12/06/2024
Wildlife like this black-tailed jackrabbit (Lepus californicus) at the San Joaquin River NWR, that live in areas with extremely hot daytime temperatures, stay cool by releasing excess body heat from their gigantic ears. A jackrabbit's ears provide a broad expanse of thin skin exposed to the surrounding air. The skin is loaded with blood vessels, as you can see in this photo. When it's hot outside, the rabbit retreats to an area with a slightly cooler temperature -- like the shade beneath a shrub. The blood vessels in the rabbit's ears expand in a process called vasodilation. That increases the blood flow from the body's core to the ears. Then the ears act like radiators allowing the rabbit's body heat to dissipate into the surrounding, slightly cooler air. This method of cooling based on blood circulation conserves water as opposed to methods like panting or sweating, through which moisture is lost from the body as it evaporates into the surrounding atmosphere. This is important to keep the animal's body from dehydrating, especially in environments where there is little or no surface water. Wildlife like jackrabbits rarely, if ever, take a drink of water. They get all the water they need from the food they eat. It's important they don't lose a drop through activities like panting or sweating. This jackrabbit was photographed last weekend courtesy of Rick Lewis.