Top 12 strangest animals in the world

The strange penis belonging to the echidna has left scientists baffledA mammal with the "weirdest" penises in the animal kingdom has baffled scientists.
The "very strange and unusual" appendage of the echidna remains a mystery to researchers who still don't understand why it has four heads.



One of the biggest monotreme mysteries is the echidna penis, which has four separate heads, or glans, at the end of the shaft. If that wasn't weird enough, only two of the

The "very long" phallus makes up a third of the animal's body while erect, is bright red and has four endings, which can all be used for the purpose of reproduction.

An echidna is similar to an anteater but has prickly fur. They live in Australia and Papua New Guinea.

University of Queensland researcher Dr Steve Johnston co-authored a study on the peculiar creature's impressive member.The penis of the echidna has four headsBut he said only "the creator God" knows why it is so bizarrely shaped.

It may be to please the insatiable female echidna, who scientists believe may mate with up to a dozen males while ovulating.

When the echidna has sex, two of the four prongs are engorged while the others are flaccid.

Experts also speculated that the animals may have Dr Johnston, of the Australian university, said: "It does look like they do it more than once, but there's still a bit of debate. We're not quite sure whether these guys are induced ovulators or not."



Echidna penises: Why they're so weird - Australian Geographic

The shape and comparative size of the creature's penis is not the only peculiarity about it, researchers say.

Dr Johnston added: "Not only is the (echidna) penis strange in the way it looks, it's also strange in terms of they don't actually urinate through their penis.



When people first hear about reproductive biologist Jane Fenelon’s research their first reaction is shock, but also, curiosity. “It’s amazing how many people have actually heard that there’s something weird about the echidna penis,” she says. “For those less informed, Jane then follows this up with an image of an echidna penis, and the feelings of shock roll back.

In late April, Jane and her colleagues published an in-depth research paper on the echidna penis. Labelled one of the “weirdest penises of the animal kingdom” by Smithsonian Magazine, the echidna penis is bright red and has four heads. ​”We’re not really sure why it looks so weird but we do know that they only use their penis for mating, not urine,” Janes says. “Because they don’t need it for urine, they had the freedom to make it much more elaborate and this is something you see in other species that only use it for mating.”

And while you may think we know all there is to know about the echidna, you’d be wrong.

The difficulty in studying the echidna is well-documented. Peggy Rismller, who has been studying echidnas for more than 30 years, was the first to discover that echidnas were laying their eggs into a pseudo-pouch, rather than hatching their eggs in burrows like their fellow monotreme, the platypus. That discovery was only made in the early 1980s, and the reproductive lives of echidnas continues to be difficult to capture.

Echidnas are a protected species, meaning scientists such as Jane can’t go around picking them up and prying at their reproductive systems. So, for this study Jane teamed up with Currumbin Wildlife Sanctuary on the Gold Coast, which operates a wildlife hospital. From it, Jane received echidnas, euthanised due to illness, to analyse.



What do we know about the echidna penis?
Prior to this study, co-author of the paper, Steve Johnston, had previously published a scientific paper documenting how echidnas were only using two of the four heads at any one time when erect. According to Jane, this is very unusual in mammals but is seen in some reptiles. Therefore, this most recent paper wanted to understand how echidnas were doing this.

The team of researchers believed that the echidna was using a valve mechanism to control which head it used. However, the paper revealed the two ‘corpora spongiosa’ (one of the main tissues that make up mammalian penises) remains entirely separate from the penis.

“Together with the split of the major blood vessel and urethra it gives the impression that the end of the echidna penis is acting like two separate glans penises, which explains how they ejaculate out of one side at a time,” Jane says.

So, what’s the point of knowing these things about an echidna’s junk? ​Well, echidnas are notoriously difficult to breed, and while Australia seemingly has echidnas in abundance, Jane says the main goal is to help with the conservation and breeding of the endangered long-beaked echidnas of Papua New Guinea.

“While understanding how the penis functions isn’t directly related to their conservation, understanding as much as possible about their reproduction in general will help us with that goal,” she says.

The next step will be understanding how the unusual structure of an echidna’s penis developed.

“We’d also like to look into how similar it is to crocodiles and turtles, which the adult form looks most like. There’s some evidence that the penis in all amniotes [reptiles, birds and mammals] has the same evolutionary origin and the monotremes are a missing piece of that puzzle.”



Australian researchers discover why only two of echidna’s four penis heads become erect at one time
The major blood vessel of the penis splits into two main branches which each supply two of the four penile heads

EchidnaMale echidnas have no scrotum and store their penis internally when not using it. Each of the four tips of the echidna penis has a branch of their urethra but only semen passes through. Photograph: Kristian Bell/Getty Images/ iStockphoto
The penis of an echidna has four heads but only two become erect at any one time. Now, Australian researchers have uncovered why.

Scientists discovered the mammal has unusual reproductive anatomy that causes male echidnas to ejaculate from only two of their four penile heads at one time.

The research, published in the peer-reviewed journal Sexual Development, found that echidna penises have similar features to those of other mammals, including platypuses, but also similarities to reptiles.

The scientists studied the internal anatomy of several echidnas that had been brought into the Currumbin Wildlife Sanctuary in Queensland with severe injuries and had to be euthanised.

Male echidnas have no scrotum and store their penis internally when not using it. Each of the four tips of the echidna penis has a branch of their urethra but only semen passes through.

The echidna penis has four heads, or glans
Australian researchers have discovered more about the echidna’s unusual reproductive anatomy. An echidna penis with four heads. Photograph: Jane Fenelon/University of Melbourne/AAAS and EurekAlert!
The researchers found that in echidnas, the major blood vessel of the penis splits into two main branches, which each supply two of the penile heads.

Jane Fenelon of the University of Melbourne, the study’s lead author, said previously it was suspected that male echidnas alternated between two of their four penile heads via a valve mechanism on the urethra, but that they did not find any evidence of this.

Instead, they found the spongy tissue of the penis, which becomes erect when filled with blood, was separated by a septum – meaning the echidna penis has two distinct halves. By directing blood flow down one of the main artery branches, the echidna is able to control which half – and which two heads – becomes erect.

“Their penis is actually acting like two separate penises that just happen to be merged together,” said Fenelon.It’s the first time we’ve seen this in mammals. We know that in other species with really elaborate penises, it normally happens because of male–male competition for females.” In that case, a multi-headed penis might decrease the time needed between mating sessions, but the evolutionary reason for the behaviour in echidnas has not been confirmed definitively.

Fenelon said the research was motivated by the behaviour of an echidna at the wildlife sanctuary, who had been observed alternating the use of his penile heads up to 10 times in a row.

Fenelon noted similarities between echidnas and platypuses which have a two-headed penis covered with spines.

“Internally, we think it’s pretty similar to an echidna, but nobody’s ever seen an erect platypus penis, so we’re not sure if they only use one of their two heads at one time,” she said.

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Echidnas and platypuses are the only two living monotremes – mammals that lay eggs instead of giving birth to live young.

Two-pronged penises are also common in Australian marsupials , including kangaroos, koalas, bilbies and wombats.

There were also anatomical similarities between the male echidna’s reproductive tracts and those of crocodiles and turtles, particularly in how the sperm enters the penis.

Female echidnas have a cloaca – a single opening that they use to urinate, defaecate, and mate. Internally, the cloaca branches into different systems, including a two-branched reproductive tract.

“We think when the penis is erect that it’s long enough to reach where the uterus branches off,” said Fenelon. Males also use their cloaca to urinate and defaecate.

Unusually, previous studies have shown that echidna sperm cells work cooperatively, swimming in connected bundles of up to 100 sperm to reach the egg.

This article was amended on 11 June 2021 because an earlier version, in some instances, mistakenly referred to echidnas and platypuses as marsupials. As another reference in the text said they are monotremes.