Bones That Look Like Other Bones: A MiniPost About Rabbits and Hares

Note: Is it morbid to look at rabbit and hare skeletons on Easter? Maybe. But more importantly, please remember that caring for rabbits as pets is a commitment – don’t buy them as an Easter Day gift for kids if you’re not committed to caring for them! More information can be found here.

So, moment of truth: how long did it take you to realise that rabbits and hares are two different animals? I’m pretty sure I was hitting double digits in age before that dawned on me…embarrassing? Maybe. But it’s an easy mistake to make: rabbits and hares look extremely alike! And that’s not just limited to their outsides either…today’s mini comparative anatomy post is about the bones of hares and rabbits!

Good rule of thumb with differentiating between hare and rabbit bones is to look at the size of the bones – hares are generally larger than rabbits. This is definitely noticeable just looking at the skulls of a hare (on the left, above) and a rabbit (on the right, above).

Hares also have larger, stronger hind legs, which can also be easily seen when you compare these bones to rabbit bones – in the above photo, are two femora, with the larger and more robust femur belonging to the hare.

Despite being from different species, however, both rabbits and hares do share similar physical traits in their skeletons, with explains why some archaeologists may have some confusion when it comes to differentiating between the two (for example, compare the two tibia bones above – besides the difference in size, they’re rather similar!).

If you’re interested in more archaeological work on hares, check on the Exploring the Easter E.g. project undertaken by the AHRC and the University of Nottingham!

References

Elena, S. (2008) Rabbits and Hares: No More Confusion! http://www.orcca.on.ca/~elena/useful/bunnies.html

Langley, L. (2014) What’s the Difference Between Rabbits and Hares? National Geographic. https://relay.nationalgeographic.com/proxy/distribution/public/amp/news/2014/12/141219-rabbits-hares-animals-science-mating-courtship

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Bones That Look Like Other Bones: A MiniPost About Rodents and Fish

Yet another minipost in my comparative anatomy series! But this one might be the strangest paring of all.

Rodents and fish – could there be any more different animals? And yet, I find that students just starting out in archaeology tend to confuse the two together. To be fair, it’s very understandable – the size of rodent bones can be comparable to the size of many fish bones. So let’s break it down and see how different they really are.

Rat and Fish Cranium

For starters, let’s look at the cranium of a rat (left) and an Atlantic cod (right). As you can see, most elements of the skeleton look completely different. The rat has the sort of skull you would expect to see with any animal, while the fish…well, fish are basically made of a head and a tail, so most fish bones you find will be part of the cranium. As I’ve mentioned before in my previous post on fish bone, they will also have a different sort of texture and look compared to mammal bone – in my opinion, its a very “fish-like” texture, a bit shiny and flaky. Always a good giveaway that you’re dealing with a fish!

Rat and Fish Vertebrae

So how is it possible to even confuse the two? Well, let’s look at something a bit trickier…here’s the vertebrae from a rat (left) and from a fish (right). Now, if you don’t know that there’s a difference in shape between rat and fish vertebrae, you might not be able to differentiate the two right away. And given how weird vertebrae can be in varying shapes between types of vertebrae in an individual body, who knows! Maybe they’re from the same animal?

Luckily, there is a visual difference between the two. Rat vertebrae look relatively similar to any other mammal vertebrae (“relatively” being the key word here, of course…but talking about the differences in mammal vertebrae is a post for a different day!). Fish, on the other hand, have very distinct-looking vertebrae and vertebral bodies. Unfortunately, distinguishing between the two can be more difficult if the vertebrae are more fragmented – I’ve seen many students get the two confused if most of the vertebral arches and “wings” are missing.

“But Alex!” I hear you say, “these bones look so different, I don’t believe that anyone could get them confused!” Okay then…let’s take two random, slightly fragmented bones from a herring and a mouse then, shall we?

Mouse scapula and herring fragment
Can you tell the difference?

As you can see, it can get tricky! Fragmentation, size, preservation of bone – these are variables that you encounter with archaeological bones that make things a bit more challenging than you’d think! The best way to get better, of course, is to practice, practice, practice. It gets easier…

…well, eventually.

 

Bones That Look Like Other Bones: Rodent Week Edition

According to Twitter, last week was #RodentWeek. So here’s another comparative anatomy minipost about some commonly found rodents: squirrels, rats, and mice!

Skulls and mandibles from left to right: squirrel, rat, and mouse.

Now, when it comes to differentiating between these three, size matters. As you can see from the above photo, there’s a huge difference between the skull of a squirrel and the skull of a mouse!

Rats and squirrels may be a toss up, depending on the age and size of the animal – but there’s differences in the shape as well! Personally, I’ve always associated squirrels with a more rounded cranium than rats, who normally have a more flattened skull, but your mileage may vary on that.

Skulls from left to right: Squirrel, rat, and mouse

What will be very difficult is if the only elements available to you are the incisors, or the front teeth. Again, size is beneficial here, as otherwise incisors will more or less look the same across the board for rodents!

Also, take another look at those skulls – lots of similarities between the mouse and rat, less so for the squirrel. And you can kinda see what I mean about the more flattened top of the rat in comparison! There’s a similar elongation that both the rat and mouse share as well.

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Mandibles from top to bottom – squirrel, rat, and mouse

For the most part, identification of rodent remains requires close examination. As you can see above, there are many slight differences between the different rodents, but it requires a bit more study than say, differentiating between a rodent and a frog.  In some cases, complete identification may not be possible without some references on hand!

That said, those incisors are often huge clues that point towards a rodent – if all else fails, at least you might be able to point to that! Those incisors also create a very specific gnaw mark on bones that will help ID the presence of rodents at the site (this will be the topic of a future blog post though!).

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Femurs from top to bottom – squirrel, rat, and mouse

I’ve spent most of this post (as I do with most of these comparative anatomy miniposts) talking about the skulls for identification – to be honest, skulls are usually the easiest part of the body to ID and compare. So here’s something a bit different – let’s quickly look at some long bones of rodents.

As I said previously, rodents require a bit more investigation in differentiating between them. As you can see by the femurs above, there are certainly some differences between a squirrel, rat, and mouse! Compare the straighter edge of the squirrel femur towards the more curved femurs of the rat and mouse, for example.

I hope these miniposts are somewhat helpful for you – obviously a more detailed comparative anatomy post would be much longer, but hey! Maybe one day I’ll write up some manuals – let me know if that sounds interesting to anyone!

Bones That Looks Like Other Bones: A MiniPost About Birds and Rabbits

I’ve been quite busy doing analysis on assemblages for my PhD project, so I don’t have much time for blogging these days. But in (belated) honour of International Rabbit Day, here’s a quick comparison of rabbits and birds!

Birds and Rabbits
Herring gull skull on the left, rabbit skull on the right

For the most part, rabbits and birds are quite distinguishable animals. I mean, one has wings and feathers and the other doesn’t – how could you mix them up?

Well…once you have just the bones, it can get tricky.

Rabbit Bird Tibias

Let’s take, for example, the tibia. Above is a photo of a bird tibia and a rabbit tibia – can you guess which is which?

They don’t look exactly alike, of course, but rabbit bones (rabbit tibia is on the bottom) have similar sharp characteristics you’d normally expect bird bones (herring gull tibia is on the top) to have.

Bird Rabbit femurs

Now this is a bit easy as the bones are marked, but you can see the similarities between the bird femur (game cock femur on the left) and the rabbit femur (on the right). Again, note the sharp edges of some of the rabbit bone that looks similar to many bird bones!

And if that isn’t confusing enough, rabbit bones tend to be just about as lightweight as bird bones!

It can be very tricky, but this is why comparative anatomy and reference collections are so important!

On Animal Teeth, or Why I’m Not a Dentist

Since my last post using comparative anatomy was rather popular, I figured I should write a similar post for this week, starting with the most important part of the skeleton for zooarchaeologists (in my opinion) – teeth!

In my experience, teeth are the best skeletal elements to recover. Why? They’re one of the more easily identifiable parts of the skeleton and one of the more variable skeletal elements across different species.

Unfortunately for me, they’re also some of the…well, grossest parts of the skeleton. Nothing will put the fear of root canals and cavities in you like looking at any worn down tooth from a cow or sheep!

Here is a small sampling of teeth from different animals and how you can easily identify them, in very informal and non-technical-sounding ways:

Pig

Pig teeth might be the weirdest looking teeth I encounter regularly (besides my own…and if you’re my dentist reading this, no I will never get braces, I can’t afford them!). The easiest way to ID them is to recognise how similar they look to human teeth…but just slightly off. Basically, I like to say that the molars look like human teeth that have popped a bit like popcorn. Yes, I’m aware of how gross that is – but that’s how I remember them!

Pig Teeth
Yuck – here are the teeth of a domestic pig.

Dog

Dog teeth have a sort of “wave”-like shape to them that makes them a bit distinct. Often, I’ve found that their molars and premolars not as pointed and sharp as a cat’s teeth (see below), but that isn’t always the case, of course. In any case, dog teeth are quite bulky in comparison to cat teeth.

Dog Mandible
A detailed look at a dog mandible (Photo Credit: Melissa Rouge, Colorado State University)

Cat

Cat teeth have a somewhat similar shape to dog teeth, but I’ve found that they are somewhat more pointy than most dog teeth (although again, this may not always be the case). In comparison to dog teeth, cat teeth are also relatively smaller and not as bulky. A larger set of teeth that may look cat-like could indicate you’ve got another member of the Felidade family (i.e; lion, lynx).

Cat teeth
The dainty, pointy teeth of a domestic cat.

Sheep

The easiest way to ID sheep teeth is to check for a “house shingle”-like appearance. I have found that in comparison to animals with similar looking teeth (cows and horses), sheep teeth are also rather thinner. Be careful, though – sheep and deer teeth are remarkably similar in size and appearance!

Sheep Teeth
The maxilla and mandible of a sheep – note that house shingle look!

Cow

As mentioned above, cow teeth are similar in appearance to sheep with a slight “house shingle”-like appearance. However, given the difference in size, cow molars and premolars will be larger and bulkier, usually.

Cow teeth
Compare these cow teeth with the sheep teeth above

Rodents

And finally, some of the smallest teeth you’ll run into: rodents! To be frank, if you find very small teeth, it is most likely from a rodent of some kind. The front incisors may be a bit more difficult to ID if found alone as they are much larger than the other teeth and may be mistaken for a bit of rib bone. These teeth are what create the pattern of gnawing attributed to rodents that looks like long striations or lines on the bone (more on that in a future post!).

Rat teeth
The skull and mandible of a rat – look at that incisor!

If you’re looking for a more in depth comparison of mammal teeth, I would recommend Mammal Bones and Teeth by Simon Hillson (1992). It’s a great guide that I use in my work with some really clear diagrams.

On Seals, the Dogs of the Sea

The other day, a group of archaeologists (myself included) stood around trays of assorted animal bones from a recent surface collection. It was just a cursory glance at the assemblage, but of course the mind immediately starts identifying bones that jump out at you.

“That’s a dog mandible…that’s a cow tooth…that’s bird, for sure…and that’s…a dog too?”

It was a fragment of a mandible that certainly looked like a dog at first glance…and yet, there was something a bit off. After looking at it for some time, it finally hit me: oh, it’s a seal. The dogs of the sea.

Seal and Canine Mandibles

When you start off in zooarchaeology, you start to find big indicators that immediately help you narrow down an identification – little “shortcuts”, if you will. Case in point – identifying seals based on comparing them to dogs.

Above, you’ll see a dog mandible and a sea mandible. Side by side, it’s a bit easier to see the difference between the two. But on its own, it’s not that difficult to mistake a seal mandible for that of a dog. I chalk it up to the teeth shape being very similar, and some slight similarities in the shape of the mandible itself (note – the mandible that was originally in question was smaller than the above mandible, so a bit easier to mistake for a dog!).

So with that in mind, it’s a bit handy to keep that in your mental toolkit. Got a mandible that looks like a dog’s, but something’s a bit…off? Might be a seal!

Seal Skull

Of course, there’s plenty of variation in dog skulls among different breeds that maybe that’s not the best conclusion to jump to, so here’s another tip: check the sort of overall bone there is. Does it look rather porous? Well, that’s an easy sign that you’re dealing with some sort of marine animal! So if you have a mandible that looks dog-like, but has a porous quality to it? Either it’s a mythical sea dog (in that case please send me photos)…or most likely, some kind of seal.

UPDATE: After further conversation with another zooarchaeologist, it turns out that dog mandible might actually be a wolf mandible! Oops…well, point still stands, I guess!

Seal pelvis