Tag: Green Anole

Jordan Bush giving her talk on the interaction between green and brown anoles at SICB 2020

Green and brown anole interacting within Jordan’s enclosures.

As brown anoles (Anolis sagrei) become more and more abundant, many people (trained and citizen scientists alike) are intrigued with exactly how the native green anole (A. carolinensis) will respond. Newspaper articles still report on these interspecific interactions, and some recent research has shown the brown anoles can be quite mean to the native green. Thankfully, it seems that the green anole may simply be moving higher into the canopy and aren’t being merely driven to extinction by the invading brown. However, we do not yet understand the nuances of how green anoles respond when brown anoles first arrive to a new location, and that’s where Jordan Bush, a sixth year PhD student in Dan Simberloff’s lab at the University of Tennessee, Knoxville, comes in.

To understand how green anoles immediately react to the novel presence of brown anoles, Jordan built 5 x 5 x 5m enclosures in which she placed 6 female and 6 male green anoles. These animals then set up territories and became acclimated to their new living space. Jordan quantified baseline behavior and territory sizes (in 3D!!!) for each individual in an enclosure.

Example 3D territories

After 10 days, Jordan introduced brown anoles in these enclosures, either two females and two males or four females and four males to investigate the effects of density, and quantified behavioral and territorial changes in the green anole. Being the careful researcher that she is, she also introduced the same number of green anoles to other enclosures so that she could show that any changes in behavior were not simply due to more animals being present. After 10 days of interacting with the brown anole, Jordan found no change in activity level, home range volume, or perch height, suggesting that, at least within an acute time frame, the green anole can handle its own against the brown anole.

SICB 2020: Collecting Ecological Data from iNaturalist Observations: an Example with Anolis Lizards

By Laura Taylor

On January 9, 2020

In All Posts

Chris Thawley presenting his work at SICB 2020

Citizen science is a collaboration between scientists and the general public to advance scientific research. A major citizen science project is iNaturalist. In iNaturalist, anyone can submit an observation of an organism, which includes the date and location. It provides a database over a large area and a long time that would be extremely costly for scientists alone to collect. However, the data’s suitability for ecological analysis is uncertain.

To shine some light on the robustness of citizen science data, Chris Thawley, a visiting assistant professor at Davidson College, worked in collaboration with Amy Kostka, an undergraduate at the University of Rhode Island. When the project was developed, Chris was a postdoc in Jason Kolbe’s lab at the University of Rhode Island. As Amy was unable to go into the field, iNaturalist provided the perfect opportunity for her to experience the research process. They decided to compare established hypotheses of native green anoles (Anolis carolinensis) and invasive brown anoles (Anolis sagrei) against the iNaturalist data. They first coded the anoles’ sex, habitat use, behavior, and morphology, and then compared their coded data against existing hypotheses.

Overall, they found that the iNaturalist data corresponded with existing hypotheses of green and brown anoles. Male brown anoles displayed more frequently than male green anoles, in accordance with results in this paper. Males had broken tails more frequently than females regardless of species, likely due to the more risky behaviors conducted by male anoles than females anoles. Green anoles perched more frequently on natural substrates and perched more frequently in a vertical orientation than brown anoles, in accordance with findings by Stuart et al. (2014). Additionally, the brown and green anoles’ reproductive time period (as measured by when hatchlings emerged) matched with the literature.

iNaturalist is a fantastic tool for individuals who are unable to conduct fieldwork, but still want the research experience. However, Chris pointed out that iNaturalist has spatial biases towards urban areas and temporal biases towards the present day. Additionally, it is necessary to sort and clean the data and to train individuals to standardize coding. This study demonstrates that iNaturalist is still a powerful tool and can be used to estimate phenological patterns, differences between sexes, and corroborate existing hypotheses. Chris hopes that, in the future, iNaturalist could be used to generate new hypotheses.

SICB 2020: Brown and Green Anoles Have Similar Activity Levels Across Temperatures

By Chris Thawley

On January 7, 2020

In New Research

Brown anoles (Anolis sagrei) are found in many urban habitats.

Invasive species are a common ecological issue worldwide. In certain situations, they can prey on, outcompete, or otherwise disrupt the ecology of native species, potentially leading to population declines or extirpation.

The brown anole (Anolis sagrei) is native to Cuba and surrounding Caribbean islands, but has been repeatedly introduced to mainland North America via Florida over the past ≈100 years. Brown anoles have continued to spread and now occupy most of Florida, along with areas of the Gulf Coast. These anoles are particularly adept at exploiting urban habitats, such as Houston and New Orleans, where they may attain higher body size and compete with the native green anole (Anolis carolinensis). Brown anoles can outcompete green anoles in habitats such as the ground or lower levels of vegetation, where they can use their larger, more muscular bodies to chase off the native anoles or even prey on young green anoles. While green anole populations are likely not extirpated by brown anoles, they shift their locations higher into vegetation, to avoid competition with brown anoles.

The ability of these species to maximize their activity at different temperatures may play a role in determining the outcomes of interactions between brown and green anoles. While green anoles are present throughout the southeastern US and can tolerate colder temperatures, brown anoles may be ancestrally adapted to higher, more tropical temperatures. Lucy Ryan, a masters student in the Gunderson Lab at Tulane University decided to investigate this possibility by monitoring the activity levels of each species at a variety of different temperatures. The research team hypothesized that, based on their thermal preferences, brown anoles would have higher activity levels than green anoles at both higher temperatures and over a wider range of temperatures. Lucy conducted focal observations of anoles to quantify activities such as feeding, displaying, and moving. They measured the temperature of each anole’s microhabitat with a copper model containing a thermocouple.

Over an 18° C range of temperatures, Ryan found that there was no difference in the activity levels of the two species. These results, while surprising, suggest that effects of temperature on activity are not driving the competitive advantage of brown anoles over green anoles. In fact, since both species’ activity rates peak at similar intermediate temperatures, this situation may increase competition between brown and green anoles. Ryan plans to continue this work through the winter and spring to determine whether there are any species differences over an entire year of activity which may impact this system. Stay tuned and follow them on Twitter!

Green anole activity rate, including dewlap displaying, shows a peak at intermediate temperatures.

SICB 2020: Green Anoles Have Higher Heat Hardening Capacity Than Brown Anoles

By Chris Thawley

On January 6, 2020

In New Research

Ectotherms rely on interactions with surrounding thermal environments to regulate their body temperature. If their body temperatures get too low or too high, ectotherms may be unable to move effectively or escape dangerous temperatures, potentially leading to death. One plastic physiological response which may help ectotherms avoid the effects of dangerously high body temperatures is heat hardening. Heat hardening is a type of physiological flexibility that entails an organism increasing its heat tolerance after a previous exposure to high temperatures. In areas with high temperatures, differences between ectotherms in their abilities to effectively conduct heat hardening could affect competition between them.

A green anole (Anolis carolinensis) basks at an elevated perch.

Sean Deery, a masters student in the Gunderson lab at Tulane University, chose to investigate heat hardening capacity in two species of anoles, the native green anole (Anolis carolinensis) and the invasive brown anole (Anolis sagrei), both of which are present in New Orleans. As brown anoles have expanded throughout the area, they have displaced green anoles, forcing them higher into vegetation, a pattern repeated in other areas of the southeastern U.S.

Brown anoles are particularly adept at exploiting urban habitats, where temperatures may be considerably higher than surrounding natural areas due to the urban heat island effect. Sean wondered whether the competitive advantage of brown anoles over green anoles might be based in part on a superior heat hardening capacity, which could support their dominance in urban areas.

(a) A male green anole and (b) and a displaying male brown anole in Florida.

To quantify heat hardening in this system, Sean captured green and brown anoles and first measured their upper critical thermal maximum (CTMax) by steadily ramping up their body temperatures until the lizards lost coordination. CTMax represents a temperature that could prove lethal to a lizard as it would be unable to escape these hot conditions. After allowing lizards to recover, Sean measured their CTMax again after periods of 2, 4, and 24 hours. Heat hardening was calculated as the difference between the initial CTMax and the subsequent measurement after exposure to those initial high temperatures.

Sean’s results were surprising: He found that brown anoles showed no evidence of heat hardening at any time after an initial measurement of CTMax. In fact, brown anoles showed a reduction in CTMax, suggesting that the initial testing may have stressed them and reduced their ability to cope physiologically with higher temperatures. Green anoles on the other hand showed a moderate heat hardening response, with significant increases in CTMax just 2 hours after exposure to high temperatures. Sean’s results also suggest that individual lizards with lower initial CTMax values showed greater heat hardening.

For now, it appears that heat hardening is not a factor driving invasions of brown anoles in the southeastern U.S., but the differences between these two species are intriguing. Sean hopes to expand on this work by investigating molecular mechanisms that may support or inhibit heat hardening, such as expression of heat shock proteins.

Seeking Support for New Research Investigating Color Change in Green Anoles

By Victoria Pagano

On October 11, 2019

In All Posts, New Research, Research Methods

Victoria Pagano’s page from the crowd-funding platform Experiment

Green anoles (Anolis carolinensis) are talked about quite frequently here on Anole Annals, with 11 articles being published in 2018 and 2019 combined! As I am sure many of you are aware, green anoles change color from green to brown, and while it is known how, it is not yet known why. Although there have been multiple field studies into what causes green anoles to change color, the data have been inconclusive. This is why an experimental study is necessary to try to determine the cause of the color change.

In this experimental study, there will be two main hypotheses tested:

The first is the well known thermoregulation hypothesis. I will be testing this by establishing separate light and heat sources, and turning them on and off for different scenarios. If anoles change color for thermoregulation, then they would turn brown more frequently when the heat is off and the light is on.

The second hypothesis is the effect of increased stress. Stress will be induced by sliding a red disk towards the anoles multiple times at a high speed. Any color change that occurs within the red disk moving and the following 10 minutes will be documented as stress-induced.

I will not be able to test the advertisement signaling hypothesis due to feasibility. Because funding and space is limited, I do not have the capacity to house male anoles, as each one needs his own setup. Therefore, testing only females is the only feasible option, and by doing so, the advertisement signaling hypothesis will not be able to be tested, as this hypothesis pertains mainly to males.

To raise funding for this project, I am using an all or nothing crowdfunding platform called Experiment. As fellow anole lovers, I hope that you can help support my scientific endeavors by visiting my project page. All forms of support are greatly appreciated, from donations, to telling your friends about the project, or even by just reading my project page and commenting your thoughts! Whatever the contribution, I am very grateful, and am simply excited to be able to share what I am doing with all of you!

If you wish to learn more about this project, you can visit the project page, “What drives the color change in green anoles?”, where I have posted my methodology, protocols, and will be posting continuous updates on the progression of the project. If you become a contributor, you will have exclusive access to more updates, and will be able to learn more about the research.

My project page stops accepting donations on November 1st at 12:00 AM PT, so be sure to make your way over to the page by then to give your support!

Thank you for taking the time to read this article. I hope that you will explore the project page, and help support this cool and unique research!