not a specific category of parental behavior, “time in nest”
often provides an estimate of overall direct parental care
(table 20.1).
Direct care
Nursing
Mothers of altricial young are the sole source of early nu-
trition for their offspring (Alberts and Gubernick 1983), but
mothers of precocial young are not. Precocial young typi-
cally supplement their diet of milk with solid food within
a few days of birth, although they continue to consume
milk for many weeks (Kleiman 1974; Gosling 1980). Nurs-
ing postures adopted by female rodents vary from crouch-
ing over pups to sitting or lying next to them (Kleiman
1974; Drewett 1983). Whatever form nursing takes, lacta-
tion is energetically costly to female mammals (Hanwell and
Peaker 1977; Stapp et al. 1991); lactation also presents chal-
lenges to water balance, although female rodents recover
some of the water and electrolytes lost in milk by consum-
ing the urine of their pups during anogenital grooming (Al-
berts and Gubernick 1983). In addition to nutrients, milk
contains antibodies that young rodents cannot produce on
their own until a few weeks after birth (Brambell 1970).
Feeding
When young rodents can eat solid food, mothers of altricial
species may bring food to the nest (e.g., woodchucks, Mar-
mota monax;Barash 1974b) while mothers of precocial spe-
cies may allow young to take food from their mouths (e.g.,
green acouchi,Myoprocta pratti;Kleiman 1974). Males,
too, feed juveniles: muskrat (Ondatra zibethicus) males pro-
vision juveniles at the home burrow (Marinelli and Messier
1995) and white-footed mice (Peromyscus leucopus) males
accompany weaned young on foraging trips (Schug et al.
1992).Grooming
Beginning at birth, pups are groomed extensively by moth-
ers and sometimes by fathers (e.g., spiny mouse, Acomys
cahirinus;Dieterlen 1962; Djungarian hamster, Phodopus
campbelli,and Siberian hamster, P. sungorus;Jones and
Wynne-Edwards 2000; prairie vole, Microtus ochrogaster;
McGuire et al. 2003). Parental grooming of the anogenital
region stimulates urination and defecation in young pups
until they are about 2 weeks old (Capek and Jelinek 1956;
Rosenblatt and Lehrman 1963). In many species, grooming
of offspring continues well beyond when it is physiologically
necessary for the young; it is likely that this grooming func-
tions in the maintenance of parent-offspring bonds (Kleiman
1974; Libhaber and Eilam 2004).Retrieving, huddling, socialization, and shoving
Other common forms of direct parental care include retriev-
ing offspring to the nest (or transporting them to another
location) and huddling with young, a behavior that provides
thermoregulatory benefits. Some direct parental interac-
tions with offspring have been described as play or social-
ization (e.g., green acouchi, Kleiman 1974; hoary marmot,
Marmota caligata;Holmes 1984a). Finally, naked mole-rat
(Heterocephalus glaber) parents shove pups around the
nest; this behavior encourages pups to flee from danger and
to avoid dangerous situations in the future (Stankowich and
Sherman 2002).Indirect care
Constructing and defending burrows and nests
Burrow or nest construction and maintenance by male and
female parents have been described in the field for muskrats
(Marinelli and Messier 1995) and for many species in the
laboratory (e.g., plateau mouse, Peromyscus melanophrys;
Ferkin 1987; volcano mouse, Neotomodon alstoni;Luis
et al. 2000). Territorial defense against conspecifics, espe-
cially around the nest, is common for most if not all ro-
dents, and helps to defend food resources or to protect
young from infanticidal conspecifics (Sherman 1981a; Wolff
1993b; Hoogland 1995; Wolff and Peterson 1998).
Small size limits most species from defending young
against predators, although male and female prairie voles re-
acted aggressively to shrews in the vicinity of the natal nest
and effectively prevented predation on their pups in semi-232 Chapter Twenty
Table 20.1 Categorization of parental behaviors displayed by voles
(Microtusspp.) under seminatural conditions (modified from McGuire and
Novak 1984, 1986)
Behavioral category Definition
Direct parental
behavior
Nursing Contact with at least one pup involving nipple
attachment
Huddling Contact with at least one pup with or without nipple
attachment
Grooming pup Licking pup
Retrieving pup Grasping in mouth pup that has left the nest and
carrying it back to the nest
Indirect parental
behavior
Nest building Gathering, shredding, and arranging nest material
Runway building Clearing, building, and maintaining runways
Food caching Carrying food to a new location where it is stored for
later use
Spatial location re-
lated to parenting
In natal nest In nest that contains young; sometimes used as an
overall measure of direct care