Maternal rats (& mice?)

I don't have a good URL to cite, but a recent news report
presented some data that might be of interest to members of
this newsgroup.

Neuroscientist Craig Kinsley recently published, in the journal
Physiology and Behavior, the results of a study comparing
female rats that have had one or more litters with those that
have had no young. The rats that have had young turned out to
be more calm, less annoyed in stressful situations, less
fearful, more curious, and better at solving problems.

The news article did not make clear whether these differences
were ascribed to hormonal change development during pregnancy
itself (apparently a thread in an earlier study by Kinsley) or
to the experience of taking care of a litter of young. (My
limited experience with humans suggests that women who've borne
and reared several children to tend to be remarkably
unflappable and capable of handling unexpected situations with
relative ease. Those who have reared large families also tend
to say "Hey, you, stop that!" rather often, much the way
experienced female rodents will carry roaming or errant young,
even though not their own, back to the nest.)

The maternally-induced qualities cited seem to ones desirable
in pet rodents, and I'm wondering if anyone else has remarked
upon them. About the only observations I've made in this area
have been that, in a community cage in which one female has
recently given birth, the other females that have not had a
litter are much more likely to eat some of the young, whereas
those who have previously taken care of their own young are
likely to pitch in and help with maternal duties. This is
merely statistical, however, and by no means a Universal Rule
-- sometimes the experienced females will eat some of the
young, possibly because they're so anxious to help by lactating
that they crave additional protein or other nutrients. (That
isn't a very intelligent or responsible approach, but I've
never found rodents to be especially intellectual or
intelligent, just (often) surprisingly clever.

Don Fitch

--
"The findings almost certainly apply to humans, he said. People
share most of their genes with rats and such basic behaviors
are very likely to be similar among mammals and probably other
species, too."