proximate tactics adopted by squirrels to maximize repro-
ductive success through duration of copulations.
Summary
Reproductive strategies and alternative reproductive behav-
iors of tree squirrels are diverse. Females are in estrus for
only a few hours on a single day of a breeding season. As
a result, females are a fitness-limiting resource for males,
with an availability that varies in time and space. Male fit-
ness is related to success in scramble competition to locate
mates, interference competition to access and defend mates,
and sperm competition to maximize fertilization of eggs of
females that mate with multiple males. Females exacerbate
and manipulate the types of competition through evasive
behavior, selection of sites for mating, mating with and so-
liciting copulations from 1 male, and removing copula-
tory plugs. Conflict, both intersexual and intrasexual, has
been remarkably influential in the evolution of mating sys-
tems of tree squirrels. Conflict among males appears to have
been particularly important in promoting evasive behavior
in females, led to reduced copulatory duration, promoted
alternative reproductive tactics, and influenced postcopu-
latory tactics for minimizing multiple paternity. Conflict
among the sexes likely acts to diminish reproductive suc-
cess of any dominant individual male, as females mate with
multiple males and often avoid active pursuit males. The re-
productive skew among males, however, is substantial, and
active pursuit males clearly are most successful. Intersexual
conflict appears to increase the number of males that are
able to mate due directly to the evasive behavior of females,
a behavior that maintains the satellite tactic among males.
The benefits to females of manipulating the types of com-
petition remain unclear. Future research must quantify the
costs and benefits of male and female tactics under differ-
ent environmental and social conditions to more clearly
elucidate the advantages of these behaviors in an arboreal
environment.Alternative Reproductive Tactics and Strategies of Tree Squirrels 95