Social interactions between mothers and young: do rattlesnakes exhibit care for their offspring?

Some very interesting subjects are being talked about over at the website, SocialSnakes. There are two articles that have been posted within the past two months that discuss extensively the parental relationship rattlesnakes share with their offspring. Before we get to them, however, some background on snake reproductive behavior should be covered. Most people would be surprised to learn that any snake would know its parents, the common image for serpents and other reptiles being that they abandon or even attempt to eat their offspring shortly after reproduction. The reality is that many reptile species exhibit complex social behavior and the systematic organization of family units complete with parental care of offspring. Certain species of snakes, probably the most maligned vertebrates on the planet, have even been shown to protect their offspring. At least three species of the genus Python are known to incubate their eggs by coiling around them and will lash out at any intruder that attempts to prey on them. Even more elaborate is the king cobra, Ophiophagus hannah, which is the only snake known to build a mound nest. The female (within a male’s territory) will then stay with the nest, while fasting, until the eggs hatch. During this time she fends off potential nest predators, sometimes at the risk of her own life.

There are also species whose social behavior we are only just discovering and that brings us to focus on our main subject: rattlesnakes! Rattlesnakes are some of the most physically advanced snakes on the planet so it should come as no surprised that they are very behaviorally advanced as well. This behavior expands to their reproduction, where males have elaborate competitive wrestling matches and pairs have been known to mate with the same partners year after year. Most enigmatic and potentially interesting of all, however, is their interaction with their offspring after birth. Rattlesnakes are vipers and, like almost all vipers, they oviviparous (yes I had to look that up to spell it) meaning that they gestate their eggs inside of their bodies until they hatch and then give birth to live young. The neonates then stay with the mother for an undetermined period of time, varying to just a couple of days to over several weeks. The reason for this is not entirely known and hypotheses generally lean toward this being a phase of ethological development for the young snakes.

Some researchers are proposing an explanation in that the mother rattlesnakes are actually exhibiting true parental care. SocialSnakes has captured some amazing photographs of a mother rattlesnake interacting with her newly birthed brood (http://socialsnakes.blogspot.com/2011/10/day-in-life-of-rattlesnake-family.html). Several of these photos seem to indicate that the mother is directing her babies away from dangerous areas, i.e. the open wilderness, and actually herding strays back into her birthing lair. Another entry (http://socialsnakes.blogspot.com/2011/10/rattlesnake-helper.html) mentions an even more interesting instance where an adult female rattlesnake apparently discouraged a juvenile from approaching a human by blocking his way and staring him down. Was this intentional? Did she associate the human with danger and then made sure the younger, less experienced snake did not slither into what might have been a predator? Did the other mother snake know that her babies would be safer in her lair and thus chose to ensure that they did not leave prematurely?

The problem with evaluating this behavior is that young snakes do not have the same care requirements as, say, baby birds, baby crocodilians or many baby amphibians. Even more so than the aforementioned baby crocodilians, neonate rattlesnakes really are ready to live independently as soon as they are born. They have all of their instincts, all of their necessary development and even their venom at the ready. The one thing that they do not have is the acquired skill and experience that can only come with age. At the same time the truth is that rattlesnakes probably do not require much parental care with all of the advantages they have from birth. What is likely happening is an elaborate system of communication involving visual, physical and possibly scent signals, many of which are already instinctive nature to these snakes honed through their advanced evolution. It does not seem to be too much of a leap to imagine that certain beneficial behaviors would be selected for and among these the behavior of a mother to come to the occasional aid of her offspring and simply guide them for the first few weeks of their delicate lives, thus assuring their survival as well as the survival of the predisposition to assure the survival of future generations.

Rattlesnakes are already shown to be social creatures, even if these data are inconclusive there is still concrete proof that mother snakes will tolerate neonates in their presence and some mothers will even actually let the young bask on their backs to obtain more heat. How would the public react if they knew how complex and social rattlesnakes and other pit vipers are? It is unlikely to completely reform their unjustly negative image completely but it certainly would not hurt them. I plan to follow up on this entry in the near future and further discuss who is behind some of this research and how new data are showing that these pit vipers may be more advanced than we could have possibly imagined.

Sources:

A rattlesnake helper? [Web log message]. (2011, October 20).

http://socialsnakes.blogspot.com/

A day in the life of a rattlesnake family [Web log message], (2011, Oct 28)

http://socialsnakes.blogspot.com/2011/10/day-in-life-of-rattlesnake-family.html