Infanticide by virgin CF‐1 and wild male house mice (Mus musculus): Effects of age, prolonged isolation, and testing procedure

Abstract

The frequency of infanticide by juvenile, young-adult, and adult male house mice (Mus musculus) was compared in CF-1 albino mice and the F1-F4 male offspring of wild mice trapped in Missouri. When tested in their home cages for their behavior toward a single 2-day-old pup after being individually housed for 5 days, juvenile CF-1 and wild males were equally likely to exhibit infanticide (about 35%). But, adult wild males were significantly more likely to exhibit infanticide (about 90%) than were adult CF-1 males (about 45%). We propose that differences in exposure to testosterone during fetal life may contribute to the difference in the incidence of infanticide between CF-1 and wild males. Prolonged isolation (45 days) significantly reduced the proportion of wild male mice that exhibited infanticide when the males were tested in their home cages, but not when the males were tested by being placed into the cage of lactating females and their 2-day-old young. Virtually all adult wild males exhibited infanticide when they were tested in their home cages (with either a 2-day-old or 7-day-old pup) or when they were placed into the cages of lactating wild female mice and their 2-day-old young. But, when adult wild males were placed with lactating wild females on Day 7 postpartum, the females attacked the males and most males were prevented from exhibiting infanticide.

Are age and sex differences in brain oxytocin receptors related to maternal and infanticidal behavior in naïve mice?

“…For example, McCarthy and vom Saal (1986) found that young (40-45 days of age) were less infanticidal (~36%) than old (~80%) male wild house mice. Svare and Mann (1981) also found an increase in infanticidal behavior from 25 to 65 days of age in CB57BL/6 and DBA strains.…”

“…Adult females and males are commonly described as spontaneously maternal or infanticidal respectively (Calamandrei and Keverne, 1994;Gandelman, 1973a,b;Gandelman and vom Saal, 1975;Leussis et al, 2008;Noirot, 1969Noirot, , 1972Stolzenberg and Rissman, 2011;Svare, and Mann, 1981). However, other authors have found that at least half of the females did not show maternal behavior, and a small percentage of naïve adult males showed paternal behavior (Alsina-Llanes et al, 2015;Brown et al, 1996;Hamaguchi-Hamadaa et al, 2004;Kennedy and Elwood, 1988;Kuroda et al, 2011;Lucas et al, 1998;McCarthy and vom Saal, 1986;Pedersen et al, 2006). In the case of young females and males, the literature suggested that they showed lower incidence of maternal or infanticidal behavior respectively (Gandelman, 1973a,b;McCarthy and vom Saal, 1986;Noirot, 1972).…”

“…However, other authors have found that at least half of the females did not show maternal behavior, and a small percentage of naïve adult males showed paternal behavior (Alsina-Llanes et al, 2015;Brown et al, 1996;Hamaguchi-Hamadaa et al, 2004;Kennedy and Elwood, 1988;Kuroda et al, 2011;Lucas et al, 1998;McCarthy and vom Saal, 1986;Pedersen et al, 2006). In the case of young females and males, the literature suggested that they showed lower incidence of maternal or infanticidal behavior respectively (Gandelman, 1973a,b;McCarthy and vom Saal, 1986;Noirot, 1972). However, in contrast to rats and prairie voles (Brunelli and Hofer, 1990;Mayer and Rosenblatt, 1979;Olazábal and Morrell, 2005;Olazábal and Young, 2006a;Stern, 1987), the ontogeny of parental and infanticidal behavior in CB57BL/6 mice had not been investigated in detail.…”

“…Several factors have been proposed in the literature to explain age and sex differences in parental and infanticidal behavior (Alsina-Llanes et al, 2015;Kuroda et al, 2011;McCarthy and vom Saal, 1986;Svare and Mann, 1981). In the current study we investigated whether the oxytocinergic system could be related to age and sex differences in parental or infanticidal behavior in naïve mice.…”

Mapping ecologically relevant social behaviours by gene knockout in wild mice

“…Importantly, wild-backcrossed females also manifested all behavioural traits that had been lost through domestication in laboratory females, including aggressive behaviour toward alien adults and newborn pups. These latter sets of behaviours are considered to be male-typical traits that are rarely exhibited by laboratory females 26,[34][35][36] , whereas in nature they serve evolutionary adaptive purposes 26,37 and are robustly exhibited in both wild males and females, thus offering an unique opportunity for mechanistic investigation in both sexes.…”