Yes, you’re counting right, this lizard has two tails!

The white arrow in the image on the left points to the new regrown tail and the other heavily deformed tail is the original one. One way you can tell is by looking at the colours of both tails. Regrown tails usually don’t have the same colouration as the rest of the tail. To explain what happened here, let’s take a few steps back.

Most people are probably aware of and have likely witnessed a lizard’s incredible ability to drop a part of itself and regrow it later. However, not all lizards are capable of doing this and it’s not any part of the lizard but only its tail. This extraordinary skill is referred to as caudal autotomy. Caudal is Latin for “having a tail” and autotomy is Greek for “self-severing”.

So what’s up with that?

The reason why many lizards are dropping their tails is to be able to see another day. Usually, lizards drop their tails when pursued by a predator. When these lizards feel like they are in immediate danger, which they cannot elude by running away, they will drop a part of their tail. The detached tail will often continue to wriggle vigorously to distract a predator and give the lizard a chance to dash for safety.

Lizards are able to do this because of special sections along the tail called breakage planes, which enable the fracture and severing of the tail. After the successful autotomy and escape from a predator, the lizard usually regrows its tail within a few weeks.

However, dropping the tail comes with quite the cost, which is why you shouldn’t encourage a lizard in doing so and instead admire it from a distance. Obviously, for the lizard it’s better to drop the tail and survive but the consequences of caudal autotomy can be quite severe in these lizards. While some lizards might experience reduced social status and mating success, for all of them it takes a toll on their health. Tail loss weakens the immune system which could allow parasites and pathogens to have a greater negative impact and it’s also energetically extremely costly. Not only does it take a lot of energy to regrow the tail itself but many lizards also store fat reserves in their tails which are lost when the tail is dropped. Additionally, the regrown tail also looks different and differs internally. Instead of regrowing vertebrae, the new tail is made up of cartilage and also does not have the same colouration as the rest of the tail and lizard.

Sometimes, tail does not detach entirely and so when the replacement tail starts to grow, the lizard will end up with two tails for one. Doesn’t seem like a bad deal you say? Well, we’re not sure on the potential negative effects of multiple tails in lizards but it could be that more tails mean more energy spent. It’s interesting to know that this brown anole was particularly easy to catch and did not attempt to escape. We would need to test some lizards with multiple tails in predator avoidance experiments or endurance exercises to really know how having more than one tail could impact a lizard.

Borrowed from Barr et al. 2019, Scientific Reports 9:18717.
Figure 1. Autotomised tail and 3D model reconstruction from micro CT of Egernia kingii showing thefractured vertebrae (1.), two intact vertebrae (2.), vertebrae and primary regeneration fusion point (3.), primarycartilage regeneration (4.), fusion point of primary and secondary cartilage regenerations (5.), and secondarycartilage regeneration (6.) Transverse C.S below correspond to lines on diagram. 1 cm tail tip taken for geneticsis missing from the 3D model.

You can find out more about this two-tailed lizard and learn more about multiple tails in our latest publication below.

After the photo for research purposes, the lizard seemed unfazed and was released back into its bush.