Many of the smallest snake species are found on oceanic islands—a pattern that holds true for other animals too.
"A number of island species have evolved extremes in size, small and large, apparently because they have come to occupy vacant niches that are normally filled [by other species] on the continents," Hedges explained.
"For example, if centipedes are missing from an island, a snake species can evolve to a smaller size and eat the food normally consumed by the centipede."
But there are limits.
Hedges believes the Barbados thread snake may be at or near the smallest size possible for snakes, due to an evolutionary trade-off between size and reproductive strategy.
Any further miniaturization, he said, would prevent the snakes from producing offspring large enough to forage independently and consume insect prey.
Among the five L. carlae individuals Hedges examined was a pregnant female bearing a single, elongated egg—a rarity among snakes, which tend to produce more offspring in a brood.
But multiple eggs mean smaller eggs, and Hedges speculated that if the Barbados thread snake's eggs were any smaller, they would result in offspring too small too survive.
Small, Smaller, Smallest
Nathan Kley, a biologist at Stony Brook University in New York, said it may be too soon to declare the Barbados thread snake the world's smallest.
Several closely related species are only fractions of an inch longer, and those species are known from only a few observations or museum specimens.
"The true natural size ranges for all of these species remains extremely poorly documented," Kley said.
"Most [thread snakes] are extraordinarily small, and most exhibit secretive, burrowing lifestyles, so they often escape detection."
Even if the new species is the shortest, Kley noted, others are even thinner, resulting in a smaller body volume.
"For my money, it's these extremely slender taxa that are more highly miniaturized," he said.
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