A double headed penis and a highly venomous spur. What you should probably know about the platypus

I wrote about the echidna in an earlier post and thought it only fair to write one for that other equally odd Australian monotreme – the platypus.  A quick recap: monotremes are the egg laying mammals and there are only three species – two types of echidna and a single species of platypus found only in Australia.

The incredible and illusive platypus. In these odd organisms, the males actually have a double headed penis and a highly venomous spur. Photo: Flickr/Cazz

So despite the platypus’s duck-like bill and beaver-like tail, its closest relative isn’t either of these. It’s the echidna! While not physically very similar looking, functionally they are. Both lay eggs, both have a single opening for all their waste stuff and sex stuff, both walk like reptiles (as explained in my echidna post), and both have multi-headed penises…

platypus penis
Photo source: Temple-Smith, P., (1973) Seasonal breeding in the platypus, with special reference to the male. Australian National University, Canberra.

As you can see above, the platypus penis is quite specialised! While its shape and structures are still not fully understood, scientists have noticed it nicely reflects what’s going on inside the female platypus.

The females have two ovaries but only the left is functional and produces eggs. In the platypus male the left head of the penis is the one that is larger and more exaggerated, supposedly helping to better target the egg producing ovary.

A second secret weapon

Platypus males have another secret weapon too, a highly potent venomous spur found on each of their hind legs. Venomous mammals are rare enough – beside the platypus there are perhaps only seven other species, but the platypus is also the only known animal to exhibit temporally differential venom production. This just means they produce venom differently at different times of the year.

In the spring breeding season the male’s venom glands swell and produce more venom, and you definitely don’t want to receive a dose of it. In humans it causes instant and excruciating pain that can’t be relieved by morphine and other first aid methods. One man who was jabbed on the finger had pain in the area up to four months later!

So despite its adorable, odd-ball appearance, the platypus really packs a punch. Who would have thought the combination of a duck bill and beaver tail could prove so successful? The platypus really is one unusual animal.

An utter odd ball: a platypus spotted in a Tasmanian creek. Photo: Flickr/Klaus

Screen Shot 2016-07-17 at 6.26.54 pmReferences 

Callaway, E. (2010). Poisonous platypuses confirm convergent evolution. Retrieved October 6, 2013, from: http://www.nature.com/news/2010/101012/full/news.2010.534.html?s=news_rss

Nekaris, K. A. I., Moore, R. S., Rode, E. J., & Fry, B. G. (2013). Mad, bad and dangerous to know: the biochemistry, ecology and evolution of slow loris venom. Journal of Venomous Animals and Toxins including Tropical Diseases, 19(1), 21.


  1. Interesting blog! Especially to a biologist like myself. I never saw a platypus in the wild, but I once had an echidna nearly walk on my shoes while I was hiking in Lamington National Forest, near the Gold Coast.


    • Thanks! I’m studying zoology so it’s all the things i’m interested in too 🙂
      I’ve only see echidnas as well, but not one as close as you in the wild! I have however patted the stomach of a domestic one, super adorable.
      What’re you researching at the moment – if you don’t mind me asking?


  2. This photo/diagram is incorrectly sourced. It is a diagram from a PhD thesis: Temple-Smith, P., (1973) Seasonal breeding in the platypus, with special reference to the male. Australian National University, Canberra.


    • Thanks for that! I do really need to go back and check my photo references on old posts – unfortunately when I first started I didn’t know how to correctly do so 😛


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