W

e describe waysin which male and female
rodents invest in their young and consider fac-
tors that might influence the level of care that
parents provide. Some of these factors pertain to the young
(e.g., degree of development at birth, gender, number of off-
spring), others to the parents (e.g., experience, concurrent
pregnancy, other mating opportunities), and still others con-
cern aspects of the physical environment in which the pa-
rental care is displayed (e.g., from small cages to seminat-
ural environments in the laboratory to field conditions). We
next describe the impact of parental care on the survival and
growth of offspring, and conclude the chapter with a pre-
liminary analysis of the evolution of parental care in voles
(Microtusand closely related species).
Throughout the chapter we focus on studies evaluating
care shown by parents toward their ownyoung from birth
through weaning and beyond. By their very nature, such
studies require monitoring parent-offspring interactions for
several weeks. We largely omit studies in which an indi-
vidual’s parental responsiveness is evaluated by short-term
tests of exposure to pups. Individuals tested in such exper-
iments often are not parents or are tested with unfamiliar
young. While our goal was to make a broad phylogenetic
survey of parental care in rodents, such care is best described
for small species of Sciurognathi, particularly for species of
Muridae such as rats, mice, voles, gerbils, and hamsters.
Comparatively little information is available for species
within Hystricognathi. Finally, because most studies on ro-
dent parental care have been conducted in laboratory envi-

ronments, such studies constitute our major data source.

We include relevant field observations whenever possible.

Forms of Parental Behavior

Parental behaviors are characterized as either director in-

direct(Kleiman and Malcolm 1981). Direct parental care

includes behaviors that have an immediate physical impact

on offspring and their survival; in rodents, such behaviors

include nursing (and feeding), grooming, transporting (most

often retrieving), and huddling with young. With the ob-

vious exception of nursing, males can exhibit all forms of

direct parental care. Males of some species show levels of

direct parental behavior comparable to those of females,

while males of other species show little or no direct paren-

tal behavior (see reviews by Elwood 1983; Dewsbury 1985;

Brown 1993). Indirect parental care includes behaviors that

may be performed by parents while away from the young;

these behaviors do not involve direct physical contact with

offspring but still affect offspring survival, although perhaps

not immediately. In rodents, indirect forms of parental care

include acquiring and defending critical resources, building

and maintaining nests and burrows, caring for pregnant

or lactating females, and defending offspring against con-

specifics or predators. Working definitions for typical direct

and indirect parental behaviors based on comparative stud-

ies of voles under seminatural conditions are shown in

table 20.1 (see McGuire and Novak 1984, 1986). While

Chapter 20Parental Care

Betty McGuire and William E. Bemis