pursuit of females are older, dominant males (greater than
3 years of age), while satellite males are younger, subordi-
nate males who remain dispersed in the area near the mat-
ing activity. Dominant males enjoy great reproductive suc-
cess because they are more successful in guarding females;
however, subordinate males still are able to gain some cop-
ulations if females break away from the dominant male
pursuers. Koprowski (1993a) suggests these younger males
are “making the best of a bad job” by promoting potential
reproductive success during a time when they cannot com-
pete with more dominant males. Male European red squir-
rels also have a sneaker alternative reproductive strategy,
but sneaker males rarely succeeded in copulating with fe-
males (Wauters et al. 1990). In tassle-eared squirrels, fe-
males appeared to initiate copulations with subordinates,
but only after copulating with the dominant male (Faren-
tinos 1980).
Dominance is also age related in the Cape ground squir-
rel. Males live in all-male bands that are composed of un-
related individuals, and dominance is established using
nonaggressive displacements (Waterman 1995). The most
dominant male is usually the first male to copulate with
a female on the day of estrus, and dominant males have
the highest copulatory success (Waterman 1998; fig. 3.3).
This species has extremely asynchronous receptivity in fe-
males, with estrus in females occurring unpredictably and
year-round.
However, the relationship between dominance and re-
productive success is not always clear (Dewsbury 1982a).
In competitive searching, skill in finding receptive females
is more important to male reproductive success than overt
conflict. Competitive searching has also been described in
European ground squirrels (S. citellus), Brant’s whistling
rats (Parotomys brantsii), and bushy-tailed woodrats (Mil-
lesi et al. 1998; Topping and Millar 1999; Jackson 1999).
Thirteen-lined ground squirrels use competitive searching
because females are widely dispersed, making it uneconom-
ical for males to control access to more than a single female
simultaneously (Schwagmeyer 1990). The influence of this
wide dispersion of females on male strategies has been dis-
cussed previously under facultative monogamy, but differs
here because the monogamous males defend nonbreeding
territories, limiting their ability to search for females. Thir-
teen-lined ground squirrels are not territorial and can range
over large areas (Schwagmeyer 1990). Male mobility is crit-
ical, and male mating success is mostly determined by abil-
ity to locate females. Males that obtained an above average
number of mates tended to search twice the amount of area
as other males (Schwagmeyer 1994). These males also spent
more time with the female on the day prior to mating com-
pared with other males (Schwagmeyer et al. 1998). Males
using female defense polygyny can switch to mate search-
ing. In hoary marmots, territorial males use mate searching
to increase reproductive success by gaining access to mat-
ing opportunities outside of their territories (Barash 1981),
similar to Arctic and Columbian ground squirrels (Murie
and McLean 1980).
Another strategy in thirteen-lined ground squirrels is
queuing, in which order of access to females is determined
by order of arrival (Schwagmeyer and Parker 1987). In this
case, the first individual gets access to the female, and the
second male waits until the first is finished. Earlier arrivals
are generally heavier, as well as better at finding females,
which creates an asymmetry that increases the costs of a
second male trying to displace the first. Because the likeli-
hood of finding another female is low, staying and waiting
gives the best reproductive payoff to the second male.Problems with use of the term polygyny
Polygyny has been described in many species of rodents, but
depicting the primary mating system of this group as polyg-
ynous may be misleading because of female reproductive
strategies. Of 33 studies that have described polygyny as
the predominant mating system in rodents, only 67% actu-
ally examined if females mate multiply. Of those that have
looked at female behavior, 65% documented females mat-
ing with more than one male (table 3.1). In the majority of
squirrels examined, for example, females mate multiply. In
Arctic ground squirrels (Spermophilus parryii), males de-
fend territories to keep out other males, but territoriality
does not provide exclusive access to females, although it
does increase the chance of being the first mate (Lacey et al.
1997). It could be that some males are just dominant over-
all, and on the day of a female’s estrus they can supplant or
at least overrule the resident male and gain access to the fe-
male (Schwagmeyer 1990). Even with the high aggression
seen among territorial male California ground squirrels, fe-
males copulated with an extremely high number of males,
averaging 6.7 partners each (Boellstorff et al. 1994).
One way to document multiple mating by females is to
examine the paternity of litters. Studies examining pater-
nity suggest that behavioral data collected during mating
are often a poor predictor of actual paternity (Travis et al.
1996). However, few polygynous species (where one male
appears to have exclusive access to multiple females) have
been tested genetically for multiple paternity. Even so, true
genetic polygyny has been established in some species of
rodents. Black-tailed prairie dogs (Cynomys ludovicianus)
have little or no multiple mating by females (about 3%; Foltz
and Hoogland 1981), even if more than a single male in-
habits a coterie. Likewise, yellow-bellied marmots have no
indication of genetic multiple paternity (Schwartz and Ar-
mitage 1980). Female gundis (Ctenodactylus gundi) typi-36 Chapter Three