The difference between deer and sheep skulls

Two of the most common skulls  that I find are deer and sheep. There's huge variation in different types of deer and breeds of sheep - but there are some rules which can tell you which are which.

They can look very similar, because they are both herbivores with eyes on the side of their heads. So, I'm going to take you how to tell the difference between the two skulls, even if you only have a small fragment of the skull. In all of this I'm using a red deer skull, as the bigger UK deer (red, sika, fallow) are closer in size to sheep than the smaller deer (such as Chinese Water Deer, muntjac and roe) and fragments can be mistaken for sheep...read on to find out more !

The shape 

Deer skulls vary hugely in size from Chinese water deer (about 12cm long) to red deer (can be up to 38cm long) but all are roughly the same shape and proportions. They are more flat and are longer than sheep skulls, with a longer nose. All  have six teeth, like sheep (three pre molars and three molars). The ear bones are smooth and round.

The job becomes easier if you have a sheep skull with horns (horns have hard bits of bones in) or a deer skull with antlers (antlers fall off each year, but the pedicles are part of the skull)

Eye sockets

Both have eyes on the side of their heads, to look for predators, but sheep skulls 'bulge' out more and are bigger in proportion to the size of the skull. Deer also have a smoother edge of the eye socket than sheep do.

Ear bones

The ear bone openings on deer are much closer to the back of the skull, and the nuchal crest (horizontal ridge at the back of the skull) is more pronounced in deer.

Teeth

Some deer have pronounced canines - Chinese Water Deer and muntjac - but most don't. Red deer tend to have have two tiny upper canine teeth jholes at the tip of the nose, whereas sheep don't.

Sheep and deer both have six teeth on each side and on each jaw (24 molars and premolars in total).  M1, M2 and M3 in both sheep and deer all have three vertical ridges on the three back molars, but the deer have two smaller ridges inbetween as well.

While we are looking at that photo, note the small hole, which is close to PM1 tooth on the top pic, but higher up and further back on the sheep, and the extra bone nubble on the sheep above the M1 tooth (the deer has it as well, bit it isn't as big)

In front of the eyes

The deer has two big features in front of the eyes, but it varies between species. There is an indentation in front of the eye socket, and an opening (fenestre) above it. Sheep don't have either of these.

Sutures

Red deer (top)  suture lines are very jagged, and are used to 'cushion' the skull during fights. The sheep is much smoother:

Zygomatic arch

Yeah, I spelt zygomatic arch wrong in the photo...sue me.

This is the underside of the skull. The zygomatic arch on the side of the skull, is much thinner in red deer.

Also on the underside...

This is a big difference, but one that most people wouldn't notice. This is the underside of both skulls. Forward of the spine hole, the bone is smooth as it goes towards the nose on the deer. But on the sheep, there are two extra bone growths on each side.

When I was younger, I had a prize "deer skull" fragment which eventually turned out to be a sheep. I hope this stops you making the same mistake !

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