(logging, reforestation, clearing brush, using herbicides, etc) can have
unforeseen consequences for wildlife. As vegetation goes through succession it
creates a variety of changing micro-environments that favor some species over
others, so as the stages of succession change the animal populations change
with them. This concept has been long known and its application to rattlesnakes
was noted in Philip Tome’s 1845 book, Thirty
Years a Hunter. Tome lived in northeastern Pennsylvania and described
frequent encounters with Timber Rattlesnakes (Crotalus horridus). Tome
described the early setters burning forests to control rattlesnakes. Of course,
in the long term this opened up the canopy and provided more basking sites. Jäggi
and Baur (1999) linked the decline of Viper
aspis populations to changes in vegetations, and other authors have made
similar reports of changes in snake populations to changes in vegetation.
and James Gibbs of the State University of New York now report that the Eastern
Massasauga (Sistrurus c. catenatus) persists
as two isolated populations at the eastern edge of the species’ geographic range,
and those two populations are threatened by the increasing density of woody plants.
They found microhabitat temperatures were substantially lower at the
closed-canopy site, where catenatus selected
the warmest available basking sites.
open-canopy catenatus selected
basking sites that afforded greater cryptic cover. And, they recommend the experimental
reduction of shrub cover to improve basking habitat at the closed-canopy site. But
they caution that management efforts to reduce shrub cover for basking should maintain
adequate cryptic cover, (that is the grasses, leaf litter, rocks, and other
cover) used by the snakes to conceal themselves.
In another paper,
Charlotte Matthews and colleagues (2010) report that the recent use of
prescribed fire and fire surrogates to reduce fuel hazards has spurred interest
in their effects on wildlife. They conducted studies to determine the impact of
“reducing fuel” in forests on amphibian and reptile populations in areas that
were twice burned, had the understory cut mechanically, and in an area that had
the understory cut mechanically followed by two burns. They trapped the
herpetofauna using pitfall and funnel traps. The study was done at the Green
River Game Land, Polk County, North Carolina. The results revealed that
salamanders were reduced in number in the twice burned, mechanically opened
habitats – possibly because this site had reduced leaf litter. While these same habitats supported larger
numbers of lizards and snakes, undoubtedly due to the increased number of
basking sites and the newly created thermal gradients.
Jaggi, C., and
B. Baur. 1999. Overgrowing forest as a possible cause for the local extinction
of Vipera aspis in the northern Swiss
Jura mountains. Amphibia-Reptilia
Matthews, C. E.,
C. E. Moorman, C. H. Greenberg, and T. A. Waldrop. 2010. Response of Reptiles and Amphibians to
Repeated Fuel Reduction Treatments. Journal
of Wildlife Management 74(6):1301-1310.
K. T. and J. P. Gibbs. 2010. Evaluating basking-habitat deficiency in the
threatened Eastern Massasauga Rattlesnake. Journal
of Wildlife Management 74(3):504-513.
P. 1854. (1989 reprint) Pioneer Life; or,
Thirty Years a Hunter. Baltimore: Gateway Press.
Labels: biodiversity, habitat alteration, shade, vegetation