Dive Behavior in Lizards Linked to Heat Loss and Predator Evasion

Lizards are known for their ability to adapt to different environments, but some of them have a surprising skill that sets them apart from other reptiles: they can 'scuba-dive'.

A new study by researchers from Binghamton University explores how these lizards use underwater submergence as a cooling strategy and what trade-offs they face in doing so.

The Scuba-Diving Champions of the Lizard World

Anoles are a diverse group of lizards that inhabit tropical and subtropical regions of the Americas. They have evolved a variety of adaptations to cope with different habitats and challenges, such as changing their skin color, expanding their throat fan, and clinging to vertical surfaces with their toe pads.

But one of the most remarkable adaptations of anoles is their ability to stay underwater for long periods of time. Some species can remain submerged for over 16 minutes, a feat that is not just about holding their breath but also linked to their body's cooling mechanisms.

The researchers, led by Alexandra M. Martin and Christopher K. Boccia, wanted to understand how anoles regulate their body temperature while underwater and what physiological costs they incur.

They conducted experiments with two species of anoles, one that lives in aquatic habitats and one that lives in terrestrial habitats, and measured their body temperature, oxygen consumption, and metabolic rate before, during, and after submergence.

The Trade-Offs of Cooling Down Underwater

The results showed that both species of anoles experienced a significant drop in body temperature while submerged, which helped them cope with extreme heat.

However, this cooling effect came at a price: the anoles also experienced a reduction in oxygen levels and an increase in metabolic rate, which could impair their performance and survival.

The researchers found that the aquatic species had a higher tolerance for hypoxia (low oxygen) and a lower metabolic rate than the terrestrial species, suggesting that they have evolved some adaptations to cope with the trade-offs of submergence.

However, both species still faced a delicate balance between cooling down and oxygen deprivation, which could limit their underwater duration and frequency.

The study, published in the journal Functional Ecology, sheds light on the complex interactions between behavior, physiology, and ecology in anoles.

It also opens up new avenues for further research on how animals adapt to changing climatic conditions and how they balance the costs and benefits of their strategies.

The Evolutionary History of Anoles

Anoles are not only fascinating for their scuba-diving abilities, but also for their evolutionary history. These lizards have undergone a remarkable diversification across the Caribbean islands, resulting in over 150 species that differ in size, shape, color, and habitat preference]p.

This diversity is the result of adaptive radiation, a process in which a single lineage splits into multiple species that adapt to different ecological niches. Anoles have evolved in response to factors such as predation, competition, food availability, and environmental conditions.

One of the most striking examples of anole adaptation is the variation in their limb length and toe pad size, which correlate with the type of perch they use.

For instance, anoles that live on narrow twigs have longer limbs and larger toe pads than those that live on broad trunks.

Anoles are also known for their dewlaps, the colorful flaps of skin under their throats that they use for communication and display.

Different species of anoles have different dewlap colors and patterns, which help them recognize and attract mates of their own kind.

They are considered a model system for studying evolution, ecology, and behavior, as they offer a rich source of data and natural experiments.

By comparing the traits and genomes of different anole species, scientists can learn how natural selection, gene flow, and speciation shape biodiversity.

The researchers hope that their findings will inspire more appreciation and conservation of these amazing lizards, which are often overlooked in the grandeur of biodiversity. They also hope that their study will spark curiosity and interest in the natural world and its wonders.