Why do Western skinks have bright blue tails?

Youthful blue tail fades then turns dirty orange.

In my last post I mentioned seeing Western skinks (Plestiodon sketonianus) hanging out with Western fence lizards. I always thought skinks were shiny because they're moist, like salamanders, but, really, it's that their scales are so smooth and rounded that they reflect light like a piece of glass. When they're young their tails are a bright, screaming blue. As they age the blue fades and eventually their tails are a dull orange brown. When I first began to watch them I thought that blue tail, though really pretty, seemed like a terrible idea. It's awfully easy to find the youngsters as they hunt just by watching for that flash of blue. It's like a bright neon sign pointing the way to an otherwise secretive creature.

A breeding male with paler tail and orange on chin and face

When I asked Google why skinks have blue tails I found many websites promoting slightly different versions of the same story, which is that Western skinks have blue tails so that predators are attracted to the tail rather than the skink's body. Then, when the predator grabs the tail, the skink separates itself from the tail and runs off to be free, if quite a bit shorter. Each time I read the story I became more skeptical about it. For instance, why would only the young skink need that kind of protection? For that matter, why would any creature want to attract a predator to any part of it's body? Why not be like so many drably colored creatures that blend beautifully into their surroundings? I decided that this explanation of the blue skink tail was a very poor one and kept following links, hoping to find something more plausible.

Western skink lying in wait for breakfast

Several pages into my Google search I came across an article written in 1970 for a publication called Herpetologica. The authors shared my skepticism about what they called the decoy theory. Although their article was about a different species of skink, they proposed that the blue tail was a way of letting mature males know not to get territorial and aggressive toward the youngsters they crossed paths with during breeding time. The authors conducted a not entirely conclusive study to support their theory. Their explanation and theory seem a bit more convincing but I think that, for now, blue tail might just be one of those lovely mysteries that must remain unsolved. For now, anyway.

Another day, another young skink hunting.

References:

•Kaweah Oaks

•California herps

•Wikipedia

•Canadian Amphibian and Reptile Conservation Network

•Function of the Blue Tail-Coloration of the Five-Lined Skink (Eumeces fasciatus)Author(s): Donald R. Clark, Jr. and Russell J. HallReviewed work(s):Source: Herpetologica, Vol. 26, No. 2 (Jun., 1970), pp. 271-274. Published by: Herpetologists' LeagueStable