Poisonous frogs face greater risk of extinction

Amphibians that use toxins to protect themselves against predators are at a higher risk of extinction than those who use other types of defence, new research has found.

"There are a number of plausible reasons why the use of chemical defence might lead to higher extinction rates," said study lead author Kevin Arbuckle University of Liverpool in England.

"For example, it could be that there is trade off which leaves prey vulnerable to other kinds of enemies, such as infectious diseases, but we do not yet understand what drives the relationship," Arbuckle noted.

As part of nature's evolutionary arms race, animals have evolved a whole host of different defence mechanisms, including chemical defences, such as poisons or irritants, camouflage, warning colouration and mimicry.

The team examined how rates of extinction and speciation - the formation of new species - varied across different defensive traits in amphibians.

They found that animals that use chemical defence show higher rates of speciation, but also higher rates of extinction, compared to those without, leading to a net reduction in species diversification (the interplay of speciation and extinction).

In contrast, the use of warning colouration and mimicry was associated with higher rates of speciation, but unchanged rates of extinction.

"In addition, our findings could help support the conservation of endangered species by allowing some predictability of extinction risk from knowledge of antipredator defences. Amphibians are a key example of this as they have suffered population declines worldwide, including many of the iconic poison-dart frogs," Arbuckle noted.

The study was published in the journal Proceedings of the National Academy of Sciences.