And the longest penis of any animal goes to…

But first, to put things into perspective. If a human male were to have a penis this large, it would be the size of an adult humpback whale! So just who exactly is the proud owner of this enormous equipment?

Well, you don’t have to think too big because this ‘wurst’ winner isn’t tall or large or big or fat… it’s a barnacle. Yep, although small, barnacles don’t lack in might and their penises are the largest, in comparison to their body size, known to the animal kingdom.

While an appendage this large wouldn’t be practical for us (how could you wear pants?), for the barnacle, having a penis that can reach eight times its body length is a BIG bonus and i’ll explain why…

Photo by Mo Riza
For barnacles, a large penis is a BIG bonus. Photo: Flickr/Mo Riza

Barnacles live a couch potato lifestyle. Their strategy is simple: why waste energy searching for food, when you can cling to a rock and wait for the food to come to you? Yet despite this laid back lifestyle they always muster the energy to mate.

But how does something that doesn’t move, reach a partner?

Obviously, it moves its long extendable penis instead.

In a hit and miss style, the penis is extended and swung around in the current hoping to make contact with another barnacle, allowing mating to occur without the barnacle moving from it’s spot (see video below)!

This awesome appendage is able to adapt to different environments too. Studies have found that the barnacles with the longest penises live further from their neighbours and that those living in more turbulent environments, i.e. more waves and stronger currents, develop thicker penises too.

This increased thickness strengthens and helps protect the penis from injury against the tougher conditions. Barnacle penises can thicken from 0.66mm in diameter to 0.76mm, relative to the conditions of their environment.

Finally, what also assists this strange mating system is that barnacles are haemaphrodites, possessing both lady and man genitalia. This makes the whole event easier again because they can mate with who ever they can land on – they don’t have to worry if it’s a male of female. It’s both.

They just worry about being long-distance love machines.

Photo: Wikipedia commons
Barnacles: Long distance love machines. Photo: Wikipedia commons


Clapham, P. J. (2000). The humpback whale. Cetacean Societies, field studies of dolphins and whales. Chicago: The University of Chicago, 173-196.

Ellis, J. A., Stebbing, M., & Harrap, S. B. (2001). Significant population variation in adult male height associated with the Y chromosome and the aromatase gene. Journal of Clinical Endocrinology & Metabolism, 86(9), 4147-4150.

Hoch, J. M. (2008). Variation in penis morphology and mating ability in the acorn barnacle,< i> Semibalanus balanoides</i>. Journal of Experimental Marine Biology and Ecology, 359(2), 126-130.

Neufeld, C. J., & Palmer, A. R. (2008). Precisely proportioned: intertidal barnacles alter penis form to suit coastal wave action. Proceedings of the Royal Society B: Biological Sciences, 275(1638), 1081-1087.


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