Jul 26
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ARKive’s Top Ten Cave Species

Cold, wet, dark… but lifeless? Certainly not! Caves are home to many weird and wonderful lifeforms with special adaptations that make living in this inhospitable environment possible. Here are our top ten troglobiotic species!

Winter wren

Winter wren photo

Strangely our first selection doesn’t live in caves at all. The scientific name of the winter wren Troglodytes troglodytes means cave dweller but this name actually comes from the way it hunts insect prey by nipping in and out of cracks and crevices.

No-eyed big-eyed wolf spider

No-eyed big-eyed wolf spider photo

When you spend all your time in the dark eyes become an unnecessary but expensive organ to maintain. Many cave species have lost their eyes altogether resulting in an identity crisis for the no-eyed big-eyed wolf spider.

Alabama cave crayfish

Alabama cave crayfish photo

A life without sunshine makes protective pigmentation unnecessary. For the Alabama cave crayfish this adaptation has made its shell translucent so it’s possible to have a peek at its insides.

Fungus gnat

Fungus gnat photo

Colonies of fungus gnat larvae hang silk threads covered in sticky beads of slime from cave roofs to catch their prey. These gruesome youngsters use bioluminescence to lure flying insects into their dangling traps.

Velvet worm

Velvet worm photo

Another pigment free cave dweller is this species of velvet worm, it is one of only two troglobiotic velvet worms to have ever been discovered.

Madagascan rousette

Madagascan rousette photo

When asked to think of animals that live in caves bats are likely to spring to mind, but many bats don’t roost in caves at all, preferring a nice snug hollow in a tree. The Madagascan rousette is one species of bat that will roost in caves.

Cave salamander

Cave salamander photo

This cave salamander is also known as the human fish. Apparently its fleshy skin makes it resemble a small person. Subterranean darkness must be the only place that this beast could be mistaken for a human!

Iran cave barb

Iran cave barb photo

Like most cave species the range of the Iran cave barb is highly restricted. This fish has only been found in one subterranean river system in south-west Iran.

Nelson cave spider

Nelson cave spider photo

The Nelson cave spider is an ambush predator that hunts in the complete darkness of its limestone cave habitat. It is New Zealand’s only protected spider and also its largest.

Cave catfish

Cave catfish photo

The cave catfish is found in the Aigamas Cave in Namibia. An opportunistic feeder it’s only apparent food source is the particles that fall into the lake from the cave above including bat droppings and animal carcasses.

Have you found an interesting cave species on ARKive that doesn’t feature in our top ten? If so, tell us about it!

Eleanor Sans, ARKive Media Researcher

Jul 21
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ARKive’s Top 10 Natural Nasties

Welcome to ARKive’s Blog of Bleurgh. That’s right people – animals and plants aren’t all the white knights they’re often made out to be. “Chum” from Finding Nemo had it right – cute, clappy dolphins just aren’t cool. Compare them to his species – a mako shark. An awesome predator and one of the fastest fish in the ocean. No competition, really.

So, are you tired of cute and fluffy animals taking the limelight? Your search for the real, unadulterated, potentially horrifying side of the natural world is over – but your understanding of why nature can be so beautiful in the way it adapts and makes a living by being utterly horrifying, is only just beginning…

Cannibalism

Cannibalism (the eating of one’s own species) is rife in the animal kingdom – sometimes the need for survival is so great that one has to turn on one’s own kind. Or sometimes its just part of a mating ritual, like one of the most well-known cannibals of all, the black widow spider. After mating with the male, the female black widow makes a habit of eating her partner. Nice.

Photo of a female black widow spider

Coprophagia

There’s no easy way to introduce this – eating faeces. This is most commonly seen in herbivores, for two reasons:

  1. Eating one’s own poo gives inefficient digesters of plants a second chance at gaining important nutrients - for example rabbits, gorillas and capybaras.
  2. Eating one’s mother’s poo helps infants to cultivate gut bacteria important in the digestion of plant material – for example koalas, where the joey eats the mother’s “pap”.

Eastern gorilla photo

Scavenging

Feeding on dead animals or plants. There are more scavengers in the natural world than I have time to list here – but as this is a competitive habit, scavengers are ruthless in their pursuit of carrion. The pomarine jaeger and northern giant petrel are excellent examples of seabird scavengers.

Photo of northern giant petrels feeding on an elephant seal carcass

Worst smell

The natural world is an undoubtedly smelly place – as sense of smell is an important method of communication and having a certain pong tends to pay off. No more so than the titan arum, the plant with the largest flower in the world. In this case, being absolutely huge isn’t enough to attract the insects it needs for pollenisation, so the titan arum flower emits a stench not dissimilar to rotting flesh, earning it the title “corpse flower” amongst locals.

Titan arum photo

“If you have any poo, throw it now”

I apologise – back to poo again. Throwing the stuff is common behaviour amongst chimpanzees and other primates. It’s an aggressive display to guard their territory. Ok, I’ll stop talking about poo now. Here’s what it looks like, though.

Photo of chimpanzee faeces

Parasitism

Parasites tend to have evolved elaborate and often stomach-churning ways of taking advantage of their hosts. Ichneumon wasps are great examples. They lay their eggs in caterpillars, and the resulting wasp larva develops inside the unfortunate host, eating its internal tissues and eventually killing the caterpillar after it pupates. Not a pretty way to go!

Ichneumon wasp photo

“Play”

This is definitely one of the more sinister behaviours. Some orcas have a somewhat less respectful way of treating the corpses of their prey, swimming underneath and using their powerful tails to propel them metres above the ocean.

Orca photo

Gremlins

You know how Gremlins, the fictional film monsters, gave birth to baby Gremlins when they were exposed to water, and how the baby Gremlins popped off their parent’s back with grotesque popping sounds? Here’s the real life version. The eggs of the Suriname toad are embedded in the female’s back during amplexus, where they are nurtured through the tadpole stage and emerge as fully-formed frogs. Gross. I don’t think they make the popping sound, though.

Photo of a Suriname toad with young emerging from its back

Vampirism

A type of parasitism, vampirism is thought to have evolved in some species as a response to extreme environments where other food sources are scarce. Introducing the “vampire finch” – some short-beaked ground-finches feed on the blood of the other inhabitats of their dry, food-scarce Galapagos Island habitats. On top of this, they have also learnt some ingenious ways of getting to the nutritious contents of Nazca booby eggs. An excellent example of “culture” in the animal kingdom.

Sharp-beaked ground-finches feeding on blood drawn from nazca booby feathers

Murder

Being a scientific organisation, ARKive tries not to use human terms to describe animal behaviour – but for want of a better word… the magellanic penguin below looks innocent enough doesn’t it? This is probably just what a film crew from NDR Naturfilm thought when they decided to film a documentary following one of these beautiful creatures. Little did they know that they would end up filming an incredible example of inexplicable and “cruel” animal behaviour. The male subject of this film was relentlessly chased down and pecked to death by a competitive male. You can view the video on ARKive here, but be warned, it’s not for the feint of heart.

Magellanic penguin photo

So, that concludes our countdown of ARKive’s Top 10 Natural Nasties. As horrifying as they are, the blessing is that we have only covered the species we have on ARKive. There’s many more out there that are just as gross and would be very happy to make you their host. So watch out!

Charlie Whittaker, ARKive Media Researcher

Jul 12
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ARKive’s Top Ten Strange Facts

Ever been sat around at a dinner party scratching your head for interesting dinner table topics? Need a scintillating fact to titillate your fellow diners? Never fear! Here is a selection of ARKive’s strangest facts to impress your friends! Dinner parties will never be the same again…..

Have I ever told you about your father?

Anglerfish photo

Anglerfish swimming

As if the angler fish wasn’t strange enough, in order to reproduce the male attaches itself parasitically to the female by biting into her skin. The male then slowly dissolves losing its mouth, organs and brain until there is nothing left but its gonads! 

Grandmother, what big eyes you have!

Philippine tarsier photo

Philippine tarsier showing large eyes

Tarsiers, like this Philippine tarsier, have such huge eyes that they cannot move them in their eye sockets. Luckily, they can turn their head a whole 360° in order to watch for their insect prey. Try looking around without moving your eyes in their sockets. If anything, it will amuse the person sat next to you! 

Disco scorpions

Emperor scorpion photo

Emperor scorpion under ultra-violet light

Scorpions such as this emperor scorpion glow when exposed to UV light. Whilst glowing under UV lights might work well in a night club, scientists are unsure as to the reason why scorpions do it. One current theory is that it helps them to judge how dark the night sky is and therefore how safe they will be from predators. 

Heat wave? Congratulations, it’s a boy!

American alligator photo

Female American alligator carrying young

The sex of some reptiles is determined by the temperature at which the eggs are incubated. In the American alligator, eggs incubated below 30°C will be female whilst eggs incubated above 34°C will be male. Often, there will be a range of temperatures across the nest meaning a mixed sex ratio is produced. 

Four times the fun

Nine-banded armadillo photo

Nine-banded armadillo walking along beach

The nine-banded armadillo is unusual in that it always gives birth to identical quadruplets. Producing multiple identical young is an unusual trait in mammals and only occurs in armadillos of the genus Dasypus. Another unusual feature of the nine-banded armadillo is that it is one of the few non-human animals that can contract the disease leprosy. 

Look in to my eyes…..

Lemon shark photo

Close up of a lemon shark eye

Sharks such as the lemon shark can be ‘hypnotised’ by holding it upside down. The shark enters a state known as tonic immobility where it remains paralysed for up to 15 minutes before it recovers. Definitely worth remembering if you’re ever stranded in shark infested waters! 

A bat that thinks it’s a mouse

Lesser short-tailed bat photo

Lesser short-tailed bat on forest floor

The lesser short-tailed bat is the most terrestrial bat in the world. Despite being able to fly, it spends a lot of its time scampering around on the forest floor in search of prey. Having evolved in the absence of ground predators in its native New Zealand, the lesser short-tailed bat fills the niche usually occupied by rodents or shrews in other parts of the world. 

A butterfly disguised as an ant

Large blue butterfly photo

Large blue butterfly adult

The large blue butterfly has a special disguise up its sleeve. As a vulnerable and plump caterpillar, it drops to the ground from its food plant and secretes a sweet fluid which attracts a particular species of red ant. It is then carried back to the ant’s nest where it eats the ants grubs before pupating and being escorted out of the nest as a butterfly the following year. Talk about hospitality! 

Here comes the aeroplane! 

Gouldian finch photo

Gouldian finch chick mouth markings

We’ve all played this game with small children in order to get more food into their mouths than ends up on the floor. The gouldian finch takes this game a step further with the chicks having unusual light reflecting mouth markings. These are thought to guide the parent in the darkened nest, you certainly wouldn’t miss this mouth

The ‘Did you know….?’ Champion!

Blue whale photo

Blue whale underwater

As the largest animal to have ever lived, the blue whale unsurprisingly has a whole plethora of astounding facts! Weighing up to an estimated 180 tonnes, they have an aorta of around 23cm in diameter, a heart the size of a small car and a tongue that can weigh the same as a small elephant! And all this from feeding on tiny crustaceans known as krill

Do you know any strange animals facts? Tell us about them! 

Becky Moran, Arkive Media Researcher 

 

Jun 23
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In the News: Major study reveals Ocean’s ‘hotspots’

75 scientists have compiled 10 years’ worth of data on the migration patterns of 23 of the Pacific Ocean’s major species, including blue whales, bluefin tuna, sharks and albatrosses, to reveal two oceanic ‘hotspots’ that are teeming with marine life.

These two vast areas in the North Pacific Ocean, one off the west coast of the United States and the other between Hawaii and Alaska, provide migration corridors for large marine predators chasing seasonal concentrations of prey. These biological hotspots, rich in life, have been described as ‘marine counterparts of East Africa’s Serengeti plain’.

Photo of blue whale underwater

Blue whale

Chasing down predators 

Between 2000 and 2009, the 23 marine species were tracked using electronic tags, to record their movements and the water conditions around them, including temperature, salinity and depth. In total, the programme deployed 4,306 electronic tags, yielding 1,791 individual animal tracks, and resulting in 265,386 days’ worth of tracking data. 

This ambitious work is being hailed as the largest ever ‘biologging’ study. 

The result is the most comprehensive view to date of how top predators follow and find the biological hotspots of the sea as seasons shift. The findings are published today in Nature

It is like asking, ‘How do lions, zebras and cheetahs use Africa as a whole continent?’, only we have done it for a vast ocean,” said Barbara Block, a marine scientist at Stanford University in California and lead author of the paper. 

We have had single-species papers before on a lot of the migration patterns, but they have never been put together as a whole.”

Photo of shortfin mako swimming in open ocean

Shortfin mako swimming in open ocean

Migration highway 

Records from the tags show two ‘hotspot’ regions where the predators’ migration routes concentrate in the North Pacific, which act like a trans-oceanic migration highway. 

These are the oceanic locations where food is most abundant, and that’s driven by high primary productivity at the base of the food chain. These areas are the savannah grasslands of the sea,” added Block. 

Upwelling nutrient-rich cold waters create an abundance of plankton, which itself supports huge swarms of krill, the founding layer of the marine food chain. This brings in many other predators, including those that feed directly on the krill like blue whales, to those that are after the fish that also feast on the krill, such as bluefin tuna

The results also showed that slightly different preferences for water temperature prevent closely related species (e.g. salmon sharks, white sharks and mako sharks) from treading on one another’s fins. Many species with very long migratory paths, such as yellowfin tuna, bluefin tuna, white sharks, elephant seals and salmon sharks, were also found to faithfully return from their migration to the same region every season.

Photo of northern bluefin tuna shoal

Northern bluefin tuna shoal

The study data has left scientists excited, “we can now predict when and where individual species are likely to be,” said Daniel Costa, an ecologist at the University of California, Santa Cruz, and a co-author of the paper. 

The ability to map the ocean’s main predators’ migration paths allows conservationists to focus their efforts to protect and conserve the biodiversity of the hotspots. 

Block says that “knowing where and when species overlap is valuable information for efforts to manage and protect critical species and ecosystems”. 

Read the paper in nature – ‘Tracking apex marine predator movements in a dynamic ocean 

Alex Royan, ARKive Species Text Author

May 25
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Spotlight on: Mimicry

In their constant struggle against predators, animals adopt a fascinating variety of strategies to avoid being eaten. Some animals may attack their predators like these African buffalo chasing away a lion, others evolve unusual body parts so they cannot be swallowed, like this porcupine pufferfish, some blend into their habitat, such as this Arctic hare, while others may try to simply avoid capture by seeing, smelling or hearing their predator before they are detected.

Photo of plain tiger (left) next to mimic butterfly (Hypolimnas missipus)

Plain tiger (left) next to mimic butterfly (Hypolimnas missipus)

Some devious animals, however, try to avoid being eaten by tricking their predators into thinking they are either dangerous or distasteful. Such strategies commonly take the form of ‘mimicry’.

What is mimicry?

Mimicry is when one species benefits from evolving a feature displayed by another species. This feature could be anything from colour or body shape, through to scent or behaviour.

Mimicry can be loosely classified into four types: defensive, aggressive, reproductive and automimicry.

Let me explain….

Defensive mimicry

In defensive mimicry, a mimicking animal tricks a predator into treating it as a something different. The most well studied forms of defensive mimicry are Batesian mimicry and Müllerian mimicry.

In Batesian mimicry, an animal mimics a trait of another organism, such that predators think it is inedible or dangerous. Often totally harmless animals develop the shape or colouration of other animals that possess a dangerous or foul-tasting toxin.

Photo of hooded malpolon with head raised

The hooded malpolon showing cobra-like defensive behaviour

For example, the hooded malpolon, or false cobra, is only mildly venomous, but it mimics the hood and defensive displays of the extremely venomous and dangerous cobras so that predators avoid it.

Photo of honey bee asleep during cold weather

Black and yellow warning colouration of the honey bee

In Müllerian mimicry, two or more species, which share anti-predator traits such as toxins, develop similar warning colourations. When a predator first eats one of these distasteful species, it soon learns to avoid eating others with the same colourations. This explains why so many bees and wasps have black and yellow stripes.

However, only female wasps and bees have stingers, and the males are harmless, which is actually an example of automimicry, leading us onto our next example.

Automimicry

Photo of African burrowing python

African burrowing boa showing similarities between the head and tail

Automimicry occurs within a single species. Male wasps are protected from predators by appearing like the venomous females. Other examples include where one part of an animal’s body resembles another. The African burrowing boa, for example, has a similar looking head and tail which confuses predators and directs their attack away from the more vulnerable head.

Aggressive mimicry

It is not just prey species that have evolved cunning tactics to deceive their predators. Some equally clever predators over the course of time have developed fascinating ways of tricking their unwitting prey.

Photo of Nepenthes holdenii upper pitcher

Close up of Nepenthes holdenii showing nectar-secreting lip

Aggressive mimicry describes predators, as well as parasites, which share the same characteristics as a harmless species, allowing them to avoid detection by their prey. Nepenthes pitcher plants, for example, secret nectar near the lip to attract feeding insects, which then slip into the pitcher and are slowly dissolved by digestive enzymes.

The cuckoo, a brood parasite that lays its eggs in the nests of other birds, which act as foster parents for the cuckoo chick, also displays aggressive mimicry. The eggs of the cuckoo bare a striking resemblance to those of the host parents. The unsuspecting host bird then incubates and feeds the impostor.   

Reproductive mimicry

Photo of fly orchid

Insect-imitating flowers of the fly orchid

Aside from predator-prey interactions, in reproductive mimicry, mimicking species improve their reproductive success by tricking other species. Some of the best examples of reproductive mimicry are found in orchids.

The fly orchid has flowers that mimic the insects that pollinate it. Male insects land on the flowers, thinking they are female insects, and make attempts to copulate. Inadvertently, the insect brushes the flower’s pollen sacs, which attach to the insect. When the insect lands on another flower, it pollinates this flower with the other’s pollen.

Give us your examples!

The examples I’ve described here are just some of the hundreds of thousands of curious species that have evolved devious and deceitful ways of tricking their predators or prey to increase their chance of survival. If you know of any other equally crafty species, then let us know, or simply look through the ARKive collection and see if you can spot any mimics.

Alex Royan, ARKive Species Text Author

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