Green anoles sleep exposed on leaves and twigs all summer long — then vanish in winter. We're building a network of collaborators to track Anolis carolinensis sleeping habits across their range. We want to know when green anoles change their sleeping perch in an effort to understand thermal adaptation at range edges.
Join the network
About the project
Anoles commonly sleep exposed on leaves and twigs so they can sense approaching predators — a snake slinking down a branch triggers a drop to the ground and escape. This survival strategy is very effective in warm tropical environments, but in temperate climates, sleeping exposed can be risky. If low overnight temperatures dip below the lizard's cold tolerance limit, it risks death.
Despite these challenges, the green anole (Anolis carolinensis), an ancestrally tropical lizard, lives as far north as Virginia. In the spring and summer, anoles can be found sleeping out on leaf tips after dark — but in the winter, they disappear completely in temperate regions. Where do they go? When do they switch their sleeping behavior?
To answer these questions, we conduct weekly evening spotlight surveys along a standardized transect. By tracking lizard abundance, perch characteristics, and air temperature throughout the seasonal transition we can pinpoint when anoles shift their behavior and begin seeking nocturnal refuges. We are excited to collaborate across the green anole's range to test for local adaptation in thermal limits or seasonal behavior patterns.
"In warm months it is common to see them sleeping exposed out on leaves, but they disappear completely in the winter. Where do they go? When does the switch happen? Let's find out!"
Pilot Project
Our study site at Georgia Tech is a 7-acre natural area on campus where cultivation of native plants is prioritized and trails provide easy access throughout. Green anoles are abundant and obvious on sunny days. Your institution's transect should follow similar principles.
Fig. 4 — Georgia Tech study site and transect. Dotted line segment is not re-surveyed (surveyed outbound only).
As ectotherms, lizards maintain body temperature by behaviorally thermoregulating — basking in the sun, escaping to thermally-stable refugia. As air temperatures drop during the cooler months, green anoles increasingly abandon their arboreal sleeping positions in favor of more thermally buffered refuges. This behavioral shift is the central focus of our weekly surveys. Tracking the timing and magnitude of this transition across sites gives us insight into inter-population variability in response to temperature and to probe whether thermal behavioral thresholds differ across the species' range.
The image to the right shows the total number of lizards encountered during a survey night. Pairing these data with concurrerent air temperature logging illustrates that sleeping behavior is closely tied to minimum air temperature. Expanding these data across the Anolis carolinensis range could reveal local adaptation.
Fig. 5 — Total green anoles observed during nocturnal surveys at the Georgia Tech study site. Each point represents a single survey night, hollow circles indicate no lizards were observed. Minimum daily air temperature recorded by iButtons in blue. Dashed lines demarcate physiological thermal minimum (light blue) and freezing (dark blue).
Joining the network
We welcome collaborators from any institution with green anole populations nearby — grad students, postdocs, faculty, and herpetology clubs are all encouraged to join. To get started, submit the Sleeping Lizard Interest form, find a suitable study site, and build your team of lizard surveyors. Here's the path from start to your first survey night.
After submission, we will meet to discuss designing the perfect transect, when your group should start surveying, how to conduct surveys, and assign your group a Site ID and related materials. This conversation ensures consistent data collection across the region.
Submit Interest FormSelect a semi-natural area with reliable green anole populations and consistent evening access throughout the year. Map a 500–1000m transect around the area, including known green anole sleeping sites.
See our example siteAll surveyors must be familiar with the full protocol before the first survey. Pay particular attention to the data collection section — consistent recording of perch type, height, and width is essential for data integrity.
Read protocolWe welcome surveyors of all experience levels, but to better account for detection probability, we require that each participant submit the following form before conducting a Sleeping Lizard Survey.
Submit Participant SurveyCore gear is simple: datasheets, clipboard, tape measure, and headlamps or flashlights. Optional temperature data is highly valuable — iButton loggers and a thermocouple allow site-specific microclimate characterization beyond what weather stations provide.
View full equipment listEnter data into the shared network spreadsheet after each survey. Back up your datasheets — scan or photograph them and store in at least two locations. The lead team reviews submissions on a rolling basis and will flag any issues.
View materialsWhat to bring
Evening surveys require minimal gear. Temperature data collection is strongly encouraged but not required to participate.
Survey methodology
All surveys must follow this protocol. Any deviations — weather, visibility, personnel — should be recorded in the datasheet and flagged to the lead team.
Surveys occur in the evening, 1 hour after sunset. This timing ensures lizards are settled into their sleeping spots, won't be disturbed by surveyors, and are detectable by spotlight.
The survey ends when the team reaches the end of the transect — do not turn back early. Record the end time on the datasheet when you arrive at the end point.
Before walking, fill in the header block on the datasheet. These fields are required — an incomplete header means the survey cannot be entered into the database.
All observers should walk together and survey both sides of the transect simultaneously, scanning vegetation with headlamps and flashlights. Check leaves, twigs, branches, trunks, rocks, and roots.
Green anoles sleeping on leaves often appear pale or white-ish under a headlamp — quite different from their daytime coloration. Look for this characteristic at the tips of branches and on the upper surfaces of leaves.
For every lizard detected, record the following fields on the datasheet before approaching or attempting capture. Movement toward the lizard changes behavior and may cause it to flee.
Capture is optional and requires IACUC approval at your institution. If a lizard is captured, measure and record body temperature as quickly as safely possible.
Do NOT capture every lizard observed. Excessive handling may cause lizards to change their sleeping habits to avoid detection. We recommend capturing a maximum of 5 lizards per survey for body temperature sampling.
Continue until the end of the transect. Fill in the final data fields before leaving the site.
Lost survey data is unrecoverable! Following every survey:
Ensure data is copied and recorded in multiple locations to prevent data loss. The paper datasheet, a scan, and the shared spreadsheet are three independent backups — maintain all three.
Downloads & resources
All documents are versioned — check the date before each field season and use the most current version.
Each site will receive a unique Google Sheet for data entry. This will be created and shared when your institution joins the project. Request via the Interest form.
Submit Interest FormTwo-sided PDF datasheet for recording survey information. Print one copy per survey night. Current version: September 2025.
Download PDFThe full protocol document, including project overview, equipment list, study site guidance, iButton deployment instructions, and complete data collection procedure. Read before your first survey.
Download PDFWe deploy iButton or HOBO temperature loggers across the site in three different treatments: tree branch, leaf litter, and under cover such as a rock or log. Reach out directly for detailed guidance.
Visit HOBO WebsiteHigh-resolution version of the Georgia Tech transect map for reference.
Download imageDepending on whether your team intends to capture lizards, your institution may require IACUC approval. We provide a template based on our approved GT protocol. Your coordinator can adapt it for submission to your institution.
Download .docxThe team
We're excited for you to join the Sleeping Lizard project. Below are quick links for submitting the necessary forms or emailing us directly.
Please prioritize the above links for project communication. For urgent field questions, text is fastest.
