How koala eyesight impacts on them today

Koalas are trying to adapt to the modern world but their eyesight is made for the tree tops. Maxine and Enigma are pictured here showing koala eyes.
Koalas are trying to adapt to the modern world but their eyesight is made for the tree tops.

We have discussed the way koala eyes work, or rather how they don’t work as well as the eyes of either predators or prey animals.  See koala eyesight post for more background information.

It’s more than their physical eyes however, it’s how their brains are hard-wired as well.

The koala is in an unusual position, being neither prey or predator on any real level. They are just going about their daily business of trying to get enough calories from all those eucalyptus leaves.  In the process of doing this, they really are not taking much notice of anything else (except other koalas).

Let us now remember we no longer have large areas of old growth forest providing acre after acre of trees that can be accessed through the branches in the canopy, or at least by coming partway down and jumping across.  The koala only had to see around itself, and use their highly developed sense of smell to know which trees were good and move through them.

The koala now finds itself too often, in a single tree, in the middle of an open paddock.  He eats his fill, has a sleep then has to climb down to the ground and set off in search of the next tree which may be tens or even hundreds of metres away.

Mist showing typical female koala head and eye shape
When a koala is awake they are usually hungry and needing calories.

But let us think about the fact that the eyes of the koala are not made to make sense of this – they do not see well at long distances. Their brains are not wired up to think – this trip could be dangerous and tell their eyes to be really sharp either.

Yes a koala that lives well into adulthood is going to learn to traverse particular areas and deal with particular dangers, but the problem is that less and less koalas are living through their early encounters with the dangers on the ground.  On top of this, the koalas are using up a lot more calories in order to take in each meal they find because they have to travel down the trunk, across the ground and then up the next trunk again.  This is significant as eucalyptus leaves are low in calories and they have to eat a large quantity of them already.

When they are travelling they are usually hungry, and so their primary focus is going to be on getting to a good tree for their next meal.  A koala with a full belly nearly always goes to sleep to aid digestion quite quickly.

So a koala walking through a paddock is needing calories and is unlikely to even see a dog coming for it unless the dog makes some good noise.  A car approaching from a distance does not register with the koalas eyes at all.  We will talk further about how koalas seems to respond to mechanical noises in another post.

Even what they can see is usually distanced from them as they should be up in a tree.  Jordan is pictured here sitting in a tree looking at me without a care as I am on the ground and he is in a tree.
Even what they can see is usually distanced from them as they should be up in a tree.

Finally, when a koala does see something approach them, it is normally on the ground and they are up in a tree.  Their tactic if concerned is to go higher up the tree.  If they are on the ground, by the time they realise there is something of concern it is usually too late.

This highlights the importance of planting clumps of trees and rows of trees connecting good feed clumps together so that koalas can be on the ground for less time and eating more quickly.

 

Do koalas have good eyesight?

There is a reason koala eyesight is not so good over distances. Even when a koala looks directly at you, it will have heard you first, then had to find you by eye.
There is a reason koala eyesight is not so good over distances.

If you pose this question through Google the answer is pretty quickly returned as “no they do not”.

Now why might that be?

To understand why we need to consider the environment they had before humans came ripping through their homeland and changing everything.

Koalas are arboreal marsupials which means they live in trees, and are mammals that give birth to tiny under-developed young that crawl into a pouch to complete development for around 6 months.

Wild male koala looking down from a pink bloodwood tree - he can see me but koalas do not have good eyesight
Wild male koala looking down from a pink bloodwood tree

However, we need to think of incredible old growth forests thick with tall trees when we think of the arboreal koala.  When you live high in the canopy of a forest, there is not a lot you can see long range.  The ground is distant and hidden by the lower branches and smaller young trees.  Anything beyond the tree you are in, is likely obscured by branches and leaves from your tree or the next.

Stella is just over 12 months old and though she has bright eyes, she relies more on her hearing than her sight.
Stella is just over 12 months old and though she has bright eyes, she relies more on her hearing than her sight.

Koalas are far from blind, but their long range sight is pretty poor because it was not needed.  Koalas are skilled at jumping from trunks and branches to move about, and they look carefully to judge the distance before taking a leap.

Koalas have an acute sense of smell, and they do have keen hearing.  Sometimes it seems their hearing is not so keen because they sleep so deeply.

If you can imagine huge forests with hundreds of koalas moving through the treetops, you can maybe imagine that they didn’t bother looking to the ground or out into the sky too often.  Their focus was within the short range area of the tree they were currently occupying.

Koalas are said to have no natural predators, but this isn’t completely true.  However the only predators that were of any real concern to koalas in the past were usually only a concern for joey’s and small juveniles, and only if they were not in the treetops.  The main predators that may take a small number of young koalas are goannas, dingoes, pythons and some powerful owls and eagles.  The incidence of these predators seems to have always been fairly low.  Coastal pythons are the only one of these predators that may attempt to take a lone young koala in the canopy.

Stevie is looking at me, but it was sound that caught her attention fast, while it took her time to find me with her eyes.
Stevie is looking at me, but it was sound that caught her attention fast, while it took her time to find me with her eyes.

This all means that koalas do not have a historical need to be on a constant lookout for predator threats, and they do not hunt as predators themselves, and so their eyesight, for long distances is somewhat poor.

Another important feature of koala sight is that their eyes are ‘forward facing’ like our eyes. This puts the koala outside the general rule which says – ‘eyes to the side, run and hide; eyes to the front, love to hunt’.  Koalas don’t hunt, and yet they did not have any real need to run and hide either, and so they have eyes that face the front which give better depth perception. It’s also one of the features that makes them look so endearing to humans.

Enigma shows us a perfect example of the forward facing eyes of a koala. Koala eyesight however is not very good over long distances.
Enigma shows us a perfect example of the forward facing eyes of a koala.

The impact for koalas in adapting to the environment we have created by invading their home is huge when you understand their eyesight limitations.