Have you ever noticed that some animals have really short arms compared to their body size? Animals like kangaroos, jerboas, pangolins, and squirrels are known for having tiny arms relative to their overall size. In this blog post, we’ll take a closer look at some of these short-armed creatures and try to understand why they evolved that way. Strap yourself in for a wild ride through the world of animals with hilariously small arms!
Kangaroo
One of the most famous short-armed animals is the kangaroo. When you think of a kangaroo, you probably imagine it hopping around on its powerful hind legs and thick tail. But have you noticed its arms are tiny in comparison? Kangaroos have arms so short they can barely reach their own head!
Kangaroos evolved short front limbs for a few key reasons. First, having small arms reduces their body weight, allowing them to hop faster and farther. The enormous strength of their hind legs and tail makes their arms less useful for locomotion. Their arms are just strong enough to grab food and groom their fur. Kangaroos have also adapted long thick tails that act as a third leg when they’re hopping around. The tail provides balance and extra propulsion with each hop.
Another theory is that kangaroos developed short arms over time as their hopping skills improved. Hopping on two legs is a more efficient way to travel at high speeds than running on four legs. As kangaroos adapted to hopping over millions of years, their front limbs became shorter and less robust. Their arms simply aren’t as necessary anymore, thanks to those super powerful hind legs!
Long Eared Jerboa
The long eared jerboa is a rodent found in the deserts of Mongolia and China. With ears over two-thirds the length of its body and teeny tiny front limbs, the jerboa looks downright hilarious! But don’t laugh too hard – those weird proportions are actually evolutionary adaptations that help the jerboa survive in its harsh desert habitat.
The massive ears of the long eared jerboa contain blood vessels that help regulate its body temperature and release excess heat. This helps keep the jerboa cool in the hot desert climate. The ears can also rotate independently to precisely locate sounds and detect predators. With hawks and foxes lurking about, those giant ears provide an early warning system!
As for the short arms, they evolved to aid the jerboa’s unique form of locomotion. Jerboas move by hopping on their long hind legs like a kangaroo, using their long tail for balance. This allows them to zip around quickly in the open desert. Their short forelimbs are used mainly for digging burrows and handling food. The tiny front paws provide little propulsion during hopping. So over time, the forelimbs of jerboas shrank in response to their hopping lifestyle.
Pangolin
Looking like a scaly anteater crossed with an artichoke, the pangolin is one of the most oddly shaped creatures in the animal kingdom. And have you noticed their teeny tiny arms? We humans may find their short limbs comical, but they serve an important purpose for the pangolin.
Pangolins use their long, sticky tongues to slurp up ants and termites from deep inside mounds and logs. The tongue can extend over 16 inches – longer than the pangolin’s entire body! After a juicy insect meal, pangolins curl into a tight ball to protect themselves from predators. Their scales overlap to form an armour-like covering over their body.
Given their specialised feeding and defensive techniques, pangolins don’t rely much on their forelimbs. They employ their arms mainly to rip open ant mounds and tear apart rotting logs while foraging. Otherwise the arms mostly just cling to the substrate as pangolins shuffle along awkwardly on their hind legs. So it makes sense that evolution led to reduced forelimb size.
In fact, pangolins spend most of their time walking on their hind legs and thick, muscular tail. The tail provides crucial balance and support as they search for their insect prey. Pangolins are a great example of how an animal’s unique lifestyle can influence the form and function of their limbs over evolutionary time.
Red Squirrel
The feisty red squirrel is known for its bushy tail, tremendous speed, and ceaseless energy. But have you noticed their forelimbs are rather small? Relative to their size, squirrels have some of the tiniest arms in the rodent kingdom!
The red squirrel’s stubby front limbs make sense when you consider how they spend their days. Squirrels rely primarily on their strong back legs for scrambling up trees, leaping through the canopy, and sprinting across the forest floor. In fact, they can zigzag between trees at speeds over 20 mph!
Meanwhile, the front paws are vital for grasping and manipulation tasks. Squirrels use their nimble forepaws to hold nuts and cones, peel back bark, hang upside down from branches, and much more. Shorter arms bring the paws in closer to the body, improving balance and control. This allows squirrels to perform amazing feats of acrobatics in the treetops.
Another theory is that over time, the muscles and bones in a squirrel’s forelimbs became reduced as they specialised in hind leg locomotion and paw dexterity. An ancestral squirrel millions of years ago may have had proportionally longer arms. But as its descendants became adapted to life in the trees, bounding across gaps and manipulating food with the front paws, forelimb length gradually decreased while the hind limbs remained robust.
Whatever the evolutionary reason, the squirrel’s tiny arms have become an important adaptation that suits its arboreal lifestyle. Those little T-rex arms allow the squirrel to dominate the treetops!
Up Next