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| One of the Ramblers, Bobbie
Epting, sent me this picture of a five-lined skink. (photo by Bobbie Epting) |
If you look closely at the
photograph you’ll see that the color and texture of the tail changes a short
distance behind the hind legs. From that point to the tip of either tail the tail
is
smooth and gray in color. The color pattern of the body – the dark brown
lateral stripe and the lighter striping on the back – all stop at the point
where the tails are attached.
This abrupt change is due to the
fact that this lizard lost its original tail at the point where the color
pattern abruptly changes. After the loss it regenerated the tail and somehow
produced the second tail off the side of the “main” tail. I don’t know how that
second tail was formed; I can only speculate. I do know that it is the only example
I have ever seen.
Many, but not all, lizards are
able to regenerate a missing tail. Some species, like the five-lined skink, have
the ability to cleanly break their tail off when they are attacked. If the
lizard is grabbed or restrained in some way the tail will be shed. It’s the
lizard, not the predator, that detaches the tail, hence the name for the
process: autotomy, meaning self-removal. Grabbing a skink by the tail is
almost a sure way of losing the lizard. Meanwhile, the terminal piece of tail is
twitching and moving about. This motion attracts the attention of the predator
and the lizard escapes, just a little short of tail.
Tail autotomy can happen in two
ways. In some lizards each vertebra in the tail has a plane of weakness in the
middle of the vertebra. When special muscles contract they fracture the
vertebra along the plane of weakness, dropping the tail. Other muscles at the
tail stump contract, stemming the loss of blood. The other method of autotomy
is to pinch the tail off between adjacent vertebrae. In either case the tail is
regenerated with a rod of cartilage replacing the vertebral column.
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| This young five-lined skink still has the bright blue tail and yellow striping. (Photo by Don Hunter) |
The young of five-lined skinks
look very different from the adults. Their body is black with five yellow lines
running from the head to tail. The final third or so of the tail is a brilliant
neon blue. When newly hatched the tail tip is held aloft and wiggled, as if
inviting something to take a bite. My professor at Kansas, Henry Fitch, who
wrote the Life History and Ecology of the Five-lined Skink thought they
might attract small invertebrates, but admitted that it was speculation on his
part.
There are three species of five-lined
skinks in Georgia: broad-headed skink, eastern five-lined skink and
southeastern fine-lined skink. These differ in habitat preference, but all look
near-identical, especially as hatchlings. The broad-headed is arboreal and
larger than the other two, so, if you see a skink in the trees it’s very likely
a broad-headed. The three species are distinguishable by details of scalation
on the head and the underside of the tail. Hatchlings of all three have the
blue tail tip and black body with five yellow stripes. As the age the blue
color vanishes and the yellow stripes disappear as the body becomes brown and,
finally, gray with darker sides.
