September 18, 2005

Serpent First: Egg-Laying Snakes Care for Young

JOHANNESBURG -- They are powerful predators that constrict their prey but female African pythons also have a maternal side unheard of among egg-laying snakes: they spend time with their young after they hatch.

The discovery underscores how little we know about the world of snakes and suggests their ways may be far more elaborate than scientists previously thought.

"I had reports from farmers that they had seen baby snakes and their mothers out together and I thought, this is crazy," said Graham Alexander, a biologist at the University of the Witwatersrand in South Africa.

But in 2003 he did intensive observations on two female southern African pythons -- commonly known as rock pythons -- and to his astonishment, they spent up to two weeks with their offspring after hatching.

Such behavior has been observed in some snake species that give live birth but never in egg-layers. In the reptile kingdom, crocodiles and some lizards are the only other species known to offer parental care.


The rock pythons are not exactly the most caring of mothers, though the time they spend with their offspring seems to confer some benefit to them.

"When a human approaches the mother disappears down a hole, abandoning her young," said Alexander.

His theory is that the mother keeps the babies warm at night, enabling them to digest the burdensome egg-yolks they hatch with.

"When the babies hatch, they can hardly crawl because they are so full of egg yolk," he said.

"... My data suggests that the female coils around the empty eggs and the babies sit on top of the eggs. Staying warm at night means that the egg yolk is digested much faster."

While a theory at this stage, the obvious benefit to the young from this is that they become mobile more quickly.

"This shows that behavior in snakes is more complex than we previously thought," said Alexander.

It also highlights our general ignorance of snakes, predators which send shivers up the spines of many people but play key roles in numerous ecosystems.

"We don't have a measure of abundance or population density of a single snake in Africa. We need that information to make well-founded decisions about how threatened species are and we don't have it... it's a big conservation need," said Alexander.

The southern African python can grow to 5 meters (yards) and weigh over 50 kgs (110 pounds), but while they are by far the largest snake in the region they are generally not regarded as man-eaters.