A Look at the Stars Running the Show: Part 1

If you ever go to Puerto Rico (really any island in the Caribbean) and walk into the forest, all eyes will be on you. Everywhere you turn, tree trunks will be littered with lizards extending their colorful throat fan called a dewlap. Most likely, you would be looking at a smaller subset of lizard species known as “trunk-ground” anoles. These species are characterized as sit-and-wait foragers. They usually perch on the lower trunks of trees and face downward toward the leaf litter on the forest floor, waiting for their prey. When they spot something, they will dart to the floor, collect their meal, and run back up the trunk. Due to this behavior, trunk-ground anoles typically have stocky bodies with large heads and long arms for jumping. They also tend to be brown in color but change the shade of brown depending on their temperature.

Puerto Rican anoles are unique from other Caribbean anoles because they divide their habitats by climate. This is illustrated by the two trunk-ground anoles in Puerto Rico, Anolis gundlachi and Anolis cristatellus. Even though these species are both trunk-ground anoles, A. gundlachi is found at high altitudes under the rainforest canopy, where temperatures are mild and cool. In contrast, A. cristatellus is found at lower altitudes closer to the coast. Less forest and shrubbery makes their habitat warmer.

I collected body and perch temperatures from 40 individuals of each species to determine if, in fact, species differ in internal body temperature. These data of average species temperatures were significant when I compared the two trunk-ground anoles, which are similar in behavior and physical traits and only differ in the climate that makes up their habitats.

 

Anolis gundlachi.Notice the stocky body, large arms, and brown color that characterize atrunk-ground anole. The picture is dark because they live under the forestcanopy which makes it hard for the sun to penetrate to the forest floor.

 

Anolis cristatellus.These lizards are also categorized as trunk-ground anoles and have the samestocky body, large arms, and brown color as A.gundlachi. However, unlike the above species, A. cristatellus lives in a warmer climate closer to the coast withless vegetation.

 

Average species body temperatures (dark blue and dark redbars) and perch temperatures (light blue and light red bars) calculated todetermine if species differed in internal body temperatures. The trunk groundanoles in Puerto Rico differed by 4.7°C.