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8 Bizarre Facts About Animal Reproduction

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There's no rule that regulates how animals obtain the necessary genetic material to reproduce—and as a result, there is a lot of weird animal sex going on out there.

1. BANANA SLUGS MATE USING PENISES ON THEIR HEADS.

Banana slugs are huge, they eat your garden, and they leave a slimy trail as they squirm across the ground. Their method of reproduction is no more pleasant than their appearance: The scientific name for one species of banana slug is Ariolimax dolichophallus, the second part of which means “long penis,” and it’s apt. The invertebrates' penises can be 6 to 8 inches long—the entire length of the slug's body. When it's time to get down, the penises grow out of pores in the head. It isn’t unusual for the penis of one slug to get stuck inside the other during copulation; to solve this uncomfortable situation, the slug on the receiving end will eat the penis that's stuck inside it.

2. MOUSE SPERM IS BIGGER THAN ELEPHANT SPERM.

Sorry, dudes: The size and shape of a male animal's sperm is more related to the biology and mating practices of the female—which is why mouse sperm is longer than the sperm of the biggest land animal on Earth, the elephant.

Two major factors in sperm size include the literal length and size of the female reproductive tract and how many mating partners the females have. Mice produce big sperm because, in most species, females have a lot of partners. The grouping of sperm can help to increase its competitiveness in promiscuous animals. Accordingly, the deer mouse has sperm equipped with small hooks that helps them clump together in groups of up to 35 sperm to fight their way to the egg. Grouping sperm allows the cluster to swim in a straighter line to the egg; the ideal number is seven. Too many spermatozoa will eventually start working against each other. Meanwhile, female elephants have a very long reproductive tract (more on that below), so male elephants have evolved to produce more but smaller sperm to combat the risk of dilution. To follow the reproductive strategy of mice sperm, elephant sperm would need to be scaled up enormously to make a difference. 

3. ELEPHANT PENISES ARE PREHENSILE.

Speaking of elephants: The elephant penis is so huge that males can rest on it like it’s a leg. When erect, it can weigh in at 66 pounds and can be more than 3 feet long. It’s also prehensile, which means that an elephant can move it around and even use it to scratch hard to reach places. As we mentioned, female elephants have long reproductive tracts—nearly 10 feet from start to finish—and the vagina doesn’t begin until about 4.27 feet in, so the elephant penis doesn't enter the vagina.

4. BEE SPERM WAGES WAR.

Male honey bee drones are infamous for extreme breeding. These bees have an internal penis—a.k.a. an endophallus—which, during copulation, is turned inside out and inserted into the queen. As he ejaculates, the drone falls back, breaking off his genitalia inside the queen and dying in the process. In theory, this sacrifice would lock his sperm inside and block out any competitors', ensuring that his genes were passed on. But unfortunately that's not what happens. As Social Insects: An Evolutionary Approach to Castes and Reproduction explains, “The next [drone] to copulate removes the mating sign [the endophallus plug] of his predecessor with the hairy ventral part of his own endophallus before he is able to insert its bulb and ejaculate the semen.” The next drone will do the same, and on and on. Of the 90 million sperm that end up in the queen's oviducts, only 7 million make it to a pouch called the spermatheca. She uses that sperm over the course of her life to fertilize eggs.

That is just the start of the story when it comes to bee sex. In species where multiple males mate with the queen, the sperm wage war with each other inside of her. (This happens in some species of ants, too.) When males get a little too violent, queens from some species will give off chemicals to calm everyone down.

5. ONE AUSTRALIAN MARSUPIAL HAS SEX UNTIL IT DIES.

The Antechinus is a mouse-like marsupial that eats insects, nests in trees, and has so much sex that it literally dies. By the time they hit 11 months old, males of this species have produced all the sperm they'll create in their short lifetimes; for the next couple of weeks, they'll go at it for up to 14 hours at a time with one female before moving on to another, over and over again, until their bodies break down. The male's fur will fall out; he'll bleed internally; he'll get gangrene and any number of other infections, ultimately dying before he reaches one year. But he's chasing tail up until the end: As Diana Fisher from the University of Queensland told National Geographic, “By the end of the mating season, physically disintegrating males may run around frantically searching for last mating opportunities. By that time, females are, not surprisingly, avoiding them.” The ladies are a little luckier, at least if they're of larger Antechinus species: Between 30 and 50 percent of them will live to produce two litters.

6. NAKED MOLE RATS HAVE DEFORMED SPERM.

The wrinkly, nearly blind naked mole rat is a successful breeder despite how inept its sperm is at being sperm. Small, malformed—many have multiple heads or are shaped oddly—and deficient in the mitochondria that most mammal sperm rely on for energy, just 15 percent, max, of the naked mole rat's sperm can swim; only 1 percent can move quickly. The animals don't produce that much sperm, either. These weird quirks may be due to the fact that the queen mates with only one male, so speedy, normal sperm isn’t necessary to guarantee the continuation of the species.

7. FEMALE NEOTROGLA PENETRATE THE MALES.

Neotrogla, a fly-like insect that lives in a cave in Brazil, is the first-ever species found that has “opposite” genitalia. The females are equipped with spiny, penis-like genitalia called gynosomes, which they use to penetrate the male; then, the insects get it on for up to 70 hours as the male transfers sperm and nutrients to the female. If the two are separated during copulation, the male’s insides will be ripped out while the female remains intact.

8. MONOGAMY MAKES FOR SMALL GORILLA PENISES.

You'd never know it by looking at them, but male gorillas have surprisingly tiny penises: They measure just 1.5 inches in length when erect. How can an animal that weighs up to 485 pounds be so humbly endowed? It's because primate mating practices are a huge factor in the evolution of the males' genitalia. When males have to compete among other males—as the sexually promiscuous bonobos do—the species' penis size is bigger. In gorilla society, male silverbacks mate with many females who are all monogamous to him. No reproductive competition equals a tiny penis. 

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NOAA, Wikimedia Commons // Public Domain
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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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Joe Raedle, Getty Images
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Animals
10 Things You Might Not Know About Grizzly Bears
Joe Raedle, Getty Images
Joe Raedle, Getty Images

Ursus arctos horribilis is better known by the more casual term of grizzly bear. These massive, brown-haired predators have a reputation as one of nature’s most formidable killing machines. Standing up to 8 feet tall and weighing 800 pounds, these fierce mammals have captivated—and frightened—humans for centuries. Keep your distance and read up on these facts about their love for munching moths, eating smaller bears, and being polar-curious.

1. THEY’RE ACTUALLY PRETTY LIGHT EATERS.

Grizzlies—more accurately, North American brown bears—are strong enough to make a meal out of whatever they like, including moose, elk, and bison. Despite their reputation for having carnivorous appetites, their diet also consists of nuts, berries, fruits, and leaves. They’ll even eat mice. The gluttony doesn’t kick in until they begin to exhibit hyperphagia, preparing for winter hibernation by chomping down enough food to gain up to three pounds a day.

2. THEY USE “CPR” TO GET AT YOUR FOOD.

A grizzly bear eats fruit in Madrid, Spain
Dani Pozo, AFP/Getty Images

More than 700 grizzlies live in or near Yellowstone National Park, which forces officials to constantly monitor how park visitors and the bears can peacefully co-exist. Because bears rummaging in food containers can lead to unwanted encounters, the park’s Grizzly & Wolf Discovery Center tests trash cans and coolers to see if they’re bear-resistant. (Nothing is truly bear-proof.) Often, a bear will use “CPR,” or jumping on a canister with its front legs, in order to make the lid pop off. Containers that can last at least 60 minutes before being opened can be advertised by their manufacturers as being appropriate for bear-inhabited environments.

3. THEY CAN CLIMB TREES.

It's a myth that grizzlies can't climb trees. Though their weight and long claws make climbing difficult [PDF], and they need support from evenly-spaced branches, grizzlies can travel vertically if they choose to.

4. THEY’LL EAT OTHER BEARS.

Two grizzly bears play in a pool at a zoo in France
Jean-Francois Monier, AFP/Getty Images

In addition to being omnivorous, grizzlies can also be classified as cannibals. They’ve been spotted eating the carcasses of black bears in Canada. Calling it a “bear-eat-bear world,” officials at Banff National Park in Alberta said the grizzlies are “opportunistic” and more than willing to devour black bears—sometimes just one-fifth their size—if the occasion calls for it. And it’s not just black bears: One study on bear eating habits published in 2017 recorded a 10-year-old male eating a 6-year-old female brown bear.

5. THEY LOVE MOTHS.

Although grizzlies enjoy eating many insects, moths are at the top of the menu. Researchers have observed that bears are willing to climb to alpine heights at Montana’s Glacier National Park in order to feast on the flying appetizers. Grizzlies will turn over rocks and spend up to 14 hours in a day devouring in excess of 40,000 moths.

6. A PAIR OF THEM ONCE LIVED ON WHITE HOUSE GROUNDS.

A grizzly bear appears at the Wild Animal Sanctuary in Keenseburg, Colorado
John Moore, Getty Images

In what would be considered an ill-advised decision, explorer Zebulon Pike decided to gift his friend President Thomas Jefferson with two grizzly cubs in 1807. Jefferson reluctantly accepted them and kept them in a cage near the north entrance to the White House, and later re-gifted the cubs to museum operator Charles Willson Peale. Sadly, one of them got shot after getting too aggressive with Peale’s family.

7. THEY CAN RUN FASTER THAN USAIN BOLT.

The bears we see in fiction or lazing about in the wild tend to look cumbersome and slow, as most anything weighing nearly a half-ton would. But in a land race, even Olympic champions would be on the losing end. Grizzlies can reportedly run 35 mph, and sustain speeds of up to 28 mph for two miles, faster than Usain Bolt’s 27.78 miles per hour stride (which he can only sustain for a few seconds).

8. THEY MATE WITH POLAR BEARS.

A grizzly bear is shown swimming at a pool in an Illinois zoo
Scott Olson, Getty Images

In parts of Alaska and Canada where grizzlies and polar bears converge, there are sometimes rare sightings of what observers call “grolar bears” or “pizzlies.” With large heads and light-colored fur, they’re a hybrid superbear birthed from some interspecies mating. Typically, it’s male grizzlies who roam into those territories, finding female polar bears to cozy up with. Researchers believe climate change is one reason the two are getting together.

9. THEY KNOW HOW TO COVER THEIR TRACKS.

When it comes to intellect, grizzlies may not get all the same publicity that birds and whales do, but they’re still pretty clever. The bears can remember hotspots for food even if it’s been 10 years since they last visited the area; some have been observed covering tracks or obscuring themselves with rocks and trees to avoid detection by hunters.

10. THEY’RE NOT OUT OF THE WOODS YET.

A grizzly bear and her cub walk in Yellowstone National Park
Karen Bleier, AFP/Getty Images

For 42 years, grizzlies at Yellowstone occupied the endangered species list. That ended in 2017, when the U.S. Fish and Wildlife Service declared that a rise in numbers—from 150 in the 1970s to more than 700 today—meant that conservation efforts had been successful. But overall, the grizzly population is still struggling: Fewer than 2000 remain in the lower 48 states, down from 50,000 two centuries ago.

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