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 in males of five species of voles Microtus

Agonistic behaviour of Microtus pennsylvanicus, M. montanus, M. californicus, M. longicaudus, and M. ochrogaster was observed in 160 staged encounters; a natural observation of sympatric species is included. No difference in the character and movements of agonistic behaviour was apparent when arena size was reduced; only a difference in the frequency of postures and movements was observed. In the smaller arena, M. montanus and M. ochrogaster exhibited a significant increase in frequency of agonistic components. The other three species did not show a significant increase. In interspecific pairings, M. montanus won over M. pennsylvanicus, M. californicus and M. longicaudus; M. ochrogaster won over M. montanus and M. pennsylvanicus. Three species used mutual avoidance in maintaining individual distance.     

An investigation of sibling recognition in Rana cascadae tadpoles

Sibling recognition was studied experimentally in tadpoles of the Cascades frog, Rana cascadae. Sibships were divided into two groups at an early developmental stage. One group was reared with siblings and the second with a mixture of siblings and non-siblings. Whe given a choice of associating with a sibling or non-sibling group, individuals reared with siblings preferred siblings. One mixed-reared group spent more time associating with unfamiliar siblings than unfamiliar nonsiblings. Tadpoles of another mixed-reared group preferred to associate with pure siblings over a mixture of siblings and non-siblings with which they were reared. When the stimulus animals were taken exclusively from the mixed-rearing tank, two mixed-reared groups showed no sibling preferences. Our results suggest that early association with non-siblings does not affect sibling recognition in this species.     

Self-grooming and sibling recognition in meadow voles,Microtus pennsylvanicus,and prairie voles,M. ochrogaster

Self-grooming in response to the odours of an opposite-sex conspecific may reflect sexual motivation on the part of the actor. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, and prairie voles,M. ochrogaster , both self-groom at different rates when exposed to the odours of their siblings as compared to those of nonsiblings. This prediction was studied under the context of social memory for siblings and the effects of isolation on memory for siblings. The hypothesis explains the self-grooming responses of meadow voles isolated from their siblings for 10 days and of prairie voles isolated from their siblings for 20 days. However, 20 days of isolation for male and female meadow voles, and 30 days of isolation for male prairie voles were sufficient to induce these animals to self-groom at a similar rate to both sibling and nonsibling odours, suggesting that after isolation these animals no longer recognized their opposite-sex siblings. Female prairie voles isolated for 30 days self-groomed more in response to the odours of male nonsiblings than to those of male siblings, suggesting that female prairie voles still recognize their male siblings after isolation. This study is the first to provide empirical evidence that, in the context of sibling recognition, self-grooming behaviour is directed at unfamiliar opposite-sex conspecifics, and that the communicative function of self-grooming (sexual motivation) is associated with social memory for siblings. Differences in the self-grooming behaviour of meadow voles and prairie voles may be associated with several aspects of their life history characteristics.     

Evidence for Inbreeding Depression and Pre-Copulatory,but Not Post Copulatory Inbreeding Avoidance in the Cabbage Beetle Colaphellus bowringi

Inbreeding is known to have adverse effects on fitness-related traits in a range of insect species. A series of theoretical and experimental studies have suggested that polyandrous insects could avoid the cost of inbreeding via pre-copulatory mate choice and/or post-copulatory mechanisms. We looked for evidence of pre-copulatory inbreeding avoidance using female mate preference trials, in which females were given the choice of mating with either of two males, a sibling and a non-sibling. We also tested for evidence of post-copulatory inbreeding avoidance by conducting double mating experiments, in which four sibling females were mated with two males sequentially, either two siblings, two non-siblings or a sibling and a non-sibling in either order. We identified substantial inbreeding depression: offspring of females mated to full siblings had lower hatching success, slower development time from egg to adult, lower survival of larval and pupal stages, and lower adult body mass than the offspring of females mated to non-sibling males. We also found evidence of pre-copulatory inbreeding avoidance, as females preferred to mate with non-sibling males. However, we did not find any evidence of post-copulatory inbreeding avoidance: egg hatching success of females mating to both sibling and non-sibling males were consistent with sperm being used without bias in relation to mate relatedness. Our results suggest that this cabbage beetle has evolved a pre-copulatory mechanism to avoid matings between close relative, but that polyandry is apparently not an inbreeding avoidance mechanism in C. bowringi.     

Effects of conspecific and heterospecific residents on patterns of immigration in two species of voles

Studies with birds have shown that presence and density of resident conspecifics and heterospecifics can influence patterns of habitat selection. There have been few studies on the effects of social cues on rates of immigration in mammals. We report results from a long-term live trapping study of immigration in two species of voles, Microtus ochrogaster Wagner, 1842 and Microtus pennsylvanicus Ord, 1815, in bluegrass habitat in east-central Illinois, USA. We compare immigration into control sites from which no individuals of either species were removed with immigration into experimental sites from which either conspecifics or heterospecifics were removed. We focus on characteristics of immigrants and rates of immigration in relation to density in destination habitats. Within each species, immigrants into control and removal sites were similar with respect to body mass and reproductive condition, indicating no major differences in the physical condition of immigrants into sites with established populations and sites without established populations. For both species, density of conspecifics at a site positively influenced rate of immigration at that site. Density of heterospecifics at destination sites did not significantly influence rate of immigration for either species. These results suggest that site selection by dispersing M. ochrogaster and M. pennsylvanicus is characterized by conspecific attraction.     

Demography of fluctuating vole populations: Phase homogeneity of demographic variables

Most research on fluctuations of arvicoline rodents has focused on changes in demographic variables across phases. Here, we examined whether demographic variables varied within a phase (trough, increase, and decline) across 30 fluctuations of Microtus ochrogaster and 14 fluctuations of Microtus pennsylvanicus over 25 years. For each species, we tested for phase homogeneity (i.e., values of demographic variables were invariant across all fluctuations within a given phase) for the following demographic variables: monthly survival (total, adult, young), proportion of reproductively active adult males and females, proportion of young, and proportion of immigrants. We found phase homogeneity for 96.7% of the 582 phase/fluctutation data sets for the seven variables, in the three phases of across all fluctuations in the three habitats for M. ochrogaster and 98.0% of 254 of those for M. pennsylvanicus in two habitats. We conclude that for each of these two species demographic variables are relatively invariant both within a phase and across fluctuations.     

Alloparenting experience affects future parental behavior and reproductive success in prairie voles (Microtus ochrogaster)

Various hypotheses have been proposed to explain the function of alloparental behavior in cooperatively breeding species. We examined whether alloparental experience as juveniles enhanced later parental care and reproductive success in the prairie vole (Microtus ochrogaster), a cooperatively breeding rodent. Juveniles cared for one litter of siblings (1EX), two litters of siblings (2EX) or no siblings (0EX). As adults, these individuals were mated to other 0EX, 1EX or 2EX voles, yielding seven different pair combinations, and we recorded measures of parental behaviors, reproductive success, and pup development. As juveniles, individuals caring for siblings for the first time were more alloparental; and as adults, 0EX females paired with 0EX males spent more time in the nest with their pups. Taken together, these results suggest that inexperienced animals spend more time in infant care. As parents, 1EX males spent more time licking their pups than 2EX and 0EX males. Pups with either a 1EX or 2EX parent gained weight faster than pups with 0EX parents during certain developmental periods. While inexperienced animals may spend more time in pup care, long-term benefits of alloparenting may become apparent in the display of certain, particularly important parental behaviors such as licking pups, and in faster weight gain of offspring.     

Suppression of reproductive maturation in male-stimulated virgin female microtus by a female urinary chemosignal

Urine from female $\text{Microtus ochrogaster}$ possesses a chemosignal that suppresses reproductive maturation in other females. Uterine enlargement in virgin females stimulated by a male was suppressed by subsequent association with another female or by application of female urine on the nose. Females so suppressed are not able to achieve estrus. Urine from virgin sibling and non-sibling females and from pregnant females possesses the suppressing effect.     

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.     

A comparison of paternal behaviour in the meadow vole Microtus pennsylvanicus,the pine vole M. pinetorum and the prairie vole M. cchrogaster

Paternal care in microtines has been studied infrequently and few studies have compared patterns of direct and indirect paternal investment. The paternal behaviour of three vole species, the meadow vole (Microtus pennsylvanicus), the pine vole (M. pinetorum) and the prairie vole (M. ochrogaster) was examined in a semi-natural setting. Prairie and pine voles were found to exhibit high levels of paternal care. Prairie vole males contributed the most direct care by remaining in the natal nest for long periods of time in contact with the pups. Pine voles contributed less direct care than prairie voles as they spent less time in the natal nest with their offspring. In addition, both prairie and pine vole males were observed to groom their pups and retrieve them back to the nest area. Prairie vole males also engaged in such indirect forms of care as nest construction and maintenance, while pine voles provided indirect care in the form of tunnel construction and food caching. Meadow vole males were the least paternal of the three species and rarely engaged in either direct or indirect care. These findings support predictions that M. pennsylvanicus is promiscuous and that male and female meadow voles occupy separate territories. They are also consistent with studies which indicate that prairie and pine voles are monogamous and have a structured social organization with members interacting closely with one another.     

Sibling and neighbour recognition in wild juvenile muskrats

Sibling and neighbour recognition were examined using wild-caught juvenile muskrats, Ondatra zibethicus, of known sibship in dyadic encounters. Behavioural asymmetry between sibling and nonsibling dyads indicated the presence of sibling recognition. Recognition of neighbours was examined using indices of agonistic and amicable behaviour calculated using exclusively non-sibling dyads. The distance between captures within non-sibling dyads was used to approximate familiarity. Amicable behaviour decreased significantly with increasing distance between captures, and, therefore, with decreasing familiarity. Agonistic behaviour was not correlated with distance between captures.     

The influence of immigration on demography of sympatric voles

We studied the influence of immigration on the dynamics ofMicrotus ochrogaster Wagner, 1842 andM. pennsylvanicus Ord, 1815 populations in alfalfa, bluegrass, and tallgrass prairie in east-central Illinois for 25 years. The numbers of immigrants in a site were positively correlated with overall population densities of the species in the vicinity of the study sites and within the study site. Population density of the other species was not correlated with immigration of either species. Immigrants did not differ significantly from residents with respect to sex-ratio and reproductive condition. Persistence of immigrantM. pennsylvanicus was lower than that of resident adults in all three habitats, while that of immigrantM. ochrogaster was lower than that of resident adults in alfalfa, where the species was most abundant. Neither the absolute number of immigrants nor the proportion of the population composed of immigrants indicated an effect of immigrants on among- and within-habitat differences in demography and population fluctuations of either species. Immigrants may have been an important factor in maintenance ofM. pennsylvanicus in alfalfa, a low-quality habitat, but the influence of immigration on the dynamics of populations inhabiting other habitats was insubstantial.     

Sibships: Cooperation and competition among immature vervet monkeys

The relationships between siblings were compared with those between non-sibling peers amongst immature vervet monkeys (Cercopithecus aethiops) in three free-ranging social groups. Using the frequency and context of friendly, supportive, aggressive, and competitive interactions, sibships were found to stand out as associative units characterized by high levels of grooming and support during aggression. Competition between siblings was related to contests over access to maternal care, especially grooming, which may have been important in the establishment of relative sibling dominance. Siblings who were close in age tended to interact more frequently than those who were distant in age, but few sex differences were found. The close and supportive nature of sibling relationships appeared to affect the social structure of the groups.     

Aggression between weanling Peromyscus and Microtus

Microtus pennsylvanicus were attacked by weanling Peromyscus of all three species tested: P. leucopus noveboracensis, P. maniculatus bairdii, and P. polionotus (colemani). However, defensive behaviours were more frequent than aggressive behaviours. Of the three species of Peremyscus tested, P. m. bairdii are most likely to meet Microtus in the field and displayed more agonistic behaviours in the laboratory. Female Peromyscus of all species tested were as likely to engage in all agonistic behaviours as were males. Inter-generic aggression developed before intra-generic aggression.     

Aggressive behaviour of male Microtus breweri and its demographic implications

Patterns of laboratory-determined aggressive behaviour and exploratory activity were examined in wild-caught male beach voles (Microtus breweri), an island-endemic species. This species is ecologically interesting because it has been found not to exhibit the super-annual population cycles typical of other rodents in the subfamily Microtinae. We found that body weight and reproductive condition were good predictors of aggressive behaviour, with heavier and reproductively active voles showing higher incidences of several stereotyped aggressive acts. Aggression also increased as the percentage of males and females who were reproductively active in the control population increased. Aggression was negatively correlated with population density, and more or less independent of dispersal rate. Dispersers and residents exhibited similar aggressive behaviour patterns. These observations are consistent with models which have proposed that population cycles in other vole species are controlled through the social interactions of individuals.     

Kin preference behaviour is present after metamorphosis in Rana cascadae frogs

Kin recognition was investigated in newly metamorphosed Rana cascadae frogs. Previous work has shown that larvae of this species prefer to associated with siblings over non-siblings. Juvenile frogs from three clutches were reared with siblings and tested for sibling preference as larvae and at 4–12 days and 39–47 days after metamorphosis. Tadpoles and froglets of the three clutches displayed a significant preference to associate with siblings.     

Multiple captures provide evidence of small mammal social behavior

Social behavior of small mammals living under natural conditions often is inferred from live-trapping data, particularly from incidents in which two or more individuals are captured together in a trap. We examined whether multiple-capture data from a long-term study of prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) were consistent with well-known species differences in social behavior (whereas prairie voles are highly social and display monogamy, meadow voles are less social and promiscuous). When possible, we also examined multiple captures of two nontarget species, northern short-tailed shrews (Blarina brevicauda) and western harvest mice (Reithrodontomys megalotis). Percent of total captures that were multiple captures and percent of total adult captures that were male–female captures were highest for prairie voles and lowest for meadow voles; values for harvest mice and shrews were in between those of the vole species, but more similar to values for meadow voles. Repeat captures of the same male–female pair occurred most commonly in prairie voles, and multiple captures of this species typically involved individuals from the same social group. Multiple captures of adults and juveniles were more common in prairie voles than meadow voles, except for captures of at least one adult male and at least one juvenile, which did not differ between the two vole species. Multiple capture data for prairie voles and meadow voles were largely consistent with established species differences in social behavior, suggesting that such data can provide an accurate indication of social and mating systems of small mammals.     

Sibling and non-sibling cannibalism by larvae of a lady beetleHarmonia axyridis Pallas (Coleoptera: Coccinellidae) in the field

Sibling (cannibalism among siblings) and non-sibling cannibalism (cannibalism among non-siblings) were studied in a natural population of a lady beetle, Harmonia axyridisPallas . Of all the eggs laid (n=2269), 24.76% (n=562) were killed by sibling cannibalism and 36.10% (n=819) were killed by non-sibling cannibalism. Sibling cannibalism occurred constantly and intensively in most egg batches throughout the entire oviposition period. On the other hand, non-sibling cannibalism was more intense in the middle and late oviposition periods, and when the egg batches were close to an aphid colony. This may be due to the high density of H. axyridis larvae relative to aphid density in the middle and late oviposition periods and also the larvae searching intensively near an aphid colony.     

Kin recognition in Rana cascadae tadpoles: maternal and paternal effects

Cascades frog (Rana cascadae) tadpoles preferentially associate with full siblings over half sibling and half siblings over non-siblings when reared with siblings or as isolates. These tadpoles can use cues of maternal or paternal origin in distinguishing siblings from non-siblings, but maternal cues are preferred over paternal cues. This suggests that a hierarchy of cue importance may exist. Our results are consistent with both a phenotypic matching and a genetic recognition system of kin recognition. Thus, both learned and innate components may play a role in R. cascadae sibling recognition. Kin recognition may facilitate preferential treatment of kin, such as cooperation in food finding or in warning against predators, and therefore those individuals behaving altruistically in kin groups can increase their inclusive fitness.