Lizards that lose and regrow their tails can go overboard and grow back more than one tail — and sometimes they sprout as many as six. Those haywire multiple tails appear a lot more often than you might think, scientists recently discovered.
Numerous reports from around the world mention multi-tailed lizards, and some sightings date to hundreds of years ago. But these cases are typically isolated and scattered, making it difficult to tell how widespread this runaway tail growth really is.
Now, for the first time, scientists have compiled reports of "abnormal regeneration" in lizard tails, in which lizards that lost their tails grew back two, three or more appendages. To do this, researchers combed through hundreds of records of more than 175 species and spanning more than 400 years; they combined scientific studies with non-peer-reviewed descriptions to create the first global database for sightings of multi-tailed lizards.
Many lizard species can shed part or all of their tails when a predator attacks, in a process called caudal autonomy; a detached tail creates a decoy that distracts predators and can allow the lizard to escape, the scientists reported in a new study, published online June 25 in the journal Biological Reviews.
Lost tails are regrown as cartilage rods, and sometimes the mechanism gets its signals crossed and the lizard acquires more than one new tail. Lizards can end up with two tails of equal length, or "twin tails," according to the study. But other outcomes are even more bizarre-looking, with multiple small tail "branches" emerging from the original stump. In 2015, in a study published in the journal Ecologica Montenegrina, researchers described a blue-throated keeled lizard (Algyroides nigropunctatus) from Kosovo that grew three new tails after losing the original one.
Another extreme example of multiple tails, also documented in 2015, was an Argentinian black-and-white tegu (Salvator merianae) that grew six tails after its original tail was partially detached due to an injury. Researchers reported this extraordinary case in the journal Cuadernos de Herpetología.
When the authors of the new study evaluated these and other descriptions and sightings — 425 in all, from 63 countries — they found that this phenomenon isn't rare or unusual. Based on the number of instances of multiple tails they reviewed, the scientists estimated that as many as 3% of lizards worldwide are likely to have extra tails.
"This is quite a surprisingly high number, and it really begins to make us wonder what ecological impacts this could have, especially noting that to the lizard, an extra tail represents a considerable increase in body mass to drag around," said lead study author James Barr, a doctoral candidate in the School of Molecular and Life Sciences at Curtin University in Perth, Australia.
Having two or more tails could be life-changing for lizards in a number of ways — from hindering future escapes from predators to affecting social interactions with other lizards, said study co-author Bill Bateman, a behavioral ecologist and an associate professor at Curtin University.
"For example, could having two tails potentially affect their ability to find a mate, and therefore reduce opportunities for reproduction? Or on the contrary, could it potentially be of benefit?" Bateman said in a statement.
"Behaviorally testing out these hypotheses would be an interesting and important future research direction, so biologists can learn more about the lifestyles of these multiple-tailed lizards," he said.
Originally published on Live Science.