THE POTENTIAL EFFECTS OF PROTECTED NESTS AND CAGE COMPLEXITY ON MATERNAL AGGRESSION IN-HOUSE MICE

I studied the behavior of nursing house mice (Mus musculus) in captivi ty and used a two-by-two factorial design to test the hypothesis that the combination of a protected nest along with a chance for the intrud ers to retreat would improve the ability of resident females to defend their litters from infanticidal males. A chance for the intruder to r etreat was manipulated by testing the resident females in either a sin gle- or a two-compartment cage. The effect of a protected nest was exa mined by providing females with a nest box having a narrow entrance. D uring each test, an infanticidal adult male was introduced into the ca ge of a resident female and her pups. I observed that neither the pres ence of a protected nest nor the chance for the intruders to retreat t o a different compartment, or a combination of the two, increased the ability of a female to defend her litter against an intruder male. Mor eover, neither of these two factors influenced the overall behavior of the resident females. I obtained similar results after using data fro m previous studies to examine the influence of both of these factors o n the efficiency of maternal aggression. Overall, these two approaches showed that females are often unable to prevent intruders from commit ting infanticide. I discuss the validity of the hypothesis that matern al aggression evolved as a mechanism to protect offspring from infanti cide. (C) 1998 Wiley-Liss, Inc.