Snakes have been filmed seemingly learning to hunt while they are still inside the womb.
Researchers at the Chiricahua Desert Museum in New Mexico observed copperhead snake fetuses moving their tails in a behavior known as "caudal luring."
This is a tactic used by certain species of snake to attract prey. Prey will often mistake the tail movements for a worm or other creature. When the prey approaches the snake, it will lunge and attack.
Not all snake species use caudal luring, but the copperhead snake—a member of the pit viper family—adopts the tactic shortly after birth.
However, the findings—published in the journal Open Science by the Royal Society—suggest that the snakes begin to learn this behavior even before they leave the womb.
Scientists have already observed prenatal behavior in mammals and birds, but this is the first time it has been observed in this species.
"Prenatal movements in humans and other vertebrates are known to be important for musculoskeletal and sensorimotor development," the study wrote. "The fetal behaviors we describe for copperheads, and possibly other snakes, may be similarly important and influence early survival and subsequent fitness."
The study said that fetal behavior in reptiles is "largely understudied."
After accidentally observing the behavior in a pregnant snake, researchers furthered their study and used ultrasonography to asses 18 other late-term pregnant copperhead snakes.
During the assessment, scientists found that 11 snake fetuses moved their tails in this way.
The study said the movements were "indistinguishable" from caudal luring. The behavior was caught on film, where the fetus can be seen wriggling its tail within the womb.
Using the same methods, scientists then tested for this behaviour in two
species of rattlesnakes, which does not caudal lure—none of the late-term fetuses showed any type of tail movements, the study said.
The study said because they only had a small sample of subjects, more research will be needed to determine whether these tail movements occur in species that do not caudal lure.
However, for copperhead snakes, it certainly appears that these tail movements are "an essential developmental precursor" to the hunting behavior.
Scientists believe that while the fetus' is still developing, their "musculature and neuromotor systems" are being prepared for "important post natal activity."
The tail movements occurred "randomly and spontaneously," which the study described as "a form of fetal motor babbling."
As reptile fetal movements are not widely studied, these findings show one of the few insights to the prenatal development of snakes.
"Although the duration of tail movements in the copperhead fetuses was relatively brief when compared to caudal luring in juveniles and older snakes, this was not
unexpected," the study said.
"Fetal movements in vertebrates, in general, are shorter lived than the same ones exhibited postnatally."
