Evolution of snake courtship decoded

Snakes may have developed courtship and male-to-male combat behaviour, such as moving undulations, neck biting, and spur-poking, over time, according to a new study.
Behaviours involved in courtship and male-to-male combat have been recorded in over 70 snake species from five families in the clade Boidae and Colubroidea, but before now, scientists had yet to look for evolutionary relationships between these behaviours.
The study by Phil Senter from Fayetteville State University in US and colleagues analysed 33 courtship and male-to-male combat behaviours in the scientific literature by plotting them to a phylogenetic tree to identify patterns.
The authors identified the patterns in behaviours, which was not always possible, and then used the fossil record to match the behaviours to the snakes' evolution.

Researchers found that male-to-male combat of common ancestors of Boidae and Colubroidae in the Late Cretaceous likely involved combatants raising the head and neck, attempting to topple each other.
Poking with spurs may have been added in the Boidae clade. In the Lampropeltini clade, the toppling behaviour was replaced by coiling without neck-raising, and body-bridging was added. Snake courtship likely involved rubbing with spurs in Boidae, researchers said.

In Colubroidea, courtship ancestrally involved chin-rubbing and head- or body-jerking.
Various colubroid clades subsequently added other behaviours, like moving undulations in Natricinae and Lampropeltini, coital neck biting in the Eurasian ratsnake clade, and tail quivering in Pantherophis.

Although many gaps in the evolution of courtship and combat in snakes remain, this study provides a first step in reconstructing the evolution of these behaviours in snakes.
The study was published in the journal PLOS ONE.