When Females Become Rivals: Ecological Collapse in Nosy Be’s Panther Chameleons
When I first visited Nosy Be in 2007, the island seemed intact, its reptilian inhabitants thriving. By 2019, however, I observed a disturbing shift: nearly half of the females of Furcifer pardalis displayed male-like traits. This year, the phenomenon has intensified—most females now exhibit these strange characteristics, with the exception of individuals in the most shaded refuges of the island.
In parallel, I conducted controlled experiments in captivity to understand the mechanisms behind this transformation. The evidence points to deforestation and warming—both global and locally induced by habitat modification—as the primary drivers. Elevated substrate temperatures translate into higher incubation temperatures.
The consequences are twofold:
Premature hatching: Incubation periods shorten, with hatchlings emerging as early as October, well before the onset of the rainy season. Survival rates plummet in the dry, overheated climate, where food is scarce and predators abound.
Disrupted sexual development: Although F. pardalis is genetically sex-determined, incubation temperature influences hormonal regulation, secondary sexual characteristics, and behavior. Females increasingly adopt male-like coloration and aggression.
This distortion of sexual signals has devastating effects. Male chameleons fail to recognize these altered females as potential mates. After brief head-bobbing exchanges, they abandon reproductive attempts, perceiving them as rivals—or even as members of another species. The females, meanwhile, engage in combat rather than courtship.
The outcome is catastrophic: a collapse in reproductive success and a local population decline exceeding 60% by my estimates.
Thus, the sadness captured in the image is not merely of one infertile female, but of a broader tragedy—a species unraveling under the combined pressures of climate change and habitat destruction. What was once paradise is now a cautionary tableau of how human-driven environmental shifts can fracture the delicate balance of life.