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Saturday, 14 April 2012

Collecting bones

Easy choice: You can always go and collect bones in the bush, but they will usually be scattered by scavengers.

My children (they are grown-up now and still talk to me) helped me round up these wombat bones from a 50-metre radius of the actual death spot, which we identified by finding a fair number of bones and teeth in one place, along with some hair and fur.

We carried the other bones back to there. Look carefully for the tooth near the bottom of the picture: no scavenger bothers to carry teeth away.

In some parts of eastern Africa, geological deposits of the past few million years can be reliably dated by searching for pig teeth, because an expert can identify a pig tooth down to an actual species, with a known date range.  To the biologist, teeth can be very interesting.

This kangaroo was probably a roadkill, found just off the road in the Margaret River area of Western Australia.
This shot appears (reversed) on page 6.

At the time, I was looking for lizards and wild-flowers, and keeping a wary eye out for snakes.

Be careful where you collect bones, because even collecting dead bones can be risky!

This dugong mandible was on Thursday Island, in a place set aside for butchery, ad the remains attract sharks when the tide is in, and crocodiles all the time.

At the time, the tide was out, so we were half-safe, but that's not really enough, so it;s better to do your own bone-cleaning at home or near home, where the risks are less.

What you need: A dead vertebrate (birds and mammals are the easiest, reptiles can be harder to work with, and snakes have very fiddly ribs). There are lots of ways to clean away the meat, so read the details below, and make up your own list of needs.

Let;s stay now, for a while, with this exercise that didn't make it into the book, because I took short-cuts: I was about to go to Western Australia (where I got the kangaroo above), when I found the bandicoot seen here, on September 1.

This shot was used in the book, in the flies chapter, page 89.
I moved it off the track where I found it, and weighed it down with a couple of stones. If you click on the picture to see a larger version, you will see that the ants were already moving in.

It was four days before I could get back, and by then, the flies were there in force.

You have to be a little bit tough in this sort of job.  I used tolls, sticks, and where necessary, bare hands to get the body into a wire bag. I strongly recommend taking gloves!

You cab see the main tools here: a bag made from a folded-over piece of chickenwire, fine-nosed pliers and medium-gauge galvanised wire.

Just stitch the dead animal in like this, but being wise in rerospect, it would be a good idea to contain it first in a fly-wire bag, or if you can't do that, leave a flat board and rocks over it, to fend off large birds!

 You see, the problem was that while I had my bag tethered to a tree, something, probably crows (Australian ravens) came and pecked through the wire, smashing the bones and ripping most of the bits out.

When I came back from Western Australia and hurried out to the site, all I had left was one forelimb, a shoulder-blade and part of the cranium (skull), plus a bit of fur, and a failure that couldn't go in the book.

Still, it's good enough to go here, if only to show you what not to do!   If you ignore my warnings, you will end up with a poor showing like mine.  Trust me, there are better ways to do it!

In museums, bones are usually cleaned by the larvae of dermestid beetles, often referred to as "museum beetles". The grubs eat all the flesh from the bone without harming any bone parts. They are really useful if you want to preserve the fine bone structures in the nose area of a mammal skull.

There is one drawback: museum beetles can get loose and attack stuffed animals, insect collections and other precious items. Around the home, they may eat your shoes, bags and belts!

Some people enjoy cleaning and mounting a skeleton for display. This often means using sharp knives and dangerous solutions—and handling smelly things. If you are young and want to try this, get advice at each stage, because you may be at risk, pets and younger children may be at risk, and the smells can definitely upset adults.

The first task, if you want to prepare a carcase yourself, is to get rid of the excess skin and meat. Cut away as much of the flesh as possible, making sure that you don't scratch the bones. Take care also that the ligaments, the strings that attach bones together, are not cut, so you know what goes where.

Young readers: if you are using a knife, seek adult advice on safety first: simple things like always cutting away from yourself, and using a cutting board—and don't use the best board in the kitchen to slice up a smelly dead animal! If you have a digital camera, take lots of shots from different angles so you can see later how the bones connect.

You can clear the rest of the meat from larger animal bodies by burying them (if possible, 'sewn' with copper wire into a piece of plastic fly-screen to stop large animals eating the whole body). Mark the spot with a stick so you can return for the bones at a later date. Small dead mammals such as mice will be clean bones and skin scraps after two or three weeks if they are stapled into a small fly-screen bag, and left under a small amount of leaf litter in a damp place, or even under a board and rocks.

While that has worked for me in the past, I recommend putting that in a chickenwire wrapping or bag. To stop scavengers carrying the bag away, wedge one edge of it securely under a rock or pin it down with a spike. Better still, surround the bag with bricks and put other bricks over the top leaving tiny gaps that keep larger animals out but still let the small animals in. You can also tether the bag to a tree: I recommend doing this.

Older tadpoles can also do a good job of cleaning up a skeleton, but you need to change the water every day. Small fish are more effective.

Warning: boiling, which you will see recommended, is slow, it scatters the bones, and often shrinks the bones slightly. Older books often suggest using "sulfurated potash" (potassium sulfide). This is a fire hazard which causes toxic fumes, so if you have a book that suggests this method, try another book, fast! Older books may also suggest using carbon tetrachloride or benzene to get rid of the grease. In one word, don't, because these chemicals are dangerous!

If you want to display the skeleton later in a life-like pose, you can leave the ligaments in place, thread a wire down the spine, and use wire to support the skull at the end of the spine, but you need to decide early, and plan ahead. Take photos and put tags on some of the larger bones. Write notes on sheets of paper to put under the bones when you take photos.

You can leave the skeleton in water for several days, then brush the remaining meat away with an old toothbrush, leaving the ligaments in place. To remove the ligaments, soak the skeleton in dilute sodium hydroxide solution in a plastic bucket, but take the bones out as soon as the ligaments come away. You will need gloves and goggles and somewhere safe to leave the bucket. Get advice!

Bones can be bleached in hydrogen peroxide or in any household bleach, but they need to be de-greased first, and that means using nasty chemicals. It's better to leave the bones unbleached. Most museum skeletons still have their natural colours. You can reduce the smell by putting clear varnish on the bones, but this spoils the look a bit.

Larger skeletons should be fully separated and rejoined with wires. Just drill small holes near the ends of the bones and thread fine wire through. You can learn a lot by going to a museum and looking to see how professionals do it. Smaller mammals such as bats can be mounted on a piece of varnished board, using an epoxy glue such as 'Araldite'.

You can also try collecting the bones from a cooked chicken and reassembling them, but you will usually end up with a headless chook that has no feet.  (If you aren't Australian, look chook up, or think about it for a moment.)

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