From the pages of Binghamton University’s

In the fascinating world of semi-aquatic lizards, the anoles have emerged as the scuba-diving champions, capable of staying submerged for over 16 minutes. However, for these cold-blooded creatures, spending time in cool running streams can come with physiological trade-offs, according to new research from Binghamton University, State University of New York.

A recent study by doctoral candidate Alexandra M. Martin, Christopher K. Boccia of Queens University in Canada, and Assistant Research Professor Lindsey Swierk explored the delicate balance between behavioral needs and physiological costs. “Diving behavior in semi-aquatic Anolis lizards results in heat loss with sex-specific cooling tolerance” recently appeared in Behavioral Ecology and Sociobiology.

“This may not sound like very much, but biologically, 20 seconds could easily be the difference between life and death,” Martin pointed out, referring to the study’s finding that male anoles stayed underwater for 20 fewer seconds than females on average.

Diving underwater allows anoles to evade predators, but it comes at the cost of up to a 6°C drop in body temperature. As ectotherms, reptiles rely on their external environment to maintain body heat, and remaining in cool water can potentially affect critical functions like muscle performance, essential for escaping predation.

“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.

The researchers found that females, who invest more energy in offspring production, trade the physiological cost of cool water for extra safety by diving longer. Males, on the other hand, shorten their dives to conserve body heat and physiological capacity, minimizing the “time out” period as their muscles recover from the cool water, which may be advantageous for courtship, mating, and territorial defense.

Like little scuba divers, anoles maintain a “dry suit” of air underwater, which may help them retain some heat. The researchers plan to further explore the function and mechanisms of this trait and others in future research.

“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,” Swierk said. “We are curious and excited to explore these ideas in the future.”

This post is an update of one from 2020. Below is the old post based on a presentation by Rachana Bhave at the 2020 SICB meetings. Rachana has now done the genetic parentage studies and published the cool paper in Behavioral Ecology. Here’s the abstract of the paper:

In promiscuous species, fitness estimates obtained from genetic parentage may often reflect both pre- and post-copulatory components of sexual selection. Directly observing copulations can help isolate the role of pre-copulatory selection, but such behavioral data are difficult to obtain in the wild and may also overlook post-copulatory factors that alter the relationship between mating success and reproductive success. To overcome these limitations, we combined genetic parentage analysis with behavioral estimates of sizespecific mating in a wild population of brown anole lizards (Anolis sagrei). Males of this species are twice as large as females and multiple mating among females is common, suggesting the scope for both pre- and post-copulatory processes to shape sexual selection on male body size. Our genetic estimates of reproductive success revealed strong positive directional selection for male size, which was also strongly associated with the number of mates inferred from parentage. In contrast, a male’s size was not associated with the fecundity of his mates or his competitive fertilization success. By simultaneously tracking copulations in the wild via the transfer of colored powder to females by males from different size quartiles, we independently confirmed that large males were more likely to mate than small males. We conclude that body size is primarily under pre-copulatory sexual selection in brown anoles, and that postcopulatory processes do not substantially alter the strength of this selection. Our study also illustrates the utility of combining both behavioral and genetic methods to estimate mating success to disentangle pre- and post-copulatory processes in promiscuous species.

And here’s the post from 2020:

If you’ve ever tried to note how often lizards mate, you’ve likely found yourself staring at an individual for hours at a time, sometimes with little to no movement at all, let alone observing copulations! Further, if you’re unable to catch the animal after your behavioral observations, you may not be able to draw any conclusions about traits that influence how successful an individual is at mating with another.

Rachana Bhave, a fourth year PhD candidate in Bob Cox’s lab at University of Virginia, studies pre- and post-copulatory sexual selection in brown anoles (Anolis sagrei). One of her interests includes estimating mating rates in the wild and, in particular, testing if traits such as body size directly influence these rates. Given the power required to detect selection statistically, using simple behavioral observations can be inefficient. Further, because selection is a measure of covariance between phenotype and fitness, one needs phenotypic values for each individual within her analyses. Thankfully, Rachana was able to come up with a robust technique to estimate mating rates using an island population of brown anoles in Florida: fluorescent powders!

To understand how size affects mating rate in the brown anole, Rachana and colleagues caught 153 adult male lizards in May and 128 adult male lizards in July, weighed them, and then assigned them to one of four fluorescent powder treatments. Each mass quartile was painted with a unique color of fluorescent powder on their cloaca and released to their initial capture location. After two days, all females on the island were captured and their cloaca were examined under UV light to look for the presence and color of fluorescent powder, which would suggest that she mated with a painted male. Using this technique, Rachana found that within two days, 24% of the captured females had mated in May and 48% had mated in July. These rates were shockingly high for such a short time frame!

Further, she found that both larger males and larger females mated significantly more than smaller males and females across the two sampling periods. Interestingly, 2% of females had multiple colors on their cloacas, which suggests they mated multiple times with males from different size classes in the two-day span. Because multiple matings within the same size class would be undetectable, this is likely an underestimation of multiple matings in the wild.

Next, Rachana plans to quantify male reproductive success using genetic parentage analysis to begin to tease apart how pre- and post-copulatory selection influences selection. We are all looking forward to her results next year! Meanwhile, you can take a look at her poster to find out more on her website.

reprinted with permission

How Do You Create a Book about All the Reptiles of a Mega-diverse Country?

Reptiles of Ecuador | Story of the book

By Alejandro Arteaga. August 2023.

 

Everyone grasps the fundamental concept of a field guide: a book designed to aid in the identification of species in the wild while offering pertinent information about them. Unlike encyclopedias, field guides strive to provide information about EVERY species within a specific animal or plant group in a given geographical area. Field guides can be comprehensive when the number of species covered is limited. For instance, a field guide centered on the crocodiles of the Americas would include only ten species.

However, how do you create a comprehensive field guide about a species-rich animal group in a mega-diverse country?

To answer this question, I will tell you the story of the Reptiles of Ecuador book, a meticulously created field guide that has gained attention due to its expansive scope, novel photographic style, open-access nature, and funding strategy.

The idea for a Reptiles of Ecuador book emerged in 2010 from a casual conversation with a wildlife photographer friend. I posed a question:

Why are there field guides for birds and mammals of Ecuador, but none dedicated to reptiles?

His response was candid: “I’m not sure… you should consider writing one.”

Andrea Ferrari, editor in chief of Anima Mundi, enjoys reading the Amphibians and Reptiles of Mindo book. Photo by Lucas Bustamante.

His suggestion caught me off guard. I had never contemplated writing a book and, even though I found the concept intriguing, at 18 years old and just commencing my studies in biology, I did not feel qualified for such a task.

Throughout my childhood, I had drawn inspiration from field guides spanning diverse animal groups, ranging from insects to birds, and more recently, amphibians and reptiles. Consequently, I had a general idea of how a field guide about herpetofauna should look like.

But I had no idea how write one.

How could I possibly compile a book encompassing ALL reptile species within a country as biodiverse as Ecuador? The nation boasts a staggering 500 reptile species!

There are 500 species of reptiles in Ecuador, including the Emerald Tree-Boa (Corallus batesii), a snake that lives in the canopy of the Amazon rainforest and is seen no more than once every few years. Photo by Jose Vieira.

Read More

We’ve reported on this a number of times previously. Here are two more examples from Costa Rica.

from the pages of Floridensis:

ANOLIS CAROLINENSIS, 15

MARCH 2018

Anolis carolinensis, the Carolina green anole;
Collier county, Florida (15 March 2018).

In Collier county, Florida, many of the Carolina green anoles sport a fairly grayish dewlap, that fold of skin under the lower jaw. Typically, the dewlap for this species is pinkish. Some consider these regionally-focused “gray-dewlapped” green anoles to be a distinct subspecies (Anolis carolinensis seminolus) separated from the rest of the Carolina green anoles, but I’m not sure there’s much data to back up an actual subspecies distinction. Seem to me to simply be a phenotypic variation in that particular stretch of south Florida. I also find more-standard pink-dewlapped Carolina greens cohabitating in the same areas. Regardless of subspecies designations, I do love coming across these fantastic variants in Collier county.

 

Want to read more about gray-dewlapped A. carolinensis? Check out previous Anole Annals post (this one, which links to two others).

 

by ANDREI SOURAKOV
Aug 15, 2023

From the Florida Museum Newsletters

Last week, I was about to go to work, when I spotted a drama unfolding on my window: a green anole had captured a sphinx moth. Of course, I had to stop and investigate.

Moth predation by anoles is not something worth blogging about in its own right, but this sphinx moth was the size of the anole’s entire body and certainly thicker than its head. These moths are very strong fliers, and the fact that this anole could hold on to it seemed quite remarkable. My bets were on the sphinx moth escaping. And if not, I was sure the anole was not going to be able to eat it.

The anole had other plans.

Soon, another green anole approached with the obvious intention of sharing in its conspecific’s success, but the hunter preferred to dine alone, rejecting the invitation to commensalism. It relocated from the window to the table below and then to an even more secluded spot on the back of a patio chair.

My curiosity piqued, I followed.

The moth eventually stopped showing any signs of life. This was interesting, as sphingids are normally very hard to kill by pinching. Perhaps the beta-defensin peptides that green anoles possess, which are similar to reptile venom, played a role in subduing its prey: the lizard had clearly secreted something while chewing on the moth, as it was quite damp by this point.

To my amazement, the moth began to disappear, heading head-first into the anole’s mouth.

The anole was doing the trick snakes pull, which I’d had no idea anoles could do: swallowing something larger than its own head, until the entire moth disappeared.

While I ended up being quite late for work that day, I had a most original excuse: “I was watching an anole swallowing a moth.” If you want to watch it too, you can click on the embedded video below.

P.S. There is a detailed page about green anoles (link below):

ADW: Anolis carolinensis: INFORMATION (animaldiversity.org)

P.P.S. Florida Museum’s Blackburn lab created a CT scan model of the green anole’s anatomy, where one can assess the size of its stomach.

From UVATODAY

Yes, Lizards Have Their Own Holiday. Learn Why They Add Color to Our World

Wait, you didn’t know that Monday is World Lizard Day? What rock have you been living under?

To celebrate, two University of Virginia lizard-ologists want you to see these tiny reptiles’ true colors shining through.

There almost aren’t enough crayons in the box to capture the scale of their scaly vibrance. Add to that their amazing ability to sometimes change colors, and you can see how it’s easy to become a fan of the fan-throated lizard, or geek-out over the crested gecko.

Christopher Robinson, a doctoral candidate in the lab of biology professor Robert Cox, is one such devotee. He’s currently a Doffermyre Family Jefferson Dissertation-Year Fellow.

“Lizards are such wonderful organisms to study,” Robinson said. “They can be stunningly beautiful, exhibiting vibrant colors and fascinating patterns that are useful for investigating principles in evolutionary biology.”

Robinson and Cox decoded for UVA Today some of the many colorful mysteries behind lizards’ pigmentation.

Q. Why do lizards around the world vary so much in their colors?

Robinson: The evolution of color is driven by the selective pressures an animal encounters in their environment, and the way that they can be seen in it. For example, the coloration of a lizard in a deeply shaded forest and a species in a bright desert are usually quite different.

Similarly, lizards that are only active at night use color differently than lizards that are active during the day.

Two of the biggest drivers of color evolution are predation and social interactions, such as finding a mate or protecting a resource.

All of these selective pressures interact to produce the stunning variation we see in lizard colors around the world.

Q. Is predation the primary driver of why the colors have evolved?

Robinson: For some species, yes, but for others, probably not. While predation is a strong selective pressure, the ability to find a mate is just as important as not being eaten.

Many species of lizards have sexually dimorphic coloration, meaning males and females have different colors. Often, females are less colorful than males. The female coloration allows them to be cryptic and avoid predators, while the vibrant male colors act as signals to mates and rivals.

Q. Does more intense color indicate they’ll taste bad to a predator?

Robinson: In Virginia, we don’t have any lizards that are unpalatable to predators, although we do have amphibians, such as the red-spotted newt, which are bright red as juveniles to warn predators that they contain lethal toxins, which are potent enough to kill humans if they are consumed.

Cox: Bright warning colors that signal toxic or unpalatable prey are common in insects and amphibians, but not in lizards or other reptiles. However, bright color can be a warning that a species is venomous.

Gila monsters and beaded lizards of the southwestern United States and Mexico are the only truly venomous lizards, and they are strikingly colored orange and black as a warning.

Q. How does color help with mating?

Robinson: Male lizards often use coloration and colorful ornaments to signal to mates, and in some species, variation in coloration is associated with individual quality. This might mean that the individual is healthy and free from parasites, able to secure food easily, or strong.

In theory, a female can then use coloration to assess whether the offspring she has with a male are likely to be successful themselves.

Q. What are the most colorful lizards we can see in Virginia?

Robinson: The lizard most people contact me about is the common five-lined skink. Juvenile skinks have dark backs with bright yellow stripes and a vibrant blue tail. But as they mature, the blue color in their tail fades, and they tend to lose their yellow stripes.

Cox: Eastern fence lizards, which we study, are also very colorful, but you might not know it at first glance.

Juveniles and adult females have subtle brown and black patterns on their backs that help them blend in with tree bark and avoid predators. Even adult males are not particularly colorful from above.

But, if you look at the underside of a male, you will see vibrant blue patches that they display to rival males or potential mates – by doing push-ups.

Q. Why do some lizards’ bodies seem to be segmented into two or more distinct colors?

Robinson: There are several reasons why this can occur, but if we revisit the example of the common five-lined skink, with a striped body and a blue tail, it is primarily an anti-predator tactic.

When the lizard moves quickly, the stripes running down its back are disorienting and make it hard for a predator to focus on the body. The blue tail serves as a visual attractant, so that predators are encouraged to attack an expendable body part.

The tail, as you may know can break off, allowing the lizard to escape and live another day while the tail regenerates.

Cox: In other species, the distinct colors may be a way of generating a contrasting pattern that stands out during visual communication with other individuals. Lizards generally do not vocalize, so most of their social communication occurs through visual displays or chemical signals.

Many lizards also have ornaments that are brightly colored and stand out from their background color. For example, we study anole lizards that use an extendable throat fan called a dewlap to communicate with one another. The color and pattern of the dewlap is highly specific to the particular species of anole.

Q. What is color-changing used for?

Robinson: Color change is often used as a social signal to indicate something about an individual’s current state. If a male lizard has just won an aggressive interaction with a rival, it may signal this by changing its color to help attract a mate, or to advertise its victory.

Because lizards do not produce their own body heat like birds or mammals, many species also use color change to thermoregulate and control their body temperature.

A lizard that is cold can darken its skin to help absorb more solar radiation and quickly warm up. Once it has reached its optimal body temperature, it can lighten its skin to slow the rate of solar absorption and maintain its preferred temperature.

Contrary to popular belief, there is much less evidence that rapid color changes are used for background matching and camouflage.

Q. What are the biological mechanisms that create the color changes?

Robinson: Different cell types contain different pigments and structures that contribute to color. For example, melanin pigment absorbs light and appears brown or black. Lizards can darken their color by dispersing melanin throughout the cells that contain it, or lighten their color by concentrating the same melanin into a small area of each cell.

Color change often involves several cell types. In the green anole, cells that reflect blue light interact with other cells that contain yellow pigment to produce their green color.

Cells containing melanin sit beneath these blue and yellow cells, but they have arms that extend above the other cells to the surface of the skin. When the lizard darkens, melanin disperses to the tips of these arms, covering the other pigment cells and producing a brown color.

Q. How will you be celebrating World Lizard Day?

Robinson: I will be working on my next lizard-based paper and likely watching “Rango” in the evening.

Cox: I’ll use it as an opportunity to read a few recent papers on lizard evolution to find some new material to incorporate into my teaching.