Scorpions' Detachable Tail Shakes Predators

by AMNH on

Research posts

A reddish-brown colored scorpion against a light beige-colored leaf.
The three points where an Ananteris scorpion can lose its tail and quickly heal are marked with dotted lines.
Mattoni et al 2015

Life’s tough in the wild and, for some animals, walking away from a close call with a predator can mean leaving a part of their body behind. The drastic, but useful, ability to detach a body part when faced with trouble is known as autotomy, and a recent paper in the journal PLOS One co-authored with Camilo Mattoni at Cordoba University, Argentina, by Curator Lorenzo Prendini sees the practice taken to a whole new extreme. Prendini and his colleagues discovered that a genus of South American scorpions can drop their tails—and part of their gut as well—to escape from predators.

When the tail of an Ananteris scorpion is tugged, it can detach at one of three weak points in its segmented structure. Even after being pulled off, the tail continues moving, a trait Prendini says helps to convince predators like lizards or rodents that they got a mouthful, even when most of their meal is skittering back into the leaf litter it calls home.

“It’s a decoy,” says Prendini. “It makes the predator think they’re in a fight while the scorpion makes a getaway.”

The wounds from the sacrificed tail heal quickly, but the costs are steep. Its main weapon relinquished, the scorpion is reduced to catching only small prey to survive. The more pressing concern is that the tail also houses the arachnid’s anus. The loss leaves the animal unable to defecate and is an eventual death sentence for the stopped-up scorpion.

Timing is everything, though, and the time gained by shedding its butt can mean the difference between genetic life and death. Thanks to their slow metabolism, scorpions can live for several months with part of their tail removed. For a scorpion on the hunt for a mate, that time is precious. 

“A month or two in the breeding season can make a dramatic difference to the fitness of a scorpion,” Prendini says, noting that scorpions are most likely to be attacked when they’re searching for a partner. “Chances are, that’s the season you’re going to get nailed by a predator on the surface, when you’re out running around every night.”

Prendini Scorpion Detach
An Ananteris scorpion before and after losing its tail to a pair of tweezers.
Mattoni et al 2015

For a scorpion suitor whose natural lifespan is just a few years anyway, giving up some of those months for the chance at one last good breeding season makes sense. This also explains why the tail-dropping behavior seems most common in breeding-age males and is rarely seen in females or adolescent scorpions.

Prendini and his colleagues first noticed the behavior in species of Ananteris in the field. After running experiments in the lab, the authors reached out to other colleagues, looking for examples of Ananteris scorpions that were missing their tails, or portions of them. Eventually, they found that fourteen different species in the genus display this behavior, leading them to speculate that it’s possibly a trait shared by all scorpions in the genus.

While autotomy is by no means unheard of among invertebrates and reptiles, Prendini calls the brand seen in Ananteris scorpions “unprecedented” because of the lasting damage it does to the animals. Lizards are known to lose tails only to regrow them later, and many spiders will drop one or more of their eight legs to escape a fight that’s not going their way. But these are wounds from which the fighters can generally recover, regrowing their tails or limbs a few months later, unlike the fatal farewell these scorpions say to their hind parts.

“To see a part of the body that includes the anus, and parts of the gut and nerve cord, lost is remarkable because it’s so much more costly,” Prendini says.