The spring of 2009 was characterized by erratic weather.  The warmer than average March undoubtedly brought a few snakes to the surface in the central Appalachians.  A general emergence did not begin until around 17-18 April when I saw 9 TR on the 18th and Randy Stechert, Chris Camacho, and Dave Prada saw 39 during the 2-day period in the Hudson Highlands of southeast New York. Unseasonably hot weather from 25-28 April compressed 15 days (about 21 April to 5 May) of emergence/egress into 4 days. I saw 23 and 35 (total of 63 TR seen by our party.) at two northern Blue Ridge dens.  There was little incentive
for snakes to bask—but rather they lay in hibernating crevices near the surface. By the end of this heat wave, many low-elevation dens were nearly emptied, most egress apparently having occurred at night.  (At 39 N I classify low-elevation as 600-1600 ft, middle is 1600-2600 ft and high is 2600-3600 ft.)   On 28 April at a low-elevation den complex in Shenandoah NP where I have seen 38 and 42 on good days, we saw only three snakes.  However on a 1 May return to the site where we had seen 35 on 26 April, 23 TR (10 juveniles) were seen and most still in hibernating crevices.  Five middle elevation sites were visited on four days from 7 to 13 May.  At four of these sites good opportunities for basking exist within a few meters of the hibernacula and fair numbers of snakes were seen—24 at a 1600 ft northern Maryland site, 23 at a 2500 ft Shenandoah NP den.  At another Shenandoah den of similar elevation located under the canopy with the basking area 200 meters distant only three snakes were seen in the den, four at the basking area and one en route.

At high elevations/high latitudes in the east a general emergence apparently had begun by 26 April when Ed McGowan saw 17
Timbers and two copperheads at a Hudson Highlands, New York den and Curt Brennan and Don Kohler saw 88 total at three north-central Pennsylvania dens.  Ed Thompson saw 16 at western Maryland den on 6 May.  On 7 May Mark Asper saw 156 TR at a north-central Pennsylvania site! The following day he returned with Curt Brennan and they saw 57, many on the move or coiled in the woods nearby.  They saw 28 at another den that day.   Apparently the hot weather of 25-28 April got many of the high elevation/high latitude snakes to the surface but then the cool down over the next week held them in place.  Emergence then peaked on 7-8 May.  On 15 May with Lance Benedict we saw one adult non-gravid female at a high-elevation (3200 ft) Shenandoah NP den and about 50 meters above the den, a gravid female with a stomach bolus.  Nothing at the basking/gestating site 150 meters distant.

Typically spring advances from west to east and at similar elevations and latitudes emergence in the western part of the range will
run a week or so ahead of that in the east. For the past two years emergence in the Midwest has been uncharacteristically late.

The extreme heat apparently bypassed the western part of Timber Rattlesnake range.  Steve Beaupre reports that in northwest
Arkansas some snakes were on the surface in mid-March but the season stalled and was running 2 weeks behind as of mid-April.  George Pisani in northeastern Kansas apparently experienced a delayed emergence (three seen in den crevices on 16 April) as well and they were still getting new emergent snakes as of 4 May.    On 12 May Phil Cochran saw six and two adults at two Minnesota dens and on 17 May Dan Keyler  saw 12 at a Minnesota den.

During the post-emergence period (the period that commences with the end of emergence and lasts until the move to shedding sites) higher than usual numbers were reported.  On 16 May with Zach Orr and Curtis Miller at a site near the Virginia/West Virginia line, we saw 16 TR mostly adults and about half in the immediate vicinity of the overwintering den, which does offer a good basking opportunities. Curt Brennan and party saw 33 TR at a spread-out north-central Pennsylvania site on 23 May.  Lance Benedict and Justin Collins reported higher than expected numbers during this period at several northern Maryland sites. 
They saw 11 (at least 4 gravid) at a new-found site on 25 May.

I have visited five of my long-term study sites during the pre-shed and shedding period.  Somewhat surprisingly on 9 June, I only
saw three snakes (no gravid females) at a Blue Ridge site near the VA/WV line (not the same site as 5/16 but same as 5/1).  Up to 14 females are known to have reproduced at this site during years of high reproduction and 6-8 is typical. Then with Stan Boder and Justin Collins at two Shenandoah NP sites on 14 June, 9 (7 gravid) and 4 (all gravid).  Most were pre-shed, one post-shed. This is above average for numbers of reproductive females but well below the records for the sites set in 1987 when 20 and 12 reproductive females were counted at these two sites. A northern Maryland site visited on 22 June had three gravid females. (On my only previous visit two gravids were seen.)  Then on 23 June Justin Collins and I were at a Shenandoah NP site and saw 14 gravid females, all but two post-shed.  Previous record for the site was 10 reproductive in 1987.

Phil Dunning reports finding a new site in east-central Pennsylvania and seeing 30-35 adults (too many piled together to get a
reliable count) with probably half of them gravid females.  On the other hand Joe and Marcy Eckley’s results on 19 June in north-central Pennsylvania were somewhat equivocal.  They saw 12 on a cool rainy day but none on a stretch of pipeline that usually holds a number of snakes.

It appears that we will have a big reproduction this year; the first big one since 2003.  Much of Pennsylvania had a big
reproduction in 2006 but not here in the Northern Blue Ridge (southeastern edge of the central Appalachians extending from
west-central Virginia northward along the border of northern Virginia and the eastern panhandle of  West Virginia, across Maryland into south-central Pennsylvania).  The unexpected low numbers on 9 June might be the result of snakes staying out in the woods foraging a little longer than usual and the shed being slightly delayed by cool wet weather.  We shall see.   It is too soon to make firm predictions on birthing dates yet but if the present weather trend continues births will start a bit later than average and drag on into October.  Emergence started a week later than average but by the end of April we were a week ahead of average. Temperatures have been a bit below average and rainfall above average since then with the result that we were running near average in cooling degree days by mid-June.   Typically (2/3 years) litters start to show up between 15 and 25 August, peak during the period 30 August to 4 September, with the last births occurring between 8 September and 1 October.  Hot dry weather speeds up the gestation and cool wet weather retards it.

W. H. Martin
whmartin@crotalus.org
Flat Earth Lane
1227 Engle Molers Rd.
Harpers Ferry, WV 25425
(304) 876-3219

 

Back