"Why I prefer the field of science over any other is this one single fact: there is no final decision, but a process of constant discovery, discussion and leaning into the evidence that shifts as well. The questions mature as the answers compete."
- Scott Jackson-Ricketts

Monday, February 1, 2010

The mysterious blue-tailed skink

One aspect of natural history that fascinates me is the hidden lives that many species of animals lead right under our noses. For example out in your yard there are literally dozens of sizable critters that you do not pay any attention to since they are hidden from your view by their nocturnal or cryptic habits. For example you would be surprised at the number of things that lurk under the leaves/compost/mulch in your flower beds or behind the shed. Probably you would be happier not to know about them! In Florida we are blessed/cursed by some remarkably huge and somewhat scary insects such as the "palmetto bugs" aka roaches, earwigs, and most impressive of all the giant whip scorpions or vinegaroons. But also living in this community of creatures of the leaf litter layer are some interesting reptiles such as geckos, scarlet king snakes and scarlet snakes, ring-necked snakes, and the lizards called skinks.

To observe this hidden life of the leaves and soil I put out pieces of plywood on the ground and occasionally pick them up and see what is underneath. In addition I bury a bucket in the ground up to the edge and put a piece of plywood over the top. This pitfall trap collects things such as lizards which are otherwise hard to catch. Look at the photo of one such bucket trap and you will see 3 skinks that were caught. These are probably all different sexes and ages of the southeastern five-lined skink. Juveniles have bright blue tails and adult males can have blue tails that are not so bright (see photo).

Most of you have likely seen these skinks when they are active foraging on the surface or even in trees. If you or a predator grabs them by the tail it breaks off and continues to wriggle, attracting the attention of the attacker while the lizard escapes. The tail will re-grow but it is not the same structure. Now the adult males of some species of skinks have long been considered venomous by rural folk who called them scorpions. This has been considered a foolish country legend until recently when it has been shown that these skinks, while not venomous, are indeed toxic if eaten by a predator. Cats in particular have been reported to be affected by a toxin if they eat these lizards. It is interesting that the blue tail color seems to serve two functions, to divert the attack of a predator to the tail instead of the head, and likely to warn predators that the lizard is toxic. The use of blue coloration for this purpose is interesting since it less commonly used to warn predators than red or orange.

Another interesting habit of these lizards is that you will occasionally find females that are "incubating" eggs by curling around them. This is not a true incubation since no heat is released by the female. But the presence of the female likely greatly enhances the survival of the eggs to hatching. Such maternal care is indeed known in some amphibians and other reptiles such as alligators and pythons and illustrates how primitive vertebrates can engage in what we might consider higher levels of behavior.
So go ahead and clutter up your yard and put out some small sheets of plywood (tell your neighbors they are "cover boards" you are using to census your leaf litter faunal communities!). You will be amazed by what you find but remember that these critters need moisture and natural compost to thrive; try not to spray any pesticides or herbicides. The resulting assemblage of critters will not only provide some exciting exploring with the kids but will produce a dividend by allowing for biological control of some pest insects by your home-grown predators.



Bill Dunson
Englewood, FL & Galax, VA

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