The Art of War... in defence

Most people think that when an animal runs away from danger, it does two or three things, because that is what we are used to seeing. An animal can run away quickly, or on the contrary attack fiercely, or try to go unnoticed with camouflage. Some of you will even think of different examples such as turtles, which hide in their shells as if it were a big defensive shield.

Well, when it comes to defensive strategies, reptiles are some of the greatest artists. Today I come to show you some of the best examples of this, from the best actors in Hollywood to the most extravagant characters. We will focus more on peculiar mechanisms than on other defensive strategies such as poison or aposematism and mimesis.

We will start this with a very common example that almost all of you will know, and that is the decoy release that is the separation of the tail in the lizards. This is known in the biological world as autotomy. This process is a very effective measure since movement is a very important factor in vision, and hunters are easily distracted by it. However, it has a very high energy cost, since a part of the body is lost that can grow back in many cases, but not in some, and you never get a tail like the original one. Imagine losing a leg and having it grow back... that would take a lot of time and energy, if it takes our body weeks or months to heal a wound! That is why one of the most important unwritten rules in the world of herpetology is the correct handling of individuals, always with great care and avoiding lizards performing this mechanism, as we do not want to reduce the chances of survival of the animals in any case.

Elgaria multicarinata after caudal autotomy. Photo from Californiaherps.com. Regeneration abnormalities that can appear after autotomy, in this case the tail was divided in three. Image extracted from internet.

But speaking of autotomy and loss of things, there is a much more peculiar and macabre example. I present to you the exhibitionist, the gecko Geckolepis megalepis, inhabitant of the island of Madagascar. This gecko is called fish-scale gecko, since it has the largest body scales in proportion to the body of all reptiles. And why exhibitionist? Because this curious gecko performs autotomy of several of its scales when it is captured by a predator, allowing it to escape. This is unique in the reptilian world, because they have a special arrangement of the skin that allows them to do this, and they have stem cells in one of the inner layers of the skin that allow the scales to grow back again.

Integumentary autotomy in Geckolepis megalepis. Source: Scherz et al. 2017, Off the scale: a new species of fish-scale gecko (Squamata: Gekkonidae: Geckolepis) with exceptionally large scales.

Another very peculiar case is that of Leonardo Granato's of the reptilian world. This is the case of some species of horned lizard, such as Phrynosoma cornutum, P. coronatum and P. solare (at least known in 8 species). In case you do not know him, Leonardo Granato is a painter who owes his fame to the fact that he paints with his eyes. But our scaly friends don't use him to paint, they use it as a defense. They have sinuses in the eye cavity, which when they reach a critical situation can fill up with blood by contracting some muscles, making the blood flow into those sinuses producing their tearing due to pressure, and with it shooting blood at their enemies. This is known as autohemorrhage.

Autohemorrhage mechanism in horned lizard.

And it is not the only form of autohemorrhage, it is also present in other species such as the dwarf boas of the genus Trophidophis, which increase blood pressure in the same way as horned lizards, but in these it passes to the eyes and mouth, and in some cases they smear this blood over the body. In this way they try to pretend to be dead, and normally this is combined with other strategies such as balling themselves up. This autohemorrhage towards the mouth has also been observed in Natrix natrix and Natrix tessellata, the cousins of our viperine snake (Natrix maura) and Iberian grass snake (Natrix astreptophora). Other species use a similar mechanism but the bleeding occurs in the cloaca, as in Rhinocheilus lecontei.

Autohemorrhage mechanism in Tropidophis canus.

Other animals, such as some snakes, specialize in making up their deaths, like in the film "Weekend at Bernie's". It is a mechanism that is often linked to the previous one, but also to the secretion of nauseous-smelling secretions through cloacal glands, which, together with the fact that they adopt a face up position in which they open their mouth, manage to create a quite credible dramatic scene about their death. This little theatre of trying to look dead is called thanatosis, and is performed by our aforementioned Iberian snakes of the genus Natrix, as well as by several species around the world. It is a rather more common mechanism than the previous ones, but equally fascinating.

Picture of viperine snake (Natrix maura) doing thanatosis. Photo by Pedro Verdejo.

There are many mechanisms that manage to deceive predators and many humans, worthy of Hollywood performances. An example of this are Natrix snakes flattening their head like a viper, and throwing fake attacks without biting, or as we have already seen imitating the coloration of some more dangerous species.

But other reptiles are much more honest, wearing incredible armour worthy of Iron Man. This is the case of the well-known turtles and tortoises, and two families of reptiles; Cordylidae and Gerrhosauridae. There are different designs of armor, some with hard flat plates of great hardness, such as that of the Sudan plated lizard (Broadleysaurus major), and other armor much more thorny as the sungazer (Smaug giganteus) or the armadillo girdled lizard (Ouroborus cataphractus), which also rolls up biting its tail to protect itself completely. Others do what they can with less developed examples than those of Stark Industries, like the thorny devil (Moloch horridus) or the horned lizards we saw before, which, with a spiked body, are able to flatten it even more and put it in a shield position to defend themselves and while they look bigger.

Different kind of armor

a) Broadleysaurus major, picture from internet.

b) Smaug giganteus, picture from internet.

c) Ouroborus cataphractus from http://biodiversityfocused.co.za by Cliff and Suretha Dorse.

d) Moloch horridus, picture from internet.

e) Phrynosoma solare, picture from internet.

And with these, we have made a quick review of some of the most unusual defence mechanisms among reptiles, which prove to be artists in the Art of War. As a final note, I would like to repeat the importance of conserving this group of animals that are so wonderful but that produce repulsion and displeasure in many people, ending up in many cases in the death of the reptiles. And I would also like to emphasize that these defensive methods are a unique but rather desperate feature, most of them being an ultimate defensive act, and they have a great energy cost for them. Therefore, it is important not to force any animal to do this in any way, as I said earlier, as this also decreases their chances of survival, as in the case of autotomy, as the organs released as a decoy are of great importance in their daily lives.