quences for the genetic structure as well as the conservation
of populations and species.
A variety of proximate triggers for natal dispersal have
been observed. In some species, a predisposition to leave
the natal area arises very early in life, due to long-term ef-
fects of hormones or nutrition on the developing individual.
However, in most species, dispersal behavior is more flexible
and may be influenced by factors such as the availability of
environmental resources, the presence of potential mates or
the opposite-sex parent, or interactions with siblings. Indi-
viduals typically do not emigrate until they are prepared to
cope with the potential risks of dispersing. In most species,
natal dispersal occurs near the time individuals reach re-
productive maturity, but may occur earlier when changes in
environmental conditions are predictable and individuals
begin mating at the onset of reproductive maturity.
A variety of hypotheses have been proposed to explain
the prevalence of female philopatry in rodents and other
mammals. Among these are the ideas that the costs of dis-
persal and benefits of philopatry are greater for females, and
that females do not need to disperse to avoid inbreeding.
Philopatry may occur among eusocial rodents such as mole-
rats due to environmental constraints on dispersal and find-
ing food, or when high coefficients of relatedness favor co-
operation among kin living in the same area. The evolution
of complex social systems among rodents and mammals in
general has been suggested to be predicated upon philopatry
and cooperation among kin living near each other.162 Chapter Thirteen