Decreased food intake in reproducing lizards: a fecundity-dependent cost of reproduction

Journal Publication ResearchOnline@JCU
Schwarzkopf, Lin
Lin Schwarzkopf
Abstract

Reproduction has been shown to be costly in viviparous skinks, both in terms of survival and in terms of growth and future reproductive output. One possible source of such costs could be a reduction in food intake, with an associated reduction in energy available for maintenance and future reproduction. Therefore, I compared food intake in male and female southern water skinks (Eulamprus tympanum), to determine whether food intake was reduced during reproduction in either sex. In addition, I measured the relationship between reduction in food intake and the total volume of offspring or testis. A reduction in food intake proportional to the volume of offspring suggests that costs associated with reduced energy intake may be fecundity dependent. Food intake was estimated using the total volume of stomach contents of individuals. Females ate significantly less (mean volume of stomach contents = 0.13 mL) than males (mean = 0.36 mL) just before parturition in January, when embryos were largest. After parturition, females ate significantly more than males. Otherwise, there were no significant differences between the food intake of males and females. Females reduced food intake by eating smaller food items. Females with relatively large numbers of ova or embryos ate relatively less, and therefore decreased food intake in females may be a fecundity-dependent cost of reproduction in these lizards. Males did not reduce food intake during periods when testes were enlarged and mating occurred. Decreased food intake during reproduction is probably an important source of reproductive costs to females of these viviparous lizards, but does not appear to be important in males.

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21

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1442-9993

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4

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8

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Wiley-Blackwell

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