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They are not really aggressive. Protective would be more accurate. They will not attack you if you leave them alone. Some of the bucks can be a bit cranky and a buck with does during mating time can be aggro.

So it's really just the males who are aggressive? I've seen a video online with a kangaroo ready to fight a guy, and he had to punch it in the face! I always thought they were docile animals, but they are actually pretty big and muscular

You have not seen anything until you have seen 2 bucks fighting over mating rights. They sit back on their tails, grab at each other with their forepaws, and when they get a good grip on their opponent, kick them viscously with their rear legs.

I have seen one gutted by another.

We have also lost a couple of dogs to them.

Wow.. I guess they are super serious when it comes to their women! In the video I saw the guy initially got into a fight with the kangaroo because it had his dog in a headlock! That would be so sad, I can't even imagine.

Yeah, saw that video.

I got attacked by one once for a loaf of bread I was carrying in a caravan park. Tourists are asked not to feed them, but can't resist. So this fella thought he'd try for my bread and grabbed me and started to wrestle me, I still have the claw scar on my arm. I punched it in the head and it had second thoughts. My biggest concern was it might turn on my 3 year old son who I was with at the time.

That's pretty intense.. you wrestled with a kangaroo! I probably would of just dropped the bread and ran lol you are brave!

Yes the mum was there. Its rare to see an aggressive kangaroo. As @andyfishman the problems are mostly kangaroos that have become adjusted to humans.