Blue-tongued skinks are named after them.

Via Bill Hughes’s Flickr photostream.

Some rattlesnakes have them.

Via The Horned Jack Lizard’s Flickr photostream.

The members of giraffidae, the okapi and the giraffe, have them.

Via djhinrich Flickr photostream.

Via zeandroid’s Flickr photostream.

And it’s one of the most notable features of the chow chow.

Via budak’s Flickr photostream.

I doubt there is a common explanation for all instance of blue tongues. The Wikipedia article on Northern Blue-Tongued Skinks says that they “have a bright blue tongue that is often used to warn off or startle predators.” While it’s clear they’re not closely related at all, it seems like a plausible explanation for the rattlesnake as well, as their “rattles” are also used to warn off predators.

It’s hard to imagine that’s true for the members of giraffidae and the chow chow though, giraffes being so tall it’s difficult to imagine any predators even seeing the tongue, and dogs usually being predators not prey. The page on giraffes on the San Diego Zoo’s website says “some people think the color is to keep the tongue from getting sunburned,” which I guess might be possible, but it doesn’t seem to explain its relative the okapi, which I imagine wouldn’t have too much risk of getting sunburns, as its short enough to get shade from tree cover, and lives in the rainforest, where there often isn’t too much sunlight that reaches the ground anyway. I wasn’t able to find an explanation for the okapi’s tongue color, most sources were more interested in the fact that they were able to lick their own ears.

I wasn’t able to find an explanation for the chow chow either, but I imagine that it’s due to human controlled breeding.

My favorite explanation for all of these tongues though is that they just eat blueberries.

From Wikipedia:

The Eastern skink (Scincus mitranus) is a lizard from the skink family (Scincidae). These skinks grow to a length of 20 cm, and have an orange-brown or sand-coloured back, and a white underside. On the side they have a line or spots in a light colour, and the back and legs have vague dark bands. The snout is shaped like a bill, and the legs and tail are short. The eastern skink can run quickly, or slide over the sand and dig itself in quickly when it is in danger. Its food consists of several kinds of arthropods, especially centipedes and beetles.

This species lives in Saudi-Arabia and the UAE, in dry and warm open areas, particularly in sand deserts. Its habitat consists of dune-like areas, and hilly landscapes with occasional dense bushes and rocky patches to hide in. The eastern skink is viviparous, which gives it an advantage compared to other species in the area, as its eggs cannot desiccate.

(An animal described as being viviparous is an animal that gives live birth, and is nourished by the mother until birth, as opposed to laying eggs and having the yolk of the egg nourish them.)

Photos via Sophie and Matt Gunner’s Flickr photostream.