How St. Martin’s Lizards Compete for Survival

TL;DR Summary

The lizards you see darting around on Sint Martin aren’t just surviving—they’re locked in a battle for resources. This study dives into how two different species of Anolis lizards interact, revealing why one island struggles with competition while the other thrives on balance.

Pacala, S. W., & Roughgarden, J. (1985). Population experiments with the Anolis lizards of St. Maarten and St. Eustatius. Ecology, 66(1), 129-141.

The Battle on St. Martin

In St. Martin, Anolis gingivinus shares its habitat with Anolis wattsi pogus, a smaller but aggressive lizard. The problem? Both species need the same resources—like food and space—to survive. With limited options, A. gingivinus is forced to adapt in ways that hurt its survival.

Reproduction Declines

“In the presence of A. wattsi pogus, A. gingivinus exhibited reduced egg production”.

Food Shortage:

“A. gingivinus showed a dramatic decrease in the average size of prey consumed”.

Forced to Higher Grounds

“Perch heights increased significantly, showing behavioral shifts caused by competition”.

This intense competition is because resources aren’t being shared effectively—both species are after the same food and space.

The Harmony on St. Eustatius

Meanwhile, over in St. Eustatius, Anolis bimaculatus and Anolis wattsi schwartzi coexist peacefully. How?

Resource partitioning

Resource partitioning is when species share their resources by dividing them up to avoid conflict. On St. Eustatius, this balance is achieved in two key ways:

Shared Food Supply

“Unlike St. Martin, where resource overlap is high, lizards on St. Eustatius partition prey sizes, reducing direct competition”.

Separate Habitats

“Spatial niches are distinct between the species, allowing coexistence without displacement”.

By dividing up food and space, these lizards avoid direct competition and thrive together.

Is This the Natural State?

The study observes these dynamics in the natural habitats of both islands, not in artificial enclosures. The lizards’ behaviors, competition, and coexistence patterns reflect real-world interactions shaped by environmental pressures and available resources.

Natural Habitat Observations

“All fieldwork was conducted in situ to ensure natural behaviors were recorded”.

On St. Martin, intense competition likely reflects environmental limitations such as lower habitat diversity, while St. Eustatius benefits from better natural resource distribution.

What’s the Difference Between the Two Islands?

St. Martin

• Less variety in habitat and food resources.

• High competition because both species need the same resources.

“The intense competition experienced by A. gingivinus leads to reduced growth rates and reproductive output” .

St. Eustatius

• More diverse habitats and prey options.

• Effective resource sharing (resource partitioning).

“By specializing in different prey sizes and habitats, both species coexist without negatively impacting one another”.

What Can St. Maarten Learn from these lizards?

This study shows that for species—or even people—to thrive together, resources need to be shared in a way that reduces conflict. On St. Eustatius, balance is achieved through specialization and cooperation, leaving enough resources for everyone.