Sunday, November 29, 2009

How poisonous is a platypus?

Q: So, I've heard that platypuses are venomous. Can you rank them in venomousness compared to some poisonous spiders, snakes, jellyfish, and little frogs?

A: Nope!

But I'll answer this anyway. Venomousness, if that's a word, is usually ranked by comparing how little of an animal's poison it takes to kill you. Like, when some guy wants to consider what the most venomous snake is, he looks at LD50 tables (which say how much poison, as a fraction of a test subject's mass, it takes to kill half of a group of test subjects - the Lethal Dose for 50%) for different methods of injecting poison into mice, and he compares the rankings of the lethality of the poison from different animals in those tables. Try not to think about the mice too much. There are also extensive LD50 listings for scorpions and other nasty critters, if you don't mind looking at an old Tripod page to find them.

Platypus venom, though, just isn't meant to kill. A male platypus has little spurs on its back legs (like foot-thumbs made of pain) that can inject venom into other animals, and it probably uses these spurs to drive off other males competing with it to mate.

Keep this end of the platypus pointed away from you at all times.

Platypus venom could kill mice, sure, so there's no reason it couldn't get onto an LD50 table - but given that it has never killed a human being, scientists have no motivation for testing it on bunches of mice. Instead, scientists study the mysterious, excruciating pain that platypus venom causes. Listen to these horror stories:
"Pain was immediate, sustained, and devastating; traditional first aid analgesic methods were ineffective. [...] Significant functional impairment of the hand persisted for three months, the cause of which is uncertain.[...] [The venom] produces savage local pain  . . .  No antivenom is available."  - The Medical Journal of Australia
"... the pain was intense and almost paralysing. But for the administration of small doses of brandy, he would have fainted on the spot: as it was, it was half and hour before he could stand without support: by that time the arm was swollen to the shoulder, and quite useless, and the pain in the hand very severe." - W.W. Spicer (1876)
"Warning signs should therefore be erected at air and sea ports warning tourists of the dangers of these venomous Australians."  - The Department of Hand Surgery, Royal North Shore Hospital, Sydney, Australia
Way ahead of you, hand surgeons. Behold, to gauge the severity of Australian threats, the Steve Irwin Memorial Crikeyometer:

This is pretty much the worst joke I could come up with.

Anyway, there are two points to take away from this investigation:
  1. Australia is weird and terrifying.
  2. Platypuses are weird and terrifying.

The platypus has an Apparent Harmlessness / Actual Hazardousness Ratio of 1.5 deceptihippos

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