The Power of Estrogen : Male Snakes

A new study has shown that boosting the estrogen levels of male garter snakes causes them to secrete the same pheromones that females use to attract suitors, and attracting dozens of other males eager to mate.

This experiment in the famed garter snake caverns of Manitoba, Canada, was one of the first in a field setting to ever quantify the effects of estrogen as a stimulant of pheromones, scientists said, in a research.

This estrogen, they said, is the same exact chemical found in many animal species, ranging from snakes to amphibians, fish, mammals and humans. The research confirms once again the unusually powerful role that estrogen can play in biology, and is also relevant to widespread concern about the environmental impact of compounds that mimic the effect of estrogen, found in some chemicals and pesticides.

In this study, male snakes were implanted with a small capsule that raised their estrogen level to about that of female snakes. After one year of this estrogen supplementation, the male snakes exuded a pheromone that caused other males to swarm to them and form the writhing "mating balls" that this species of garter snake is known for.

And just as the pheromone production could be stimulated, it could be taken away, the scientists found. When the supplementation was removed for a year, the males reverted to normal function and behavior.

The red-sided garter snake studied in this research depends totally upon pheromones for males to be attracted to and identify female snakes. But the chemical cues are so extraordinary that in an instant, the male can determine the species, population, season, reproductive condition, size and age of its possible partner.

In garter snakes, the experiments showed just how powerful the mechanism is. When male snakes had their estrogen levels elevated, their pheromone production was so strong that other male snakes actually preferred them to small female snakes.

The area where this research was done is a natural wonder, many scientists say, attracting hordes of tourists. Each spring, tens of thousands of snakes emerge from limestone caves north of Manitoba, Canada.