Why do long eared have big ears?

To regulate body temperature

The long ears of jackrabbits help them to regulate their body temperature. Jackrabbits are adapted to live in hot, dry climates, and their large ears help them to dissipate heat. The blood vessels in the ears are close to the surface of the skin, so when the ears are exposed to a breeze, the blood can cool down and help to lower the rabbit's overall body temperature.

To hear predators

Long ears also help jackrabbits to hear predators. Jackrabbits have very sensitive hearing, and their large ears help them to detect sounds from a long distance away. This gives them time to escape if they are in danger.

To communicate with other jackrabbits

Jackrabbits use their ears to communicate with each other. They can make a variety of sounds with their ears, including thumping, stamping, and clicking. These sounds can be used to warn other jackrabbits of danger, to signal their location, or to attract mates.