12 April 2013

My First Skull

One of the benefits of regular camera trapping trips is that you end up spending a lot of time in the field looking for good camera locations, and as a result you are bound to stumble upon some interesting things.

This skull was found amongst some other bigger bones that was damaged by a fire

When I saw this skull a new world opened up to me. Suddenly I could see myself as an Amateur Skull Collector. This is the first time I've found such an interesting and well preserved skull and as a result I'm very excited about it.

Now, I'm no skull expert and some of my terminology might be wrong, but I hope my general interpretation is correct. Please feel free to correct me in the comments section below.

One of the first thoughts to pop into my mind was: What species could it be?

The business end of the skull, notice the well developed teeth, jaw and nasal opening

The first thing I noticed was the formidable teeth. Clearly this is a coldblooded killer. With large canines to kill with and the rest of the teeth designed to cut through flesh, I knew that I was dealing with a strict carnivore.

The next clue was its size...

This photograph shows the size of the skull which is about 2x5cm

It is a small sturdy scull. The small size narrowed it down considerably. Of all the small carnivores found at Tygerberg, this surely had to be an African Striped Weasel. Fortunately for you, and me, I camera trapped another one of these little weasels just a week before finding the skull.

African Striped Weasel (Slangmuishond - Poecilogale albinucha) camera trapped at Tygerberg Nature Reserve in Cape Town, Western Cape

I took the skull home to try and clean it. I also wanted to examine it in more detail. What truck me was just how tightly the lower jaw slides into the upper jaw. The photograph doesn't do it justice.

Scissor like teeth and cracked "cheekbone" clearly visible

The presence of these little rodent killers in Cape Town is still not know by many people. Recent discoveries of African Striped Weasels in the Cederberg area has filtered through to the biological community, but most of the updated distribution maps I've seen are still reluctant to adjust the distribution all the way down to Cape Town, yet I now have three records, spanning over two years, of African Striped Weasels at Tygerberg Nature Reserve.

Sub-Saharan Africa has a relative shortage of species from the Weasel (Mustelidae) family. One theory is that the Mongoose (Herpestidae) and Genet (Viverridea) families already occupies most of the habitat niches leaving little room for the weasels to claim for their own. Specializing in hunting rodents in their burrows obviously gave this weasel it's edge.

It is also interesting to compare the three terrestrial species of Mustelidea found in South Africa: African Striped Weasel, Striped Polecat and Honey Badger. They have surprisingly many things in common, for instance they all have similar black and white warning colouration, they can secrete a foul smelling substance when threatened, they are also awkward movers that aren't particularly agile or swift, they are all hardy and tough with thick loose fitting skins and (in particular two of the species) have a great knack for digging and are keen underground hunters. In a sense the biggest difference between these species is their size.

The remaining two species of Mustelidea found in this part of the world part of the Otter subfamily, and again we find ourselves dealing with habitat specialists.

The jaw is strikingly compact and powerful, opening up for a surprisingly large gape

Another interesting thing about this weasel is that the tooth at the back of the mouth on the top jaw is turned 90 degrees and creates another cutting surface with the tooth on the lower jaw.

Closeup of the eye socket and top of the upper jaw

The eye-socket isn't encircled by bone, as is the case in most mongooses. Maybe this is as a result of their burrowing lifestyle. They hunt rodents in their burrows and I'm guessing protruding bones around the eye might be a liability. It is said that the African Striped Weasel can turn around in any burrow that is wide enough to allow its head to turn.

You can also see how the roots of some teeth actually protrude through the upper jaw.

They rely heavily on smell to find food, since it is the best way to hunt in the dark tunnels for rodents. It is said that these weasels will pass within 5 cm of a mouse without reacting if it can't smell it.

Skull showing damage that might have been related to the cause of death

So, how did this individual die? Well, the left hand side of the skull clearly shows some damage. Two cracks on the cheekbone and some damage to the cavity at the base of the skull can clearly be observed in the photographs. My guess is that it was killed by a bigger predator. Maybe the fact that I could not find the rest of the skeleton in the area is a clue? Maybe a bird of prey, possibly and owl, caught it and the bird's talons damaged the skull, or maybe it was taken out by one of the Caracal. I'm not sure.

Finding a skull is great and all, but how do you go about cleaning it? Luckily I recalled a recent post by Trailblazer (over here) that got me started. In the end I soaked the skull in roughly 4% Peroxide for about 10 minutes. I then rinsed it well with tap water and left it to dry.

The skull happily bubbling away in a jar full of Peroxide

I then secured the teeth with Superglue. The skull seemed a little brittle and I decided to go with one coating of spray-on Polyurethane to seal it. The end product looks decent enough, although some of the very fine texture is lost by the Polyurethane. I'm also not very fond of the semi-glossy look, but it isn't too bad and might fade a bit over time. I hope the Polyurethane will help to preserve the skull over time. If there are any experts out there with some advice, then please feel free to post a comment below.

The final product

I can't wait to find another skull. I'd love to build up a collection of small mammal skulls. Now if only I can get my hands on a mongoose skull to compare this one with...

2 comments:

  1. I think that skull looks great! I can't see any semi-gloss/gloss from the pics...but with the polyurethane, it's hard to not have some gloss.

    At least it will help preserve the skull.

    Nice work!!

    ReplyDelete
  2. Google skeletonhttp://www.skullsunlimited.com/search_results.php?search_term=skunk

    and look up 'meerkat skeleton - images'

    There's is mine of info available -

    ReplyDelete