Anoles are the scuba-diving champions of the lizard world

Anoles have been dubbed as the “scuba-diving” champions of the lizard world, due to a unique ability to remain submerged for an impressive duration of more than 16 minutes. This fascinating behavior showcases the complex interplay between the lizards‘ adaptive behaviors and the physiological costs associated with their aquatic escapades. 

The research was conducted by Binghamton University Professor Lindsey Swierk and doctoral candidate Alexandra M. Martin, along with Christopher K. Boccia of Queens University in Canada.

Evading predators 

In earlier work, the researchers found that anoles craft an air bubble over their nostrils to breathe underwater, primarily as a means to escape predators. 

According to Marin, while anole’s first line of defense is to run away on land, they will often dive underwater to evade predators’ – or researchers’ – pursuit.

Diving lizards 

The study’s findings indicate a notable difference in dive duration between male and female anoles, with males surfacing approximately 20 fewer seconds than females. 

“This may not sound like very much, but biologically, 20 seconds could easily be the difference between life and death,” Martin said. “A hungry bird may decide that searching for an extra 20 seconds simply isn’t worth the energy it might cost and would rather search for better luck downstream.”

Drawbacks of diving

However, the act of diving is not without its drawbacks. The researchers observed that diving could lead to a substantial drop in body temperature, by up to 6°C. 

Given that anoles are ectotherms, dependent on external sources for thermoregulation, prolonged exposure to cold water can adversely affect various physiological functions, including those critical for predator evasion. 

Optimization problem 

“Semi-aquatic anoles seem to have evolved a sex-specific tradeoff between finding safety underwater and retaining body heat on land. This represents what behavioral ecologists call an ‘optimization problem,’ where animals have to balance the costs and benefits of performing particular behaviors,” Swierk explained.

Despite the absence of sex differences in oxygen consumption, the study suggests that dive time disparities are influenced by factors other than respiratory efficiency. 

Martin shed light on the reproductive strategies of Anolis aquaticus, noting the divergent priorities between males and females – while females invest more energy in producing offspring, males spend more time on courtship and mating activities – which could explain their differing behaviors when faced with the threat of predation. 

Intriguing research 

The researchers are intrigued by the anoles’ ability to maintain a “dry suit” of air underwater, possibly aiding in heat retention. Swierk expressed enthusiasm for further exploration of these diving lizards.

“The ways that animals can adapt to environmental pressures are astounding and have continued to inspire humans to push the boundaries of bio-inspired design. We are curious and excited to explore these ideas in the future,” she concluded.

This study – published in the journal Behavioral Ecology and Sociobiology – not only contributes to our understanding of anoles’ unique adaptations but also highlights the importance of considering both behavioral needs and physiological costs in the study of animal ecology.

More about anoles

Anoles are a diverse and fascinating group of lizards found mainly in the Americas, with a significant number of species present in the Caribbean islands. 

Appearance 

These reptiles are known for their vibrant colors and the ability to change their skin color, although this ability varies among species and is not as pronounced as in true chameleons. 

Anoles are particularly noted for their dewlaps, which are colorful throat fans that can be extended and used for communication purposes such as territorial displays or attracting mates.

Habitats

Anoles have adapted to a wide range of habitats, from rainforests to deserts, demonstrating a remarkable versatility. Their diet mainly consists of insects and other small prey, which they hunt using their keen vision. Some larger species might also feed on smaller lizards and other vertebrates.

Evolutionary biology 

One of the most interesting aspects of anoles is their role as a model organism in studies of evolutionary biology, especially in the context of adaptive radiation and speciation. 

Adaptive radiation refers to the process through which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches.

Caribbean anoles

Caribbean anoles have been particularly well-studied in this regard, with different species evolving distinct morphological and behavioral traits adapted to specific microenvironments within the islands, such as ground, trunk, or canopy dwelling.

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