Investigation of female house mice (Mus musculus domesticus) by males in relation to the presence and absence of anogenital odors from dominant or subordinate males

Abstract

Females in promiscuous species (e.g. house mice; Mus musculus domesticus) may mate with multiple males, which can negatively influence the reproductive success of males because of the risk of sperm competition or injury due to male-male competition. Thus, selection should favor those that can discern not only if a female has recently been in contact with another male (potential risk of sperm competition), but whether the other male with which the female had been in contact is dominant (potential risk of injury) or subordinate to the investigating male.After establishing the dominance ranks of pairs of males, we determined each male’s preferred (P) and non-preferred (NP) female (Trial 1). In Trial 2, one of the females of the pair (P or NP) was treated with the anogenital odor of the male’s opponent, and we tested if the proportion of time males spent investigating their initially P and NP females was altered by the presence or absence (treated or untreated) of their opponent’s odor.In Trial 2, contrary to our prediction, males did not spend a smaller proportion of time investigating the female that was treated than they spent investigating the female that was untreated. In fact, in Trial 2, all males spent a similar proportion of time investigating both females regardless of which female (P or NP) was treated. In addition, contrary to our prediction, subordinate and dominant males did not respond differently with respect to the presence of their opponent’s odor. Males also spent more total time investigating both females when one of the two females was treated (Trial 2) than when neither female was treated (Trial 1). Our data suggest that males may have been attempting to reduce the risk of sperm competition by spending more time investigating females to determine if either female had recently mated.