Voracious Arachnids: Harvestmen Caught Attacking Live Frogs

Although a handful of similar predation cases had been previously documented, unexpected scenes involving harvestmen and frogs were observed in the tropical forests of South America.

Harvestmen vs. Anurans

As a rule, invertebrates typically comprise the meals of larger members of this order or of vertebrates. Published in the journal Ecology and Evolution, the new study reveals a markedly different scenario for harvestmen, or opilions, these arachnids equipped with long and slender legs.

As biologist Luis Fernando Garcia explains, harvestmen are rather slow and fragile creatures, while frogs, in this case anurans, prove to be robust, lively, and agile. Consequently, the four predation cases recently documented did not fail to surprise researchers.

“It was quite remarkable to see them feed on relatively large amphibians, and, in some cases, to hold them immobile while they were still alive,” the researcher notes. “Such observations illustrate the complex dynamics of biology and our ignorance of interactions within tropical ecosystems.”

Powerful pedipalps

Often portrayed as harmless, these arachnids do not produce venom, which suggests they use their powerful pedipalps (spike-like appendages) to capture their prey.

“These structures are equipped with spiny projections that allow them to hold their prey firmly as they feed,” explains Garcia. “By targeting key areas, they would hinder their prey’s movements, as has previously been observed in predatory beetles of the Epomis genus.”

While he does not rule out the possibility that the targeted frogs were sleeping or weakened by disease or injury, the scientist notes that one of the photographed amphibian species is now considered threatened. “Better understanding this predator–prey dynamic could thus help guide conservation efforts,” he concludes.

A few years ago, a species of harvestman that strikingly resembled… a rabbit was filmed in Ecuador.