Amphibians which have a toxic defense against predators — such as the iconic poison dart frogs — have a much higher risk of extinction than species which use other types of defense mechanisms, research shows. The key finding of this study is that poisonous species are 60% more likely to be threatened than species without chemical defenses.
That might seem counterintuitive.
Dr Arbuckle previously suggested three main possibilities to explain higher extinction rates in toxic amphibians, and figuring out which of these have been important are the focus of another study.
The different ideas are:
- Costly chemical hypothesis: Chemical defense is energetically costly;
- Marginal habitats hypothesis: Chemical defense allows shifts to ‘marginal’ (low carrying capacity) habitats, which are intrinsically more vulnerable, and;
- Slow life-history hypothesis: Chemical defense is associated with slow life-histories, which damages the recovery of populations after declines.
All the listed problems of shipping poison around are probably factors. These pitfalls may help account for why most life forms don’t use chemical defenses. Not as easy as it sounds.
See also: Was the Great Dying of the Permian era as bad as claimed?
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