their natal burrows. Further, 1-year-old males that are sex-
ually immature usually reside in the natal territory. Con-
sequently, most adult male prairie dogs are surrounded by
juvenile kin when they are exposed to badgers in June:
breeding males have nearby juvenile offspring, and non-
breeding 1-year-old males have nearby parents, adult and
juvenile siblings, juvenile nieces and nephews, adult and
juvenile cousins, and so forth. Male prairie dogs with kin
in the home territory are more likely to call than are males
without nearby kin —but only for black-tailed prairie dogs
is this difference significant (fig. 37.1b). Sample sizes are
larger for black-tailed prairie dogs than for the other two
species, and perhaps additional data for Gunnison’s and
Utah prairie dogs would lead to significance as well. Notice,
however, that 33% of male black-tailed prairie dogs and
31% of male Gunnison’s prairie dogs call when they have
no kinwithin the home territory (fig. 37.1b). These high
frequencies indicate that some factor in addition to kinship
is important for alarm calling among male prairie dogs.
Perhaps calling to warn potential mates,which are usually
unrelated or only distantly related, is important for males.
Or perhaps a male’s alarm call announces his competitive
status, good health, freedom from parasites, and willing-
ness to call in the future — and therefore is important in
both male-male competition and female choice.
Figure 37.2b shows alarm calling by adult male prairie
dogs that have one or more of the following in the home ter-
ritory: (1) juvenile offspring, (2) parent or adult littermate
sibling, or (3) more distant adult and juvenile nondescen-
dent kin. For black-tailed and Gunnison’s prairie dogs, call-
ing frequencies are relatively high (i.e., 25% for all three
classes), and males with nondescendent kin in the home
territory call as often as males with nearby offspring. The
reason for this latter equivalence, I speculate, pertains to
demography once again. The probability of copulating in
the first year is only 6% for male black-tailed prairie dogs
and only 24% for male Gunnison’s prairie dogs (Hoogland
2001). Further, nonbreeding yearling males of both species
usually remain in the natal territory, and thus commonly
have nondescendent kin nearby. Natural selection thus eas-
ily can favor calling by male black-tailed and Gunnison’s
prairie dogs with only nondescendent kin nearby, as argued
earlier for females.
But why do male Utah prairie dogs call so rarely in re-
sponse to the badger (fig.s 37.1b, 37.2b)? The males least
likely to call are fathers (at a frequency of 7%), and this
paternal reticence, coupled with the calling frequency of
25% for males with nearby parents or siblings, is primarily
responsible for the significant difference for male Utah prai-
rie dogs in figure 37.2b. The silence of male Utah prairie
dogs has baffled me for years. Recently I formulated a test-
able hypothesis that pertains to male body mass. Male and
female black-tailed prairie dogs, which do not hibernate,
attain maximal body mass in late fall (Hoogland 2003a)—
several months after completion of our experiments with
the badger. Male and female Gunnison’s prairie dogs, which
do hibernate, usually attain maximal body mass and ini-442 Chapter Thirty-Seven
Figure 37.2 Alarm calling by prairie dogs with different categories of nearby
kin in the home territory for (a) females and (b) males. Individuals with parents
or littermate siblings in the home territory did not also have offspring there, and
individuals with more distant nondescendant kin in the home territory did not
also have either parents, siblings, or offspring there. Shown here are means
1 SE; the number above each SE line indicates the number of individuals
observed (each approximately seven times per year). P-values are from Kruskal-
Wallis analysis of variance. Data are from Hoogland 1995, 1996, and unpub-
lished data.