Thursday, April 25, 2013

Spring 2013


Spring is here. The budding of various species of deciduous trees is beautifully shaded in various hues of green; the Blue Ridge wilderness is awakening. The understory is for a seasonal moment bathed in sunshine, and the colorful wildflowers take this brief opportunity to spread their petals. Pollinators are everywhere, buzzing, flitting, flapping, and rapidly darting from nectar-baring plant to other nectar-baring plants of the same species. Thus the flowers breed. Mother bear is trailed by her cubs; they playfully tumble in the leaves making a mockery of mother’s foraging efforts. And in the warmest reaches of the Blue Ridge wilderness, ectothermic reptiles of various species are beginning their seasonal activities.

Early spring is when the timber rattlesnakes begin to stir; they greet the warmest days with just a glimpse of their coils, which are remarkably brilliant against a backdrop of fluffy leaves. With nighttime temperatures still hovering dangerously close to freezing, they will remain close to their refugia until a trend of reliable weather activates them to begin their seasonal migration. On the subject of hibernating timber rattlesnakes, it seems reasonable to assume that a species known for their impressive assemblages would be erupting from underground en-masse on a warm spring day; however, this does not seem to be the case at southern latitudes.

An interesting study published in August 2010 by Jeffery Mohr, revealed that highland South Carolina timber rattlesnakes overwinter singly and occasionally in pairs, much like their piedmont/coastal ecotypes the canebrake. Based on my observations, it could be forgiven to assume the same could be said of Georgia’s highland timber rattlesnake, being on roughly the same latitude as the South Carolina population. Telemetry studies of the seasonal temporal and spatial activities of Georgia mountain horridus can confirm or deny the aforementioned assumption. Northern Populations of Timber Rattlesnakes appear to be strongly communal, social animals that tend to aggregate/live in centralized “colonies”. The occupation of historical colonies is primarily dictated by environmental constraints and has lead to shared hibernacula, gestation and basking sites. Colonies are primarily found on open, rocky, south facing slopes, at higher elevations.

The difference in aggregation as fostered by the environment is not necessarily a disadvantage to their sociality as much as it is a testament to the forces of natural selection at work in shaping society at high latitudes. As Mohr suggests in his paper, timber rattlesnakes in the north are faced with longer, colder winters, coupled with fewer choices of available overwintering sites that can protect them from prolonged spells of freezing temperatures. Conversely, southern populations frequently see mild winters with very few lengthy stretches of freezing temperatures, so it is likely that there are a variety of microhabitats in the environment that can adequately serve as hibernacula. Thus, the southern climate relative to the environment did not select for communal denning.