Late term fetus caudal luring behavior in a pitviper

With the advent of powerful imaging tools, the prenatal behavior of vertebrates is far more complex than previously believed, especially concerning humans, other mammals, and birds. Surprisingly, the fetal behavior of squamate reptiles (lizards, snakes, and amphisbaenians), a group of over 11,000 extant species, are largely understudied. Using ultrasonography, 18 late-term pregnant copperhead snakes (Agkistrodon contortrix) from a single population were inspected for fecundity (number of fetuses). Unexpectedly, during the ultrasound procedure that involved 97 fetuses, we observed sinusoidal tail movements in 11 individuals from eight different copperhead mothers. These movements were indistinguishable from caudal luring, a mimetic ambush predatory strategy which is exhibited by newborn copperheads and other snakes. Caudal luring is initiated shortly after birth and is employed to attract susceptible vertebrate prey. Using the same ultrasound equipment and methods, we tested for this beh...