Rare footage of a fierce rumble between two platypuses has emerged from Tasmania, one of the Down Under strongholds for this wondrously weird little semiaquatic mammal known for its duck-like "bill."

Esme Atkinson captured and shared the video via Instagram describing the showdown as a "Platypus fight club!". According to The Guardian, she spotted the contestants along the water’s edge near a dam on the farm where she works in northern Tasmania and watched the pugilistic proceedings for some 20 minutes. "They did not let up in the time I was there, I could have stayed for longer but felt I was imposing," Atkinson’s quoted as saying.

The tussle she filmed is a vigorous one, to say the least, with much thrashing and grappling along the shoreline. Uncommon to actually spy though it might be (as the retiring, mainly nocturnal platypus is in general), the fight has a clear-cut explanation: It likely represents a territorial match between two male platypuses keen on spending some quality time with receptive females.

As the late-winter and spring breeding season approaches, male platypuses generally get more aggressive. And this mounting feistiness coincides with enhancement of their primary weapon, one that sets them apart from nearly all other mammals (and seems incongruous for such a cuddly-looking little bugger): a venomous spur on both of their hindlegs.

This time of year, the spurs enlarge, and the glands that supply them beef up venom production. (Female platypuses boast a vestigial spur structure when young, but it doesn’t deliver venom and usually falls off within their first year.)

Although it’s possible venomous spurs originally evolved as a defensive weapon – they land a very painful, though non-fatal, wound in humans – biologists believe their primary function in the male platypus these days is for duking it out over breeding territory and access to females. The spur can be "cocked" at a right angle to the hindleg when the platypus is ready to deliver a venom-barbed kick.

Male platypuses are commonly observed during the breeding season bearing spur wounds, although it appears that envenomation during these battles mainly just results in injury and perhaps temporary paralysis, not (typically) death.

Atkinson told The Guardian she saw what she believed to be one of the two platypus warriors the day after filming the showdown: "He was on the dam spending a lot of time on his back scratching. He must have been itchy from his war wounds."

Platypuses occupy their own singular family within the monotremes, the eccentric order of egg-laying mammals that also includes four species of echidna. (Male echidnas, by the by, also have hindleg spurs, but they’re not venomous.)

Restricted to the rivers of the eastern Australian mainland, mainly east of the Great Dividing Range, as well as most of Tasmania, platypuses are classed as "Near Threatened" by the International Union for the Conservation of Nature, and have declined in many parts of their limited range. Habitat destruction and alteration (including via dams and climate change) and degradation of water quality are primary threats to this river-, lake-, and wetland-dwelling critter, though platypuses also get snared in fishing nets, drown in crayfish/yabby traps, and turn into roadkill. In Tasmania specifically, some also develop ulcers and ultimately die from a pernicious fungal disease called mucormycosis. (The Tasmanian government requests that people report any potentially diseased platypuses they see).

Domestic dogs also pose a threat to platypuses, especially when allowed off-leash around riverbanks and lakeshores. That said, a male platypus may deliver a potent lesson to an attacking canine: Those venomous spurs have taken more than a few dogs out.

Top header image: David Cook, Flickr