It's not so much their breeding habits which is the problem, it's people. Building estates in the habitat where the roo's usually live pushes them out into other areas, sometimes joining up with other mobs, or forces them to come in and feed in backyards. Farmers clear thousands of hectares for their cattle or crops, which in alot of cases is irrigated, perfect feed for roo's.

Kangaroos' will breed as much as they can while the food is available. They are able to hold the sperm from the male and then use it once there is enough feed. A pretty neat survival trick. But seeing as there is now so much food around from farmers, even in people backyards (they also love the irrigated, green golf courses). They will breed while the getting is good.

There is also the other side though. Where I live, our small town is surrounded by farm land, cotton mostly (and something else, I have no idea what it is) ..I'm lucky if I get to spot two roo's a month. We are over run with feral cats, feral dogs, foxes, hares and feral pigs. A sad state. All of which are more of a problem then our native fauna.

And another note, they are loosing their natural predator, the Dingo. Farmers again the problem (and the Government) they go out and poison/shoot/trap them to their hearts content and get the reward money for bringing back the scalp in Queensland. That in itself in a bigger issue.

^.^ I'm sorry for the about of text, but I just had to comment.
Love the artwork too FayV!