Mammals
Long-eared Jerboa
Euchoreutes naso · also called long-eared jerboa
The long-eared jerboa is a desert rodent that looks assembled from spare parts: a body the size of a plum, back legs like a miniature kangaroo, a long tail with a flag on the end, and ears so large they seem to belong to a different animal. Those ears are the biggest of any mammal for its size, and it uses them to hunt insects in the dark of the Gobi.
Overview
The long-eared jerboa lives in the deserts of Mongolia and northern China, on sandy valley floors with sparse vegetation. Its body is only 7–9 cm long, with a 15–16 cm tufted tail, and it weighs about 24–38 g. The fur is sandy and pale, matching the ground.
The ears
Its ears are around 5 cm long — about a third longer than its head and roughly two-thirds of its body length — the greatest ear-to-body ratio known in any mammal. Large thin ears give it acute hearing for locating insect prey and detecting owls and foxes across open desert, and they also shed heat without costing water.
A two-legged life
The jerboa travels in kangaroo-like bounds on its long hind legs, front limbs tucked away, tail balancing and propping. It can swerve sharply mid-hop to catch a flying moth or dodge a predator. By day it shelters in burrows it digs and plugs with soil to keep cool and hidden, and it sleeps through the Gobi winter on stored fat.
Status
The long-eared jerboa is listed as Least Concern, though with much uncertainty. It lives sparsely across remote country, and the main local threats are mining, heavy grazing, habitat disturbance, and domestic cats. It was not even filmed alive in the wild until a 2007 expedition.
Long-eared Jerboa: common questions
Why does the long-eared jerboa have such enormous ears?
Its ears are the largest of any mammal relative to body size, and the leading explanation is that they serve the same purposes as the oversized ears of the fennec fox and other desert animals. Large, thin, well-supplied ears pick up very faint sounds, which helps a small nocturnal hunter locate insects moving in the dark and detect the approach of owls, foxes, and snakes across open ground where there is little to hide behind. Big ears also shed heat, acting as radiators that help the animal stay cool in a hot climate without losing water through sweating or panting.
Is the long-eared jerboa related to mice or to kangaroos?
To mice. It is a rodent, in the jerboa family, and its kangaroo-like body is a case of convergent evolution rather than kinship. Living in open desert, where fast, unpredictable movement is the best defence and food is widely scattered, has repeatedly produced small mammals that hop on long hind legs with a balancing tail, including jerboas in Asia and Africa, kangaroo rats in North America, and hopping mice in Australia, none of them closely related to kangaroos or to each other.
How does it survive in the desert without drinking?
Like many small desert mammals it gets almost all the water it needs from its food, especially the body fluids of the insects it eats, and it loses very little. It is active only at night, when the air is cool and humid, and spends the hot day sealed in a burrow where the air stays moist. Its kidneys are highly efficient at concentrating urine, and behaviours such as plugging the burrow entrance further reduce water loss. In the cold season it avoids the problem entirely by going dormant underground.
Is the long-eared jerboa endangered?
It is currently listed as Least Concern, meaning it is not considered at high risk of extinction, but that assessment comes with a lot of uncertainty because the animal is so hard to survey. It lives at low density across a large, remote area, and the main concerns are localised — expansion of mining and its infrastructure, heavy livestock grazing that changes the vegetation, general disturbance of the fragile desert surface, and predation by feral and domestic cats near settlements. Conservationists regard it as a species to keep monitoring rather than one in immediate danger.