You don't breed often in captivity. 1943. 1999. 2009. It's a private thing. You look too different. Feel too solitary. Mammal without kin. Beak/bill, flippers, feet/claws. And you are a male—so, spurred. Your mate lays eggs—no one sees this. It's private.

You feed from the water, thirst for air, fluoresce in the right light, record the electricity of living things. You are acutely sensitive to pressure. You swim blind.

You have 52 chromosomes. Unlike the female, who is all female (10 Xs!), you are dual: 5X, 5Y. Your differences multiply.

When you sleep in a cool burrow, you dry, curl. If it warms, you stretch, lengthen, not unlike a rabbit at rest in summer. When monitored, your brain registers a higher voltage than other mammals. Observed, you have the longest REM sleep periods of any. You twitch vigorously in sleep, like a dog. Humans don't know if you dream. You know if you dream.

You eat a fifth of your body weight every day. Feed for 8-16 hours in a 24-hour period (usually). You make up to 1,600 foraging dives per session. Usually (but by no means exclusively) you do this at night. Mostly you eat benthic insects, small bottom dwellers. You are limited in your prey by your lack of true adult teeth. For you lose the baby teeth you are born with, including the egg tooth that you used to hatch yourself. You do not replace them. You store food in your cheeks, then rise, surface, and grind with rough grinding pads. These grow continuously. You continuously wear them down.

You were conceived, laid, and incubated in your shell, in the curve of your mother's furred belly, for less than two weeks. You were born tiny, immature. You crawled across your mother's belly, swept your bill for milk oozing from patches of her skin. The milk was thicker, richer, contained far more solids than a cow's. After several months you were grown. You entered the water on your own. No one taught you to find food or swim. You learned.

Upon maturity, you produced venom.

There is no evidence you communicate with sounds—except the occasional irritable growl. You have, however, unusually well-developed smell sensors and scent glands, things associated in other mammals with robust intra-species communications.

When you mate, a female decides when. You might grasp her tail, be towed along for great distances until, and if, she is ready. You might use any number of positions when you mate. Sometimes the position is determined by your relative sizes. Your sperm are thready, reptile-like. They form bundles that have 3x the velocity of a lone sperm. You will try to mate with many females. You will not raise your offspring.

One day in 1973 a human girl asks her mother and father if a female platypus menstruates, or, goes into estrous. The girl has just learned these attributes are characteristic of all mammals, but not of egg layers. In school, they are teaching her to categorize creatures.

Her parents don't know. They don't even know if platypuses are male and female. They launch into long speculations about androgyny and asexual reproduction. To the girl's embarrassment, they love her question. They conduct their own research for months, years. Seek the opinions of biologists.

When the girl is an adult they buy her tea towels, thimbles, and t-shirts with platypuses on them. She will continue to find these in boxes after their divorce, their deaths. They never find the answer to her question. She finds the answer is not known. You don't know about this girl. You will never meet this girl. She will never meet you.

You spend most of your time alone. According to one online source, the most-asked question about you is: What are you called, plural?

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SOURCES:

• Australian Platypus Conservancy, 27 July 2021, platypus.asn.au. 
• B.P. Setchell, W.G. Breed. "Anatomy, Vasculature, and Innervation of the Male Reproductive Tract" in Knobil and Neill's Physiology of Reproduction (Third Edition), 2006, 771-825.
• Jones, Russell Campbell et al. "Reproduction in Monotremes." Encyclopedia of Reproduction (Second Edition) edited by Michael K. Skinner, Academic Press, 2018, 602-608.

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In the context of current societal churn on issues of gender and sex, and language thereabouts, I found myself writing this piece for an exercise I can't remember, something about inhabitation of other creatures and the second person. As a child, I found the categorical confusion of Platypusses (Platypi?) fleetingly interesting. My parents, both educators of different sorts, were, on the other hand, determined to give me the information on sex and gender that they were never able to discuss with their parents—and they found it easier to do so in the context of other creatures. They inhabited my brief interest in these creatures with the depth and long term tenacity of adults who must have had something else they really wanted to talk about, other tensions beneath the surface. Instead of gender knowledge, I took from them an abiding curiosity in the workings of other life-forms. I wondered about this piece as I re-read and revised it. Why did I worry at the categories, at something unknowable in another creature's femininity as a child? Why did I write in personal address to, in fact inhabiting, the male of another species? I begin to think that gender, not unlike god, is some body-deep knowledge others feel; that is just out of reach for me.