BEHAVIORAL BIOLOGY, 13, 113-119 (1975), Abstract No. 4158
BRIEF REPORT
Placentophagia in Nonpregnant Nulliparous
Mice: A Genetic Investigation1
MARK B. KRISTAL and BASIL E. ELEFTHERIOU
Department of Psychology,
State University of New York at Buffalo,
Buffalo, New York 14226
and
The Jackson Laboratory,
Bar Harbor, Maine 04609
The genetic influence on the response of nonpregnant nulliparous
mice to foster placenta was investigated. Two highly inbred strains (BALB/
cBy and C57BL∕6By), their F1 hybrids, a backcross generation, and seven
recombinant-inbred strains derived from the F2 generation were tested. It
was concluded that there is a genetic component to the response of female,
mice to placenta in the absence of previous experience, and that more than
one, but possibly as few as two loci are involved. Alternative explanations
of average dominance for placentophagia and for no placentophagia (by the
promotion of competing responses) were considered.
Placentophagia, the eating of the “afterbirth,” is manifested by females
of most placental mammalian species during parturition. Despite the fact that
in these species placentophagia is an integral component of perinatal maternal
behavior, little is understood of the causes and consequences of the phe-
nomenon. Parturition, or at least pregnancy, would seem to be the critical
factor in the initiation of placentophagia. Recent studies have indicated,
however, that parturition serves more as the mechanism for the presentation
of placenta than as the causal factor in the initiation of placentophagia, since
placentophagia was observed in a proportion of nonpregnant female rodents
when placenta was made available (Kristal, 1973; Kristal and Williams, 1973;
Sachs, 1969). Furthermore, the behavior is strongly dependent on experience,
1This research was supported, in part, by Training Grant MH-12126, from the
National Institute of Mental Health to the Jackson Laboratory, where the animals in the
present study were tested (The Jackson Laboratory is fully accredited by the American
Association for Accreditation of Laboratory Animal Care), in part by funds from the
Department of Psychology, State University of New York at Buffalo, and in part by
Grant HD-05860 from the Institute of Child Health and Development.
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Copyright ©1975 by Academic Press, Inc.
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