Fennekin is one of those pokémon that has a near-perfect counterpart in our world. In this case, behold, the Fennec Fox:
It shares Fennekin’s fox-like appearance, golden-colored fur, small stature, and of course, its very large and very adorable ears. Fennec foxes are native to the Sahara desert in North Africa. They are the smallest foxes on our planet, growing only to about 16 inches (0.4 m) long - exact same as Fennekin is listed in the pokédex!
Fennekin’s pokédex entry tells us that Fennekin commonly eats sticks. Fennec foxes primarily eat insects, but also eat plenty of roots and leaves in their diet like Fennekin as well! Scientists think that they eat these mostly for the plant’s water content - water is hard to come by in the deserts where they live, so eating plants is how these foxes stay hydrated.
But what about those huge ears?
The first reason that these foxes have such large ears is because it helps them hunt their food. Since they eat bugs, they need to be able to hear faint sounds of bugs moving underground in order to hunt their prey. They are known to tilt their ears from side to side, listening for movement underground, before digging up their meal. Their large ears make it possible to hear such tiny sounds, making it easier for them to eat.
The other benefit to having such large ears is that their large surface area helps radiate away the fox’s body heat, keeping it cool in the hot desert environment. Human’s sweat to help regulate our temperature, but for a desert creature like the Fennec fox, water is precious, and you can’t waste any by sweating it away. So, it’s expansive ears, which are filled with blood vessels close to the surface of its skin, help dissipate off that excess heat and helps the fox stay cool. This is called thermoregulation, and the pokédex tells us that Fennekin does it too! As a fire type pokémon, Fennekin is probably very hot all the time - it’s large ears make it possible to regulate its body temperature efficiently.
Fennekin’s large ears help it hunt bug pokémon underground, and regulate its body temperature by expelling excess heat through the ear’s large surface area. It eats plant material to help stay hydrated.
