The development of social behaviour between siblings and non-siblings of the voles Microtus ochrogaster and Microtus pennsylvanicus

It has been suggested that the strength and duration of sibling relations during the juvenile period may reflect the social structure of mammal species. Two Microtus species with contrasting social systems, M. ochrogaster and M. pennsylvanicus, were chosen for a comparative study of juvenile social behaviour. Young were observed in sibling and non-sibling dyadic encounters from the second until the seventh week of age. Social interactions consisted mainly of body nosing of the partner, and included behaviours interpreted as investigation, socialization and settling. Only minor sex differences in body nosing scores occurred, but some ontogenetic trends were noted. When the species were compared, M. ochrogaster received higher scores for body nosing and sitting in contact, and displayed more reciprocity in their nosing, than did M. pennsylvanicus, whether siblings or non-siblings were considered. When the sibling types were compared, non-sibling dyads received higher nosing scores than did siblings in both species, but the disparity was greater in M. ochrogaster than in M. pennsylvanicus. These results are interpreted with reference to known behavioural and developmental correlates of the extended family system in naturally occurring M. ochrogaster and the less communal social system in M. pennsylvanicus.     

Self-grooming induced by sexual chemical signals in male root voles (Microtus oeconomus Pallas)

Sniffing is one-way animals collect chemical signals, and many males self-groom when they encounter the odor of opposite-sex conspecifics. We tested the hypothesis that sexual chemical signals from females can induce self-grooming behavior in male root voles (Microtus oeconomus Pallas). Specifically, we investigated the sniffing pattern of male root voles in response to odors from the head, trunk, and tail areas of lactating and non-lactating females. The self-grooming behavior of males in response to female individual odorant stimuli was documented, and the relationship between self-grooming and sniffing of odors from the head, trunk, and tails areas were analyzed. Sniffing pattern results showed that males are most interested in odors from the head area, and more interested in odors from the tail as compared to the trunk area. Males displayed different sniffing and self-grooming behaviors when they were exposed to odors from lactating females as compared to non-lactating females. Males also spent more time sniffing and engaged in more sniffing behaviors in response to odors from the lactating females’ tail area as compared to the same odors from non-lactating females. Similarly, males spent more time self-grooming and engaged in more self-grooming behaviors in the presence of individual odors from lactating females as compared to individual odors from non-lactating females. Partial correlation analyses revealed that the frequency of self-grooming was significantly correlated with the frequency of tail area sniffs. Results from this experiment suggest that sexual attractiveness of lactating females is stronger than that of non-lactating females. Furthermore, the partial correlation analysis demonstrated that self-grooming in males is induced by odors from the tail area of females. Collectively, these results support the hypothesis that sexual chemical signals from females can induce self-grooming behavior in male root voles. Self-grooming may also reflect the groomer's sexual motivation and facilitate sexual interactions.     

A comparison of maternal behaviour in the meadow vole (Microtus pennsylvanicus), prairie vole (M. ochrogaster) and pine vole (M. pinetorum)

The maternal behaviour of three species of voles was compared using a semi-naturalistic laboratory system. Meadow vole females spent more time out of the nest, and exhibited less maternal behaviour in terms of nursing and brooding, and more non-social behaviour such as locomoting, eating, and drinking, than the females of the other two species. Across all species, maternal behaviour decreased from parturition onward, while non-social behaviour increased. Paternal care was well developed in the prairie vole and pine vole, but was never observed in the meadow vole. During the first postnatal week, male prairie voles showed a tendency to enter the nest when the female left the young unattended. This trend was not apparent in the male pine vole. The physical parameters of pup development, including eye opening and the development of fur, were similar in all three species. Behavioural development, however, was most rapid in the meadow vole, intermediate in the prairie vole, and slowest in the pine vole. These results are compared with those of previous field and laboratory studies, and are discussed with reference to the life-history strategy of each species.     

Sibling recognition in the prairie vole, Microtus ochrogaster

Since mating is seldom observed between sibling prairie voles, Microtus ochrogaster, this, behavioural discrimination was used to investigate sibling recognition in this species. Cross-fostering of 1–3-day-old pups demonstrated that unrelated pups reared together did not breed, whereas siblings reared apart bred readily when paired at weaning. When unrelated voles were paired at 14 days of age, prior to sexual maturity, significantly fewer pairs bred than when strangers were paired at 21 days of age. Separation of 21-day-old siblings for 8 days before pairing overcame incest avoidance; a 15-day separation was required for breeding by siblings that had remained together until they were 50 days old. These results indicate that sibling recognition and, consequently, incest avoidance depend on association prior to weaning.     

Agonistic behaviour over food and perch space in male Quelea quelea

A measure commonly used in previous studies of fighting in Quelea quelea (the Dominance Index) was found to be unsuitable for the ranking of animals in small groups. It is argued as preferable to study interactions between pairs of individuals within groups. Rank relationships between individuals were found to be similar in competition over food and perch space in two series of observations 8 weeks apart. Fights within the groups did not show an overall decrease with time since group formation but were related to flight activity (between perches) and time spent at the food hopper. Success in competition at the food hopper gave priority of access to the food, but success in competition over perching space did not lead to those birds winning more encounters sitting in a central position within the resting groups. These results are discussed in relation to possible advantages to individuals and to the ecology of Quelea.     

Scent marking and mate choice in the prairie vole, Microtus ochrogaster

Scent marking is common among male and female rodents and might be used in male-male competition and as a mechanism for mate attraction. I tested the hypotheses that females would choose males based on their frequency and placement of scent marks, and that a female would advertise interest in a particular male by placing her scent marks on or near those of a preferred mating partner. In a series of experiments conducted with prairie voles, Microtus ochrogaster, females did not choose mates based on the frequency or placement of scent marks by males nor did they advertise their interest in a particular male through the frequency or placement of scent marks. The number of males chosen that scent-marked more than their opponents did not differ significantly between females exposed (11 of 15) and not exposed (10 of 15) to scents of males. Females exposed and not exposed to scents of males preferred seven of the same males that had scent-marked more than their opponents. When a third group of females was exposed to four times more scent of the less preferred than preferred males, they still chose the preferred males. Thus, the frequency and placement of scent marks by males were not used to assess males for mate choice nor did female prairie voles use scent to advertise their preference for a mating partner. In that scent marking is common in male and female mammals, scent quality might be more important than quantity in male-male competition and mate attraction.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .     

The behaviour of mature and immature male bank voles (Clethrionomys glareolus)

Neutral-arena encounters were staged between pairs of sexually mature male bank voles (Clethrionomys glareolus), between pairs of immature males, and between pairs consisting of one of each. Mature males exhibited more aggressive components of behaviour to each other than did immature males, but mature males did not attack immature males in ‘mixed’ encounters. The relevance of these results to the population ecology of voles is discussed.     

Precocial sexual behaviour in imprinted male turkeys (Meleagris gallopavo)

Imprinted male turkeys were isolated from the imprinted surrogate for one week following training. When returned to the surrogate, a significant proportion of the birds exhibited precocial sexual courting only toward the model. This precocial sexual activity occurred in the absence of exogenously administered androgens.     

Aggressive behaviour and its relation to oviposition in the domestic fowl

Hens in battery cages behave differently from those housed in pens. A knowledge of the factors which govern the differences is important from both practical and theoretical viewpoints. Laying hens of two strains were housed in cages or pens and the incidence of aggression before and after laying was studied. In stable groups little aggression was seen, so a strange bird was introduced to stimulate aggressive behaviour. Under these circumstances the incidence in caged light hybrids rose considerably before oviposition and fell sharply afterwards. This pattern was not seen in light hybrids kept in pens, nor in medium hybrids, whether caged or penned. Other workers have shown that caged light hybrids may be in a state of frustration before laying, and it is postulated that pre-laying aggression is triggered by frustration rather than by hormonal changes.     

Aggressive behaviour of male mice (Mus musculus) towards familiar and unfamiliar opponents.

Two types of colonies of laboratory mice were employed; hierarchically organized ones formed by placing five unfamiliar 8-week-old mice in a cage together and amicably organized colonies in which four male litter mates were kept together throughout the whole period of the experiment. During a 21-day pre-experimental period intra-colony aggressive behaviour was recorded. A dominant animal and ranked subordinates occurred in every hierarchical colony, whilst no aggression was recorded in any of the amicable colonies. During a 25-day period unfamiliar adult male or female mice were introduced daily into the amicable or hierarchical colonies for 10 min. In a third experiment juvenile mice 17, 24, 31 or 38 days old were introduced into hierarchically organized colonies during a 20-day period. In all hierarchical colonies the stranger was attacked irrespective of sex and age; the majority of attacks were carried out by the dominant mouse. Aggression by the dominant declined exponentially throughout the experimental period and regression analyses compared the different data. Unfamiliar adult females were the recipients of fewer attacks than unfamiliar adult males and the age of juvenile strangers was found to be an important factor. Amicably organized mice initially did not attack strangers, but over a period of 25 days the number of attacks on unfamiliar males gradually increased.     

Sexual behaviour and novel stimuli in male japanese quail (coturnix coturnix japonica)

Sexual performance levels following the presentation of a novel stimulus were examined in male Japanese quail. During a 1-hr observation period males were presented either with a new stimulus female each 20 min, with the same female removed briefly at 20-min intervals or with the same female left undisturbed. Although the latency to grab the neck of the famel was shorter in the group receiving a fresh female after 20 min, the overall number of completed copulations was unaffected by the treatments. It is concluded, therefore, that novelty is not an important factor governing sexual performance levels of male Japanese quail under these test conditions.