Monday, September 28, 2009

Reptilian preview

Trying its best to be unseen, a timber rattlesnake trusts its camouflage. (©Scott Weidensaul)

Yes, I know this blog is about owl why is that timber rattlesnake staring at you?

Last week, our 2009 research crew arrived and started training - and part of their training regimen was two days of radio-tracking rare timber rattlers on South Mountain, the same area where they'll be tracking owls. Last Thursday morning we joined state DCNR biologist Aura Stauffer (also a longtime volunteer member of our banding crew) to seek out several of the rattlers that the state tagged with implanted radio transmitters this summer.

Eastern timber rattlers have been on the ropes for years, with habitat fragmentation and persecution sadly reducing the population of this shy, docile reptile in Pennsylvania, to the point where it's a candidate for state endangered species listing. (There's more information about their ecology and status here.)
The South Mountain population is especially threatened, surrounded as it is by a sea of agriculture and development.

Aura led research tech Drew Weber, interns Hannah Panci and Kim Romano, me and my 15-year-old nephew Connor (who has helped with our banding and tracking since he was little) up into the rain-damp woods. Hannah, who is new to telemetry, took the receiver and yagi antenna, and with Aura's help directed us up through thick oak and pine woods with a dense understory of mountain laurel. This late in the season, Aura was expecting the snakes to move from their foraging areas to near their hibernacula - the winter den sites whose locations are unknown, and a major focus of the study.

The signal beeped more and more loudly, and Aura announced that we were getting close. Although we were all (except Aura) wearing bite-proof leggings, we watched our feet, while Aura used her snake hook to knock down some greenbrier vines. We paraded single file uphill, but just as Hannah stopped, turned, and said, "I think we walked past it," Connor gasped and pointed at Drew's feet.

The rattler, a large dark-morph male, was less than a foot from Drew - but typical for the species, it never rattled or showed the slightest aggression. Neither did the next one we tracked, which was a few hundred meters away, or a third that Kim found around lunchtime, a stunning yellow-morph female (above) curled up in the sun in a recent timber cut, even when I was lying two feet away for a better camera angle. Aura's stepped directly on rattlesnakes a few times and not been bitten. If only people showed as much tolerance for rattlers as the snakes do for people.

The highlight of the day, however, was the last stop, a small rock field deep in the woods. Walking in while Drew tracked the signal, I all but stepped on an untagged rattlesnake that did give a warning buzz as it slid down a chipmunk hole. Then we began to walk carefully up the slope of the rocks, where Aura pointed out five or six females and 14 newborn babies, known as neonates.

Suck rock fields are rookeries - sites where gravid females gather all summer to bask in the sun, not eating, only moving from sun to shade to keep their internal temperature perfectly balanced for the growing embryos. Then each female gives birth to about half a dozen babies around Labor Day, and the family remains together for a short while.

Only a few weeks old, a baby rattler surveys a hostile world (©Scott Weidensaul)

Rookery rocks are one place where rattlesnakes buzz more often than not, and the rocks were alive with the cicada-like rattles. The adult females slid underground quickly, just poking out to look at us, but the babies were curious, sometimes coming closer for a better look.

The reproductive cycle of the timber rattlesnake is glacial. A female mates one year, gives birth the next, and may have to take a year or two off before mating again to rebuild her energy reserves. A Pennsylvania rattler may only reproduce a couple of times in her life, and at the northern edge of their range, in the Adirondacks and southern New England, she may get only one chance to give birth.

Knowing the odds arrayed against this quiet, badly misunderstood species, it was a special privilege to see so many rattlers in one day, including a new generation facing an uncertain future.

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