How big could a kangaroo get before it became unable to function?

November 26, 2018 9:15 AM

So I learned recently that kangaroos are one of those species with indeterminate growth; they keep growing, slowly, their entire lives. Obviously there must be some kind of body/mass/energy ratio calculation that will eventually mean they are too big to survive. How big could a kangaroo get before this happens?

I know there are complex physics reasons why animals have an upper and lower size limit, but I have no idea how that all works. I also know that of course old age and predators will take down most 'roos before they get too big. I just want to know if my dream of having a riding-size kangaroo could ever be achieved, perhaps with mad science.

Thanks!

posted by The otter lady to Science & Nature (6 answers total)

Best answer: Do you know about Australian megafauna? Procoptodon was the largest kangaroo.

I always dreamed of riding a Diprotodon.
posted by zamboni at 9:19 AM on November 26, 2018 [6 favorites]

Best answer: I should point out that Procoptodon goliah probably didn't hop. Sorry.
posted by zamboni at 9:24 AM on November 26, 2018 [1 favorite]

Best answer: > my dream of having a riding-size kangaroo

From the mobility section of the Procoptodon wiki page: "Procoptodon goliah were unable to hop as a mode of transportation, and would have been unable to accelerate sufficiently due to their mass.[...] Research suggests that the most optimal weight for a large hopping marsupial is approximately 50–60 kg. Larger animals, especially the massive P. goliah, would be substantially more at risk of tendon breakage while hopping."

It looks like you'll have to go back in time to when you were a small child and just ride a regular kangaroo.
posted by komara at 9:28 AM on November 26, 2018 [4 favorites]

Response by poster: Curses! Ah well, thank you anyway!
posted by The otter lady at 2:47 PM on November 26, 2018

Best answer: JBS Haldane’s essay On Being the Right Size talks about this exact question for a variety of animal species. You might find it interesting.
posted by BusyBusyBusy at 2:54 PM on November 26, 2018 [5 favorites]

Best answer: Male red kangaroos can grow to be huge. I'm not sure how big you are, but if you were on the smaller side, you could probably ride one. Of course, male kangaroos are vicious as f!@#$, so in the process it would punch you a few times and rip out your stomach with his hind legs. Everything in Australia wants to kill you and our roos are no exception...
posted by Jubey at 3:55 PM on November 26, 2018 [6 favorites]