by Greg Mayer
The cantil (Agkistrodon bilineatus), or Mexican moccasin, is a pit viper closely related to the water moccasin and copperhead of the United States. Like a number of other snakes, it moves its tail in a manner thought to attract the attention of prey, enticing them to come closer or look away from the snake’s business end, a behavior called caudal luring.
In juvenile cantils, the effect is accentuated by the bright color of the tail tip; this color fades with age.
There are several subspecies, distributed discontinuously from northern Mexico to northern Costa Rica. I’m not sure which subspecies the ones pictured here are.
Parkinson, C.L., K.R. Zamudio and H.W. Greene. 2000. Phylogeography of the pitviper clade Agkistrodon: historical ecology, species status, and conservation of cantils Molecular Ecology 9:411-420. pdf