Reproductive biology

Elapids tend to reproduce once a year in spring, often after bouts of male combat over females. All coral snakes, mam-bas, terrestrial kraits, sea kraits, almost all cobras, and approximately half of the Australo-Papuan elapids are egg layers. Most snakes lay eggs, but viviparity (live-bearing) has evolved multiple times independently. Live-bearing is more common in species that live in cool climates because it is thought that mothers are able to control the developmental temperature of their offspring by behavioral thermoregulation. This ability is an important advantage in a short summer. The only cobra to evolve live-bearing is the southern African Rinkhal's cobra, which is reported to have litters of as many as 60 offspring. In Australia there is a diverse radiation of live-bearing elapids. Approximately half of the 20 genera and more than 90 species in Australia are live-bearers.

Hymens Before And After
A night adder (Causus rhombeatus) embryo at 40-days-old in South Africa. (Photo by John Visser. Bruce Coleman, Inc. Reproduced by permission.)
Biology Reproductive Advantage
Spitting cobra mechanism. (Illustration by Dan Erickson)

movements. It was found that the snakes spend the summer far up in the forest canopy, where they hide in hollows, but that they use only large trees. The investigators also found that during the winter the snakes are very particular about the size of the rocks they use—too thin, and the snake becomes too hot; too thick, and the snake is not warm enough. Unfortunately for the snakes, the rocks are the same size that land-scapers sell for gardens. Both large trees and appropriate-sized rocks must be preserved for the species to survive.

Much less is known about the conservation status of other elapid species. Hundreds of thousands of cobras are collected from the wild in Indonesia and other parts of Asia for the reptile skin trade. The cobra skins are turned into belts, wallets, and other pieces of apparel. There is little in formation about the effect of this practice on cobra populations. Similarly, degradation of the marine habitats of sea kraits and seasnakes is probably having an effect, but the effect has not been quantified. Loss of habitat is a primary concern for many elapid species because many of them are habitat specialists.

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