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

A gathering of lizards

Where the lizards gather

 I've read that Western fence lizards (Sceloporus occidentalis) tend to be loners, defending their territory fiercely. There's a rocky place at Howarth Park where I like to sit and watch lizards, birds, insects and the occasional California ground squirrel go about their business. In winter the lizards are tucked away under rocks and in the ground but when the sun warms up those rock, the lizards come out of hibernation.

Fence lizards and a skink hanging out

One morning in early spring I arrived just as the sun hit the rocks and was pleasantly surprised to find a gathering of several lizards andl Western skinks (Plestiodon skiltonianus) hanging (literally) together on the vertical face of the rock. As I watched a few more emerged from holes in the wall and within an hour most had dispersed and could be found hunting within view.

Western fence lizards easing out of a tiny cave in a big wall of rock

Entranced, I returned several mornings in a row. The first couple of days the gathering was large. The weather became unseasonable warm and by the time I arrived (between 7:30 and 8 a.m.) the lizards were already out hunting. The skinks appear to come out later than the lizards and I was usually able to see them straggle out, sun for a bit and then glide off for some breakfast. After a few days, the gathering was much smaller but when I looked closely I could see lizards and a few skinks scattered among the rocks, hunting and defending territory.

Dressing up to do battle

 

One afternoon, at the end of March, I went looking for one of my favorite spring wildflowers, Marah oreganus, also known as Manroot and Wild cucumber. It sprawls along rocky places and I had recently discovered that it grows wantonly  in a partially quarried rocky area in Howarth Park. As usual, I had trouble figuring out how to draw this long, sprawling plant and was thinking about giving up when I heard a tiny ruckus on the next rock over. I looked up to see two Western fence lizards (Sceloporus occidentalis), in colors I'd never seen before, fighting and posturing with great vigor. I thought there might be a female involved and I soon found her, peering out of a crevasse on a ledge below the action. The males continued to interact with one another for quite a while. Then one of them left, only to return again, and they picked up where they'd left off. A bit later they both went to opposite ends of the slab and rested up for the next round. The female had climbed out of the crevasse and looked a bit exhausted, though she began to recover (from what?) before very long. As the males resumed their battle, a young lizard climbed up the to view the proceedings from the edge of the rock. One of the males chased him away and I watched as he headed my way, only to stop short when he noticed me noticing him. When I once again turned my attention to the territory struggle, the female had climbed up the cliff and was standing next to one of the males. The other male turned around and headed off slowly through the grasses at the edge of the battleground. I watched him until he disappeared and when I looked back at the victor and his mate, I was astonished to find that his brilliant colors and pattern had reverted to a pattern almost identical to her drab brown!