Wednesday, June 19, 2013

Tale of a Skink

Male five-lined skink- Patrick Coin
This time of year, five-lined skinks, Eumeces fasciatus, run daily around on our deck.  Most sources say they prefer moist rocky areas and forests.  On Bull Creek they seem to specialize in our house deck, rock garden and occasionally the interior of the house.  The males vigorously defend their portion of the deck against other males.

Adult females are dark brown with five yellow lines along their bodies while the males are more tan to light brown.  In mating season the males' throats and jaws turn a bright orange, advertising their availability.  They begin chasing the females as spring first arrives, grabbing their necks with their jaws; a real love bite.

Egg laying occurs from April through June with the female brooding the 8-12 eggs.  If she detects a defective egg, she bites the end, sucks out the contents and then eats the shell.  Soon the black colored babies are running around, flashing their long bright blue tails.  Some think the blue tails protect them from the larger aggressive males.  I wonder if this doesn't also serve as an advantage to young vulnerable skinks avoiding predators.

The bright blue tail also may be an advantage in escaping predators.  It might attract them to a non-essential feature they can afford to lose.  Skinks, like some lizards, have an interesting way of escaping predators.  When caught by the tail, they simply self amputate it, a process called autotomy.  The blood vessels immediately clamp down and the body seems none the worse for wear. When this occurs, the tail continues to twitch, hopefully distracting or satisfying the predator while the victim runs for cover.

When they are spotted by a predator, young five-lined skinks will sometime twitch their tails enticingly, a distracting invitation to lunch for the attacker, allowing them to live to grow a new one.  This regrowth requires a lot of energy and the tail is never as long or as decorated as the original, the the animal doesn't seem to miss the original.

Last week I netted an adult female as she ran by.  Planning to photograph her, I was holding her by the body and used my finger to straighten out her tail for a picture.  Without any pressure, the entire tail fell off onto the deck.  This has been occasionally reported to occur even when the skink presses its tail against something solid.  The skink was still laying calmly in my hand as the tail danced on the deck.  I switched to video and watched the tail twitch just like any other predator would.  You can see the tail twitch on this video.

Once I put the skink on the deck it skittered off to grow a new tail.  No skinks were injured in making this video, although one was shortened temporarily,

Addendum, 5-10-2015:
A question was raised about the difference between a lizard and a skink.  

Encyclopedia Britannica give a worldly view.
"Skinks are morphologically distinct from other lizards in their almost cylindrical body with no marked neck, long tail, short or even absent limbs, and scales that are smooth, semicircular and imbricated (overlapping)."
 More practical from our mid-western point of view, our resident herpetologist Brian Edmond gave me this description. 
"A skink is the common name for a successful family of lizards (Scincidae) that is worldwide in distribution. They are distinguished in Missouri from other lizards by having smooth, shiny, scales. This probably doesn't serve to physically distinguish skinks from other groups everywhere in the world."
"All skinks are lizards, but not all lizards are skinks."  That, I can remember.
Thanks to Patrick Coin for use of his photographs.  More are at this Flickr.com site.
More pictures are at fcps.edu.

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