The demise of tropical snakes, an ‘invisible’ outcome of biodiversity loss

That tropical amphibian populations have been crippled by the chytrid fungus is well-known, but a new study linking this loss to an “invisible” decline of tropical snake communities suggests that the permeating impacts of the biodiversity crisis are not as apparent. Based on these findings, the researchers say ecosystem structures could be deteriorating faster than expected from the cascading effects of disease, invasive species, habitat loss and climate change. Thus, “fast-moving policies are essential…to mitigate the impacts of the world’s biodiversity crisis,” they say. Species extinction rates over the past two centuries are up to 100 times higher than they’ve ever been in human history. Biodiversity loss is most acute in the tropics, where nearly 12% of animal species are classified as endangered, vulnerable or near threatened. These losses can cause ripple effects on the food chain, but evidence of these impacts is often lacking because of a dearth of ecological data across several species, especially those that are rare or hard to detect. Elise Zipkin and colleagues addressed this issue by developing a model that incorporates previously observed data and accounts for imperfect detection and ecological variation among species. They used it to estimate the species richness, community composition, occurrence rates and body size of more elusive tropical snakes. They applied their model to a survey of snakes across a major national forest in Panama – seven years before and six years after a chytridiomycosis epizootic wiped out more than 75% of the amphibian prey. They found that after the epizootic, the total number of observed snake species declined from 30 to 21, with an 85% chance probability that species richness was indeed lower after the amphibian decline. However, a few species fared better after the epizootic – possibly because they could more easily modify their diets than others. Overall, biodiversity loss led to a smaller, less diverse snake community, which may have upward effects on higher-order predators – an area for future investigation, the authors say.

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