Today's main threat to the endangered koala is us: our new houses, our cars and our large dogs. And then there are diseases.
Moving between trees - koala endangered by dogs and cars
There's an ongoing debate in Australia over whether the koala needs protection as an endangered species. One of the main problems is that it's not easy to get an accurate count. We simply don't have reliable numbers. More koala facts
There's general agreement, though, on the main threats to the Australian koala today.
While it's no longer hunted for its pelt, as it was in the 19th and early 20th centuries, with the result that it was almost wiped out in many areas, humans remain the number one enemy.
We continue to destroy koala habitat for our farms and homes, it drowns in our Sydney swimming pools, our pet dogs attack it and we kill and injure it with our cars.
Habitat loss is the single biggest threat to Australian koalas today.
The highest density of koala populations are found in the areas of the most fertile soils. Trees grow more abundantly there and their leaves have more nutritional value than in poorer soils.
But the more fertile soils are also the soils that are better for farming and on which our towns and suburbs are expanding. So it's exactly these trees that we burn or cut down.
It has been estimated that, of the eucalypts growing when white settlement started, over 80% have disappeared.
In clearing land we often cut through koala habitats, isolating a small group from the larger group, isolating one animal's home range from others, or cutting the marsupial's home range in two.
We force koalas to cross roads to find food, to mate or to find their own home range when they leave their mothers'. Our back yards fence the koala in with dogs which will kill it or pools in which it drowns.
Where we clear land more aggressively we effectively maroon koalas in whatever patch remains to them.
This can result in inbreeding, has the potential for overpopulation of the area leading to defoliation of the food trees and starvation for the marsupial. It also leads to stress which makes the koala more vulnerable to Chlamydia.
Habitat loss: A fire starts
More koala habitat lost
Koalas are territorial animals. They find and adopt a home range. This will contain all the food trees they need to live on, the particular species that each particular animal prefers and adapts to.
Each animal's home range runs along with, and slightly overlaps, the home ranges of other koalas. These other animals may be used to mate with. Once established the koala stays in its home range for life.
If this range is destroyed the koala is put under great stress. It has evolved to be a very specialised feeder of a small number of eucalypt trees, especially the particular trees it learnt to feed on as a joey, while travelling on its mother's back through her home range.
The preferred tree varies from one animal to another and, when forced to change its habitat, a koala may starve for lack of its preferred tree, even while surrounded by other eucalypts which could have provided it with food.
Koalas in Australia are very vulnerable to today's bushfires.
Before European settlement the Aborigines in Australia used fire to manage the land. They would regularly burn areas of land under their control in a chequerboard pattern, alternating cleared and uncleared land year by year, or season by season.
This provided them with a regular supply of tasty new shoots coming up as the land regenerated and allowed native animals to go to adjoining uncleared areas for safety.
This koala was rescued from a fire
And it prevented a buildup of flammable material - dead trees, leaves and so on - so that the fires, when they burnt, were not too fierce and not too hot.
The fires would therefore pass quickly across the land, doing no more than scorching the healthy trees.
Koalas sitting high in the branches could simply stay there, relatively unaffected.
These land management practices are no longer the norm. Much greater fireloads are carried in parks and forests and bushfires consequently burn hotter and for longer.
The heat is often so intense that fireballs explode high up in the canopies and fires jump cleared pastures to roar on unchecked.
Marooned in a little island of trees with no tree or bush corridors out, endangered koalas stand little chance of surviving these intense fires and many become victims.
Dogs attack koalas. Sad but true. The family pet, if it's over 9 kgs or so, can kill or seriously maim a koala that wanders across its path. Along with cars, dogs are the second largest killers of koala in Australia.
If they're lucky, a koala ambulance will take them to a special koala hospital. More often they die.
The suburbs are therefore very dangerous for this marsupial. In Sydney or elsewhere. The endangered koala's food trees can be scattered, requiring it to come down from one tree and cross to the next. While on the ground it is doubly endangered. Koala attacks by dogs are on the increase.
If it gets trapped in a fenced-in back yard with a dog the koala often has no ready means of escape. People living in areas with koala populations are being encouraged to provide a wooden branch or plank that will let a trapped animal clamber up and over the back yard fence.
Cars endanger koalas
Cars are the other great threat to the endangered koala, especially in built-up areas.
The outskirts of Sydney or other Australian cities and our increasing development of north-eastern New South Wales see increasing koala road fatalities.
As always, speed kills. At high speeds it's too late to stop when you see a koala on the road, you've already hit it.
No Road Sense! Endangered Koala!
Koala signs are erected to to make motorists aware of their presence and of the need to slow down.
Sadly the research shows that the signs have very little effect on speed.
There has been some action on providing endangered koala tunnels under main roads in parts of Australia.
But it's a volunteer-driven initiative rather than a government policy and, for the most part, the koala is left to fend for itself on Australian roads.
The Sign of a Diseased Koala
Chlamydia is endemic in many Australian koala populations.
The two main symptoms are pink eyes, the sign of conjunctivitis, and 'wet bottom', the sign of urinary tract infections, the latter easily recognised by the orange-red colour bottom which results.
Blindness, pneumonia and sterility all result from the disease.
Chlamydia is thought to be present in almost all koala populations. It may form a natural means of population control in healthy populations.
It seems to become a problem in conjunction with stress. This might be caused by loss of habitat, insufficient food supplies and so on.
Let's not lose the cute koala