Bones That Look Like Other Bones: Rodent Bones VS Bird Bones

Note: As you can see, I’m no longer on hiatus! But there will be some changes to my blogging moving forward…as much as I love writing, I need to put my PhD studies first. This means that blog posts will not be weekly, but will come out a bit more inconsistently – basically whenever I have a bit of free time to blog! 

Hopefully you’ll still tune in for some weird, archaeological ramblings, even if they’re only every once in a while. Thanks to everyone who has stuck around this long!

Today’s comparative mini-post comes from a question I received from Trisha J. (thanks Trisha!),  who asked for a bit of a comparison between rodent and bird bones. Now, while I have written about both rodents and birds before, I’ve never actually compared the two in one of these posts – which is a bit of a surprise, as I totally get the confusion between them! They can look pretty similar,

IMG_E5452
Herring gull skull (left) and brown rat skull (right)

Before we start, let me first preface this by saying we’ll be looking specifically at small bird bones – obviously, as you can see in the photo below, birds come in a wide variety of shapes and sizes! So we will be working under the impression that it’s easier to confusion small bird bones with rodent bones…unless you’re working with Rodents of Unusual Size, I guess?

IMG_E5445
Herring gull humerus (left) and corvid humerus (right)

Unfortunately there isn’t an easy tip for differentiating between bird and rodent bones quickly – although bird bones are known for being particularly light in weight to allow for flight, rodent bones have a similar weight due to size. Thankfully, bone shapes are pretty distinct between the two. See some of the example photos below to see how each differ!

IMG_E5446
Corvid humerus (left) and brown rat humerus (right)
IMG_E5450
Corvid femur (left) and brown rat femur (right)
IMG_E5451
Corvid ulna (left) and brown rat ulna (right)

If you’re dealing with bone fragments that are similar in size to either a small bird or rodent, I would highly suggest using some form of reference (photo or physical) to base your identification off of. They can certainly be quite tricky! You can also use small variations, such as the presence of “nubs” on bird ulnae, to help differentiation. Also remember that birds have bones that are not present in rodents (tibio-tarsus, furncula, etc.), so memorising their general shape will be helpful.

With skulls, if you have complete specimens, it’ll be pretty easy – the bird will usually have a beak attached!

IMG_E5447
Corvid skull (left) and brown rat skull (right)

Of course, life isn’t fair and you will often have a skull fragment on your hands. In that case, remember that bird skulls, in particular the cranial vaults, have very rounded and bulbous skulls (see below).

IMG_E5448
Jackdaw (bird) skull fragment

And if you’re unlucky enough to have vertebrae and ribs on your hands…well, good luck! Well, maybe at least with the ribs…vertebrae can be very tricky, especially when they’re very small. However, bird vertebrae tend to have a “body” (the thickest part of the vertebra) that curves inward and are a bit more narrow in shape.

IMG_E5449
Corvid vertebra (left) and brown rat vertebra (right)

Have a question about zooarchaeology? Or an idea for a future blog post? Remember you can contact me through the blog by heading to my Contact page.

References

Cohen, A. and Serjeantson, D. (1996) A Manual for the Identification of  Bird Bones from Archaeological Sites. Archetype Publications Ltd.

Prehn, N. et al. (2018) Beginner’s Guide to Identifying British Mammal Bones. Natural History Museum. http://www.nhm.ac.uk/content/dam/nhmwww/take-part/identify-nature/british-mammal-bones-ID-guide.pdf

 

Advertisements

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.

Processed with VSCO with a6 preset
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!).

Processed with VSCO with a6 preset
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!