In this column I will discuss small lizards found at our Refuge. Anoles, curly-tails, geckos, and skinks are all reptiles. Lizards are reptiles because they have scales, teeth, and a thin-shelled egg.
One of these photos is a fictional gecko and the other is our native American anole. Can you tell which is which? Return to these photos after reading the column and try again.
Fictional or real?
Fictional or real?
True or False?
We will answer this series of questions in this column. Think about each and decide if each is true or false. Remember truth is often stranger than fiction.
The "alien" Cuban anole, Anolis sagrei, will competitively exclude our American anole, Anolis carolinensis.
"Alien" geckos, such as Hemidactylus turcicus, will not displace any native species since geckos are nocturnal and occupy habitats not used by any native lizard.
Our "alien" curly-tailed lizard, Leiocephalus carinatus, occupies habitats that our two Anole species use, so it may outcompete them.
Skinks, anoles, and geckos often drop their tails to distract predators.
Our most common Refuge lizards are Anoles in the genus Anolis. This male Cuban Anole Anolis sagrei shows the typical display with extended dewlap. What you cannot see is that the males often do pushups while displaying their dewlaps.
Mark Renz photo of male Cuban Anole displaying.
What do you think about the question posed on the photo? In fact the answer is both come hither to females and stay away from my turf to males. A poem from BIOGRAFFITI: A Natural Selection by John Burns describes both functions of the display.
An Ole for Anolis
The male of an anole named sagrei
Is subject to sexual selection
As he seeks an existence of harmony
And the chances to make a connection.
He maneuvers for adequate holdings
(O plot for becoming attractive!)
By resorting to dewlap unfoldings,
Being robust, and frightfully active.
He both acts the competitive wizard
And succeeds in enticing a friend
Who will mate him. But being a lizard,
He does it by halves in the end.
The last two couplets refer to the fact that all lizards have a bifurcate penis and so can copulate either "right-handed" or "left-handed."
American anoles mating
Close-up of everted bifurcated penis of an anole
American Anole and Cuban Anole
Our native American anole was originally from Cuba and our Cuban anole has only arrived recently. I can remember visiting my Aunt and Uncle in Coral Gables in the 1950's when only American anoles were present and were common In bushes and gardens. The first Cuban anole I saw was in the 1960's. Now Cuban anoles are the most common lizard seen throughout south Florida and American anoles are apparently much less common. What happened? Before you can answer the question for yourself we have to review how to tell the difference between the two species.
If you see displaying males the color of the dewlaps is red orange in the Cuban anole and purple in the American anole. Females have a tiny dewlap and do not extend it in with pushup displays.
Displaying American anole next to displaying Cuban anole.
Size is not a reliable indicator of species.
Another difference is in microhabitat and body build. American anoles are more slender with a more elongated nose and are more often on thin branches high in bushes and trees. Cuban anoles are stouter with a blunter nose and are more often on the ground or low in bushes or on tree trunks.
Cuban anole on boardwalk railing
American anole on thin branch
And yet another difference is color and color variation. American anoles can change color from brown to green to match their background and, except for a light dorsal stripe on some females, have no markings. Cuban anoles cannot change color but they are incredibly varied in shades of brown and tan and in the pattern of dark markings. It would be of interest to see whether Cuban anoles pick their background to best match their color and markings.
Color and marking variation in two Cuban anoles.
"Cuban Anoles" Do Not Eliminate "American Anoles" in Florida
Jonathan Losos and his colleagues have deciphered the history of the interactions between the so-called Cuban Anolis sagrei and the so-called American Anolis carolinensis. Originally neither occurred in Florida so in fact both are aliens. Both occurred, and still occur, in Cuba. Some time in the past Anolis carolinensis got to Florida and expanded its habitat to include low bushes and even the ground. As I wrote above, it was common in south Florida in the 1950's. Anolis sagrei got to the Keys in the late 1800's, has spread, and has become the most abundant anole. Now it is hard to find Anolis carolinensis but it is not gone; it has just reverted to its ancestral habitat in tall shrubs and thin branches of trees. Anolis sagrei does very well in its ancestral habitat on the ground and on low bushes and the bottom of tree trunks. Incidentally it uses human habitats such as fences, sidewalks, and lawns with bush refuges near by.
I have wondered whether the Cuban anole has always been more aggressive than the American and whether it has a faster reproductive rate. Both would help explain why it is more abundant than the American anole ever was. What we need is a bioassay of biting tenacity and data on number of eggs laid and time to maturity to evaluate my dual hypothesis.
Interestingly the Cuban anole may be moving further up trees now that the much larger curly-tail lizard has become widely established in south Florida.
An even more recent immigrant to south Florida than the Cuban anole is the curly-tailed lizard Leiocephalus carinatus from the rocky coasts of the Bahamas. This large lizard was apparently released in Palm Beach back in 1959. It first became common around malls and has become increasingly common in the last few years. It has quickly spread to porches, alleys, driveways and other hard-surface habitats. It was first seen at our Refuge only two years ago but is now common around the Visitor Center and by the boulders on top of the levee by the boat launch area.
A curly-tailed lizard about 10 inches long.
Why do you suppose this lizard bobs its head and curls its tail? Here are hypotheses H1, H2, H3, and H4.
H1. To attract a mate
H2. To advertise its territory
H3. To let a predator know it sees the predator
H4. To attract a predator to bite its tail instead of its head
Watch them to eliminate possible hypotheses. I do not often see them with stubby or obviously regenerated tails though most lizard species will drop their tails if attacked. All curly-tails, including small juveniles, curl their tails so it is not just males and not just territorial display. They always do it as they are heading toward a building, a rock, or other hiding place. As you approach it bobs its head and curls up its tail so you can see the bright yellowish white underside. Then it runs a bit further, looks over its shoulder and lowers its tail to the ground. If you approach closer it again curls up its tail and runs. Thus I favor H3. It is as if the curly-tail is telling the predator. I see you and am faster than you are so don't bother to even try to catch me.
Defenses When Caught by a Predator
If a predator gets close to a small species of lizard or catches it, the lizard can constrict special tail muscles so the tail breaks off at a special spot. Elastic elements at that spot constrict and seal the blood vessels.
A just detached anole tail.
A second response when caught fits the adage that the best defense is a good offense. Any anole you pick up will invariably bite and hold on. This lets you do the ear-ring trick as a fun demonstration.
An anole on Dr. Tom's ear. The fork at the tip
of the tail shows that it has partly regenerated.
Some times nothing distracts a predator;
this snake has almost swallowed a Cuban anole.
Skinks have smooth shiny scales with no pronounced neck and a long cylindrical body. Their tail is especially long and thin.
As Douglas Florian writes:
Along the ground I'm found -- I slink
Through grass I pass -- I am a skink.
Bite my tail and it releases.
I don't fight back -- I fall to pieces.
Juvenile skinks of many species have electric blue tails that they twitch and this directs the attack of the daytime predator, almost always a bird with color vision. It is apparently a country myth that the blue tail causes neurological disruption if a cat eats it.
Juvenile skink with electric blue tail.
Geckos are nocturnal and many make a chirping sound. Their tail wiggles vigorously for many minutes when it detaches. This presumably keeps the attention of nocturnal mammals that do not have color vision but do have excellent night vision and sense of touch. It usually works for our cat.
Geckos: True? False?
1. Geckos can walk on water and so are called "Jesu Christie" lizards.
2. Geckos congregate where insects are attracted to lights on porches at night and so do not compete with any native lizard or frog species.
3. Geckos can walk upside down on smooth surfaces like glass.
Try to decide true or false before reading any further.
1. False. Actually geckos cannot walk on water but there is a small Central and South American lizard that runs so fast that it can move across water without sinking. Google Basiliscus.
2. True. Go out on your porch in the morning and look for bits of poop on the floor where it joins the wall. If you find poop then go out at night and you may find a gecko walking upside down on the ceiling.
Leopard gecko, Hemidactylus turcicus.
3. True. Bioengineers are still trying to make a tape that is as sticky as duct tape but can release and re-adhere more than once per second just as a gecko does as it runs upside down across a smooth ceiling. Google gecko feet to see how the micro-structure of the toe pads allows the gecko to do this.
Gecko's feet each have five toes and each toe has ~ 15 lamellae.
A square mm of lamella has 14,000 hair-like setae.
And each seta has ~ 500 very teeny spathulae.
Douglas Florian visual poem about geckos.
REVIEW QUESTIONS: Try to answer True or False and your reasons before scrolling down for my answers.
Q1. Many lizard species have responded to predation as an agent of natural selection by evolving so they do not lose their head over a little piece of tail. True? False? Explain!
Q2. Our American anole, Anolis carolinensis, is a native species whereas the Cuban anole, Anolis sagrei, is an alien species. True?
Q3. Anoles, and other lizards, can copulate "left-handed"or "right-handed". True? False? Explain!
Q4. The ground-dwelling curly-tailed lizard, Leiocephalus carinatus, has caused our Cuban anole to move up into trees. True? False? Explain!
A1. The answer is TRUE. Most, if not all, small lizard species have a specialized adaptation so they can drop their tail when attacked and do not bleed to death.
A2. The answer is FALSE. Both of our common Anoles are aliens in that they were not originally in Florida. They coevolved, among other places, in Cuba where their body builds and microhabitats are different.
A3. The answer is TRUE. All lizards have a bifurcate eversible penis. It is called a hemi-penis since it has two halves either of which can be used when copulating.
A4. The answer is FALSE. Curly-tailed lizard habitat, on its native Bahamas and here in Florida, is hard substrates near natural holes and crevices. When our Cuban anole occurs on sidewalks or grass it is often next to dense and often thorny bushes that serve as refuges from predation. Our American anole is the species that occurs up in trees and it was there before the curly-tails invaded.
Fictional Gecko vs. Real American Anole
Return to the first two images and compare them to other images in this column. The fictional lizard is the GEICO GECKO but several things are not like real geckos. The eyes are too big and there is no vertical pupil. There are no little claws at the end of the toes. The body build is too svelte. And geckos are never all bright green. In fact it looks more like our American anole than like any gecko.