Rodent Societies: An Ecological & Evolutionary Perspective

In addition to seasonal variation in patterns of parental
care within a species, there may also be geographic varia-
tion. Inexperienced male and female prairie voles from an
Illinois population displayed higher levels of parental re-
sponsiveness (time spent huddling) when presented with
two unfamiliar pups than did individuals from a Kansas
population (Roberts et al. 1998). The authors considered
the Illinois site to have abundant resources and the Kansas
site to have scarce resources, but did not discuss geographic
variation in parental behavior with respect to differing re-
source levels. Geographic variation in parental behavior
also characterizes meadow voles. Male meadow voles from
Manitoba and Ontario nest with females and young and
display substantial pup care even when housed in large en-
closures (Storey and Snow 1987); these results differ from
the separate nesting and low pup care displayed by males
from Massachusetts when provided with similar space (Mc-
Guire and Novak 1984; Oliveras and Novak 1986). In-
creased pup care by meadow vole males from Canada cor-
relates with harsher environmental conditions, particularly
colder temperatures (Storey and Snow 1987).
Characteristics of the physical environment could either
directly influence level of male parental behavior or indi-
rectly influence it through effects on the behavior of females.
The latter scenario seems more likely. For example, a test-
ing environment’s size could influence the ability of fe-
males to defend the nest against entry by males and this,
in turn, influences male interactions with young. In small
cages, mothers may be unable to defend the nest against en-

try by males. Thus males may spend time in the nest with

young, especially if nest material is the only cover available

in the cage. In contrast, the increased space available in

seminatural environments may enable females to more ef-

fectively exclude males from the natal nest. Additionally,

with cover available throughout the testing environment,

separate nesting by males is more likely, and this results

in limited male interaction with young pups. Paternal inter-

action with offspring may increase once pups are capable

of leaving the natal nest; increased paternal interaction with

increasing pup age has been reported for meadow voles

(Oliveras and Novak 1986; Storey and Snow 1987) and

white-footed mice (Schug et al. 1992). Similarly, the re-

ported seasonal and geographic variation in paternal be-

havior may actually represent variation in the tolerance of

females to fathers in the natal nest (Storey et al. 1994; Rob-

erts et al. 1998).

Effects of Paternal Presence on Survival

and Growth of Offspring

Effects of maternal separation on growth, development,

physiology, and behavior of young rodents are reviewed by

Lehmann and Feldon (2000), Levine (2001), and Braun

et al. (2003). Our focus is paternal presence, particularly

laboratory studies that compare pups reared by both par-

ents with pups reared by mothers alone in testing environ-

ments ranging from standard to seminatural to challenging

Parental Care 239

Figure 20.1 Comparison of time in the nest for both parents for meadow voles (Microtus pennsylvanicus) and montane voles (M. montanus)as

a function of testing environment. A. Time in nest (total time per 30 min observation period) in small cages; data from Hartung and Dewsbury

(1979). B. Time in nest (total time per 15 min observation period) in seminatural environments; data from McGuire and Novak (1984, 1986).