their investment (Marinelli and Messier 1995). When male
rodents provide care for young, decreased maternal behav-
ior in the presence of males has been interpreted as evidence
of reduced maternal workload. When males are present but
do not care for offspring, decreased maternal behavior has
been attributed to disruption caused by paternal presence;
increased maternal care in such circumstances is rare. Un-
changed levels of maternal behavior in the presence of fa-
thers are reported for wild house mice (studied in labora-
tory cages; König and Markl 1987), prairie voles (studied
in seminatural laboratory environments; Wang and Novak
1992; Wilson 1982b), meadow voles (studied in seminat-
ural laboratory environments; Storey et al. 1994) and col-
lared lemmings (Dicrostonyx richardsoni,studied in labo-
ratory cages; Shilton and Brooks 1989).
Maternal response is a major factor influencing the level
of paternal care. For example, females of biparental species
frequently exclude males from the natal nest during par-
turition and for about a day thereafter, but subsequently
permit males to fully interact with young (gerbils; Elwood
1975; southern grasshopper mice, Onychomys torridus;
McCarty and Southwick 1977b; spiny mice; Porter et al.
1980; white-footed and deer mice, Peromyscus spp.;Wolff
and Cicirello 1991; prairie voles; McGuire et al. 2003). In
other species, female aggression toward mates may extend
throughout the preweaning period (meadow voles; McGuire
and Novak 1984; montane voles, Microtus montanus;Mc-
Guire and Novak 1986; white-footed mice; Xia and Mil-
lar 1988; but see Wolff and Cicerello 1991); in such species,
male interactions with young occur primarily after wean-
ing. Indeed, increases in male-offspring interactions with
pup age have been reported for meadow voles (Oliveras and
Novak 1986; Storey and Snow 1987) and montane voles
(McGuire and Novak 1986) in the laboratory, and post-
weaning paternal care of young has been reported in a nat-
ural population of white-footed mice (P. leucopus;Schug
et al. 1992) and deer mice, P. maniculatus(Wolff and Cici-
rello 1991). The duration of maternal aggression toward fa-
thers is not necessarily consistent within a species; for ex-
ample, female red-backed voles vary in the intensity and
duration of aggressive behavior toward fathers, and this pro-
duces variation in levels of paternal care (McGuire 1997).
Few studies have examined experimentally how mater-
nal presence affects paternal behavior (apparently polygy-
nous taxa, such as spiny mice, Makin and Porter 1984 and
collared lemmings, Shilton and Brooks 1989; and polygy-
nous meadow voles, Storey et al. 1994). Maternal removal
is problematic because it interferes with suckling and pup
nutrition. Such removal is less problematic in species with
precocial young, such as the spiny mouse, for which Makin
and Porter (1984) conducted near-daily observations of par-
ents from day 1 to day 23 postpartum. On any given day,
they observed pairs with their young and then temporarily
removed mothers to observe paternal behavior. Males hud-
dled with their offspring more when the mother was absent
than when she was present, again confirming that females
regulate interactions between fathers and offspring.
Juveniles also can affect care shown by parents to a
younger litter. Norway rat mothers attack juveniles before
and after the new litter is born, but juveniles still spend time
in the nest with neonates (Gilbert et al. 1983). Maternal
care in the presence of such juveniles is similar to that dis-
played in their absence (Grota and Ader 1969; Gilbert et al.
1983). Female spiny mice nest with their mate and juveniles
from the previous litter both before and after a new litter is
born, but keep both males and juveniles away from the nest
on the day of parturition (Porter et al. 1980). Under semi-
natural conditions, female meadow voles aggressively ex-
clude juveniles from the nest containing the new litter (Wang
and Novak 1992); increased nest defense resulted in greater
maternal workload compared to females rearing pups with-
out juveniles present. In contrast, female prairie voles allow
juveniles in the natal nest and experience reduced maternal
workload in the presence of juveniles if the father is also
present (Wang and Novak 1992). Presence of juveniles also
may reduce paternal workload in prairie voles, but this is
the only species for which data exist (Wang and Novak
1992).
Levels of paternal care positively correlate with paternity
(Westneat and Sherman 1993), but this topic has received
little attention in rodents, with most studies focusing on in-
fanticidal rather than paternal behavior. An exception con-
cerns work with meadow voles (Storey and Snow 1987). In
one experiment, males spent less time in the nest with their
mate’s pups when another adult male was housed in a
nearby wire enclosure. A second experiment compared lev-
els of nest attendance by males housed with their mate and
pups to that of males housed with a female rearing young
of another male; time spent with pups was much higher for
fathers than for nonfathers. Thus reduced paternal care in
meadow voles correlates with uncertain paternity.Parenting experience
Rodents can gain parenting experience by helping to care
for a younger litter in their social group (alloparental care)
or by caring for their own young in successive litters. In the
laboratory, alloparental experience results in enhanced re-
productive performance, pup growth, and development in
gerbils (Salo and French 1989), but the effects of alloparen-
tal experience in other species are slight and often mixed
(Solomon and Getz 1997). For example, adult prairie voles
with alloparental experience did not differ in their parental
behavior from those without alloparental experience, butParental Care 237