Wednesday, May 16, 2012

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?

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