Whether looking at animals in the wild or watching viral videos online, you may have noticed some creatures have a penchant for standing on their hind legs. This curious behavior captures our imagination, leaving us to wonder – why do some animals stand up?
If you’re short on time, here’s a quick answer: Animals stand up for a variety of reasons, usually related to seeing their surroundings more clearly, reaching food sources, maintaining balance, or even communicating.
In this comprehensive guide, we’ll explore over a dozen animals that commonly stand upright, discussing unique reasons certain creatures assume this bipedal stance as well as what capabilities allow them to do so.
Anatomical Adaptations for Standing
Strong Hind Limbs and Flexible Ankles
Animals that stand upright have evolved powerful hind limbs and flexible ankles to support their body weight. For instance, kangaroos have enlarged hind limbs with long feet and thick Achilles tendons that act like springs, allowing them to hop bipedally.
Their ankles can rotate more than 180 degrees, providing the flexibility needed for jumping. Other animals like bears and gorillas have short, robust hind limbs and broad feet to distribute their massive weight.
Anatomical analysis shows their ankle bones are shaped to lock the foot in place while standing, providing rigid support.
A Balancing Counterweight
To balance upright, animals have evolved heavy upper bodies and tails as counterweights. Take the kangaroo – its muscular tail is so heavy it acts as a third leg when balanced on its hind legs. Lizards like the basilisk have enlarged upper bodies and tails up to 60% of their total body length, shifting their center of gravity rearward.
This counterweight lets them run upright on water! Bipeds like ostriches and penguins also have thick, heavy bodies to keep them stable. Their lower center of gravity and wide stance help resist forces that could tip them over.
Pretty amazing that nature has engineered such effective counterweights for balance.
An S-Shaped Spine
The S-shaped spine is key for animals that stand upright. Humans, bears, and kangaroos all have a spine gently curved in an S shape, which functions as a shock absorber. The curves distribute weight evenly across the vertebrae, preventing excessive forces from damaging the spine.
At the same time, the S-shape stores elastic energy with each step like a spring, reducing the work needed for walking and standing. Researchers believe the S-spine evolved independently in diverse lineages as a biomechanical solution for supporting an upright body on the hind limbs.
It’s one of the defining features quadrupedal mammals retained as they adapted to bipedalism and standing.
Seeing and Reaching
Gaining a Wider View
Many animals that stand up have evolved the ability to do so in order to gain a wider view of their surroundings. This allows them to spot potential predators from further away, giving them more time to escape or prepare to defend themselves.
It also lets them scan a larger area when foraging for food, improving their chances of finding scattered resources.
Giraffes are a prime example of this benefit. Their incredibly long necks allow them to feed from tall trees that shorter herbivores cannot reach. More importantly, their elevated vantage point enables them to keep watch over the open savannahs where they live.
Even when standing among bushes and trees, giraffes can see over most obstacles near them, vigilantly monitoring for lions and other threats.
Large birds like ostriches and emus also use their height to their advantage. Their upright stance gives them a panoramic view while walking or running through grasslands and open forests. This allows them to spot predators like big cats trying to ambush them from a greater distance.
Many bird species will perch atop trees or high points and stand upright to get a better lay of the land.
Accessing Heightened Food Sources
Another key benefit of standing up for animals is the ability to access food sources at greater heights. As mentioned, giraffes are the quintessential example of this. Their extreme stature enables them to reach leaves, flowers, and fruits located near the tops of acacia trees and other lofty vegetation.
Other long-necked herbivores like camels and bison also stand upright to graze leaves from branches several feet off the ground.
Large primates like gorillas and orangutans stand upright both for better visibility and to gather food in treetops. Their dexterous hands help them climb and forage in fruit trees. Gripping branches with their feet, they can stand fully upright and reach for succulent fruits.
Orangutans have even been observed using sticks to poke down fruit from overhead branches while standing.
Even smaller animals stand upright to reach food, though often only briefly. Squirrels and some birds like parrots will stand on their hind legs to reach nuts or fruit above them. Kangaroo rats also hop upright to reach and prune higher seed pods and vegetation.
Though limited in duration, this upright stance still helps numerous species access food that would otherwise be out of reach.
So by standing upright, animals from giraffes to squirrels gain access to expanded food sources unavailable to them when lower to the ground. This provides an advantage over more horizontally oriented creatures in environments where food tends to be stratified vertically.
It’s an excellent example of how diverse species have evolved for better survival in their ecological niches.
Specific Animals That Stand
Bears
Bears often stand on their hind legs to get a better view of their surroundings. They can stand bipedally for extended periods of time to spot food, detect threats, or interact with other bears. According to a 2021 study by Yellowstone National Park (source), brown and black bears were observed standing for an average of 42 seconds at a time, with the longest standing time being just over 2 minutes.
Primates
Most primates have the ability to stand bipedally for at least short periods. Chimpanzees often stand upright when they need to reach food high up in trees. A 2020 study by Harvard University (source) used 3D motion capture to analyze upright walking in chimps, finding that despite some limitations, they are proficient at bipedal standing and walking.
Kangaroos and Wallabies
As marsupials, kangaroos and wallabies are well-adapted for hopping and standing on their muscular hind legs. Their long, thick tails provide balance as they stand upright. Both species spend more time on all fours when grazing, but quickly stand up to box, interact with others, survey their surroundings, or hop to a new location.
According to the San Diego Zoo (source), red kangaroos can reach speeds of over 35 miles per hour for short bursts thanks to their powerful hind legs.
Prairie Dogs
Prairie dogs stand on their hind legs to keep a look out for predators while others feed. They make high-pitched alarm calls to warn the colony about threats like hawks, coyotes, or wandering humans. According to the National Wildlife Federation (source), prairie dogs can see long distances and spot predators even when low to the ground in their burrows.
Squirrels
Tree squirrels like eastern gray squirrels commonly stand upright to survey their surroundings and search for food. As reported by the publication Treehugger (source), they may flick their tails or make other signals while standing to communicate with other squirrels.
The ability to stand on their hind legs gives squirrels better vision and hearing to help them watch for predators and rivals encroaching on their territory.
Birds
Many birds stand on one or both legs, often tucking the unused leg up against their bodies. According to a 2022 study from the University of Queensland (source), birds may stand on one leg to conserve heat and regulate body temperature.
The study found that storks and pelicans face their lifted leg towards the sun, exposing their unfeathered legs and feet to solar radiation to cool off in hot weather.
Conclusion
In examining these upright species, we gain appreciation for the diversity of the animal kingdom. Each creature has evolved specialized adaptations allowing bipedal stances useful for survival needs like spotting predators or foraging above ground.
While some animals merely hop up briefly, others can walk and run on two feet. Whatever their purpose, seeing animals stand on hind legs continues to fill us with a sense of wonder.
