Have you ever done a headstand, hung upside down from the monkey bars, or inverted your body for some other reason? Chances are, you could only stay in this position for so long before the pressure got intense in your head and it felt like you were having trouble breathing.
While humans can tolerate being upside down for some time, we just don’t have the evolutionary traits to stop our blood pressure from rising and all our organs from pressing into our lungs. But there are some animals out there that do.
So, which animals live upside down?
Animals that live upside down include upside-down jellyfish, sloths, horseshoe crabs, bats, and some spiders. Some animals like nuthatches and the spiny bush viper forage and hunt upside down, respectively. Additionally, manatees, sloths, and bats sleep upside down. Finally, there’s an entire ecosystem of upside down animals in the Antarctic.
Below, we’ll take a closer look at animals that live upside down and the traits that their species have that make them capable of doing that. I’ll also talk a little about why they need to be able to hang out upside down in the first place.
8 Animals That Live Upside Down
So, let’s discover together the animals that live upside down!
1. Upside Down Jellyfish
The upside down jellyfish lives in areas with sheltered water like lakes, estuaries, and mangrove forests. Instead of floating freely through the water like you’d expect from a jellyfish, their bell is flat on the top and they sit on the water’s floor, letting their arms float upward toward the sun.
Upside down jellyfish don’t make a lot of effort when it comes to eating. They sustain themselves using a symbiotic relationship with algae that grows on their arms. The algae get a place to live, while the jellyfish eats byproducts from the algae growing.
Algae is able to grow even at the bottom of lakes because the arms stretch upward toward the sun, allowing the algae to photosynthesize and produce the food that the jellyfish needs. The algae produce about 90% of the jellyfish’ food intake, while the other 10% comes from zooplankton floating by.
Even though this jellyfish spends a lot of time just lounging around on the sea floor, they are also capable of swimming. They move by contracting their bell like other jellyfish.
Unlike other birds, nuthatches spend a lot of their lives upside down. They can often be found foraging as they move downward on tree trunks, which is much different than other birds in the area.
While there’s no confirmed scientific reason for a nuthatch’s behavior, it’s believed this evolved trait helps them compete with birds like the Eurasian tree creeper and red-headed woodpecker that also forage in the area. As time went on, the nuthatches that were capable of foraging upside down were more likely to survive and produce offspring.
Since nuthatches move downward, they end up foraging from a different angle. This lets them see food that other birds usually overlook.
Nuthatches store food that is less likely to be eaten by other birds for the same reason. While it would be possible for other birds to fly and forage from the same angle, it takes a lot more energy to fly while eating than to grasp onto a tree trunk.
Nuthatches are able to move and forage down a tree because of the big toe called the hallux on the back of their feet that helps them grip the tree trunk. They also have three smaller toes on the front of their foot. Plus, nuthatches have a big food compared to their small body, so their feet are really strong.
Sloths are one of the few animals in the animal kingdom that spend most of their lives hanging upside down in trees. The reason that sloths spend so much time upside down is because their brown color helps them blend into the trees while they keep a watchful eye out for predators.
The reason sloths live upside down comes down to their diet. Sloths primarily eat leaves, twigs, and buds from trees. These foods digest pretty slowly, especially when you consider that a sloth has an incredibly slow metabolism. This is the reason they move so slowly.
Sloths are a mammal like humans, however, their insides are a little different than ours. They have developed adhesion that hold things like their liver, intestines, and other organs in place when they are inverted. This is important because their organs don’t push into their lungs when they are upside down, so sloths are able to breathe.
Additionally, with sloths, these adhesions are especially important because their slow metabolism means that they hold their waste in for a long period of time. This also means that their digestive tract is especially heavy- it’s estimated that a sloth’s digestive organs and the waste in its body make up a third of the sloth’s total weight.
4. Horseshoe Crabs
The horseshoe crab doesn’t spend its entire life upside down, but it often floats upside down when it wants to navigate waves and travel across the water. Horseshoe crabs are able to travel both ways because of the shape of their shell and how water current flows with it- similar to the way wind moves an airplane.
When horseshoe crabs are feet-side down, the water moves up and over their shell. The flow of the water weighs them down enough that they stay on the floor of coastal areas where they call home, but it’s not so heavy that they can’t walk across the ocean floor.
Horseshoe crabs can also flip themselves over to travel across the top of the water. When they flip over, the same dynamics that keep them on the ocean floor give them upward momentum.
Horseshoe crabs keep moving upward until they flip back over and can even move with the waves. Their buoyancy and fluid dynamics serve the purpose of letting them swim while expending less energy.
While horseshoe crabs seem like a simple species, they have some amazing healing abilities that humans are still trying to fully understand.
The mighty manatee spends around 12 hours of each day asleep, so it spends about half of its time upside down. Manatees sleep upside down because it’s important that they get to the surface of the water as quickly as possible when they run out of air.
Even with a large lung capacity, manatees have to return to the surface around three times per hour when they are sleeping. Their respiratory rate also slows during this time, so they aren’t using as much oxygen.
Like many other maritime mammals, manatees engage in unihemispheric sleep. This means that their brain function is essentially halved, as one side of their brain rests and the other keeps the manatee moving to the surface for air.
Bats are one of those creatures that have evolved a LOT when you compare modern-day bats to their ancestors. Ancestral bats could walk on their feet. While bats today cannot do this, being unable to walk does make their bodies lighter and better adapted to flying.
Bat ancestors ate a lot of insects and they’d catch them by waiting for them to run up the bark of trees. Instead of trying to run up the tree faster than an insect, they’d wait while hanging upside down for something to run up the tree trunk. This tendency to hang out upside down is something that has been passed down to modern-day bats.
Bats sleep upside down because of tendons that make their legs and knees lock while they are hanging. By grasping with their feet, they can use the weight of their body to hang upside down almost effortlessly.
The only time bats aren’t hanging upside down is when they’re flying around looking for something to eat. They roost upside down, hibernate upside down, and even retire to their roosting spot and hang upside down when it’s time for them to die.
7. Certain Species of Spider
There are a LOT of different spider species out there and there have already been around 50,000 identified by scientists, so I’m not going to list all the species of spider out here that prefer living upside down.
Some honorable mentions include the cellar spider (Daddy long legs), cobweb spiders (including the Black Window), and orb weavers.
Those spider species that do hang out all day long have much longer legs than spiders that move across the ground because those spiders on the ground need stability when they walk.
For spiders with longer legs, it’s more energy efficient to move upside down instead of walking on the ground.
Often, these spiders also have pendulum-shaped bodies. Much like a pendulum moves back and forth because of gravity, these types of spiders take advantage of their shape and swing through webs, trees, rafters, and whatever else is in their natural habitat using gravity. This limits how much energy they have to expend.
Energy expenditure aside, spiders like orb weavers also hang out upside down because of their hunting style. Since they move quicker while moving down their web than up, they hang out facing downward so they can act quickly when something flies into their web.
8. Spiny Bush Viper
The spiny bush viper has a prehensile tail that helps it hang from trees, so it uses this to its advantage while on the hunt. They grip the tree and then drop down onto prey below. There are also some semi-aquatic snakes that hang from trees and then drop to the water below.
There are also other reptiles that can hang upside down like skinks and chameleons. However, they don’t hang out for an extended period of time because of the pressure it puts on their internal organs.
The Upside Down Ecosystem in the Antarctic
Researchers stumbled upon an entire ecosystem of aquatic animals living upside down in the Antarctic around 2010 while testing the limits of an underwater robot. This ecosystem was living under a sheet of ice in Antarctica and surprisingly, the entire ecosystem works upside down.
This ecosystem appeared to be dependent on sea anemones, which were positioned upside down in the ice. Between the tentacles that were poking up, there were worms, crustaceans, and even fish that looked like they were swimming upside down.
Unfortunately, there’s not a whole lot that is known about this ecosystem yet because of the location, plus it’s a relatively new discovery. It will definitely be interesting to see how the fish have adapted to live in this particular area in the ice and what is responsible for their upside down movement.
Which Animals Sleep Upside Down?
There are not a lot of animals that sleep upside down because there’s no real purpose for it. That being said, sloths, bats, and manatees are all known to rest upside down.
Bats roost upside down by using the weight of gravity and locking their legs into place, while slots use their curved toes to hold onto branches to sleep. Manatees also sleep upside down, which kind of looks like them laying on their back.
Which Animals Sleep Upside Down With Their Tail?
There are several animals that don’t necessarily live upside down, but they do sleep upside down. Others spend their time resting upside down at night and hunting upside down during the day.
For an animal to be able to sleep upside down, it has to be able to hang onto the branches without expending a lot of energy. Animals that sleep upside down often have a prehensile tail that securely wraps around branches so they can hang easily. This also lets them use their feet freely if they hang during the day.
With that being said, there actually aren’t any animals that sleep upside down using their tail. Most animals you see hanging from their tails in trees do so during the day and retire to a den or other home at night.
Which Animals Sleep Upside Down in Trees?
Of the three animals I mentioned earlier that sleep upside down, bats and sloths sleep upside down in trees. However, bats do not sleep exclusively in trees and also may be found in caves, buildings, and rock crevices. They’re especially likely to be found near places that have a water source like a nearby pond.
Contrary to what many people believe, the opossum doesn’t actually sleep upside down in trees. You’re more likely to see an opossum hanging upside down during the daytime when it wants use of all four feet. Additionally, opossums lose the ability to hold themselves up using their tail when they get older and overweight.
How Do Mammals That Live Upside Down Like the Sloth Breathe?
If you’ve ever hung upside down for an extended period of time, then you might be wondering how these animals deal with all the pressure that comes from blood rushing to their head and all their organs pressing into their lungs and making it harder to breathe. However, animals that live upside down have quite a few features that differ from those of the average person or animal.
That’s not to say that other people and animals cannot tolerate being upside down at all. In fact, inversion tables are pretty commonly used to help align the spine by taking all pressure off your joints as a means to “reduce the effects of gravity on the spine”. However, inversion tables aren’t generally used for a long period of time because of the effects of being upside down on the human body.
You see, when you stay inverted for too long, all your heavier organs like your liver and intestines move upward (or technically downward) and push into your heart. Additionally, all the blood rushes to your head and it gets very hard for the heart to pump blood where it needs to go.
Animals like sloths that live upside down don’t have to worry about this same problem. Sloths actually have organs that are fixed in place because of adhesions that attach their insides to their body. This means that when they hang upside down, the weight of gravity isn’t putting all that extra strain on their lungs and heart.
Many animals in the world today have incredible adaptations, including those animals that live upside down. Critters like the sloth and bats spend a lot of their lives inverted, while creatures like the manatee only go upside down to sleep.
Critters like horseshoe crabs, upside down jellyfish, and certain species of spiders also spend a lot of time upside down. Nuthatches invert themselves to forage, while certain kinds of snakes hunt by hanging from tree branches and dropping onto prey below.
Hopefully, this article has provided some fun, interesting facts about all these upside down animals!