Which animal has the longest tail relative to its body size?

The animal with the longest tail relative to its body size is the male Asian Paradise Flycatcher. The male of this species has a body length of around 19cm and a tail length of up to 32cm, which means that the tail can be up to 1.7 times the length of its body. The Asian Paradise Flycatcher is a small passerine bird that is found in forests and woodlands throughout Asia, from India to Indonesia.

The male's tail is long and beautiful, with two long, thin streamers that can be twice as long as the rest of the tail feathers. The tail is used during courtship displays, where the male performs an aerial dance to attract a mate. The tail feathers are also used for balance and steering during flight. In contrast, the female of the species has a much shorter tail, which is only around 10cm long.