Priscilla, Lois, and Arli (Arizona Black Rattlesnakes) spent their pregnancy together at a rookery from May through August, 2010. Arli moved away to a private nest shortly before giving birth, while Priscilla and Lois stayed at the rookery.
On 30 August 2010 we observed Priscilla (pregnant adult female) discouraging House (neonate / newborn) from potential exposure to a human predator. Priscilla was still pregnant at this time, so House had a different mother. To our knowledge, this is the first observation of helping (aka babysitting) in a snake. Perhaps this is why some female rattlesnakes aggregate during gestation and remain together after giving birth.
Yes: Rattlesnakes babysit their neighbors’ kids!
Here are photos of the event described above, plus a few more of Priscilla babysitting House.