Male koala walking and scent-marking trees

Male koalas have home ranges: an area of land that they live in. Depending on their status, they may or may not tolerate other males using part of all of their home range. Dominant males in the You Yangs do not seem to tolerate other males in their home range. They are possibly territorial, which means they defend a long-term home range from other males. (1)

Read about Koala Home Ranges here.

Male koalas will mark their home range with their scent. It is a way of communicating with other koalas. It could be a calling card for females – to attract them – or for other males – to discourage them, or even to say they are willing to fight for this patch.

The following photographs show Lluvia: a 3 year old young, sub-dominant male during breeding season, walking through an area and scent-marking a tree.

The area Lluvia is walking is a home range recently vacated by a dominant male. Lluvia stayed in this area for several months. Two other adult males – a mature male named Zack, and an older male named Cruiz – were also seen in this area over the same months, and sometimes on the same day as Lluvia.

Lluvia approaches a River Red Gum tree.

He stops and sniffs at the base of the tree.

He has a look around. You can see his scent gland – the dark stain in the middle of his chest.

He approaches the tree.

Then prepares to rub his scent gland against it.

That done, he moves on to the next tree.

Koala scent marking becomes more frequent in the breeding season (2), and males are more likely to scent-mark a tree that has been occupied by another male. So Lluvia may have been marking a tree recently used by Zack or Cruiz.

Read more about Koala Scent Glands here, and about Koala Communication by Scent here.

 

REFERENCES:

1. There is some debate over whether koalas are territorial or not. Territoriality is defined as “the sociographical area that an animal of a particular species consistently defends against conspecifics.” In the You Yangs, some males have very large, long-term home ranges with almost no overlap by the neighbouring males. We consider these to be dominant males. It is possible that these dominant males do defend their home range from other males in some way.   Also in the You Yangs, many males have home ranges with a large degree of overlap with other males – we consider these sub-dominant males, and these are not territorial.

2. (1) Ellis, WAH, Melzer A, Bercovitch F “Spatiotemporal dynamics of habitat use by koalas: the checkerboard model” Behav Ecol Sociobiol (2009) 63: 1181-1188

How koalas communicate – part 1: Scent

Honker, schnoz, snout, beak – whatever you want to call it, we koalas have BIG noses!  But why?

Koalas have BIG noses!

Well, it’s all about keeping in touch with our own kind over hectares upon hectares of bushland.   Contrary to popular opinion, koalas live in a community.  We are not just solitary all the time.  We are highly alert to and aware of the movements of other members of our community.  Our social structure is complex (1), and in some ways similar to that of chimpanzees and other primates.

Our food source limits our ability to spend time with others of our own kind directly – our eucalyptus trees possess relatively few leaves, and are easily defoliated if too many koalas eat from the same tree too often – so we’ve found other ways of communicating.

so much nose to smell you with!!

Scent is one easy, non-threatening way to stay in touch.  We can deposit a scent weeks ahead of it being smelled, all without having to disturb anyone’s personal space!  Having a large, sensitive nose is very helpful here.  Even you humans, with your poorly-developed sense of smell, can smell the secretions from our scent glands when they are fresh.  We koalas can smell them for days after they’ve been deposited, probably even weeks!  We can also pick up minute differences in the perfume chemistry to identify certain individuals.

Male koalas have a large, bare-skin gland on the centre of our chests.  Mature males display the most prominent sternal scent glands.  A sticky, oily secretion exudes from this gland.  We use it to rub our scent on trees in our home range.  Check out this cool video of me scent-marking my trees recently:

The scent glands of younger males are less prominent – see mine when I was 3 years old:

So next time you’re in the Bush, try sniffing a few trees.  You might look like a nut, but you’ll surprised at how much you can smell.

 

Read more about Koala Scent Glands

 

REFERENCES:

(1) Ellis, WAH, Melzer A, Bercovitch F “Spatiotemporal dynamics of habitat use by koalas: the checkerboard model” Behav Ecol Sociobiol (2009) 63: 1181-1188