaviour between familiar related and familiar unrelated offspring or between unfamiliar related and unfamiliar unrelated offspring. Our results suggest that the mechanism of parent–offspring discrimination in Brandt's voles could be familiarity.

Does high social rank position affect winter survival of Willow Tits Poecile montanus negatively under prolonged conditions of extremely low ambient temperature?

January 2010 was the coldest for more than 30 years in south Norway, with ambient temperatures in parts of central Norway between -30 and -40 oC. The January survival rates of individually colour-ringed Willow Tits Poecile montanus were studied by comparing the numbers of survivors from 10 flocks under the extremely low ambient temperatures in 2010 with that of 8-9 flocks under milder conditions in the two previous years. All flocks consisted of an adult mated pair and two to four unrelated juveniles, and in the flock hierarchy males generally dominated the females and the adults dominated the juveniles of their own sex. As expected, relatively fewer low-ranked juveniles survived January 2010 than in the previous years (0-20%, mean 13% vs 0-89%, mean 56%). But also the January survival rate of the top ranked males, the alpha birds, of the flocks in 2010 was lower (40%) than that during the two previous winters (88% and 89%). Because the top-ranked adult males have about 10% higher day-time oxygen consumption rates than the lower ranking birds in the same flock, the energetic requirements are higher for the alpha males than for the other flock members. This extra energy demand may have negatively influenced their survival during the long extremely cold period.

The causal role of odours in the development of recognition templates and social preferences

Despite decades of theoretical interest in the role of kin recognition in mate choice and nepotism, data on both the mechanisms and functions of recognition are available for only a few species. Even less common are demonstrations of direct causal links between the production and perceptual components of recognition and subsequent social preferences. Belding's ground squirrels, Spermophilus beldingi, produce odours that vary with kinship and can be used to discriminate classes of kin. However, the links between odours, recognition templates and differential treatment of conspecifics have not been shown empirically. Here I examined whether the manipulation of odour recognition templates influences juvenile behaviours. I induced recognition errors by exposing young to odours from a foreign mother before natal emergence. According to phenotype-matching mechanisms, developing young should incorporate all encountered odours into their kin template and later treat individuals matching the template as kin. As in previous studies, the most preferred play partners were littermates, but young also interacted preferentially with juveniles from the foreign family, whose odours were similar to the foreign mother and therefore matched their templates, compared with unfamiliar, unrelated juveniles. This preference for juveniles of the foreign family could not be due to relatedness or direct familiarity prior to emergence. Patterns of nasal investigations mirrored those of play bouts. This is a novel demonstration of a causal link between recognition cues, recognition templates and ‘kin’-differentiated behaviours, and highlights the potency of social odours during development on later social dynamics.

Audience effects

Audience effects

Parental care protects against infanticide in the lizard Egernia saxatilis (Scincidae)

Reports of postpartum parental care in squamate reptiles (lizards and snakes) are rare and generally anecdotal. We investigated parental care in black rock skinks, Egernia saxatilis, from southeastern Australia. These lizards live in small family groups, with adults defending territories against conspecifics. Juvenile lizards live within their parents' territory and may thus be protected from infanticide. In staged encounters in the laboratory, adults frequently attacked unrelated juveniles but not their own offspring, and the parent's presence significantly reduced the incidence of this infanticidal aggression. This protection arose not through specific ‘parental’ behaviours, but because adults tended to ignore juveniles when another (potentially threatening) adult was present. When two family groups were placed in the same enclosure, one family rapidly became dominant over the other. Juveniles of the dominant family derived thermoregulatory and foraging benefits from their parents' status. Thus, some lizards do show postpartum parental care, and may thereby significantly benefit their progeny via reduced risk of infanticide and better access to thermal and nutritional resources.

True paternal care in a multi-male primate society.

Although male parental care is rare among mammals, adult males of many cercopithecine primate species provide care for infants and juveniles. This care is often in the form of grooming, carrying, support in agonistic interactions, and protection against infanticide. For these behaviours to be interpreted as true parental care, males must selectively direct care towards their own offspring and this care must result in fitness benefits. With the exception of males defending probable offspring from infanticide, male primates living in multi-male, multi-female social groups have not been shown to selectively direct care towards their own offspring. We determined paternity for 75 juveniles in a population of wild savannah baboons (Papio cynocephalus) and collected data on interventions in agonistic disputes by adult males on behalf of juveniles as a form of male care. Here we show that adult males differentiate their offspring from unrelated juveniles and selectively support their offspring in agonistic disputes. As support in agonistic disputes is likely to contribute to rank acquisition and protect juveniles from injury and stress, this can be considered true parental care.

Do male cheetahs Acinonyx jubatus commit infanticide?

Infanticide, in which males kill unrelated juveniles presumably to advance their genetic contribution has been documented in many felids, a notable exception being the cheetah Acinonyx jubatus. Males apparently always tolerate cubs during encounters between females with litters but indefinite paternity has confused the issue in previous reports. We observed cheetah females with cubs interact with known sire and non-sire males, and infanticide never occurred. Sires and non-sires also did not differ in the frequency of different aggressive behaviours directed towards females and cubs during encounters. We suggest that cheetahs are unusual among wild felids in that males do not kill unrelated cubs and discuss possible reasons why infanticide does not occur in the species.

Successful formation of a large chimpanzee group out of two preexisting subgroups

AbstractDescriptions of the formation of relatively large groups of unfamiliar chimpanzees (Pan troglodytes) in captivity are scarce in the literature. Nineteen chimpanzees from preexisting subgroups were introduced into a social group at the Yerkes Regional Primate Research Center. The group included two adult males, six adult females along with six dependent infants, and five unrelated juveniles, four of whom had been hand‐raised in a nursery unit. Here we provide details on dyadic and multiparty introductions as well as technical details on the indoor/outdoor compound. The introduction process itself took more than 3 weeks, and was completed without major injuries. The introductions combined with 4 years of follow‐up data on aggression, grooming, and affiliative behavior confirm that even chimpanzees from an environment that does not promote complex social skills can be formed into a large multimale–multifemale group. During the introductions, low rates of agonistic behavior among adult females were offset by high rates of affiliative behavior. The two adult males, however, showed contact aggression during the first 10 minutes, after which such behavior virtually disappeared, whereas affiliative behavior increased. Three months after their first introduction, the two males reversed dominance ranks within the group, and hierarchical stability has been maintained since. During the 4‐year postintroductory period, grooming rates slightly decreased, but group cohesion was maintained. The frequency of aggression among all adults, including the males, increased during the 4‐year period, but aggression was generally of low intensity after the first year. Zoo Biol 20:501–515, 2001. © 2002 Wiley‐Liss, Inc.

Socialization in spectacled parrotlets (Forpus conspicillatus): how juveniles compensate for the lack of siblings

Socialization, that is, the process of the integration of an individual into the social system and the acquisition of basic social traits, has been studied in a variety of vertebrate species. Deprivation experiments have shown that the lack of early affiliative relationships has negative long-term effects on social behaviour and reproduction. Most studies emphasized the importance of the mother-infant relationship. However, it soon became evident that peer relationships to like-aged conspecifics, such as siblings and unrelated juveniles of nearly the same age, are also important for socialization. Whether individuals, deprived of one of these important social components, are able to compensate for this lack is not known. Here I tested the hypothesis that in spectacled parrotlets (Forpus conspicillatus), singletons (i.e., those that grew up without siblings) were able to compensate for this social lack by establishing and strengthening other relationships. In spectacled parrotlets socialization depends on the formation of long-lasting sibling groups. However, singletons without nest mates are quite common (about 6%), both in captivity and in nature. In this study I analysed the affiliative interactions with other group members of five singletons in comparison to eight siblings, from fledging to the 36th week after fledging, within a group of adult and juvenile conspecifics. In contrast to siblings, the singletons prolonged the relationships with their parents. Then they established a ”host sibling group” with other like-aged individuals. All singletons became well integrated into the group and established exclusive pair bonds. It is concluded that juvenile singletons of spectacled parrotlets are able to compensate for the lack of siblings by the development of alternative socialization tactics.

Sociogenic Stress and Rodent Reproduction

MARCHLEWSKA-KOJ, A. Sociogenic stress and rodent reproduction. NEUROSCI BIOBEHAV REV. 21(5),699–703, 1997.—Social stress, which is a part of the interaction between animals, can be defined as the set of physical stresses caused specifically by the presence and actions of certain conspecifics. Dense populations are characterized by considerably increased intermale and interfemale aggressive behavior. This establishes a hierarchy which influences reproduction of the animals. Aggression of adults toward unrelated juveniles harms the physiological development of attacked young. Stress from crowding during pregnancy can affect reproductive activity even through the second generation. During postnatal development, sexual maturation of juveniles can be delayed by the presence of group-living adults. In adult females, disturbance of homeostasis after fertilization can evoke untimely termination of pregnancy. In monogamous rodents, removal of the male partner reduces the number of parturitions. In several species, recently inseminated females exposed to a strange male will lose developing embryos. Thus, sociogenic stressors are among the most important factors affecting fecundity in animals. © 1997 Elsevier Science Ltd.

Socialization of Spectacled ParrotletsForpus conspicillatus: the role of parents, crèches and sibling groups in nature

The social development of individually marked Spectacled Parrotlets was studied in their natural habitat in Colombia from the fledging day onwards up to five weeks later. The parents actively reassembled their family by guiding the second and subsequent fledglings, which were leaving the nest in intervals of 1–2 days into the tree where their previously fledged nest mates were staying. Several neighbouring breeding pairs assembled their offspring in the same tree and established a creche there. They deprived their newly fledged offspring of affiliative interactions from the first day after fledging onwards. The parents stayed in the vicinity of the creche locality for short periods only. Most of the time they were out, mainly for foraging activities. After returning they fed exclusively their own young. In the evening the pairs guided their offspring into high and dense roosting trees, and every morning the creche was re-established. The fledglings passed through four developmental periods. (1) A short period of strong affiliative relationships with the parents. (2) A period of interactions with their siblings as well as with unrelated juveniles of approximately the same age in an immobile creche. (3) A mobile creche period in which all creche members together explored the environment of the creche tree. (4) A period in which the crechlings established strong sibling relationships and finally became independent of the parents. Socialization in creches and long-lasting sibling relationships might be the outcome of an early parent-offspring conflict that is decided predominantly by the parents. It enables the parents to prepare themselves for a subsequent breeding period by minimizing the time they spend with the young, which nevertheless are provided with excellent conditions for socialization.

Social dynamics in salmonid fishes: do kin make better neighbours?

Abstract. Kin discrimination has been reported in a number of animal taxa, including fish; however, functional explanations for this ability have not been examined. To determine whether kin discrimination has an effect on the social dynamics in Atlantic salmon, Salmo salar, and rainbow trout, Oncorhynchus mykiss , groups of full-siblings and unrelated juveniles were studied in an artificial stream tank. Both species have been previously shown to discriminate kin. The form and frequency of aggressive interactions, and the mean distance to nearest neighbours was recorded. Mean frequency of aggressive interactions was found to be significantly higher in non-kin groups of both species compared with kin groups, and the mean distance to nearest neighbour was significantly lower in kin groups. In addition, kin groups used a significantly lower proportion of 'overtly aggressive' territorial defence modal action patterns and a significantly higher proportion of 'passive' territorial defence modal action patterns compared with non-kin in both species. These results suggest that inclusive fitness benefits may be associated with maintaining territories near kin versus non-kin conspecifics.

Surrogate Feeding and Adoptive Behavior in Mourning Doves

Both mourning dove (Zenaida macroura) parents incubate the eggs and feed and brood the young until fledged (Taylor 1941, Harris et al. 1963). Fledglings are fed consistently by at least one parent through 27 days posthatching (PH) but also begin feeding themselves at 17 days PH. After 16 days PH, feeding of fledglings is primarily the responsibility of the male parent (Hitchcock and Mirarchi 1984). Numerous reports of surrogate feeding (adults performing intraor interspecific feeding of juveniles other than, or in addition to, their own), helpers at the nest, and intraand interspecific adoption in avian species have been summarized by Skutch (1976). Among columbids, wood pigeons (Columba palumbus) (Murton and Isaacson 1962), white-winged doves (Z. asiatica) (Saunders 1944), rock doves (C. livia) (Levi 1957), and ringed turtle-doves (Streptopelia risoria) (Hansen 1971) have exhibited intraspecific feeding of unrelated juveniles. Additionally, surrogate feedings have occurred between mourning doves and other species of doves in both wild and captive situations (Neff 1945). To our knowledge, however, no reports of surrogate feedings or adoptive behavior among wild mourning doves have been published. Such information is necessary to answer questions about parent-fledgling interactions that are asked during the continuing controversy over hunting mourning doves in September.

Vervet Monkey Alarm Calls: Manipulation Through Shared Information?

AbstractHigh-ranking male and female vervet monkeys in Amboseli National Park alarm-call at higher frequencies than do low-ranking males and females. This correlation between rank and alarm-calling does not occur because high-ranking animals have more offspring or close kin than low-ranking animals. Similarly, high-ranking animals do not seem to have greater opportunities to spot potential predators; they do not scan the habitat more than low-ranking animals, nor are they more likely to be in the forefront of group progressions. It seems possible that low-ranking animals may spot predators as often as high-ranking animals, but that they do not always alert other group members to approaching danger. As a further test of the possibility that monkeys may vary the rate of alarm-calling depending on social contexts, an experiment was conducted on captive vervet monkeys in which adult females were presented with a predator in the presence of either their offspring or an unrelated juvenile. Adult females alarm-called significantly more often when with their offspring than with unrelated juveniles. A similar experiment conducted on adult males showed that males alarm-called at higher rates in the presence of adult females than in the presence of other adult males. The results of both experiments and observations suggest that monkeys may vary the rate at which they warn others of danger. The withholding of information may be an effective means to deceive others, because it is relatively difficult to detect cheaters. The possible advantages of selectivity in alarm call production are discussed.

Adult-young interactions in island and mainland populations of the deermouse Peromyscus maniculatus.

The demographic and ecological characteristics of island populations of small mammals have received increasing attention in recent years, but few studies have compared the behavioral characteristics of island populations with those of mainland populations. Behavior is considered an important variable because it is believed by many to be a crucial factor affecting the population dynamics and demography of natural populations. In particular, among many species of rodents, the social behavior of adults towards juveniles is cited as an important factor influencing dispersal patterns and population regulation. The present study compares social interactions between adults and juveniles of island and mainland populations of the deermouse Peromyscus maniculatus, and attempts to relate differences in behavior to the demographic differences between the two populations. Adult mice were trapped on the mainland of British Columbia and on one of the Gulf Islands off the British Columbia coast, and allowed to breed in the laboratory. Male and female juveniles from both populations were then tested with their own parents and with unrelated male and female adults. The results demonstrate that island adults show almost no aggression towards either own or unrelated young. Mainland adults likewise show little aggression towards their own young, but a proportion of the population, consisting of both male and female adults, shows severe aggression towards unrelated juveniles of both sexes. These results suggest four major conclusions: 1) behavior may be the mechanism responsible for the demographic differences reported for these island and mainland populations; 2) female aggression may be a more important factor in deermouse population dynamics than has been previously recognized; 3) since parents show little aggression towards their own young, adult aggression may be a significant factor in juvenile mortality and emigration only after juveniles have initiated dispersal away from their natal sites; and 4) adult aggression controls the number of both male and female juveniles which are recruited into the population.