Removing the Blinders

“To endow animals with human emotions has long been a scientific taboo. But if we do not, we risk missing something fundamental, about both animals and us.”

de Waal (1997)

“Science is only as good as the question, and we cannot learn the answers to questions we don’t ask.”

Jesús Rivas (2020)

Many scientists, in their efforts to be unbiased and avoid anthropomorphism, engage in anthropodenial: the refusal to acknowledge humanlike characteristics of non-human animals (de Waal 1997). This seemed to be especially prevalent among many herpetologists, who assumed reptiles weren’t capable of certain things, didn’t ask the questions, and missed some interesting observations because of this bias (Burghardt 2020).

A bunch of babies coiled on and near Eve (Arizona Black Rattlesnakes)
A bunch of babies coiled on and near Eve (Arizona Black Rattlesnakes)

For example, numerous observations of rattlesnake families dating back more than a hundred years were dismissed by the godfather of rattlesnake biology, Laurence Klauber (1956):

Their propinquity, such as it is, does not result from any maternal solicitude; rather it is only because the refuge sought by the mother is also used as a hiding place by the young.

Klauber (1956)

In 1992, Harry Greene and colleagues published an article on viper parental care, presenting evidence that not only do families aggregate, but mother snakes actively defend their newborns.

Was there some technological advance at that time that finally revealed this behavior to scientists? No. But, it’s difficult to see what you don’t look for and these authors took the time to look. They also reviewed others’ observations of parental care in vipers, demonstrating that this behavior is widespread and more than mere attendance.

When we began our study of social snake behavior in 2010, we were armed with cameras, binoculars, and field notebooks. With these simple tools we managed to document behavior that was once readily dismissed. How? We were looking for it. We asked the questions. And maybe more importantly, we largely left the snakes alone and let them tell their own stories.

This is Woody’s story.

A very pregnant Woody (Arizona Black Rattlesnake)
A very pregnant Woody (Arizona Black Rattlesnake)

We first encountered Woody (Arizona Black Rattlesnake, Crotalus cerberus) in a pile of rocks and a jumble of downed pines in May 2010, about 150 yards from any known winter dens. We visited this area a number of times through the summer, and found her almost every time, relaxing near some rocks or coiled among woody debris (for which she is named). Because of her camouflage, we would have to search around for her, which sometimes brought us in close proximity, but Woody was even-tempered, never rattling or attempting escape.

Then one day in late August, everything changed.

We discovered several newborn rattlesnakes basking near Woody’s favored spot. As we approached to get a closer look, but no closer than we had approached Woody so many other times, we heard muffled rattling from under the rocks. As we started snapping photos of the little ones, Woody poked her head out of her shelter and then proceeded to crawl from her refuge toward us, still rattling, and glaring directly at us. Our once-placid Woody was now fearless and wanted us to know she would not tolerate our advance. Impressed with her maternal instincts and not wanting to distress her or her babies, we quickly backed off.

Woody, Arizona Black Rattlesnake, guarding her babies inside their nest.
Woody, Arizona Black Rattlesnake, guarding her babies inside their nest.

We were more careful in future visits to Woody’s nest, but she remained a vigilant mother: rattling from within her shelter if we got too close, or assuming a defensive posture between us and her kids (as shown in the photo on the back cover). The young caught on too, retreating into shelter if mom was upset.

Eventually the babies shed and the family split up, each trying to get a meal before it was time to enter their den for the winter. Since Woody’s nest wasn’t located close to a known den, we weren’t sure when we would see her again. Was Woody’s den located at or near her nest site? Would she show up at one of the dens we already monitored?

Woody and Adam, Arizona Black Rattlesnakes, spring 2011.
Woody and Adam, Arizona Black Rattlesnakes, spring 2011.

On the very first day we visited the dens in April 2011, we spotted Woody, basking in a popular spot with several other snakes, including some little ones that were born the previous summer. One of these juveniles turned out to be Woody’s baby, Adam.

The photo on the left is Adam (newborn on left) and Woody (right), at her nest in August 2010. The photo on the right is Adam at their den in April 2011.
The photo on the left is Adam (newborn on left) and Woody (right), at her nest in August 2010. Woody’s nest was farther away than most in 2010, but Adam found his way to their den (photo on right taken at den basking area in spring 2011).

In 2011 we starting using timelapse cameras, which caught Woody and Adam as they basked together that day:

Although it is not unusual to see adult and juvenile rattlesnakes basking together, Woody seemed to be particularly interested in Adam. Does her maternal regard for her offspring’s well-being extend beyond the nest? If her mothering is genetic and beneficial to Adam, then such care could evolve. We observed similar behavior in another female, Eve, following a juvenile from the previous year’s nest (see this post for more on that).

Many underestimate the wonders and complexity of the natural world, especially when it comes to snakes. The more we remain open to the possibilities of nature, the more we will be able to see. Early rattlesnake admirers dismissed maternal care for mere coincidence, but these moms make big sacrifices for their young both before and after birth. With this window of understanding now open, what more will we discover about the social lives of snakes?

References

Burghardt, G. M. 2020. Insights found in century-old writings on animal behaviour and some cautions for today. Animal Behaviour 164:241-249

de Waal, F. B. M. 1997. Are we in anthropodenial? Discover 18:50-53.

Greene, H. W., P. May, D. L. Hardy Sr., J. M. Sciturro and T. Farrell. 2002. Parental behavior by vipers. Pp. 179-205 in G. W. Schuett, M. Hoggren, M. E. Douglas, and H. W. Greene, eds. Biology of the Vipers. Eagle Mountain Publishing, Eagle Mountain, Utah.

Klauber, L. M. 1997. Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind. 2nd ed. University of California Press, Berkeley, California.

Rivas, J. 2020. Anaconda: The Secret Life of the World’s Largest Snake. Oxford University Press, New York, New York.