Why are rabbit ears so long? A rabbit has big ears to cool itself down, not just to hear predators.
Rabbits are herbivores and are obviously preyed upon by various other animals. Their large ears can swivel independently and can pick up sounds from up to 3km away. They can turn each ear 270 degrees, which means they can hear in every direction around them. Their ears can alert them to danger and give them time to flee.
A rabbit’s ears are usually relaxed and lie either side of the rabbit’s head. When the rabbit is startled, they tense the muscles in their ears and the ears stand up. The shape of the rabbit’s ear makes it an effective funnel for sound. The sound waves are directed by the outer ear and then slowed down by the middle ear before reaching the inner ear. The inner ear is a fluid-filled canal, similar to our ears. However, they have more hairs, which makes their ears far more sensitive than ours. They can hear frequencies from 96 Hz to 49,000 Hz. We can only hear 20 Hz to 20,000 Hz.
Like all mammals, rabbits can compare the frequency of sound coming in to each ear to pinpoint where a sound is coming from. They can analyze its strength and work out if it is near or far. If they detect that the sound is close, they will run. The average rabbit can run at about 48 km/h. Hares have longer legs and can run faster than rabbits. They often reach speeds of 72 km/h. They have this ability to run away from prey and are not long distance runners. They tired very quickly.
The back legs of a rabbit are longer than their forelegs. They are digitigrade runners which means they run on their toes, giving them a lot more speed than animals that walk on the soles of their feet like us. The fact that their hind legs are so long means that they can run uphill very easily. A rabbit may aim for hills when running away because it will give them a slight advantage over their pursuer. They can also turn extremely quickly, zigzagging as they run. When they run, they usually tuck their ears down so that they don’t slow the rabbit down.
However, their ears have another, possibly more important purpose. Rabbits come from the hot climates of southern Spain and France. They generally have a body temperature between 38 and 40 degrees centigrade. In order to maintain this, they use their large ears to lose heat. They have a large number of thin blood vessels that run through their ears, close to the surface. The rabbits can adjust the amount of blood that flows through these vessels. When it is hot, the large surface area of the ears allows them to lose heat from their blood. When it is cold, the amount of blood is reduced, the vessels contract and the rabbits can keep warm. This is a technique that elephants use as well. They have ears with a very large surface area and they can also control the amount of blood that flows into the ear. Elephants have the ability to flap their ears to increase the amount of heat that is radiated out.
Rabbits have been introduced to many different countries, but the ones that live in the warmest places have the largest ears. In the UK, the average ear length is 60 mm and in much hotter Australia it is 80 mm.
A lot of people have rabbits as pets, but they are considered to be pests in many countries. Wild rabbits have been caught and eaten for over 3000 years. From about the 1st century BC they were commonly farmed for their meat and fur. Many countries still eat rabbit meat. People started to keep them as pets in the late 1700s but they were hunted as well to control their numbers. Rabbits will eat vegetables and crops growing on farms and they multiply very quickly. In the 18th century, Thomas Austin, one of the first European settlers to Australia, took some rabbits with him from England to hunt. There are no natural predators of the rabbit in Australia and their population exploded. They cause millions of dollars of damage every year.
So, why are rabbit ears so long? So that they can hear predators coming from a long way away and so that they can regulate their heat. And this is what I learned today.
Sources
https://www.discoverwildlife.com/animal-facts/mammals/why-do-rabbits-have-such-long-ears/
https://www.rabbitcaretips.com/how-well-can-rabbits-hear/
http://www.pef.uni-lj.si/eprolab/comlab/sttop/sttop-is/TG/Life_science/Elephants.htm
https://en.wikipedia.org/wiki/Rabbit
https://en.wikipedia.org/wiki/Domestic_rabbit