Oddities | Animals Do It Too

The Swimming Penis

Male argonaut octopuses have a detachable, sperm-filled arm that swims to the female on its own — scientists originally thought it was a parasitic worm.

The 30-Minute Mating

Boar ejaculation can last up to 30 minutes — one of the longest mating durations of any mammal.

Finding Nemo's Real Story

All clownfish are born male, and can permanently change to female — meaning in Finding Nemo, Marlin would have become Nemo's mom.

Chew It Off

When banana slugs get stuck during mating (their penises can be as long as their bodies), one partner may chew off the other's penis to separate.

Dad's Having the Baby

Male seahorses are the ones who get pregnant and give birth, carrying up to 2,000 babies in a specialized brood pouch.

Ten Sex Chromosomes

While humans have 2 sex chromosomes (XX or XY), platypuses have 10 — the most complex sex determination system known in mammals.

Eating Your Siblings in the Womb

In sand tiger sharks, embryos eat their siblings in the womb — only the two largest (one per uterus) survive to be born.

Males Not Required

Some whiptail lizard species are entirely female and reproduce through cloning — but they still perform mating rituals with each other.

The Sounds of Slow Love

Giant tortoises make loud groaning sounds during mating that can be heard from far away — and mating sessions can last several hours.

Death by Celibacy

Female ferrets can die if they go into heat and don't mate — prolonged estrogen exposure causes fatal bone marrow suppression.

Babies Burst from Mom's Back

Surinam toad eggs embed into the mother's back skin, where they develop for 3-4 months before fully-formed toadlets burst out of her back.

Polyandrous Bird Moms

Female jacanas mate with multiple males, then leave each male to incubate and raise the chicks alone while she defends territory and finds more mates.

Chewing Off Your Own Penis

Banana slugs sometimes chew off their partner's penis after mating — or their own if it gets stuck. The penis doesn't grow back.

The 24-Hour Window

Female giant pandas are only fertile for 24-48 hours per year, making them one of the hardest animals to breed in captivity.

Mating Once a Decade

Kakapos only breed every 2-4 years when rimu trees fruit heavily — and some individuals have gone over a decade between breeding attempts.

Evolutionary Self-Care

Male Cape ground squirrels frequently masturbate to ejaculation — scientists believe it's a strategy to keep sperm fresh for competition.

Flipper Fun

Male walruses have been observed masturbating with their front flippers — aided by their enormous penis bone.

Rubbing One Out (On a Tree)

Male deer have been observed achieving erections and apparent ejaculation while rubbing their antlers on trees — behavior some researchers interpret as masturbation.

Climate Change Babies

Grizzly bears and polar bears are mating in the wild, producing fertile 'grolar bear' or 'pizzly bear' hybrids — a consequence of climate change pushing their ranges together.

All-Female Fish Army

Amazon mollies are an all-female species that 'steals' sperm from males of other species to trigger reproduction — but doesn't use any of the male's DNA.

When Dolphins Meet False Killer Whales

Wholphins — hybrids of bottlenose dolphins and false killer whales — have been born both in captivity and documented in the wild.

The Biggest Cat That Shouldn't Exist

Ligers — offspring of male lions and female tigers — can grow to over 900 pounds, making them the largest cats on Earth, bigger than either parent species.

10,000 Years of Sterile Offspring

Humans have been breeding mules (horse × donkey) for over 10,000 years, despite knowing that nearly all mules are sterile and can't reproduce.

Confused Waterfowl

Male ducks are notorious for attempting to mate with other species — researchers have documented them trying with over 40 different bird species and even other animals.

Romance Through Regurgitation

White-fronted parrots show affection by vomiting into each other's mouths — and the male vomits into the female's mouth before and during mating.

Sealed Shut Until Mating Season

Mouse lemurs and dwarf lemurs develop a membrane that seals their vaginal opening completely closed outside of breeding season.

The Sealed-Off Females

Female European moles have 'ovotestes' that produce testosterone, and they have no external vagina except during breeding season.

27 Facts