natural environments (Getz et al. 1992). Parental defense
against small predators also has been reported for free-living
black-tailed prairie dogs (Cynomys ludovicianus,Hoogland
1995) and naked mole-rats (Lacey and Sherman 1991). Sev-
eral species warn their young with antipredator calls (e.g.,
Belding’s ground squirrel,Spermophilus beldingi;Sherman
1981b; hoary marmot; Holmes 1984a; black-tailed prai-
rie dog; Hoogland 1995; yellow-bellied marmot, Marmota
flaviventris;Blumstein et al. 1997; Blumstein, chap. 27 this
volume). Finally, coypus (Myocastor coypus) may delay
parturition in response to the threat of predation (Gosling
et al. 1988).
Food caching
Pine vole parents (Microtus pinetorum) carry food to spe-
cific locations where they store it in a pile for later use, and
males bring food directly to the natal nest (McGuire and
Novak 1984; Oliveras and Novak 1986). This behavior by
male pine voles may constitute male provisioning of food
for lactating females.
Attendance at the nest
A behavior recently reported for social voles (Microtus so-
cialis guentheri), termed “forced babysitting,” does not fit
the traditional categorization of direct or indirect care, but
is relevant to parental behavior. One parent, typically the
male, aggressively drags the other back to the nest to re-
main with the pups while it leaves the nest (Libhaber and
Eilam 2002). Male and female prairie voles coordinate ar-
rivals and departures at the natal nest such that young are
rarely left unattended, but the aggressive dragging of forced
babysitting does not occur (McGuire and Novak 1984).
Factors that Influence Parental Behavior
In this section, we discuss seven factors that influence
parental behavior. As in previous sections, most research
on these topics emphasizes sciurognaths and is laboratory
based.
Degree of development of young at birth
The degree of development of young varies along a con-
tinuum from altricial species typical of the Sciurognathi to
precocial species typical of the Hystricognathi. Altricial
species are born naked with closed eyes and ears, have poor
sensory and locomotor abilities for several days after birth,
and are confined to a nest. In contrast, precocial species
have longer gestation periods, and their young are often
fully furred, with open eyes and ears at birth, and can loco-
mote almost immediately (Kleiman 1972; Weir 1974). Al-
tricial young rely exclusively on milk for about the first
2 weeks of life and then gradually begin to consume solid
food; in contrast, precocial young may supplement milk
with solid food immediately after birth (Kunkele and Trill-
mich 1997). Although most sciurognaths are altricial, ex-
ceptions occur (e.g., spiny mouse; Dieterlen 1962; Porter
and Doane 1978).
Species with altricial young tend to give birth from a sit-
ting or lying position and young are expelled in front of
the female (e.g., Djungarian hamster and Siberian ham-
ster; Jones and Wynne-Edwards 2000; prairie vole; Mc-
Guire et al. 2003). In several species with precocial young,
parturient females assume a standing position and expel the
young behind their body (e.g., spiny mouse; Dieterlen 1962;
guinea pig,Cavia porcellus;Kunkel and Kunkel 1964; green
acouchi; Kleiman 1972). Kleiman (1972) and Dieterlen
(1962) noted that standing postures during parturition are
assumed by other mammals with precocial young, such
as ungulates, and suggested that standing during parturi-
tion may be an adaptation to the delivery of large, well-
developed offspring. However, at least one species of rodent
with precocial young, the cuis (Galea musteloides), gives
birth from a sitting or lying position (Rood 1972); more
data are needed to confirm that differences in birth position
correspond to degree of development of young. Maternal
aggression during and after parturition is characteristic of
species with precocial young (Kleiman 1972) and of those
with altricial young (Dewsbury 1985; McGuire et al. 2003),
and likely functions to deter infanticidal conspecifics (Maes-
tripieri and Alleva 1990; Wolff and Peterson 1998).
Rodents with precocial young often exhibit lower levels
of nest building and pup retrieval than do species with al-
tricial young (Kleiman 1974). For example, some species
with precocial young do not build a nest (e.g., guinea pig;
Kunkel and Kunkel 1964) or build only a temporary nest to
which they retrieve young for only a few days after parturi-
tion (green acouchi; Kleiman 1972). Mothers of precocial
young typically use maternal contact calls to inform their
highly mobile offspring of their location and to induce fol-
lowing (Kleiman 1972). In contrast, females with altricial
young often build an elaborate nest before parturition and
maintain the nest through the preweaning period (Nor-
way rat, Rattus norvegicus;Denenberg et al. 1969; meadow
vole, Microtus pennsylvanicus;pine vole; and prairie vole;
McGuire and Novak 1984). Typically, altricial young first
venture from the natal nest a few days after their eyes have
opened, and these brief forays trigger initially frequent re-
trieval back to the nest by mothers (and fathers in some spe-
cies). In several species of voles, for example, eyes open 10 –
12 days postpartum, and a day or two later pups begin to
make brief trips from the natal nest; retrieval by mothers
occurs frequently during the early forays but then declinesParental Care 233