Separation at weaning from the family is stressful for naturally group-living, but not solitary-living, male African striped miceRhabdomys

Abstract

Early separation from a family is stressful for young mammals, but might be more stressful for group-living than solitary species. Using juvenile males of three African striped mice Rhabdomys taxa that are either group (R. pumilio) or solitary (R. dilectus dilectus and R. d. chakae) living, we predicted greater separation anxiety in R. pumilio than R. dilectus because group-living could reduce anxiety in R. pumilio. Three brothers from each of 10 litters per taxon were randomly assigned soon after natural weaning (25 days) to one of three treatments for 10 days: (1) remained with the family (philopatric); (2) separated from the family by a wire mesh barrier (separated); and (3) isolated from the family (isolated). Males were individually tested in a four-arm maze to assess their anxiety responses and sampled for corticosterone concentrations 20 mins and 10 days later. Compared to R. dilectus males, R. pumilio males showed a greater treatment response to separation: philopatric males used the light arms of the maze less and had higher corticosterone concentrations compared to isolated males, which spent the most time in the light arms and had the lowest corticosterone concentrations overall; separated males showed an intermediate behavioural response, but had similar corticosterone concentrations to philopatric males. Thus, separation from a family group is more stressful in group-living Rhabdomys and this stress response dissipates with time. Philopatry and group-living may be more important for young R. pumilio, whereas dispersal at weaning is an important life history event for solitary R. dilectus.

Anxiety and exploratory behavior in the African striped mouse, Rhabdomys, taxa are partially modified by the physical rearing environment

“…Perhaps the treatment (adding a platform, either simulating cover or no cover) itself might have increased the anxiety of R. pumilio (i.e., positive genotype–environment effect; Plomin, DeFries, & Loehlin, ) or resulted in unmatched treatment effects. (b) Another possible explanation could be the greater stress shown by R. pumilio compared to the other taxa following separation from the family group in early life (Mackay et al, ). However, this stress response dissipates with time (Mackay et al, ) and does not appear to influence the behavior of adult R. pumilio in several of our studies.…”

“…(b) Another possible explanation could be the greater stress shown by R. pumilio compared to the other taxa following separation from the family group in early life (Mackay et al, ). However, this stress response dissipates with time (Mackay et al, ) and does not appear to influence the behavior of adult R. pumilio in several of our studies. (c) Paternal care has been documented in R. pumilio in nature and in captivity but only in captivity in R. dilectus (Schradin & Pillay, ).…”

“…At weaning, 1–2 pups (1 male and/or 1 female) from each litter were placed individually into tanks with cover identical to the tanks in which they were reared (Figure ). Rhabdomys is not stressed by individual housing because young of most taxa can disperse from the natal nest and live alone (Mackay, Rymer, & Pillay, ). The exception is young R. pumilio which were initially stressed when housed alone after weaning but this stress dissipates within 10 days after separation (Mackay et al, ).…”

“…Rhabdomys is not stressed by individual housing because young of most taxa can disperse from the natal nest and live alone (Mackay, Rymer, & Pillay, 2014). The exception is young R. pumilio which were initially stressed when housed alone after weaning but this stress dissipates within 10 days after separation (Mackay et al, 2014). At 60 days of age (early adulthood), the exploratory behavior and anxiety response of all F1 mice (#4, Figure 2 1-2 pups (1 male and/or 1 female) from each F2 litter from both treatments were placed individually into tanks identical to those in which they were born and reared (i.e., there was no switching between treatments).…”

Costs and benefits of social connectivity in juvenile Greylag geese

“…Social isolation, for example, might be a powerful stressor in group-living species. In mammals, social isolation can lead to an increase in cortisol levels, as shown for instance in immature common marmosets ( Callithrix jacchus ) 10 , and in group-living juvenile male African striped mice ( Rhabdomys pumilio ) 11 . Also in birds, isolation from the social group resulted in higher corticosterone levels in gregarious European starlings ( Sturnus vulgaris ) 12 and zebra finches ( Taeniopygia guttata ) 13 .…”