Zubat

Zubat is a blue, bat-like Pokémon. While it lacks eyes, it has pointed ears with purple insides and a mouth with two sharp teeth on each jaw. A male will have larger fangs than a female. It has purple wing membranes supported by two, elongated fingers, and two long, thin, tails.

Zubat lives in abundance in caves. It has evolved to have neither eyes nor nostrils, it instead navigates through dark environments and tight caves with echolocation. As demonstrated in the anime, it will leave its abode at night with a mass of other Zubat in order to seek prey. During the daytime, Zubat sleeps hanging upside down in caves, forests, or under the eaves of old buildings, avoiding sunlight at all costs. Zubat also gather together in groups during the morning in order to stay warm while they sleep. Daylight causes Zubat to become unhealthy, and prolonged exposure can even burn its skin.

However, captured and trained Zubat have been recorded as being much more tenacious in the daytime, even when directly exposed to sunbeams. In colder conditions, Zubat gathers with others of its kind for warmth.

(Source: Bulbapedia)