Facultative sex-ratio adjustment in Norway rats: litters born asynchronously are female biased

Blumberg, Mark S.; Mennella, Julie A.; Moltz, Howard; McClintock, Martha K.

doi:10.1007/bf00170607

Cited by 9 publications

(2 citation statements)

References 43 publications

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“…Subsequent data suggests that there is no such phenomenon either in the moose (Nygren & Kojala 1997), or the common marmoset (Rothe et al 1992). In contrast there has been confirmation of the suggestions in regard to the pig (Brooks et al 1991) and the mouse (Krackow 1992 a); and fresh data supporting the suggestion in the rat (Blumberg et al 1992;Hornig & McClintock 1997), the sheep (James 1976-though see Skjervold 1979, in some hamster litters (Clark et al 1991), the spotted hyena (Hofer & East 1997;James et al 1999) and in roe deer (Macdonald and Johnson 2008). Thus there can be no doubt that in some species, and under some circumstances, this variance is sub-binomial.…”

Section: The Empirical Evidencementioning

confidence: 92%

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

James

2009

Journal of Theoretical Biology

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Section: The Empirical Evidencementioning

confidence: 92%

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

James

2009

Journal of Theoretical Biology

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“…Litters of Norway rats (Rattus norvegicus) born asynchronously show interlitter competition that results in the litters becoming female-biased. Since this alteration in sex ratio occurs without reduction of litter size, it suggests that alteration of the secondary sex ratio occurred as a result of the competition (36). Experimental social stress can also influence a prosimian primate.…”

Section: Discussionmentioning

confidence: 99%

Mother's prior intrauterine position affects the sex ratio of her offspring in house mice.

Vandenbergh

Huggett

1994

Proc. Natl. Acad. Sci. U.S.A.

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Sex ratio alterations related to environmental factors occur in several mammals, but no mechanism has been identified to explain the adjustment. Intrauterine position (IUP) may provide the context in which such alterations occur. Previous studies on house mice and gerbils reveal that the position of a fetus in the uterus in relation to the sex of its neighbors influences its later anatomy, physiology, and behavior. The anogenital distance (AGD) of females located between two males (2M) is longer than that of females not between two males (OM). We have found that the IUP, as determined by cesarean section and by an index of the AGD, correlates with the sex ratio of the litters produced by female mice. The sex ratio of the first Litter born to 2M females was 58% males, for iM females was 51% males and for OM females was 42% males. The effect on sex ratio continues into the second litter. The number of pups produced by mothers of different HUPs in her first two litters did not differ, suggesting that the sex ratio adjustment occurs prior to parturition. These results provide a basis for the natural variability observed in sex ratios of litter-bearing ammals, and suggest that one or more intrauterine mechanisms may be responsible for environmentally related sex ratio alterations.Parental reproductive fitness would increase if the sex ratio of their offspring could be adjusted to relate to environmental conditions. Trivers and Willard (1) hypothesized that under favorable environmental conditions males would be favored and that under adverse conditions females would be favored in polygynous species because a few strong males could sire many grandchildren, whereas females have a more sure but limited reproductive potential.A local resource competition model has been proposed (2, 3) to explain sex ratio alterations specifically for those species in which females show fidelity to their natal area and males leave the natal area to breed elsewhere. In this model, daughters of high-ranking mothers may achieve high reproductive success through inheriting the mother's high rank. However, since males breed in different groups, their reproductive success is presumably not influenced by the mother's rank. Thus, the local resource competition model predicts that, for certain species, high-ranking females would produce a female-biased sex ratio (3).Among invertebrates, breeding adults can adjust the sex ratio oftheir offspring to maximize their fitness (4). Data from mammals have been more controversial. Clutton-Brock and Iason (5) review a number of studies conforming to a high standard of evidence and conclude that significant variation in sex ratios at birth in nonhuman mammals exists and that sex ratio varies with the costs or benefits of producing male or female offspring. Investigators have also shown that manipulating food can influence sex ratios at birth. Experimentally supplementing the food supply of wild opossums (Didelphis marsupialis) results in male-biased sex ratios (6), and restricting the food available ...

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Sex ratio at birth in Norway rats: comment on Hornig & McClintock

James

1997

Animal Behaviour

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Facultative sex-ratio adjustment in Norway rats: litters born asynchronously are female biased

Cited by 9 publications

References 43 publications

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

The variances of the distributions of the combinations of the sexes within mammalian litters: Notes to mark the centenary of the problem

Mother's prior intrauterine position affects the sex ratio of her offspring in house mice.

Sex ratio at birth in Norway rats: comment on Hornig & McClintock

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