Evolution, and in particular sexual selection - the evolution of traits that increase an animal’s attractiveness to the opposite sex or allow them to outcompete sexual rivals - has produced some quite elaborate and even beautiful ornamentations.
Think the peacock’s iridescent tail, or the magnificent antlers of a red deer. Some of the animal body parts evolution has bestowed, though useful, are however less beautiful and more downright weird.
All of the body parts on this list have very important functions, be that in attracting mates, capturing prey, or communicating with others, but they may surprise you.
Read on to learn more about some of the strangest animal appendages out there.
Weirdest body parts in the animal kingdom
Proboscis monkey’s nose (Nasalis larvatus)
You can see why this monkey is named for its nose (or proboscis) - it certainly is striking! This strangely-snouted primate is endemic to the Asian island nation of Borneo and can be found living in the trees of swampy mangrove forests, and along rivers.
The pendulous nose belongs to the male proboscis monkey, with that of the female being much daintier (although still fairly pig-like). Its function is thought to be, perhaps surprisingly, to attract the opposite sex. In order to call to females, the male emits as loud and deep a roar as he can.
This advertises his health and dominance to prospective mates. Having such a long and flappy nose is thought to allow them to produce louder calls by acting as an echo chamber.
So there you have it, a massive nose can make you sexier.
Aye aye’s finger (Daubentonia madagascariensis)
Another primate, but this time a lemur, aye ayes are found in Madagascar. A nocturnal feeder, they have a very unusual method of finding food, which involves the use of a very special finger.
This long and thin almost skeletal-looking middle finger is used to tap on trees to locate cavities in the wood that house insect larvae. The aye aye will use its rodent-like and perpetually growing incisor teeth to gnaw into the wood and then use the same elongated finger to extract the grubs.
Upsettingly, it also sometimes uses its long finger to pick its nose! Aye ayes have been seen inserting much of the 8cm finger down their noses and back into their throats, afterwards licking the finger clean of mucus.
Burrowing asp’s backwards fangs (Atractaspis genus)
This next animal might not look too weird at first, but if you look closely, you might notice something unusual. Instead of downwards their fangs point backwards.
These long and thin fangs, reminiscent of a stiletto dagger, give the snake its other common name, the stiletto snake.
This genus of snake hunts underground and the unusual angle of its fangs are to allow it to strike moles and other burrowing mammals in a confined space and even as they try to escape. These fangs can be used when the snake’s mouth is not open all the way, so are easier to employ in a small space than that of other snakes.
To inject venom, they only have to come up alongside their prey and use one fang to stab it.
You can find out more about the snake at the African Snakebite Institute
And it's definitely worthy a place on our weirdest snakes list
Hammer-headed bat’s giant noses (Hypsignathus monstrosus)
The largest bat in continental Africa, this species certainly looks like a bruiser, and the giant schnoz doesn't help! As with proboscis monkeys, the large nose is unique to males, with females looking very different (and much smaller in general).
These noses are actually resonating chambers stuck to the front of their faces - large air sacs that allow them to produce very loud honking sounds. Although it might make them look like gargoyles, the ability to be very loud helps them get attention from females and ultimately aids reproductive success.
Chameleon’s hemipenes
There are lots of strange things about these charismatic lizards - from their protruding, rotating eyes, to their impressively lengthy and ballistically employed tongue.
The weirdest attribute they possess however must surely be the male chameleon’s reproductive organs - the hemipenes. Male chameleons have not one, but two, of these structures, located at the base of their tail. They are usually tucked away within their bodies and are only generally visible when they are mating or stressed. And they are quite a sight.
Rather than what you might expect for a male reproductive organ, each hemipenis is a very complex and even ornamented structure, with many spines and grooves, reminiscent perhaps of an orchid, or some other voluptuous flower. The strange shape of these organs is thought to aid in transferring sperm, as well as stimulating the female…
You can find out more from this study
The spermaceti organ in sperm whales (Physeter macrocephalus)
Despite the name, and in contrast to the previous organ on the list, this body part actually has nothing to do with sperm or reproduction. It is thought to be involved in the production of sound and echolocation, but its precise function is unclear.
This organ, unique to sperm whales, is located in their heads, just on top of their melon (another fascinating body part involved in communication and echolocation in toothed whales).
The spermaceti is filled with a pale yellow waxy fluid known commonly as sperm oil. Luckily for whalers of previous centuries, who prized this oil for it’s uses in lighting and lubrication, the organ contains a lot of oil - as much as 2,000 litres. It was high demand for this commodity that led to the near extinction of sperm whales in the 19th Century, before whaling bans were enforced.
Spotted hyena pseudo penis (Crocuta crocuta)
This next species possesses a very unique body part indeed - female spotted hyenas are the only placental mammals (as opposed to marsupials) to have a pseudo-penis (one of the weirdest penises in the world) and to lack an external vaginal opening.
In these hyenas, the genitals of the female closely resemble that of the male, with the clitoris positioned and shaped like a penis - making it very difficult for observers to distinguish between the sexes. They also have no external vagina, as the labia are fused to form a pseudo-scrotum.
Females both mate and give birth through this pseudo-penis. The reason for these unusual genitals is thought to be to give females greater control over who they mate with, as it gives them a ‘masculine camouflage’ and acts as a blocker of the reproductive tract.
Geoffroy's spider monkey pendulous clitoris (Ateles geoffroyi)
Another sexual organ - are you sensing a theme here? Similarly to female spotted hyenas, female Geoffrey’s spider monkeys are commonly mistaken for males, due to their extra-long dangling clitorises! Unlike the hyenas’, these are not quite as similar looking as the corresponding male genitals (they are in fact longer however!), and spider monkeys still have external vaginas.
Rather than being a defence, these unusual clitorises function as an advertisement, aiding males in determining the sexual receptiveness of a female, through touch and smell.
Anglerfish luminescent esca (Lophiiformes order)
This next animal is surely one of the weirdest out there - it lives mostly in the deep and dark, males are a fraction of the size of females of the same species, and in some species the male fuses to the female for life upon reproduction, becoming a permanent parasite!
You might say that a male fused to your side (and even bloodstream) is the weirdest body part you can have, but this is perhaps just overtaken by the glowing fishing lure that female anglerfish have sticking out the top of their heads.
Known as the esca, this appendage, a dorsal spine topped with a bulb of bioluminescent bacteria functions to attract unlucky fish, which quickly become prey. It also serves to attract the attention of males to aid in reproduction.
Wallace’s sphinx moth’s foot-long tongue (Xanthopan praedicta)
This next species comes with a fascinating science-history tale, as well as an impressive appendage. In 1862 Charlies Darwin was sent a specimen of an orchid from Madagascar with an extremely long nectar tube, leading him to reply in a letter 'Good heavens, what insect can suck it!'.
He hypothesised that it would take an insect with a similarly long tongue to reach the nectar. A few years later, Darwin’s contemporary and fellow evolutionary theorist, Alfred Russel Wallace similarly speculated about the existence of such a long-tongued insect, writing “that such a moth exists in Madagascar may be safely predicted, and naturalists who visit that island should search for it with as much confidence as astronomers searched for the planet Neptune, – and they will be equally successful.'
Well, he was eventually proven right by the discovery of this moth species and its proboscis that can reach up to 35cm in length!
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