Reproductive effort and costs of reproduction in female European ground squirrels |
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Authors: | Susanne Huber Eva Millesi Manfred Walzl John Dittami Walter Arnold |
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Institution: | (1) Research Institute of Wildlife Ecology, University of Veterinary Medicine of Vienna, Savoyenstrasse 1, A-1160 Wien, Austria e-mail: susanne.huber@vu-wien.ac.at, AT;(2) Institute of Zoology, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria, AT |
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Abstract: | Reproductive effort, factors affecting reproductive output and costs of reproduction were studied in primiparous yearling
compared to multiparous older female European ground squirrels (Spermophilus citellus). Yearling females weaned smaller litters than older ones. Litter size increased with posthibernation body mass at the expense
of slightly lighter young for yearling but not for older mothers. In older females, on the other hand, emergence body mass
influenced offspring mass, whereas litter size was affected by oestrus date. High reproductive effort entailed reproductive
costs in terms of reduced subsequent fecundity but not subsequent survival for both yearling and older females. The production
of large litters and long duration of lactation delayed subsequent oestrus, which, in turn, correlated negatively with litter
size. During the second half of lactation, oestradiol levels were significantly elevated, indicating the initiation of follicular
maturation processes. Oestradiol levels during that time correlated negatively with current, but positively with subsequent
litter size. We therefore assume that inhibitory effects of lactation on gonadal development may mediate the negative relationship
between reproductive effort and subsequent reproductive timing in adults. This effect is absent in yearlings because they
are reproducing for the first time. Reproductive output in yearlings was influenced by interactions between structural growth
and puberty.
Received: 22 March 1999 / Accepted: 7 June 1999 |
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Keywords: | Ground squirrel Female Reproduction Lactation Gonad development |
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