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Forensics with owl pellets…

October 28, 2008

Another MADD event – we must be near the end now!  We had been given a batch of barn owl pellets, from the roost at our Lorton Meadows Reserve.  Wouldn’t it be a good idea to find out what the owls have been eating?

Faye and Lorretta hard at work

Faye and Lorretta hard at work

We found plenty of bones and fur – plus a few surprises.  Read on to find out all about it..

The event had really started the night before, when Faye, Anthony and me (Steve), set some longworth traps out around the Compost heap to try and catch a few live samples for the session..   Next morning and …. success!  We had 2 wood mice for everyone to admire.

One of the wood mice - happy to be in from the cold for a while!

One of the wood mice - happy to be in from the cold for a while!

Before we knew it, the time had flown and we had literally minutes to gulp down our tea and prepare the room (in that order of course!) ready for the volunteers who were coming to give us a hand.

Faye and Anthony admire their work in preparing the room...

Faye and Anthony admire their work in preparing the room...

Then, we were off!  Zac and his Dad were first through the door, followed swiftly by lots more families.  We had anticipated quite a few children – it was half term, and anyway, what child doesn’t like the experience of unwrapping hidden treasures, even if they are just bits of bone inside an owl pellet!!  In all, 25 people were busy with their forensic investigations. 

Zac gets stuck in!

Zac gets stuck in!

Just in case anyone is wondering what an owl pellet is….

Owls tend to swallow their prey whole.  No tearing it up and taking neat chunks – the whole lot goes in, head first!   The owls digestive juices soon get to work, but they can’t break down everything.  So, about 6 – 8 hours after their meal, the owl has to get rid of all the undigested bits…  It does this by bringing up a pellet – in a neat and tidy package!  It’s all very compact and there is no mess.  Just wanted to make sure you knew that we were not investigating owl poo! 

So what do we do with the pellet?  Basically, it’s simply a matter of teasing it apart, very gently, and sorting out all the bones and the fur from the bits we were after – the skulls!  The skulls generally remain intact, and by looking closely at the dentition, it is possible to tell what species have been nabbed by the owl for it’s dinner.

Skull and lower mandibles of a shrew

Skull and lower mandibles of a shrew

Shrew teeth are amazing!  If Shrews were bigger they would be the stuff of nightmares!  Not only do they have rows of sharp pointed teeth – but the teeth are also tipped with red!  It does make them easy to identify as well and we had plenty of shrews in our tally for the session.

A vole skull - check out those crazy teeth!

A vole skull - check out those crazy teeth!

Voles and mice have huge incisors, then a gap before the molars.  Voles have zig zag teeth, and mice have more regular teeth – a bit more like ours I suppose..

The idea is to tease the pellet apart and neatly organsie it all so that you can determine how many, and what type, of prey species are present.  Faye won the prize for best tray, closely followed by Anthony, with Amanda being voted bottom of the ‘organised tray’ awards!

Wow!  How organised is that? Top marks to Faye..

Wow! How organised is that? Top marks to Faye..

I even managed to get to learn all about the ends of bones – distal means anatomically located at the far end of a reference point, and proximal means located at the near end, I think!..  It was all to do with trying to identify a rabbit bone – so if you are ever in that position, give us a call and Anthony and Faye will be happy to explain it all!

At the end of the session there was a clear winner – with field voles being the most frequent, closely followed by shrews.  We also had a couple of wood mice and bank voles – plus a surprise couple of maybugs.  The one other surprise that delighted the kids but not the adults, were the grubs that crawled out as the pellets were broken up!!

Another succesful day – I wonder what is in store for tomorrow?  Best tune in again to find out!

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