With more than 100,000 plant and animal species, rivers abound with wildlife. Even fish living in these freshwater habitats are made up of hundreds of species.
The Mississippi River in the US, by itself, boasts more than one hundred species of fish.
That being said, fish are far from being the only animals living in rivers. Animals ranging from mammals to amphibians to reptiles to birds also call rivers home.
Below are 15 different types of animals that live in rivers. While some of these animals are widely known to inhabit rivers, others aren’t—and may just surprise you!
Table of Contents
1. American Alligators
Once an animal on the verge of extinction, the American alligator, thanks to state and federal laws and concerted efforts to preserve natural habitats, now thrives in the southeastern portion of the US, primarily in Louisiana and Florida.
When one looks at an American alligator’s armored, scale-covered body, impressive musculature, and clenching jaws, it should come as no surprise that they’re distantly related to the clade Dinosauria reptiles (popularly known as dinosaurs).
Although alligators are known to inhabit rivers, they can also be found in lakes, swamps, and marshes. Out of water, they can be quite heavy and clumsy.
After all, they range from 9 to 15 feet in length and can weigh around 1,000 pounds.
Under water, they’re expert swimmers, preying on fish, small mammals, and snakes. However, when hungry, an American alligator might be found preying on almost anything, including carcasses, domestic pets, and even humans.
When born, they’re known as hatchlings. These infants can be anywhere from 6 to 8 inches in length.
Due to their small size and vulnerable nature, juveniles are enticing prey for raccoons, bobcats, and birds, as well as other alligators, so they typically stay with their mothers for protection and survival for around two years.
2. Blue Crabs
Named due to its blue-colored claws, the blue crab is armed with a brownish shell, also referred to as a carapace. Unlike males, females have red-tipped pincers.
Blue crabs are among the most harvested animals on earth, coveted by humans worldwide for their sweet and tender meat. Even their scientific name (callinectes sapidus), which means “savory beautiful swimmer,” is a testament to this fact.
These freshwater omnivores can be found from the lagoons of Nova Scotia to the Gulf of Mexico. They can even be found as far down as Uruguay.
Closely related to the lobster and shrimp, the blue crab uses its prickly covering and pointer pincers to ward off predators.
Blue crabs aren’t picky eaters, feeding on virtually anything. Food for these creatures may include fish, plants, mussels, carcasses, and even other blue crabs.
Males can be as wide as 9 inches. With their paddle-shaped hind appendages, blue crabs make well-adapted swimmers.
They’re highly sensitive to changes in their habitats and the environment. Several of their populations, especially in the Chesapeake Bay in the eastern part of the US, have seen a dramatic decline in population.
This is bad news not only for blue crabs, but also for the ecosystems they live in because blue crabs play an important role in controlling the populations of the species they often prey on.
Because of the detrimental effects of overharvesting, regulations have been put in place to ensure that blue crabs remain a thriving species.
3. Amazon River Dolphins
Each spring, during heavy rainfall in South America, the famous Amazon River, along with its tributaries, begin to expand. Over the course of time, the Amazon Rainforest becomes flooded, resulting in a vast freshwater sea.
The Amazon river dolphin, also known as the boto, swims into this seasonal sea, which lasts for about half a year.
Just like their cousins inhabiting the ocean, botos wear the well-known dolphin smile, but, unlike their oceanic dolphin counterparts, they have characteristically long, skinny beaks and round, bulging noses.
Males can have a pinkish color, which is most likely scar tissue resulting from rough play or fighting over mates. The pinker their color, the more appealing the males are to the females.
This is especially true during mating season, which happens when the water has retreated and the dolphins are once again limited to the river channel.
To impress females, males sometimes hold their prey, such as turtles, up in the air or beat against the water with branches in their mouths.
Pregnancy lasts between 11 and 15 months for female botos. Young botos nurse for over a year, keeping close to their mothers for protection.
Botos, due to their flexible vertebrae, have the ability to easily maneuver between trees and through branches.
Their long snout also allows them to dig through river mud for prey, such as crustaceans, or swim through branches in search of fish.
They also benefit from echolocation, which helps them navigate through the dark water and locate their prey. The largest among the four species of dolphin, botos can grow as long as 8 feet and weigh as much as 450 pounds.
The only danger to Amazon river dolphins are humans, who harvest them for catfish bait or trap them by accident in gill nets.
There’s a traditional belief in the Amazon that the boto is a magical creature. The belief holds that boto can come ashore in human form wearing a hat to hide its blowhole.
4. American Eels
The American eel is a catadromous species, which means it lives in freshwater during its adult life before migrating to the ocean to spawn. Once it has spawned, the eel dies.
Humans are among the biggest threats to the American eel, harvesting this animal for both bait and food.
Most of the harvesting takes place along the Atlantic Coast, where eels are known to thrive, and then the eels are exported abroad.
Eel is rarely eaten in the US, but many countries in Asia and Europe treat the eel as a celebrated delicacy.
Due to overharvesting, the US and Canada have set regulations to manage the hunting of eels and restore their populations.
The American eel can be as long as 20 inches and weigh as much as 16 pounds.
Their young are born in the Sargasso Sea, hatching after about 2 to 3 weeks. The ocean currents carry the young until they get to the coastline. Afterwards, they swim upstream.
Throughout this whole process, the eel undergoes a series of transformations, and it takes them between 5 and 25 years to reach sexual maturity.
Adult American eels usually eat at night, feasting on small fish, worms, crustaceans, and mollusks.
5. Diving Bell Spiders
The diving bell spider, commonly known as the water spider, is different from most of its arachnid cousins because it spends the majority of its time under water.
What makes this creature even more interesting is the fact that it can stay under water for such long periods of time even though its body is like that of a normal terrestrial spider.
Interestingly, these spiders are so adept at being underwater that they only seldomly have to rise to the water’s surface for air.
Male water spiders (7.8 to 18.7 mm) are, on average, larger than females (7.8 to 13.1 mm). The larger the male’s body size, the better its mobility and, therefore, the better its chances of finding mates and prey.
On land, the water spider appears to have a dark velvet-colored abdomen, as well as a brown cephalothorax. However, under water, they look more silvery in appearance, and this is largely due to the air bubble surrounding their abdomen.
The hair on the spider’s abdomen allows it to capture air bubbles.
To create a “diving bell,” as the air bubble is often referred to, the spider rises to the surface, captures a bubble of air, hauls the bubble underwater, and releases it under a canopy-like cover.
This “canopy” is made of a silk sheet fastened between stems of water plants.
It’s inside this diving bell that the spider spends the majority of its time. The spider does almost everything in this sac, from eating to resting to reproducing, only coming up to the surface of the water to gulp air.
The males’ longer chelicera, longer front legs, and longer bodies give them an advantage over females when it comes to diving underwater.
Although the water spider’s bite is known for being painful to humans, it’s not believed to be particularly dangerous. The worst possible effects of the spider’s bite are fever or inflammation.
The water spider much prefers to prey on crustaceans as well as aquatic insects.
6. Red-Eared Slider Turtles
A popular household pet, the red-eared slider turtle is an animal that starts off very small but grows to a very large size over a long period of time.
Therefore, they need to live in larger habitats, areas in which they can freely and easily move around.
Although young sliders have a bright green shell, the color dulls as they get older. Instead of teeth, sliders have a beak made of keratin protein lying on top of their jawbones so they can rip apart and tear their food.
The carapace is the top portion of the shell, and the bottom part is the plastron. Both the carapace and the plastron are covered in scutes, which are bony plates with a keratin protein covering.
Sliders are social creatures that enjoy each other’s company. They’re also expert swimmers that spend the majority of their time underwater.
Male sliders can be distinguished from females with their smaller size, longer nails and tails, and curved plastrons, which help them during mating.
These turtles are omnivorous creatures with a palette for a wide variety of foods, including fruits, fishes, amphibians, and underwater vegetation and invertebrates.
7. Belted Crayfish
Physical features of the belted crayfish include its medium-small size and tan color overlaid by green and red bands on the animal’s abdomen.
There’s also a blackish band on the carapace, spanning the cervical groove (which separates the head and thorax). Another blackish band can be seen where the carapace and abdomen are joined together.
The crawfish’s pincers are narrow compared to those of other stream crawfish, but they aren’t exceptionally long.
Living in streams ranging from creeks to rivers, the belted crayfish prefers soft currents and coarse rock. During the daytime, this creature hides underneath rocks. It’s during the nighttime that it forages for food.
It cannot traverse land and, thus, is limited to certain river systems.
Although the crayfish is known to inhabit the Meramec River and Big River drainages in Missouri, it was recently introduced into the drainages of St. Francis River.
They’ve become particularly invasive in the St. Francis River drainages, where they’ve been feeding on and displacing organisms within that aquatic system.
A generally omnivorous creature, the belted crayfish enjoys feeding on many types of plants and animals.
At the same time, it’s a huge source of meat for humans, as well as many animals that live in or around water, including snakes, fish, turtles, raccoons, birds, and mink.
8. River Otters
Although river otters mostly inhabit areas around rivers, they’re also known to live near lakes and streams.
Playful animals that enjoy sliding down muddy hills during the summer and wrestling on snow and ice during the winter, river otters tend to live near water that’s bordered by woods and wetlands (e.g., marshes).
With their long, slender bodies, webbed hind feet, and strong tails, they’re excellent swimmers that can stay under water for as long as four minutes.
While under water, they keep their eyes and eyes shut to prevent water from entering.
As aquatic creatures, they often hunt under water, preying on fish, their primary food. Once they catch their prey, they drag them onto shore to feast on their bounty.
River otters spend a large portion of their time under water, but they do enjoy traveling across land too, oftentimes looking for a mate.
When they travel across land, they can be observed running a few steps before sliding on their bellies.
9. Brazos Water Snakes
Almost exclusively confined to the northern parts of the Brazos River drainage, the brazos water snake is recognized by the Texas Parks and Wildlife Department as a threatened species.
It’s also under the protection of Texas Parks and Wildlife Code.
The snake can be identified by its brown/gray or brown/green combination. It also has a checkerboard appearance, which, along with its pink or orange belly and yellow or cream-colored neck, make it hard to miss out in the wild.
The brazos water snake prefers living in water that has fast currents, rocky floors, and lots of vegetation. The snake tends to hide under rocks or among vegetation when it senses danger, and it also likes to inhabit rocky riffles.
It typically feeds on small fish, but it’s also been known to prey on a variety of animals, such as crayfish, frogs, and salamanders.
Due to the brazos water snake’s reclusive tendencies and the fact that it lives in a remote location, not much else is known about this species.
10. Chain Pickerel
The chain pickerel can be found anywhere from the St. Lawrence drainage in Canada all the way down to the state of Florida in the US.
It can also be spotted in the southern Mississippi drainage, as well as throughout the state of New Hampshire.
The fish’s torpedo-shaped body, huge mouth filled with sharp teeth, and large dorsal and anal fins give this species an advantage as hunters.
They like to actively prey on other species of fish, as well as frogs, snakes, ducklings, and muskrats. When hiding from predators, they take cover in aquatic vegetation, where they also like to spawn.
Although the chain pickerel grow quickly in size, they live for a relatively short time. Despite the chain pickerel’s aggressive nature, they’re easy for humans to harvest.
Due to their high numbers, the chain pickerel isn’t considered a threatened species, and there aren’t any conservation/management standards in place for this fish.
11. Blue Catfish
The blue catfish, which can be found in Ohio, Missouri, Mississippi, and the Rio Grande River basins, was introduced to Virginia during the 1970s and 1980s.
Since then, they’ve been listed as an invasive species in the Chesapeake Bay tributaries.
Due to their rare ability to “taste” what’s around them (with the help of sensory tissues), they make avid hunters.
Their wide-ranging diet includes clams, worms, crustaceans, insects, smaller fish, and frogs, but their diet changes by the season. During the spring, summer, and fall, the blue catfish prefers feeding on aquatic vegetation.
When attacked by bald eagles and osprey, blue catfish use their serrated spinal barbs to defend themselves. The spines contain glands that release toxins, which can infiltrate wounds on the predators’ bodies and cause a great deal of pain.
To avoid being preyed on, young blue catfish scour for food at night, rather than during the day, mainly eating zooplankton and tiny aquatic insects.
Males and females work closely together when giving birth to and raising their young. It’s the males that prepare the nest, and once that process is complete, they expel pheromones to attract and bring females to the nest.
Blue catfish reproduce rapidly, creating 4,000 to 8,000 eggs for every kilogram of body weight. When the eggs are finished being fertilized, the males drive the females away so they can be in charge of protecting the eggs.
Although both males and females play an active role in raising the young, it’s the males who serve as the primary caretakers.
Blue catfish live for an average of 9-10 years, but some have lived as long as 25 years.
12. River Frogs
Although similar in appearance to their bullfrog cousins, river frogs are fairly easy to distinguish by the light spots on their lips, especially on the lower jaw.
Males can be distinguished by their throats, which are more yellowish than females’. Females can be identified by their tympanum, which is either smaller than the eye or the same size.
Just like their green frog relatives, river frogs don’t have dorsolateral ridges, which are raised skin along the sides of a frog’s back.
Instead, river frogs have rougher and more wrinkled skin throughout their bodies, making them relatively easy to identify.
Tadpoles can be identified by their large size (they can reach a length of up to 5 inches) and black margin on their fin.
Unlike most other frogs that have large tadpoles, river frog tadpoles exhibit schooling behavior, which means they swim together.
Found throughout the Coastal Plain of the southeastern portion of the US, river frogs inhabit a wide variety of habitats, including swamps, creeks, and rivers.
Rather than scurry away or hide from their predators, these nocturnal creatures play dead or release an unpleasant odor whenever they sense danger.
Although river frogs are relatively common in Georgia’s southern Coastal Plain, they’re believed to have become extinct in North Carolina.
And it’s population continues to decline in the East. Habitat loss due to human activity is mostly to blame for this.
However, as of now, there are no state or federal laws in place to protect this species.
13. Eurasian Beavers
Once a widespread species in Great Britain and throughout Europe, the Eurasian beaver, also known as the European beaver, saw a massive decline in population in several countries for many years.
By the 16th century, it was already extinct in Britain and, in 1900, its population consisted of only 1,200 beavers.
Thankfully, the population has been partially restored, thanks to laws and efforts to protect this species and the reintroduction of this species to European countries like Scotland, France, Germany, and Austria.
In fact, the Scottish government formally recognized this creature as a native species in 2016.
Their distinctively broad, flat tail makes Eurasian beavers excellent swimmers and divers. They can dive for as long as 5 to 6 minutes and can also burrow into the bank.
If there are no banks for them to use, they build their own lodges using branches and soil.
They’re also known (perhaps most famously so) for building dams, developing floodplains that add protection to their lodge and make it easier for them to forage.
Their diet depends on the season. They feast on aquatic and herbaceous plants during the summer and eat bark during the winter.
Eurasian beavers also store wood for the winter by felling young trees during the autumn months of October and November.
In the past, humans extensively hunted the beavers for their meat, fur, and castoream. The beavers were also commonly attacked by wolves and lynx.
Now, their biggest threats are foxes and certain raptors, such as the white-tailed eagle.
14. Diving Ducks
There may be several diving duck species (e.g., canvasback, scaups, goldeneyes, and redheads), but they all have one special ability: they can dive well beneath the water’s surface and hunt and forage for food, using their feet to move underwater.
The unfortunate cost of their physical makeup, however, is that they’re awkward and ungainly on land. Therefore, these creatures spend most of their time in or on water.
Canvasbacks fly with rapid beats, making them, despite their heaviness, the fastest flyers among the diving duck family.
Their diet includes insects, fish, and aquatic plants.
While populations of certain duck species (such as canvasbacks and redheads) have oscillated throughout the years, scaups are in fairly high abundance.
This is, perhaps, due to the range of their breeding area, which includes 1.2 billion acres of boreal forest in Canada. Another possible contributing factor is that their foods, such as insects, crustaceans, mollusks, and aquatic plants and seeds, are widely available.
15. River Dragonflies
One would be hard-pressed to find a person who’s never heard of this four-winged insect known for its long, colorful body.
Dragonflies are usually sighted darting from one place to another or hovering over an area while they’re searching for prey.
Dragonflies are predatory, trapping other flying insects with their hairy legs. After capturing their prey, they feast using their powerful jaws, starting with the prey’s head.
Females lay their eggs by dropping them in the water or placing them in a plant near water. The larvae hatch out of their eggs about 10 days later.
The larvae spend several years underwater—for some species, up to 8 years. During this stage, they eat tadpoles, aquatic insects, and small fish even.
To escape from larger fish, their common predators, they forcefully squirt water from the ends of their abdomens, propelling them at a great speed away from the danger.
When the larva is ready to transition into adulthood, it stops eating and clutches firmly onto something. In a slow fashion, the adult dragonfly sheds itself of its outer skin. Then it unfurls its wings and, as the wings dry, the dragonfly rests.
Once the dragonfly feels rested and its wings are dry, it flies away in search of its first meal as an adult dragonfly.