Freshwater lakes are thought to account for an estimated 4% of the Earth’s surface.
Lakes are typically bodies of water with a certain depth, size, and shape and can connect to other water sources. Most lakes are freshwater, however, there are some lakes on planet Earth that have brackish water.
Lakes are a valuable ecosystem for a huge diversity of animals. Some animals spend their entire lives submerged within lakes. Other animals use lakes solely to breed or feed.
So, what are some of the animals that live in lakes?
Across the globe, a huge variety of animals live in lakes. Some, such as ducks and turtles, can be found across the globe. Others, such as cichlids, are endemic to one region. Some animals, such as beavers, play an important role in the wider ecosystem. Others, such as introduced zebra mussels, negatively affect native species.
We’ll be exploring the types of animals, both terrestrial and freshwater, that can be found in lakes across each of our continents.
North America
Let’s begin by exploring the species that are found in North American lakes.
Beaver
Starting off with a bang! The iconic North American beaver.
Referred to as a keystone species, beavers alter entire ecosystems to benefit a wide range of species. Using their large, chisel-like incisors, they chop down trees and vegetation to construct dams and lodges.
These dams restrict and divert water, creating wetlands and marshes that significantly increase the biodiversity of mammals, birds, amphibians, reptiles, and insects. Such animals that are positively affected by beavers include minks and ospreys.
Lakes, where beaver lodges can be found, are incredibly important for beavers. With one underwater access point, lodges serve as a refuge point against terrestrial predators.
Beavers have a widespread distribution and can be found in lakes and rivers across North America, including Canada, the USA, and North Mexico.
They are the second largest rodent alive today (the capybara claims the no.1 spot), weighing up to 50kg.
American Mink
The American mink is a species of mustelid, related to weasels and otters.
Minks have soft, short, and dense fur, making them an ideal candidate for the exploitation of their fur. Millions of minks suffer in fur farms around the world.
In the native range, however, their dense fur helps keep them warm against the frigid North American elements whilst diving underwater.
American minks live in forested areas, close to water sources, such as lakes, where they hunt a range of aquatic prey, such as fish, amphibians, and crustaceans.
Loon
Picture the scene:
You’re camping by a lake, alone in the North American wilderness. Suddenly, a haunting wail resonates from one side of the lake. And then the other side of the lake.
Pretty spooky, right?
Fortunately, these eerie calls come from a species of aquatic bird (and not some otherworldly being): the common loon – a duck-like bird with distinct black and white markings.
These diving birds prefer clear lakes of North America, where they hunt aquatic prey by sight. Their diet primarily consists of fish, however, loons will also consume amphibians and crustaceans, such as crayfish.
Much like a chicken, loons have been observed eating pebbles from lake floors. It is thought that these pebbles are stored in the gizzard, the area of a bird’s stomach to aid in the grinding of food, and help break down the hard parts, such as shell and bone, of its prey.
Zebra Mussel
In the Great Lakes of North America, a silent assassin lurks.
An assassin that costs governments in North America billions of dollars each year to control. The zebra mussel.
A mussel. Really? I can almost see the eye roll.
But, this invasive species, brought in through ship ballast water, reproduce incredibly fast and plagues water intake pipes. This is a big problem for any facility drawing water from the Great Lakes, such as water treatment plants and power plants.
But, that’s not all. The invasive, non-native zebra mussel is killing off local, native species.
Native freshwater mussels in the Great Lakes are experiencing mass die-offs. This could be, in part, caused by pathogens introduced by the zebra mussels. Another theory suggests that the faster maturing zebra mussel takes over the food and spawning grounds of the zebra mussels.
But native mussel species are not the only animals taking the brunt of the damage. Fish species that lay eggs in rock crevices in the Great Lakes are also starting to decrease. As the zebra mussels take hold of more ground (or rocks, in this case), fish eggs cannot successfully hatch, as the predation rate is significantly increased.
Sea Lamprey
From one assassin to another.
But whereas the zebra mussel unintentionally kills off its competition, the sea lamprey actively seeks its victims out.
Juvenile sea lampreys are parasitic and latch on to prey fish. Using a suction-like mouth, filled with hundreds of razor sharp teeth and a rasping tongue, the sea lamprey punctures the fish’s skin, draining it of its blood. Oftentimes, the host fish will die from blood loss or infections.
Mature sea lampreys migrate to lakes and rivers to spawn and lay eggs in unpolluted, sandy gravel. Like salmon, they are referred to as diadromous – an animal that can tolerate both fresh and saltwater.
Osprey
Preying almost entirely on fish, the osprey will spend its life close to freshwater sources, such as lakes.
With such slippery prey, the osprey must have the relevant adaptations to allow them to hunt. And they do.
As with most birds of prey, the osprey has four sharp talons – three at the front and one at the back. However, unlike most raptors, ospreys are able to rotate one of the front talons towards the back when grasping fish.
The talons are equipped with short, stiff spikes, or spicules, that provide extra grip on their flapping prey.
Another unique adaptation of the osprey is the evolution of oily feathers. Thought to be the only species of raptor with this oily plumage, ospreys can readily shake off any excess water after diving in for the kill.
There is only one single species of Osprey, and it has a global distribution. However, the highest density of ospreys anywhere in the world can be found in Chesapeake Bay, on the Eastern U.S. coastline.
South America
The diversity of South American lakes is also incredible, so let’s take a look!
Giant River Otter
At around 6 feet, or 1.8 meters, in length, the giant river otter of South America is the largest otter species in the world. Despite its size, these giant river otters are incredibly elusive, and not much is known about their life histories.
They are found in slow moving rivers and lakes throughout the Amazonian basin, as well as Orinoco and La Plata systems.
They are often found in groups of up to 9 individuals, but they have been known to forage independently. Although fish make up a large proportion of their diet, the giant river otter also preys upon smaller mammals, crustaceans, and birds.
The illegal fur trade, hunting, pollution, habitat loss, and net entanglement have threatened the survival of this species. They are now classed as endangered by the IUCN.
Bull Shark
Sharks?! In a lake? Have I gone mad?
Well, nearly. But not quite.
Approximately 5% of all shark species can tolerate freshwater for a short amount of time. Bull sharks, however, are one of the only species of sharks that can thrive in freshwater for long periods of time – up to 4 years!
Some bull sharks have been tracked over 2,500 km up the Amazon River!
But how do they do this?
The answer can be found in their kidneys.
When entering a body of freshwater, the bull shark must expel excess salts from their body. The kidneys are responsible for producing large amounts of urine that can quickly dispose of any salt in their bodies.
Bull sharks have also been discovered in the brackish waters of Lake Maracaibo, Venezuela.
Arguably a bay, rather than a lake, lake Maracaibo is an important nursing ground for bull sharks.
Spectacled Caiman
Named after the pair of spectacles they wear when hunting…
Kidding, just imagine.
The spectacled caiman gets its name from the bony ridge between and around the eyes, which, to some, gives off the impression of glasses. Each to their own, I guess.
The spectacled caiman has one of the largest geographic ranges of all crocodilian species, stretching from North to South America. They are, however, most commonly found in lakes, rivers, and swamps of South America.
As with most reptiles, spectacled caimans are cold blooded and bask on river or lake banks to warm up.
They also dig nests in these banks and lay a clutch of up to 40 hard-shelled eggs. Some individuals insulate their brood with the surrounding vegetation.
Unlike mammals, caimans do not possess sex-determining genes. This means the sex of their offspring is determined by the temperature of the surroundings. Around 30 degrees Celsius or cooler, the developing offspring will be male. If the clutch is over 31 degrees Celsius, the developing brood will become female.
Electric Eel
Despite their name, an electric eel isn’t an eel. Rather, it is a neotropical freshwater fish species more related to catfish.
They are, however, very much electric.
In fact, electric eels can emit enormous electrical charges of over 600 volts of electricity – that’s the same as a high-voltage generator or five times an average U.S. power socket.
But how can a fish give off electrical charges?
An electric eel contains three specialized electric organs: The Main organ, Hunter’s organ, and Sach’s organ. Within these organs, over 6,000 modified muscle cells, called electrolytes, act as mini batteries, storing electrical power.
The main organ and Hunter’s organ are responsible for stunning prey, such as other fish, crustaceans, and small vertebrates, and deterring predators.
The Sach’s organ, found at the rear of the eel, emits low-level voltage that enables the eel to navigate the murky lakes and rivers of the Amazon and Orinoco basins.
Surinam Toad
For those suffering from trypophobia, read no further (although you should, as this is one nifty adaptation).
A fully aquatic species, the Surinam toad lives in pools of water across the Amazon basin.
A Surinam toad attracts a mate by creating a series of clicking noises underwater. The louder the click, the more irresistible the male.
This is when the magic happens.
As a female releases an egg, it is fertilized by the male and pressed into the back of the female. This process can occur up to 100 times, until the back of the female Surinam toad is covered in eggs.
In the hours following the egg deposit, skin grows around the eggs, encapsulating them in honeycomb-like holes. Here, the eggs will develop, under the direct care of the mother, for 80 days.
After the developmental stage, tiny Surinam toadlets emerge from under the female’s skin. The back pockets, where the tadpoles had been developing, loosen, and waving feet can be seen. From here, the toadlets are now fully independent.
Albeit uncomfortable, but ingenious, evolutionary strategy to ensure the survival of the Surinam offspring.
Green Anaconda
Forget Snakes On A Plane, we’re talking snakes in a lake!
If you thought snakes were just restricted to the land, you’re in for a shock (rivaling that of the electric eel).
The green anaconda is found in slow moving waterways and lakes of South America, from Columbia to Paraguay.
Unlike other snakes, the green anaconda is non-venomous. But this doesn’t mean it is any less frightening. To kill their prey, they coil their incredibly large body, sometimes exceeding 10 meters, around their prey and squeeze. This process is referred to as constriction.
They are one of the few predators of South America that targets other apex predators, such as caimans!
Green anacondas rely on the water not only to feed, but also to mate, where they form breeding balls of up to 12 males. The males coil around the female, wrestling other males for the chance to win mating rights with the female.
After 9 months, the female will give birth to live young.
Europe
Let’s check out the lake critters of Europe!
White-Clawed Crayfish
Not to be confused with the non-native, invasive signal crayfish from North America, the white-clawed crayfish is an endangered crustacean of European waterways.
Found in clean, unpolluted rivers and lakes, the white-clawed crayfish has a bronze body with pale cream undersides on its claws.
They are omnivorous, feeding on a wider variety of plant and animal matter.
However, they are in serious decline.
One of their biggest threats comes from the introduction of the bigger, more aggressive signal crayfish. Not only can the signal crayfish outcompete the white-clawed crayfish on resources, such as food and space, but it has also spread the crayfish plague, in which the white-clawed crayfish has no natural immunity.
Fortunately, the white clawed crayfish is now a protected species, and many organizations are working on the removal of the non-native signal crayfish.
Grey Heron
The grey heron is a large wading bird found across much of Europe, Africa, and Asia.
They can be found near almost any water source, including lakes and ponds, where they prey on a range of aquatic and semi-aquatic animals, such as fish, amphibians, mammals, and other birds.
The grey heron is an ambush hunter, slowing stalking areas of still water. With its long legs and neck, it can swoop down and pluck any unsuspecting victim from the water below.
Grey herons will nest in large trees close to hunting grounds. Nests, known as heronries, can be used for many generations. With every additional year used, the nest of a grey heron can grow substantially and house between 2 – 5 chicks.
Water Vole
All rats are rodents, but not all rodents are rats.
This is especially the case for the water vole.
Although strikingly similar to a brown rat, there are some obvious differences – both physically and physiologically.
For starters, unlike a rat, water voles have furry tails, small ears, and a rounded nose. In contrast, rats have naked tails, with large ears and an elongated snout.
Unlike rats, water voles are becoming increasingly rare. In their native range of Europe, they are threatened with extinction due to predation by the introduced American mink and habitat degradation.
Water voles are a semi aquatic rodent, found around lakes and riverbanks. They require areas with lush riparian habitats, in which they forage for a wide variety of plants, as well as dig burrows.
Great Cormorant
Once considered just a coastal bird, the great cormorant can now be found in most inland water sources – from estuaries to lakes – in Europe.
Cormorants are large, almost reptilian-looking birds, that can be found perching on lake-side outcrops, with their wings extended outwards. They display this behavior after diving underwater in search of prey to dry out their feathers.
However, they also display this behavior to aid with prey consumption. The stretched out motion of the wings and snake-like neck allows the gullet to open fully and the prey to be swallowed head first.
Cormorants hunt in an array of habitats, including lakes, and typically seek out fish between 5cm – 15cm in length. They will also travel vast distances, by flying close to the water surface, in search of other prey species, such as mollusks and crustaceans.
Cormorants are a species of bird that can walk, swim and fly. They can swim at depths of up to 30 meters.
Great Crested Newt
Whoever said dragons aren’t real has obviously never seen a great crested newt.
Granted, they can’t breathe fire. Nor do they have thick, scaly skin. They don’t even have big, sharp teeth.
But, with just the right amount of imagination, the great crested newt could pass as a miniature dragon. Right?
Like all amphibians, great crested newts breed in lakes and ponds. During the spring breeding months, males develop an intimidating, albeit impressive, crest along their back. Of course, the bigger the crest, the higher likelihood a female will choose a male to mate with. Size is everything in the newt world.
A female will lay up to 300 eggs which, after around 21 days, hatch into ferocious, nocturnal killing machines, gobbling up anything small enough.
At over 7 inches long, the great crested newt is the largest newt species on the European continent. Despite their large size, they are one of the most endangered newt species, due to habitat loss and intensive agricultural practices. They are, however, now largely protected across Europe.
Tisza Mayfly
At just under 5 inches, the Tisza mayfly is one of Europe’s largest mayfly species.
Named after the Tisza River, an economically important river flowing through Central and Eastern Europe, this mayfly species will spend its entire life around rivers and lakes.
In early summer, after spending many years on the river or lake floor, a mass hatching event occurs. Many millions of mayflies erupt from the water, forming a smoke-like swarm.
This is the beginning of the breeding frenzy.
Females fly into the dense swarm of males. Using its elongated front legs, a male mayfly will pluck out a female mayfly and mate with her mid-air.
After copulation, the female will fly close to the water’s surface, dipping her abdomen just under the surface to release her eggs. Whilst the female is quickly preyed upon by other aquatic life, her developing brood sink onto the substrate below and continue developing until the cycle begins again.
Most adult mayflies have an incredibly short lifespan – no more than 24 hours. But hey, their one job in life is to pass on genetic material. So, whilst some say mayflies lead a short life, I say they lead an efficient one.
Unfortunately, due to the pollution of lakes and rivers, mayfly populations are crashing drastically. This is having knock-on effects on the wider food chain that rely on the mayflies as a source of food.
Africa
Of course, we have to explore the incredible animals on the African continent!
Hippopotamus
Did you know, there are two species of hippo found on the African continent: the pygmy hippo and the common hippo.
Whilst the pygmy hippo is cool, and deserves a title of its own, we’re going to focus on the common hippo.
Weighing just under 4,000kg, the common hippo is the second heaviest land animal, after the elephant.
However, the term “land animal” is used loosely here. During the day, a hippo will spend most of its time (up to 16 hours) submerged in rivers and lakes or wallowing in the cooling mud pits. Come nightfall, the hippo leaves the lake and forages on land.
Now, although semi-aquatic, hippos cannot swim. Instead, they rely on a series of underwater leaps and prances to propel themselves along. Despite their cumbersome bodies, a hippo can move with surprising speed and agility, due to their buoyant fat and lightweight bone structure.
Elegant imagery aside, hippos are one of the most dangerous animals in Africa, killing more people than lions and crocodiles combined. They are fiercely territorial and you most certainly do not want to mess with one.
Barbel
Being a hippo is exhausting work. A constant battle of feeding and sleeping. A hard life.
Sometimes, all a hippo needs is a bit of relaxation and down time.
A hippo spa, if you will.
Well, that’s where our next lake-residing specialist comes in: the barbel.
Trailing behind a bloat of hippos, shoals of barbels can be found. Whilst on the move, barbels feast upon the excessive quantities of nutrient-rich poop hippos produce.
But that’s just for starters.
Once the hippos have come to a halt, the real banquette begins. Using their sucker-like mouth, the barbels move over the hippos bodies, ridding the large mammal of dead skin and parasites, such as lice and ticks.
After, in a true symbiosis fashion, the hippos open their mouths for the barbel to clean any leftover food and parasites stuck in between their large teeth and tongue.
The barbel are the three in one healthcare specialists of the African lakes: waste removal, skin rejuvenation, and dental hygiene.
Sign me up.
Big Mouth Hap Cichlid
The world is a dangerous place. Lakes especially so.
Predators lurk just about everywhere, waiting to snap up anything small enough.
And baby cichlids are the perfect snack.
The big mouth hap is a species of cichlid endemic to Lake Malawi, East Africa. It is found nowhere else on Earth.
However, over 800 other cichlid species call Lake Malawi home. Cichlids that would love nothing more than to devour the young of other cichlids.
So, with one big gulp, the mother’s big mouth hap scoops all her offspring into her oversized mouth. But she’s not swallowing them. Instead, she keeps her brood in her mouth and out of reach of potential predators, in a process referred to as “mouth brooding”. Her offspring will stay here for up to 6 weeks.
Shoebill
When we think of birds, we think of grace and elegance.
But not the shoebill.
This prehistoric wading bird stands 1.5 meters tall. It has a dinosaur-like quality about it; menacing and dominating.
Their large, foot-long bill ends in a sharp hook – a specialized adaptation to help it catch their slippery prey of lungfish, eels, and snakes.
Oftentimes, the shoebill will lay two eggs. However, there is a dark side to this strategy.
Rearing chicks is energetically costly. So, to maximize efficiency, the shoebills will allocate all their resources to the stronger of the two chicks (normally the first hatched). This leaves the second, insurance chick, to fend for itself.
Without the care of its mother, a fledgling shoebill will most likely perish.
Lesser Flamingo
Now, despite its name, this is a bird of true regal glamour.
The smallest of all six flamingo species, the lesser flamingo can be found in much of Africa – from Senegal to South Africa, and everywhere in between. However, they have a preference for the salty lakes of the Eastern Rift Valley.
During the breeding season of October – February, as many as 1,000,000 individuals flock together to mate. They are the most numerous of the flamingo species.
But, let’s get to the nitty gritty.
Why do flamingos stand on one leg? And why are flamingos so flamboyantly pink?
Firstly, it is thought flamingos stand on one leg to conserve body heat. Even in Africa, the temperatures can get particularly cold, especially at night, and flamingos can regulate their internal temperatures by keeping one leg out of the water.
And the pinkness?
Well, this is caused by the diet they eat. In the lakes they call homes, the lesser flamingo consumes copious amounts of brine shrimp and pink algae, both of which are high in carotenoids (natural red and yellow pigments). The body of the flamingo is able to synthesize these pigments and, voila, feathers turn pink.
Lake Oku Clawed Frog
Another endemic one for you.
This time, we’re heading to the small crater lake of Lake Oku, in Northwest Cameroon.
Here, the Lake Oku clawed frog can be found.
This small, critically endangered amphibian is a fully-aquatic frog species, thought to never leave the water.
They get their name from the small claws at the back of their hind feet.
A frog with claws?! Has the world gone mad?
Well, they use these claws for multiple purposes.
Firstly, these small frogs are carnivorous scavengers. They prey upon small fish and crustaceans within Lake Oku, as well as dead organic matter. The claws help the frog tear up food into smaller, bite sized pieces.
Secondly, the claws are used as an anti-predator defense mechanism. Not only do they appear intimidating to potential predators, but they can also deliver a nasty scratch. No easy meal.
Asia
It’s time to move to Asia and it’s lake critters!
Labyrinth Fish
Now, there isn’t a particular species of fish called the labyrinth fish.
Rather, it is a collective term for fish with a labyrinth organ – a specialized organ that allows fish to breathe in air. The most common of these fish are betta fish and gouramis.
But why do these fish possess such an organ?
Labyrinth fish can be found in freshwater lakes in Asia. However, these are often oxygen-poor bodies of water. To compensate, a labyrinth fish can take a gulp of fresh air and pump oxygen over blood vessels just above the gills.
Males also take in air when they construct their nests. Referred to as “bubble builders”, males build and guard a nest of floating bubbles to provide a source of oxygen to their developing offspring.
Baikal Seal
Lake Baikal, found in Asia, has many attributes.
It is the deepest lake in the world, reaching depths of 1,600 meters.
It is also the world’s oldest lake, thought to have formed over 30 million years ago.
Lake Baikal is also home to the world’s only freshwater seal: the Baikal seal.
The Baikal seal is one of the smallest pinniped species in the world, measuring under 1.4 meters in length.
This freshwater seal can spend up to an hour under the lake ice hunting for the Baikal oilfish, another endemic species of Lake Baikal. These fish can be found at depths of up to 150 meters. However, the seal can dive to depths of up to 300 meters, owing to their incredible ability to store excess oxygen in their blood.
Fishing Cat
Most cats refuse to go anywhere near water.
But not the fishing cat.
Found around lakes, especially oxbow lakes, and wetlands of South and Southeast Asia, the fishing cat is a nocturnal, ambush hunter.
The fishing cat is an excellent swimmer and diver, regularly swimming underwater to pursue their prey – most of which consists of fish. They have also been known to prey upon water birds, amphibians, and reptiles.
Being a semi-aquatic species of feline, they have a few nifty evolutionary advantages that enable them to excel in this ecological niche.
Firstly, the paws of the fishing cat are partially webbed. This allows them to propel themselves in the water.
They also have two layers of fur. The first layer, packed close to the skin, is incredibly dense. Water cannot penetrate this layer, keeping the cat dry when swimming. The second, longer layer of fur, further insulates the fishing cat.
Yangtze Giant Softshell Turtle
The rarest reptile you’ve properly never heard of.
Not only is it the largest freshwater turtle in the world, but it is also the most endangered, with just two individuals remaining.
Found in Lake Tai and the Yangtze River in South-eastern China and Vietnam, the Yangtze giant softshell turtle has been persecuted for centuries for its meat and eggs. Pollution and habitat loss are also serious threats.
What’s more, the last known female has reportedly been found dead via an unknown cause. Could we be watching an extinction unfold before our very eyes?
The illusive aquatic behavior of this turtle makes it hard to observe in the wild. During the day, it spends most of its time submerged motionless within the murky waters. The only time it comes out of the water is to lay eggs and breathe, using their pig-like snout.
Bronze-Winged Jacana
Found on lakes across South and Southeast Asia, the bronze-winged jacana is a species of rail bird.
Similar to coots and other rail species, the bronze winged jacana uses floating vegetation, such as water lilies, to forage and escape predators. Their long legs and toes help evenly distribute their weight, preventing them from sinking through the aquatic vegetation.
Female jacanas are polyandrous – this means they have many male partners. A female jacana can have up to four males in her group, or hareem, and females compete fiercely with other females to maintain their male hareem.
Unlike most bird species, males incubate the eggs and raise jacana chicks. When threatened, a male will take the chicks under his wing. Quite literally. The end result looks like a many-legged monster, with spindly appendages extending from all sides.
Oceania
Finally, we have Oceania!
Platypus
What has a bill like a duck, venom like a snake, webbed feet like an otter, lays eggs like a bird, and a tail like a beaver?
No, it’s not Frankenstein’s monster.
It is, in fact, a platypus; a rather unusual and unique mammal found in lakes across Eastern Australia and Tasmania.
Like sharks, the platypus uses electroreception. Thousands of electroreceptors can be found in the bill which can pick up electrical signals from its prey, much of which is buried in the underwater mud.
The platypus is also one of the world’s only venomous animals. The males have a sharp spur on their hind foot, which is connected to a venom gland. These spurs are mostly used in self-defense and the venom can cause excruciating pain, comparable to being stung by hundreds of hornets.
Another unusual trait among these primitive mammals is their ability to lay eggs. Females construct specialized nursery burrows where two small, leathery eggs will be laid. Platypus pups, or puggles, break through this leathery egg casing with the help of the egg tooth.
Australian Lungfish
From one primitive animal to another, the Australian lungfish is one of six extant lungfish species and is endemic to the lakes and waterways of South-eastern Queensland.
Dubbed a living fossil, the Australian lungfish has remained largely unchanged for over 100 million years. What’s more, it is thought that the Australian lungfish is one of the oldest living freshwater fish species, reaching ages in excess of 100 years.
They get their name from their ability to breathe in air. By swimming to the surface, they can swallow air into a single dorsal lung. This organ is used much like our own – to supply oxygen into their bodies.
Australian lungfish do have gills and only rely on air breathing in times of hardships, such as droughts or deoxygenated water sources (much like the labyrinth fish).
Freshwater Crocodile
Everyone’s heard of the saltwater crocodile.
But have you heard about its smaller cousin, the freshwater crocodile?
Despite being smaller than saltwater crocs, freshwater crocs can still grow to considerable lengths of up to 2.5 meters.
They can be found in lakes and rivers in Northern Australia. Although they can tolerate saltwater, they tend to keep away from the habitat of their salt-loving cousins, due to their larger size and aggressive nature.
Despite their large size, they stick to a diet of mostly invertebrates and small vertebrates, such as amphibians, birds, and other reptiles.
However, this diet is proving to be their downfall.
The cane toad is an introduced and invasive amphibian that has spread across much of Australia. These toads secrete a toxic milky substance which, if ingested, can cause high fatality rates in a wide range of species – including freshwater crocodiles.
Brolga
Unless you are from Australia or New Guinea, you’d be forgiven if you’ve never heard of the brolga.
Also known as the Australian crane, the brolga belongs to the crane family. It is a tall wetland bird, reaching heights of 1.4 meters. The brolga has long legs and a snake-like neck, much like a heron, ending with a sharp, pointed beak.
They use these powerful beaks to uproot vegetation, looking for invertebrates or vegetation. They also eat reptiles and amphibians.
Brolgas are monogamous, mating with just a single partner their entire life. To attract a mate, the brolga undergoes a rigorous dance routine, involving a series of jumps, stretches, bowing, and strutting. A typical night out.
Keelback
The keelback is a semi-aquatic, non-venomous snake found across much of Australia.
A non-venomous snake in Australia? Practically unheard of.
As the keelback contains no venom, nor does it use constriction to suffocate prey, they often eat their prey of small vertebrates, such as amphibians and lizards, live and whole.
The keelback can be found in wet or moist habitats, close to lakes or swamps. At dusk, they can be seen swimming through the water column of a lake in search of food and shelter.
Incredibly, the keelback is one of the few Australian species that can successfully eat the invasive cane toad, making them an important part of the ecosystem.
Giant Water Spider
It wouldn’t be right to talk about Oceania and not talk about spiders.
And, as one of Australia’s largest spiders, with a legspan of around 18cm, the giant water spider deserves a spot on the list.
The giant water spider is mostly nocturnal, hunting small fish, tadpoles, and aquatic insects in small lakes and ponds across Australia.
Aided by water surface tension, and small hairs on their legs, these semi-aquatic predators are able to walk on the surface of the water.
Not only can they walk on water, they can successfully dive underwater and stay submerged for up to 30 minutes.
No, they don’t have gills. Instead, the same tiny hairs that support them on the water can help trap air pockets, giving the spider a fresh supply of oxygen whilst underwater.
There’s just no escape from spiders in Australia.
Final Thoughts
An astonishing array of species, from every animal class, can be found in and around freshwater lakes across planet Earth.
Lakes are some of the most biologically diverse places on planet Earth, with many endemic species calling these aquatic environments home.
Unfortunately, many of these species are at risk. Pollution, habitat loss, invasive species, dam creation, and climate change are threatening the survival of animals that live in lakes.
The loss of any animal is a great loss, but there are some that will have dire consequences on the wider ecosystem. The beaver, for example, can alter an ecosystem to increase biodiversity – and not just lake biodiversity.
We need to actively conserve these important habitats, not just for our own supply of freshwater, but for the wider ecosystem and the benefits we reap from lakes.
