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Strange bones: the broken roe deer tibia


This week's been very busy: today was my last day of the school year (in Scotland the summer break starts and ends about three weeks earlier than in England), I've been working on a lot of things behind the scenes, and tomorrow morning I'm off on Scout camp for five days. So today I'm going to do a follow-up post about some interesting bones.

Last week I wrote about exploring a wood I was last in a few years ago, and finding the partial remains of a roe deer while I was sheltering under a tree from the rain. The skeleton wasn't terribly interesting, except for the left tibia which was broken. In the end, I brought back both tibias, but when I started asking questions on Twitter from experts I realised there was probably enough to write an entire post about the injury.

Here's a recap of what I found from the rest of the bones. I could tell straight away from the tibia that it was from a deer, because of the size and shape, and that it was from a young deer because the top and bottom of the bone hadn't yet fused properly. There are both red and roe deer in this wood, but the size meant it could only be from a roe deer. In roe deer, the ends of the bones fuse at around 12-18 months, so it must have been younger than that. This is the top of the unbroken tibia with the end balanced on top of the main bone, but the two are completely loose:

I found half the pelvis, which told me it was from a female, because of the angle at the back end of it was wider. I was hoping to find the left side of the pelvis, which would have told me whether the deer had been long crippled on that side by whether the hip socket had began to fill with bone, but unfortunately I couldn't find it.

Then I found the skull, which confirmed it was a female roe deer, with the back molar tooth (M3) not yet descended, which meant it was about 9 months old, and meant it would have died in mid February/March (because roe deer are all born in mid May-June-ish). The bones were too clean for it to have died this year, so it must have been last year at the earliest.

This is the right tibia (at the bottom) compared to the same one from Julie, one of my my adult doe skeletons. As you can see, Julie's one is bigger, but the newly found bone is almost the same length because the bottom of the bone is loose and wasn't found. However the main difference is that Julie, the adult's tibia is much thicker and wider.

I broke my tibia last year. It was incredibly painful, even with hospital treatment, painkillers, and a plastercast. The odd thing I noticed was that that the break was near the knee end, which is thicker. That made me think it was a break from impact or the leg striking something solid, rather than a spiral fracture which is what I had when my foot wanted to twist one way but my knee wanted to go the other.

This shows exactly where on the roe deer the injury was. Deer have quite long thin legs, but the injury was quite high up on the leg. I'm not sure how the deer would have got this injury, but they spend their time running over uneven ground with long grass and heather concealing holes or rocks.

The broken leg would have been impossible to walk on, meaning it's possible this deer couldn't move far at all to feed or to run away from foxes or other predators.

I know that broken bones are survivable for deer because of rehealed bones I have found like this tibia, this femur, this deer which was born without a back foot,  and this red deer front leg, but I don't think this one survived the injury for very long.

When I looked very closely at the non-broken tibia, I saw a small hairline crack. The only time I have seen similar cracks is when I once put a wet bone too close to the fire, and the heat cracked it. It might have happened in the sun, but it might also have happened at the time of the original injury, although there is no sign of bone regrowth. I think it's probably more likely it happened after death.

The deer lived for some time after the injury. The lower part of the tibia would have still been still in the leg, and the bone has tried to regrow to join the two pieces together. When the roe deer died, the bottom part of the tibia was moved or lost. My best guess is that the roe deer lived for about one or two weeks after the injury. 

UPDATE: Ben Garrod, the BBC presenter thinks it was a bit longer:

He knows more about these things than I do, so he'd probably right, but either way, it must have been in immense pain, and there may have been other tissue injuries, infection or bleeding which led to its death.

The side view shows the broken end of the shaft and the extra bone growth. I'm not sure what the staining is around the lower part of the shaft.

The deer would have been in pain, cold, hungry, in shock, unable to move, and no other deer could help it. I feel really sorry for this deer because its last few days would have been terrible. Nature is cruel.

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Adrienne SW_NM_ARCH on Twitter said...

Bone is amazing. There are two organs in the human body that regenerate: Bones and the Liver. The bone growth around the tibial shaft could also be sequestering an infection. I noticed cloaca in photo #8. Bone will sequester an infection, but amazingly will also attempt to rid itself of it. Unfortunately, the cloaca opens into the systemic system thereby causing a septic infection which possibly killed the deer. Cancer in bone also develops a sequestration and cloaca.

Jake said...

By cloaca, do you mean a hole from which infected pus can come out of ?

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