crimination among males leads to differences in reproduc-
tive success for these males, (3) that female preferences are
associated with particular male traits, and (4) variability
among males in the preferred traits has a genetic basis (Eber-
hard 1996).
Although there is evidence from many rodent species
that females actively seek copulations with preferred males,
we still need to know more about the traits preferred by fe-
males. Moreover, most mate choice studies have been con-
ducted in the laboratory. To assess whether these data are
relevant to the field (Wolff 2003c), we need field studies
designed to determine preferred mating partners as com-
pared to available choices (see Getz et al. 2004). Finally, fe-
males likely use more than one trait when assessing poten-
tial mates (e.g., Burley 1981) and observed preferences may,
therefore, represent tradeoffs among the traits possessed by
available mates.
The growing use of genetic markers to examine parent-
age in natural populations of rodents has consistently shown
that litters are multiply sired in a variety of species. Nu-
merous hypotheses have been proposed to explain why fe-
males mate with multiple males, but there are few data
available to test these hypotheses. Future field studies com-
paring the reproductive success of females with multiply
sired litters to that of females with litters sired by a single
male are crucial to enhancing our understanding of the
functional significance of MMM.
In addition to the male with whom a female mates, a
female’s reproductive success is also determined by her be-
havior after pups are born. Data suggest that the main-
tenance of a territory, tolerance of philopatric offspring,
bequeathal of the natal territory to offspring by female dis-
persal, formation of female kin groups, and cooperative
breeding are behaviors that affect female reproductive suc-
cess in many rodents. However, the extent to which they
affect a female’s reproductive success is unknown. Further-
more, for each of these behaviors alternative hypotheses
have been proposed as to how they contribute to greater fe-
male reproductive success. Although the data necessary to
discriminate among these hypotheses are often difficult to
obtain, it is important for future studies to attempt to do so
to better understand the many questions remaining regard-
ing how the postcopulatory behavior of female rodents may
affect their fitness.56 Chapter Four