A climbing wombat?

We couldn’t resist posting this fine picture of a Koala (Phascolarctos cinereus) that was sent to us by Ian from the Yellow Creek Dairy Creek Landcare Group. The koala sauntered past Ian as he was fencing on his property near Yea.

Koalas are a relatively rare occurrence in our district. There have been only 9 recorded since 2000 on the Victorian Biodiversity Atlas data base within a 15 km radius of Ian’s property – an area that includes Flowerdale and Strath Creek. A few of the sightings have been animals translocated from French Island to Mt. Disappointment Forest in 2004.

It is interesting to ponder the ancestry of koalas. They are quite agile (though vulnerable) on the ground and are not at first sight obviously adapted for arboreal existence: dumpy, no prehensile tail (or any tail to speak of!), no gliding membranes and relatively small forward-facing eyes not particularly suited to night-time manoeuvring among branches. To compensate for these deficiencies they do of course have powerful hands and feet with long sharp claws.

So what are the roots of this unique creature? Apparently the fossil records provide very little information about the origins of koalas and their relationship to other marsupials. Comparisons with the characteristics of living marsupials offer the best clues, and it turns out that koalas share many features with wombats, such as a rudimentary tail, a backward-opening pouch with only two teats, granulated rather than ridged pads on the hands and feet, cheek pouches, a unique gastric gland – and they even have similar hook-shaped sperm quite different from those of other marsupials.

All these mutual characteristics led biologists to deduce that the koala shared a common ancestor with the wombat. Furthermore, that ancestor was almost certainly terrestrial (ground-dwelling) – more wombat than koala!