Venomous Snakes in Cold Climates: Ecology of the Australian Genus Drysdalia (Serpentes: Elapidae)

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Abstract
The southern Australian elapid snake genus Drysdalia comprises 4 spp. living under a wide variety of climatic conditions. D. coronoides covers the entire range from relatively warm through to extremely cold areas. Dissection of > 650 Drysdalia specimens provided data on reproductive cycles, food habits and general ecology. Attention is focused on those aspects of D. coronoides ecology that reflect the harsh environment occupied by southern populations of this species. Body sizes of all 4 Drysdalia spp. are similar and sexual size dimorphism is negligible. About 90% of the diet of D. coronoides, D. mastersi and D. rhodogaster consists of scincid lizards, but D. coronata takes anurans and lizards in equal numbers. Reproduction does not reduce food intake in D. coronoides. All 4 spp. are live-bearers, with ovulation in spring and parturition in late summer. Adults reproduce every year except in the coldest climate (Tasmanian), where females reproduce only once in every 2-3 yr. Sex ratio at birth is 1:1 in D. coronoides and D. rhodogaster. Neonatal body size is negatively correlated with maternal size in D. coronoides. Clutch sizes generally fall within the range of 3-5 offspring. Inferred growth rates are low in D. coronoides (maturity at 2 1/2 yr of age) but rapid in D. coronata (maturity at 1 1/2 yr). Possibly, the following aspects of D. coronoides ecology are effects of, or adaptations to, occupancy of cold climates: cessation of activity and feeding in winter; low growth rate and delayed sexual maturation; viviparity; continued feeding by females when gravid; and lowered frequency of reproduction in females.

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