Tail Loss In Aggressive Interactions: An Example From Sitana ponticeriana

A previous discussion on this blog has raised the following question: in which situations is a lizard most likely to lose its tail? Common wisdom has it that tails are most frequently lost in the avoidance of predators, and observational evidence backs this up, at least in the case of anoles–no AA reader has observed tail loss in a male-male aggressive interaction. But what about other lizards?

In Sitana ponticeriana, an agamid lizard that I often post about on this blog, a couple of observations point to the likelihood of male-male competition as a driver of tail loss. Tail loss is not uncommon–in the locality I have sampled best, 13.5% of lizards have lost their tails. Males are about 1.7 times as likely to lose their tails as females (16.5% of males vs. 9.6% of females). Further, lizard predators aren’t too common in this locality–fewer than 30 individuals of potential lizard predator species were spotted or heard in over two months of sampling, and no predation attempts were observed.

But more excitingly, I had the chance to observe firsthand the loss of a tail during a male-male fight this summer! The resident lizard had lost much of his tail prior to the fight, a measly 5.4 cm remaining. The intruder, however, had an almost complete tail. Here is a rather blurred photo of the two males facing each other:

The tagged resident male is on the left, and the intruder on the right. Sitana start out with really long tails, and you can see the intruder’s tail extending beyond the rock on the right.

As is usual, the fight took place at lightning speed and was over in a few seconds. Here is a photo of the tail left behind by the fleeing intruder:

And finally, here is a photo of the winner, about 20 minutes after the battle. Not having much of a tail did not seem to impede his victory:

Later in the summer, I witnessed another fight, this time an incredibly prolonged encounter. Tragically, and in keeping with the corollary to the Principle of Unsympathetic Magic postulated by Janson Jones, I left my cameras behind that day. At the fight’s peak, the two males were biting each other on the tail, close to the base, for over seven minutes, and it is easy to imagine how such battles can result in the loss of tails. Anoles, in contrast, tend to bite each others’ heads while fighting, and this difference in battle stances between Anolis and Sitana would result in tail loss as a consequence of male-male aggression in the latter but not the former.