We, humans, may not be endowed by nature with great physical abilities: powerful muscles or weaponry like fangs, claws, horns and so on.

But there is one chapter where we excel: sex.

I'm not talking about sexual activity - at it has been proved that bonobo (which is also wrongly named "dwarf chimpanzee") has more sex and much varied than the human being - but about penis size.

Man is the ape, the monkey and the primate with the biggest penis!

Gorilla males, which dwarf humans in size, have minute penises compared to ours, no thicker and longer than a pencil. Other apes do not reach even this size.

In some African countries, saying that one is 'hung like a gorilla' is considered an insult.

That's about us, but which is the largest penis in nature?

Well, despite the huge size of penises in elephants and odd hoofed mammals (like rhinos and horses), the biggest penis indeed belongs to the biggest animal: the blue whale. The largest measured penis reached 2,4 m (8 feet) (photo above:the penis of a killer whale).

Accurate measurements are difficult to be made because the whale's erect length can only be observed during mating.

Moreover, whales (and dolphins) have some control over their penises: they can move it and - to a certain degree - bend its tip to facilitate mating! In a way, we were expecting this result, but this is like a human having a 10 cm penis, because the blue whale can reach 33 m (100 feet) body length.

In relative terms, the title belongs to ... a duck!

The Argentine Blue-bill or Argentine Lake Duck (Oxyura vittata) is a small South American stiff duck. What's paradoxical in this equation is that most birds do not even have a penis, except ostriches (and related groups, like kiwi and tinamous), ducks, geese and swans.

Bird penis in flaccid state curled up inside the cloaca. Well, a specimen of Argentine blue-bill duck had a remarkable 42.5 cm (17 inches) long penis (photo center) (the average length of this species is 20 cm (8 inches))!

The flaccid penis is coiled but fully erect is twice the size of the bird: it is like us having a 3.5 m (12 feet) penis...

Biologists believe that the remarkable size of this penis may have evolved in response to competitive pressure in these highly promiscuous species, removing sperm from previous matings in the manner of a bottlebrush.

This is the longest relative penis in vertebrates, animals related with us.

But there is a type of crustacean (crab related animals) - called barnacles - that provides us another surprise. Barnacles look more like small shells and are indeed sedentary animals, living fixed on rocks or man made structures (or sometimes even on whales!) with a muscular stalk or not. Gooseneck barnacle is one of the most expensive seafoods! Like many sedentary animals, barnacles are hermaphroditic and alternate male and female roles over time.

Neighboring barnacles interfecundate between them, and to be able to do this, they employ the longest penis in the animal kingdom, in proportion to their body length: it is 40 times bigger than the animal's body (photo bellow).

As the barnacles measure just a few cm, their penises won't be so obvious for humans...

There is another mystery unsolved: male cephalopods (squids, cattlefish, octopuses) have one of their arms, named hectocotylus, turned into a penis. As some wrecked giant squids had arms longer than 8 m (25 feet), how big would their hectocotylus be?

Photo credit: K. Mc Cracken