Wednesday, February 18, 2009

Herpetological Breeding Congregations

Let's have a look at some Reptiles and Amphibians that breed in groups.

California Newts (Taricha torosa)

The typical method of mating amongst California Newts involves the male amplexing (grasping the female for mating in a kind of hug). He then rubs his nose on her chin, and if she accepts, he then releases her, and deposits a sperm packet on the bottom of the pond or stream where they have come to reproduce. She takes the sperm packet up into her cloaca, fertilizes the eggs, then shortly after lays them (in small masses) on objects in the water.

In areas where there are more males then females, competition for females can be quite intense.

When there are MANY more males than females, these large breeding congregations occur. These breeding masses are usually seen in small streams that flow into ponds.

Taricha torosa egg mass

The closely related Rough Skinned Newt (T. granulosa) has a similar breeding regime, and occasionally gathers in breeding groups, as well.

African Foam Nest Treefrog (Chiromantis xerampelina)

Also known as African Gray Treefrogs, they mate in congregations in trees with branches overhanging seasonal bodies water. The group whips up a lather of foam made of skin secretions and sperm, into which the eggs are deposited.

These groups can vary in number.

Frogs within the mass may pair off or pile on in groups. With so many eggs and sperm mixing together in the foam nest, the paternity of any individual frog is unsure.

The outside of the foam nest hardens, with the eggs developing in the wet frothy inside.

When the tadpoles have hatched, and then reached a certain size, they wriggle vigorously. This action dissolves the hard shell in spots, and the tadpoles drip out into the pond below.

Red-sided Garter Snakes (Thamnophis sirtalis parietalis)

The Red-sided Garter ranges over the Central U.S. and Central and Western Canada.

In parts of their range, especially in Canada, they hibernate in caves and hollows in large numbers.

When they emerge in Spring, the males come out first, followed by the females days later.

The largest breeding congregations are known from historic sites, which may have been used for hundreds of years, in Manitoba (a province of Canada).

Unlike our previous 2 animals in the post, both amphibians, these reptiles fertilize the eggs internally (the males placing the sperm into the female directly). Therefore, despite the great competition for the larger females, only one male fertilizes a female. She then slithers off, and eventually gives live birth, as garter snakes do.

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