Even Awesome Moms Need a Break
We first observed babysitting in 2010, when we started studying rattlesnake nesting. Fifteen years later, here’s what we’ve learned about this surprising behavior, based on observations of 43 mamas and litters at 18 rookeries.
Alloparenting — caring for young that are not direct offspring, but may be related (nieces, nephews, grandkids, siblings).
Babysitting — a mutualistic (everyone benefits) type of alloparenting.
Nest — (verb) give birth and care for babies until they shed their skin for the first time at 1-2 weeks old; (noun) site where nesting happens.
Rookery — site where two or more rattlesnakes nest.
The most common setup for babysitting is at a rookery with pregnant snakes of varying ages, even generations. The oldest mama gives birth first and the youngest last. After giving birth, the older mama stays in the shelter rather than hanging on the surface with or very near the babies, which is what we see at solo nest sites. The younger female(s) gets stuck caring for her nestmate’s babies and eventually her own too (the eldest female does not pitch in later).
Perhaps this seems unfair to the younger females, but this breeding strategy is mutualistic. While the older mama rests, the younger, less experienced ones gain parenting practice. Females that share a rookery are likely to be related, and there’s a fitness benefit in increasing your relative’s chance of surviving too. Babysitting is a benefit to rattlesnakes that chose to aggregate during gestation and remain together after giving birth.
Priscilla & House
Priscilla was the first rattlesnake we observed babysitting. She spent her pregnancy with Lois and Arli (Arizona Black Rattlesnakes) at a rookery from May through August. Arli moved a few yards away to a private nest shortly before giving birth, while Priscilla and Lois stayed at the rookery.
Lois gave birth next, and afterward we never observed her out with the babies, only resting inside the shelter. Priscilla was still pregnant, so she tended Lois’ babies, and seemed to form an especially close relationship with one, House.
We observed Priscilla and House snuggling together often and one day, she kept him from wandering into a potentially dangerous situation. As Jeff described in The Nurturing Nature of Rattlesnakes:
Beside a still-pregnant Priscilla, House squirmed and fidgeted beside her as I watched through binoculars.1 Soon, he began to crawl out into the open and in my direction.2 From her relaxed coil (she was accustomed to our visits), Priscilla darted out her head to intercept House’s advance, her face directly in front of his.3 He immediately stopped, paused briefly, returned to the shelter of the rock and coiled into stillness.4 Basking would have to wait.
To our knowledge, this was the first observation of babysitting in a snake. But not our last!
Adrian
Adrian (Arizona Black Rattlesnake) babysitting her nestmates’ babies during her first pregnancy in 2015 (above). We first met Adrian in spring 2011 at a large communal den, when she was just a few months old. We saw her again at the den the following spring, and again in 2014. She had her first litter in 2015 when she was five years old and as usual, babysat her nestmates’ newborns before giving birth to, and caring for, her own. In 2019 we observed her with babies all by herself in a strange place for a nest (right). While most nests consist of a rock shelter, Adrian had selected a soil burrow. Surprises like these keep us coming back for more snake-watching!
And as always, there are some fascinating exceptions to the usual story — check out the boxes below. Isn’t nature cool?
Babysitting — it’s not just for girls
Males occasionally babysit too. Although we haven’t observed any active care or protective behavior from males, just the presence of a large rattlesnake may deter some predators.
Roger (adult male Arizona Black Rattlesnake) showed up at this rookery shortly after the babies were born and jumped right into alloparenting. The babies behaved as they do with their mamas and female babysitters: they followed him away from shelter, into the sun, and back again.
Babysitting — it’s not for everyone
This mama Black-tailed Rattlesnake is guarding her new babies, because oops, I got too close to this rookery! Behind her is another mama with more babies. Not pictured is their still-pregnant nestmate, basking a few feet away with no babies. At this rookery (and so far, only this rookery), we never observed the last female that gave birth babysitting.
Rattlesnake Family Stories
Want more details about rattlesnake family life? Read Rattlesnakes are Awesome Moms! More videos and stories? Check these out:
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