Spring Babies

Spring is in the air. Spring is a special time for snake enthusiasts because it marks the start of the rattlesnake active season. Rattlesnakes spend the winter in "hibernation" where they den in burrows or rocky outcrops. Some species of rattlesnake (for instance, Timber Rattlesnakes) overwinter in large communal dens with dozens of individuals sharing the same space. It was recently discovered that den-mates are often kin, and that rattlesnakes may preferentially den with their relatives. The species I study, the Northern Pacific Rattlesnake, is not known to den communally although we did see at least 6 snakes over-winter in the same rocky outcrop this year.

Spring also marks the time when neonate rattlesnakes become young-of-the-years. Female rattlesnakes give birth (yes, live birth) during the fall before they retreat to their winter dens. The babies they produce are called neonates and in order to survive the winter, the neonates must find a meal or they will starve to death. Neonates, which are about the size of a pencil, are too small to consume squirrels, but they will eat insects and lizards. After the neonates eat, they will over-winter together at the site where they were born. These babies then emerge in spring and disperse from their natal homes. During the first year of their lives, baby rattlesnakes are called "young-of-the-years." Their rattles will consist of one natal button at the very tip and a couple of segments below to signify their shedding events. Once these individuals reach two-years of age, they will be called juveniles.

I have been traversing the hills of BORR to capture adult snakes for our upcoming field season (we start next Wednesday!), and I can't help but notice the freshness of spring. Babies are out and about. This little guy (or gal?) we found coiled in the grass next to a large rock. Perhaps, this was its overwintering site?

..and it's not just rattlesnakes that are producing babies. Last week I found a nest with a baby Red-tailed Hawk. Hopefully, the mother refrains from eating any of our study snakes!

In October I found a burrow where neonates had recently been born. I check in on the babies every time I visit the field site. I saw a total of four neonates in the fall (but the mother could have given birth to more), but only one remained when I returned this spring. Either the others were hiding in the burrow or they did not make it through the winter. By now, that one neonate has dispersed...I hope it is doing well.

Here is a video of the neonates moving about their burrow after I first found them in October. The video shows how small the neonates are compared to adult rattlesnakes (the burrow is about the size of a tennis ball and the neonates are about the size of a pencil). Although the video is long, if you are patient you will see that one neonate spends more than 10 minutes exploring the area around its home burrow (it emerges at 1:05 on the video, and the video is sped up to 3-4x for the sake of time). It flicks its tongue in and out as it moves about, presumably picking up chemical cues from its environment. Will it use these cues later in life to navigate back to this burrow next winter?

Snake-snake Interactions: do they have meaning?

When multiple species of snake live in the same habitat, how do they interact? Do they communicate with each other? At the Blue Oak Ranch Reserve where human presence is greatly reduced, snake diversity is high and many species occur at high population densities (see species accounts one and two). Our cameras have captured a few rattlesnakes investigating other species of snake. On June 22, Mace Windu, a male Northern Pacific rattlesnake interacted with a king snake and a gopher snake (at separate times). Below are recordings of these interactions (you may want to watch on YouTube to view better video quality). 

A king snake bumps into Mace while slithering through the grass. Mace is sitting in ambush in the shadow as the king snake moves through the grass. The king snake retracts its head after it realizes that a rattlesnake is there. It quickly flees and Mace extends his head, as if curious.  

A couple of hours later, a gopher snake runs into Mace. The camera is not directly pointed at Mace, but he is partially visible resting in the shade of a rock. A gopher snake moves toward Mace and stops once it realizes that a rattlesnake is there. It quickly takes off, and Mace extends his head and body toward the gopher snake. Is Mace just curious or is he communicating with the gopher snake?

These recordings make me curious about snake-snake interactions: 

How often do different species of snake interact, and when they do, what are the nature of these interactions?

Can different species of snake communicate with each other? 

King snakes are predators of young rattlesnakes, but how do they interact with adults like Mace? 

At BORR, many species of snake live in the same habitat and must interact in some way. Our cameras have been catching glimpses of these interesting snake-snake interactions so hopefully with more video footage we can learn more about them!

Best News Article Yet!

Over the past couple of weeks our research has been featured in several news articles (Time, MSNBC, Huffington Post, Fox News), but the article in the San Jose Mercury News is by far the most informative and scientifically accurate. The reporters came out with me last Monday as I searched for snakes for the up-coming field season. They were very excited to learn more about rattlesnakes and the research that is being performed in their own backyard. Check it out!

Strike and a Miss

Below is an awesome screenshot from one of our field recordings. In it, Greeata, a female rattlesnake strikes at an adult squirrel that has been harassing her for the past two minutes. The blue arrow is pointed at Greeata's open mouth as she lunges her head out of the log. The orange arrow is pointed at the squirrel's head as it dodges the snake strike. 

This screenshot is intriguing because we rarely observe strikes on squirrels that are actively harassing snakes. This is because squirrels are more likely to evade a strike when they are aware of the snake's presence and snakes don't want to waste time and energy on a strike that will be unsuccessful.  This poses the question, why did Greeata strike at this squirrel? Was it a defensive strike rather than a predatory strike? She should have known her strike would be a miss and saved it for another day. One aspect of rattlesnake behavior that I am particularly interested in is the inter-individual variation in strike reactivity. There may be a continuum of behavioral types where some individuals are more judicious, strike less often, but have better strike accuracy while others are more reactive, strike more often, but have less strike accuracy. I hope to capture more snake strikes to analyze this fascinating aspect of rattlesnake hunting behavior.