Sickle tail explained

The sickle tail is the single phenotypic characteristic that seems to separate dogs from wolves.^[1] Dogs who have tails tend to have an upward curve in the tail, which is called the sickle tail. Wolves' tails, on the other hand, hang straight; this is called the brush tail—similar to that of a fox.

Notes and References

1. Book: Míklósi, Ádám . Dog behaviour, evolution, and cognition . 2007 . Oxford University Press . Oxford . 978-0-19-929585-2 .