Our Research

Methodology

We observed the Swamper and the Highlander on Utila Island, Honduras, between January 6–14, 2026. We collected behavioral data across multiple locations representing the island’s range of habitats, including Don Quickset, the Canal, Trade Winds, Neptunes, Oyster Bay, Turtle Harbor Wildlife Refuge, and the Iguana Research and Breeding Station. These sites included mangrove forests, neotropical savanna areas, coastal environments, and semi-disturbed mangrove habitats. We typically conducted observations between 8:00 AM and 12:00 PM, with additional sampling between 1:00 PM and 5:00 PM when weather conditions allowed. We searched for iguanas on foot and focused particularly on previously identified Swamper territories documented by D. Maryon.

Once we located an individual iguana, we recorded behavioral observations using video cameras and continued recording until the individual left the area or reached a maximum observation time of one hour. For each observation, we recorded environmental and contextual variables including temperature, weather conditions, GPS coordinates, initial observed behavior, species identification, sex (when possible), approximate age class, and habitat type. This standardized approach allowed us to interpret behavioral data within relevant ecological and environmental contexts.

We used three camera systems to record behavior: a Breggo 5K video camcorder, a Nikon D5300 equipped with a 55–200 mm lens, and a Canon EOS Rebel T6 equipped with a 75–300 mm lens. We mounted cameras on tripods when possible to reduce movement and improve video stability. These multiple recording systems gave us flexibility in field conditions while maintaining consistent documentation of behavior across sites and individuals.

We analyzed video data using a two-pass coding system designed to improve behavioral classification accuracy and ensure reliable ethogram development. In the first pass, we viewed all recorded videos and documented all observable behaviors. During this exploratory phase, we noted recurring behaviors and grouped them into five preliminary categories: stationary behavior, head movement, moving behavior, head bobbing, and out-of-focus or obscured behavior. After this initial review, we consolidated behaviors into a formal ethogram with operational definitions based on observed patterns and relevant literature.

In the second pass, we applied the finalized ethogram using Behavioral Observation Research Interactive Software (BORIS), an open-source behavioral coding platform (Friard & Gamba, 2016). BORIS version 9.8.5 allowed us to code behavioral events systematically. We randomly assigned each video and distributed them evenly among multiple coders. Coders recorded start and stop times for each defined behavioral category, which allowed us to calculate proportional time allocation across behaviors for each species. We exported output data as comma-separated-value (CSV) files for subsequent statistical analysis and visualization in R (R Core Team, 2025).

To assess coding reliability, we selected a randomly chosen 10% subset of videos from each species and had all observers independently code them. We excluded these videos from redistribution during the remainder of the coding process. We calculated intercoder reliability using Krippendorff’s alpha through an R-based script. Krippendorff’s alpha measures agreement among observers beyond chance, with values ranging from 0 (no agreement beyond chance) to 1 (perfect agreement) (Krippendorff, 2004). This approach provided a standardized measure of consistency and reliability across behavioral coding.

Together, this methodology allowed us to quantify iguana behavior in a structured and repeatable way across species and habitats and supported comparative analysis of time allocation among key behavioral categories.

Results

Across both species, the dominant behavior was remaining stationary. Highlanders spent approximately 71% of their time stationary, while Swampers spent nearly 89% of their time still. Although both species strongly favored remaining motionless, they differed substantially in the behaviors they displayed when active.

Highlanders were significantly more likely to move their bodies and travel through their environment, while Swampers relied more heavily on subtle head movements rather than full-body movement. Head bobbing behaviors were rare in both species. These differences created distinct behavioral profiles between the two iguanas, with Highlanders appearing more mobile overall and Swampers displaying more limited, low-visibility movement patterns. Age also influenced behavior. Juvenile iguanas spent more time stationary, while adults were more likely to move around their environments. This pattern was observed across both species. Sex, however, had little influence on behavior overall, with males and females behaving similarly across most behavioral categories.

Together, these findings highlight clear behavioral differences between the two species despite their shared environment on Utila Island. While both species relied heavily on remaining stationary, Highlanders showed greater overall movement, whereas Swampers appeared to minimize body movement and instead rely on smaller head movements while remaining concealed within their habitat.

Discussion

This study represents one of the first direct behavioral comparisons between the Swamper and the Highlander under natural conditions on Utila Island. The behavioral differences observed between the two species likely reflect differences in habitat use and predator avoidance strategies. Highlanders, which are commonly found in more open and human-influenced environments, appeared more behaviorally active and mobile. In contrast, Swampers spent much more time stationary and relied more heavily on subtle head movements, which may help them remain concealed within dense mangrove habitats.

The strong preference for remaining stationary in both species suggests that minimizing movement may play an important role in energy conservation or predator avoidance. However, the differences in how each species allocated active behaviors point toward different ecological adaptations. Highlanders may rely more on fleeing or active exploration, while Swampers may depend more heavily on camouflage and remaining undetected. Age-related differences in movement also suggest that juveniles may reduce activity to avoid attracting predators.

Like all field studies, this project had limitations. Environmental conditions such as weather, temperature, and time of day may have influenced behavior, and visibility differences between habitats may have affected observations. Additionally, the study occurred outside peak breeding season, meaning some social or reproductive behaviors may not have been captured. Despite these limitations, the findings provide valuable insight into the behavioral ecology of both species and may help inform future conservation efforts, particularly for the critically endangered Swamper iguana and the mangrove ecosystems it depends on.

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