Homing lizards

From yesterday’s animal news in the NYT Science Times, a tantalizing story, “Mystery of the Lizards That Know the Way Home”, by James Gorman, about anoles.

Wikipedia on anoles and why they are scientifically interesting:

Anolis … is a genus of iguanian (anole) lizards belonging to the family Dactyloidae. With 391 species, Anolis represents the world’s most species-rich amniote tetrapod genus. [Amniote tetrapod picks out the mammals, birds, and retiles, vs. amphibians and fishes; note that tetrapod here refers to the taxonomic superclass Tetrapoda and does not mean ‘four-footed’.]

… Anolis lizards are some of the best examples of both adaptive radiation and convergent evolution. Populations of lizards on isolated islands diverge to occupy separate ecological niches, mostly in terms of the location within the vegetation where they forage (such as in the crown of trees vs. the trunk vs. underlying shrubs). These divergences in habitat are accompanied by morphological changes primarily related to moving on the substrate diameter they most frequently encounter, with twig ecomorphs having short limbs, while trunk ecomorphs have long limbs.

In addition, these patterns repeat on numerous islands, with animals in similar habitats converging on similar body forms repeatedly. This demonstrates adaptive radiation can actually be predictable based on habitat encountered.

The green, or Carolina, anole Anolis carolinensis:


Now the main point of the NYT story:

Anoles are particularly abundant in the dense vegetation of the rain forests in Puerto Rico, where [Manuel Leal, a biologist at the University of Missouri] studies them. Each species is tied to a very specific environment. For instance, many live on tree trunks, but only a particular part of the trunk.

Trunk-ground anoles live only in the space from the ground up to six feet or so. Trunk-crown anoles live above them, up to the crown of the tree. Twig anoles live way up high.

Several years ago, Dr. Leal was studying competition between two species. If he removed all of the trunk-ground anoles, he wondered, would the trunk-crown lizards extend their territory farther down the tree? He ran into a problem, however. He would take the trunk-ground lizards far from their home territory to make room for their upstairs neighbors, and then release them. But in a reptilian version of the children’s song, “The Cat Came Back,” the lizards wouldn’t stay away. “Lizards kept showing up in the territory that had just been scoured for lizards,” he said.

Leal considered a wide range of explanations for this homing behavior in his anoles and ruled them out one by one. Now:

he is so eager to hear theories about the homing lizard that he is sharing his email address. Anyone with a suggestion about how the lizards navigate or how their ability might be tested can email him at lealmizzou@gmail.com.

He will be in the field, with anoles, until mid-July. After that, he says, he’ll answer any emails with promising ideas. Think of it as a tip line for science.

(Caution: read the account of his investigations so far in the NYT story before writing Leal.)

Names. I was fascinated by the name anole, hoping that it had something to do with the Greek-derived element ana– ‘up’ (the opposite of kata- ‘down’; compare anode and cathode). But no; NOAD2 says:

ORIGIN early 18th cent.: from Carib.

Not fully daunted, I pressed on to play with the possibility of a word cathole /kæθol/ (the N-N compound cathole /kæt.hol/, with several senses, is obviously irrelevant here). That was a dead end, but it led me to the linguist Andreas Kathol /kæθol/; from SRI’s website:

Andreas Kathol, Ph.D., is a research linguist in SRI International’s Speech Technology and Research (STAR) Laboratory. His research interests include natural language syntax and semantics, grammar modeling for speech applications, machine translation (rule-based and statistical), dialog systems, crowdsourcing for data collection and other tasks, usability of speech-enabled systems, and Arabic linguistics.

(SRI is in Menlo Park CA, just up the road from Palo Alto. And Andreas is a Stanford Ph.D.)

Andreas squinting into the sun in Menlo Park:


The twisty path has led from Puerto Rican lizards to S.F. peninsula computational linguists.

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