updated every other day

This is a series about animal penises (the term used loosely to mean any organ which transfers sperm), posted daily. I’m working on a poster which incorporates all of the animals pictured here.

NEW! #dailypeen merch! Just in time for the holidays- who doesn’t want apparel/ household goods/ stationary with animal dicks on them? I know I do. (I’m honestly most excited about the socks.)


Priaprim: Shibukawa, K., Tran, D.D. and Tran, L.X., 2012. Phallostethus cuulong, a new species of priapiumfish (Actinopterygii: Atheriniformes: Phallostethidae) from the Vietnamese Mekong. Zootaxa, 3363(1), pp.45-51.

Sea slug: Anthes, N. and Michiels, N.K., 2007. Precopulatory stabbing, hypodermic injections and unilateral copulations in a hermaphroditic sea slug. Biology Letters, 3(2), pp.121-124.

Duck: Brennan, P.L., Clark, C.J. and Prum, R.O., 2010. Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Proceedings of the Royal Society B: Biological Sciences, 277(1686), pp.1309-1314.

Echidna: Johnston, S.D., Smith, B., Pyne, M., Stenzel, D. and Holt, W.V., 2007. One-sided ejaculation of echidna sperm bundles. The American Naturalist, 170(6), pp.E162-E164.

Leopard slug: Davison, Angus, 2019. Leopard slugs mate in the most beautifully bizarre way – and nobody knows why. The Conversation. https://theconversation.com/leopard-slugs-mate-in-the-most-beautifully-bizarre-way-and-nobody-knows-why-128284

The leopard slug image is a composite of several references.

Penis worm: Shipley, Arthur Everett (1911). “Priapuloidea”. In Chisholm, Hugh (ed.). Encyclopædia Britannica. 22 (11th ed.). Cambridge University Press. p. 313.


Alligator reference:

edyong209, 2013. Alligator penis surprise. SERIOUSLY WATCH THIS! Youtube. Attributed to Brandon Moore. https://www.youtube.com/watch?v=3ED_exG3qLk&feature=emb_logo&ab_channel=edyong20

Kelly, D.A., 2013. Penile anatomy and hypotheses of erectile function in the American alligator (Alligator mississippiensis): muscular eversion and elastic retraction. The Anatomical Record, 296(3), pp.488-494.

Snake: Keogh, J.S., 1999. Evolutionary implications of hemipenial morphology in the terrestrial Australian elapid snakes. Zoological Journal of the Linnean Society, 125(2), pp.239-278.

Shark: Jones, C.J., Walker, T.I., Bell, J.D., Reardon, M.B., Ambrosio, C.E., Almeida, A. and Hamlett, W.C., 2005. Male genital ducts and copulatory appendages in chondrichthyans. Reproductive Biology and Phylogeny of Chondrichthyes: Sharks, Batoids and Chimaeras, ed. WC Hamlett, pp.361-393.

Baculum: Austin, C.R., and Short, R.V. eds., 1986. Reproduction in Mammals. Cambridge University Press.

Barnacles: Neufeld, C.J. and 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), pp.1081-1087.

Elephant: 4028mdk09, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0&gt;, via Wikimedia Commons

Ostrich: Brennan, P.L. and Prum, R.O., 2012. The erection mechanism of the ratite penis. Journal of Zoology, 286(2), pp.140-144.

Dog: Kleiman, D.G. and Eisenberg, J.F., 1973. Comparisons of canid and felid social systems from an evolutionary perspective. Animal behaviour21(4), pp.637-659.

Hart, B.L. and Kitchell, R.L., 1965. External morphology of the erect glans penis of the dog. The Anatomical Record152(2), pp.193-198.

Wolvix1965, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons. https://commons.wikimedia.org/wiki/File:German_Shepherd_penis_1.jpg

scientific illustration + art