Readers’ wildlife photos

Today’s photos are of lizards, come from Ephraim Heller, and were taken in Trinidad and Tobago. Ephraim’s captions and IDs are indented, and you can click on the photos to enlarge them.

Many people have said to me “the hummingbirds are nice, but what about the lizards of Trinidad and Tobago?” Perhaps not literally true, but grant me poetic license. Preparing this post gave me an opportunity to learn about lizards. Trinidad and Tobago is home to about 49 species of lizards in 11 families in 4 clades.

Clade #1: T&T is home to four iguanian families (Iguania): Dactyloidae (anoles), Iguanidae (iguanas), Polychrotidae (polychrotids), and Tropiduridae (treerunners). Iguania are characterized by visual communication (dewlaps, crests, color change), fleshy non-forked tongues, and sit-and-wait predatory behavior, along with various osteological arrangements.

Here’s a Caribbean treerunner (Plica caribeana):

The green Iguana (Iguana iguana) possesses a parietal eye, a small, pale scale on the top of the head that is a photosensory organ, connected to the pineal gland via its own nerve pathway. It cannot form images, but it detects changes in light intensity and shadow, giving the animal an early warning system against aerial predators approaching from above. It also contributes to circadian rhythm regulation and thermoregulation, which is particularly important for a reptile that ferments its food. Green iguanas eat leaves, relying on a hindgut microbial fermentation system to break down plant fiber.

Green iguanas have a social structure. Dominant males hold territories that contain smaller males, females, and juveniles, with larger males claiming better display perches and more access to females. During mating season males shift toward red or orange hues, becoming more conspicuous; a defeated male that loses his territory returns to a dull brown within hours and holds this color until he reclaims his position.

This one is angry with me:

Trinidad has only one native anole, the leaf anole (Anolis planiceps). Other species are introductions that arrived from other Caribbean islands, likely through human commerce. When a leaf anole detects a threat it can run bipedally, a behavior seen in a number of small lizards and interpreted as a burst-speed adaptation.

Here’s an unidentified anole. Perhaps a reader can identify it:

Clade #2: T&T is home to three gecko families (Gekkota): Gekkonidae (true geckos), Phyllodactylidae (leaf-toed geckos), and Sphaerodactylidae (sphaerodactyl geckos).

Gekkota are distinguished primarily by their feet and eyes. Most geckos have adhesive toe pads with microscopic hair-like structures (setae) that generate van der Waals forces, allowing them to cling to smooth surfaces. The eye is typically large with a vertical or elliptical pupil, and the eyelid is fused into a fixed transparent scale (the “spectacle”) rather than a moveable lid.

I photographed the northern turnip-tailed gecko (Thecadactylus rapicauda). The name comes from the tail, a fat-storage organ. It is also detachable: autotomy (self-amputation) serves as a predator-distraction mechanism. The regenerated tail is typically wider at the tip than at the base, allegedly looking like a turnip. One cool but useless fact: this gecko is able to lick the transparent scale covering each eye.

For completeness, here’s a bit of information about the two lizard clades that I did not photograph.

Clade #3: there are two species of Amphisbaenia in the family amphisbaenidae. These are legless worm lizards. Adapted for living underground, the key distinguishing features are: annular (ring-like) body scales arranged in complete rings around the body, which no true lizard possesses; a highly consolidated, rigid skull adapted for head-first burrowing, with the two sides of the skull fused to form a battering ram; vestigial or absent eyes covered by scales; no external ear openings; and reduced or absent limbs in most families. They move using a unique accordion-like rectilinear locomotion rather than lateral undulation. Sadly, I have no photos of worm lizards as they live underground.

Clade #4: finally, there are three scincoid families (Scincoidea): Scincidae (skinks), Teiidae (teiids), and Gymnophthalmidae (microteiids). Scincoidea is defined primarily by molecular phylogenetics, not by a single morphological characteristic. Bony plates underlaying the scales are present in skinks, giving them their characteristic armored, smooth texture.