The Girl Every Guy is After

By Megan Clark

Lady Gray Ratsnakes are never short of attention from their male counterparts. A polyandrous species, females tend to mate with multiple males. A study published in 2005 found that out of 34 clutches of ratsnake eggs studied, a whopping 88% of them were sired by multiple snakes, some with three fathers to one clutch! Baby snakes hatch amongst step-brothers and step-sisters, oblivious to the
mating rituals that brought them into this world.

In April or May the Gray Ratsnake emerges from its over-wintering site, or hibernaculum, and the population disperses. The fun begins a month later when mating season begins. Unlike some snakes who take part in a “mating ball,” where 50 snakes or more may gather to mate all at once, the Gray Ratsnake female mates with one male at a time. Macho males put on the moves through a ritual “combat dance” and tail-tangling with other males. The winner, of course, gets the girl. But if she’s already chosen the biggest and best male, why mate again? It seems the female ratsnake has her reasons…

Ratsnake populations are not often especially dense, and so although populations from different hibernacula overlap, a female still runs the risk of mating with a male from her own hibernaculum. These males are likely closely related to her. For the sake of genetic diversity it is better for her to mate with a distantly related male. Mating with many makes this more likely. Multiple mating is also good insurance against infertile males or sperm that are incompatible with her eggs. Indeed her strategy does work: more eggs successfully hatch when multiple males have fertilized a clutch.

To read more about this study, visit http://mysite.science.uottawa.ca/gblouin/publications.html#Y2005
and http://mysite.science.uottawa.ca/gblouin/publications/022_2005_brs_sex_selection.pdf

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