Species Spotlight: Common Box Turtle

Hi everyone!

Apologies for the lack of Species Spotlight last week. Xplore hosted our first self-run Darganfod Science Festival last weekend, so last week was very hectic! To make up for it, we'll do two Species Spotlights this week, beginning with the common box turtle (Terrapene carolina), spotted by participant looghna_dainty_mac_bay in Hendersonville, Tennessee.

First off - what an awesome observation! I'm sure those of us in Wales/elsewhere in the UK are mind-blown by the thought of spotting a wild turtle* just knocking about on our doorsteps. However, I'm sure this is, if not a common, a relatively unsurprising occurrence in Hendersonville, given than the common box turtle is the state reptile of Tennessee (If we had a national reptile in Wales, we'd have about three to choose from).

  • or tortoise - read on to find out the difference between a turtle and a tortoise. Until then, I will use the term "turtle" to mean both turtles and tortoises (this is for a good reason, as you shall see).

The common box turtle gets its name from the fact that, as well as being able to retract its head into its shell like the rest of the turtle order, it can actually completely enclose itself in its shell, forming a box! It is able to do this as it possesses a hinged lower shell.

Contrary to cartoon depictions (they have a lot to answer for), a turtle's shell is not some sort of mobile home, analogous to that of a hermit crab's. No, a turtle's shell IS the turtle! The shell is formed from the turtle's own bones, including its ribs, parts of its pelvis, and parts of its spine (this is the case for all turtles, not just the common box). The cool/mildly horrifying thing is that a turtle hiding in its shell is basically the equivalent of us hiding in our own ribcages. For an idea of what this might look like (because I'm sure that's where your mind just went) check out this webpage - https://www.demilked.com/animal-anatomy-compared-to-human-satoshi-kawasaki/ - this shows the human equivalents of several animal anatomies, including the fact that a horse's "foot" is basically the same as us walking around on our fingers.

On the subject of turtle shells - please do NOT ever paint on a turtle's shell. As we have just seen, their shell is a living part of their body. They absorb vitamins through their shell via UV radiation from the Sun, so waiting their shell can make them very poorly, or may even be fatal.

The common box turtle has several subspecies (I know we've been talking about species and their confusions and I now I've just thrown another word into the mix - I can only apologise on behalf of biologists everywhere). A SUBSPECIES is a rank below species. I said a few weeks ago that biologists still aren't settled on what a specie is, but one of the most common traits that a group of animals must possess in order to be classified as a species is the ability to interbreed with one another to produce FERTILE offspring. That word "fertile" is important - lions and tigers, for example, can mate to produce ligers or tigons (yes, really), but these are all sterile.

Subspecies can interbreed to produce fertile offspring, so they are part of the same species. Subspecies are distinguished purely on morphology (i.e. what they look like). This is one of the rare times when morphology is the only thing needed to make a distinction. The common box turtle has six subspecies, generally distinguished by their shell patterns.

(A side note on subspecies - the most well-known subspecies is.... the dog! As in domesticated/pet dogs! They are all part of the wolf species (Canis lupus), so, yes, you are literally sharing your house with a wolf. Canis lupus is actually the species with the most subspecies: 38 in all! They're all wolves, but are distinguished by their looks. Other wolf subspecies include the arctic wolf and the dingo).

Anyway, let's move on to the big question - what's the difference between a turtle and a tortoise? Are turtles tortoises? Are tortoises turtles? WHAT'S A TERRAPIN? Do they even exist (I'll answer that straight away: yes, they're not fish.... there's no such thing as a fish... if someone finds a fish, I'll do a blog post about that).

Turtle is the name of an Order of reptiles. Reptiles are a Class, which is a higher rank than Order, and includes lizards, snakes, and crocodilians, as well as turtles/tortoises. Example equivalents: insect is the class, beetle is the order; mammal is the class, primate is the order). There are over 350 species in this order - that's a lot of turtles!

The turtle order (which sounds like a great Teenage Mutant Ninja Turtles spin-off) has the scientific name Testudines, but it is most often referred to simply as turtles. This order contains ALL the animals that we refer to as turtles, tortoises, or terrapins: "turtle" is basically the catch-all term for anything that looks turtle-y.

Tortoises and terrapins refer to just a few specific animals in this order. That means that all tortoises and terrapins are turtles, but not all turtles are tortoises (or terrapins). Specifically, "tortoise" is a family in the turtle order, with the scientific name Testudinidae (I know, I know, it sounds so similar to Testudines). Tortoises differ from the rest of the order in several ways, including being entirely land-dwelling, whereas other turtles spend at least part of their life cycle in water; and having "elephantine" limbs, rather than flipper-like limbs.

Terrapins aren't really a proper scientific "thing" (basically they're not all a distinct group, like tortoises). Instead, terrapin is just a name given to several species of small turtle. Terrapins can be found all across the turtle order, whereas tortoises are ALL in one group (family).

Wow! I know that's a lot of info, so let's sum up - turtles are a group of reptiles; tortoises are a group of turtles; terrapins are a general name for some small turtles.

We'll finish with some tortoise news! We tend to think of tortoises as docile, plodding, unthreatening beings (because, for the most part, they are). However, recent footage from the Seychelles has shown a tortoise stalking and eating a live bird! This is completely unprecedented behaviour, and tortoises are hardly built to be hunters! This goes to show how much about the natural world we still have to learn - so keep sending your observations in! Read all about it and even see the footage here - https://www.smithsonianmag.com/smart-news/giant-tortoise-stuns-scientists-eating-bird-180978511/

I'll be back later in the week with a new Species Spotlight.
Diolch
Kieran

Julkaistu elokuu 25, 2021 10:30 AP. käyttäjältä kieran-182 kieran-182

Kommentit

Ei vielä kommentteja.

Lisää kommentti

Kirjaudu sisään tai Rekisteröidy lisätäksesi kommentteja