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Age-Specific Weight Change of Female Spermophilus elegans (Rodentia: Sciuridae)

Sharon Pfeifer
The Southwestern Naturalist
Vol. 30, No. 3 (Aug. 28, 1985), pp. 357-362
DOI: 10.2307/3671267
Stable URL: http://www.jstor.org/stable/3671267
Page Count: 6
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Age-Specific Weight Change of Female Spermophilus elegans (Rodentia: Sciuridae)
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Abstract

Two hundred and fifty weight values for Spermophilus elegans females were analyzed by age class and reproductive status to clarify the pattern of female weight growth. During their first active season, juvenile females attained 80% of yearling and 74% of adult prehibernatory weights. Juveniles that survived hibernation to become yearlings were significantly lighter than adults at spring emergence because of incomplete weight growth in the first active season and greater overwinter weight loss. Yearlings continued to grow during the second active season and reproduced. Postemergent litter sizes of yearlings were smaller than those of adults. Production of smaller litters or the failure to successfully wean litters probably enabled yearlings to attain 95% of adult pre- and posthibernatory weight values by the end of the second season. Nonreproductive females of both yearling and adult age classes gained significantly more weight by mid to late summer than did females with weaned young, but immergence times were similar for the four age-reproductive classes. Previous accounts have stated that juvenile ground squirrels attain 100% adult weight in their first active season. The results of this study indicate that the growth process of S. elegans females is more gradual and requires two full active seasons before yearling weight values are equivalent to those of adult females.

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