Black-tailed Jack Rabbit Black a.k.a. Desert Hare

Look at the six and one half inch ears in this photo, they are used for more than hearing see note below marked with *
The Black-tailed Jackrabbit is also known as the Desert Hare. It is a common hare found in Western USA and Mexico. It can be found at nearly all elevations ranging from sea level to up to 9000 feet. Like all jackrabbits, the Black-tailed Jackrabbit has the characteristic long ears, and long rear legs. Its fur is dark brownish grey peppered with black. Its ears are tipped with black, and it has a black stripe down its back. The tail is black above but white beneath.
The Black-tailed Jackrabbit is commonly seen on pasture and waste land during the day, though it is mostly nocturnal. They feed on cactus, sagebrush, mesquite, grasses, and crop plants. They drink little, deriving most of their water from food. Like most hares, Black-tailed Jackrabbits do not use burrows, but rest during the day in a scrape in the pasture called a form, relying on their acute hearing and speed to evade predators.
They are preyed upon by coyotes, foxes, bobcats, weasels and hawks. Unlike rabbits they are largely solitary animals. They will also thump the ground with their hind legs as an alarm signal.
Up to four litters may be produced in a year, with up to eight young in a litter. They are born in a form, above ground. Gestation is around 45 days and the young are active and relatively independent from birth, and their mothers only nurse them for a short time.
Black-tailed Jackrabbit populations are characterized by extreme "boom-bust" cycles. These cycles can be very localized: Jackrabbits may be plentiful in one valley and almost absent from an adjacent valley. Population crashes are mostly due to disease (especially Tularemia), although environmental factors such as food availability can also play a part. The high birthrate of the jackrabbit allows populations to recover quickly after a crash. These cycles also have a large effect on predator populations, causing similar population cycles in predators such as coyotes and hawks.

*Jackrabbits live in the desert, where they're exposed to extremely hot daytime temperatures. But, these animals are able to stay cool by releasing excess heat from their oversized ears.

The jackrabbit’s large ears provide an expansive surface area of exposed skin loaded with blood vessels. When the surrounding air temperature is slightly below the rabbit’s body temperature, as when it retreats from hot desert sun into shade, the blood vessels in the outer part of its ears widen in a process called vasodilation. This results in greater circulation of warm blood from the body’s core to the jackrabbit’s ears, where heat is lost to the cooler surrounding air.

This cooling mechanism based on blood circulation helps to prevent overheating and maintain the jackrabbit’s body temperature within set boundaries. It’s also an important water conservation technique given the jackrabbit's arid habitat, as it reduces the need for evaporative cooling mechanisms, such as panting or sweating, which involve the loss of water. At air temperatures around 30° Celsius, convection from the jackrabbit's ears can shed all of the animal’s excess heat.

Read less