PA rattlesnakes victims of hatred, habitat destruction / Massasauga is endangered, while timber rattlesnake may be listed as threatened
During a trip across Pennsylvania in the summer of 1802, French botanist Francois Andre Michaux discovered that frontier dwellers had a keen interest in the stateís native plants,especially the ones that could be used to treat rattlesnake bites.
Near Bedford, he paused to question a man bitten an hour before, but found, he was so absorbed that it was impossible to get the least answer from him. But the botanist noted that the settlers used a variety of succulent plants to treat the wound.
The loathing the settlers had for the serpents was evident as Michaux travelled through the mountains. We found a great many of them killed upon the road.
If roads are any indication, the public perception of the reptile has not changed much.
Ben Jellen, a herpetologist with the Western Pennsylvania Conservancy, implanted radio tags on 25 endangered massasauga rattlesnakes earlier this year to track their movements. Three met their demise on the roads.
Some people do stop and try to shoo them off the road, but the majority of people try to run them over and think they are doing a good thing for the environment, Jellen said. You can talk to them until you are blue in the face and you canít change their mind.
What has changed over the past several centuries is the number of rattlesnakes. They are certainly less common today than they were when Michaux crossed the state,one hunter of that era described finding a a pile of rattlesnakes as large as an outdoor bake-oven basking in the sun.
Today, not only is the massasauga endangered, but the timber rattlesnake, the stateís most common rattler, is a candidate for being listed as threatened in the state,and is the subject of proposed new regulations to help stem any further decline.
Timber rattlesnakes have been declining throughout their range in recent decades because of overcollecting, habitat loss and wanton killing. It is listed as threatened, endangered, or a species of special concern in most of the states where it is found.
To stem the decline in Pennsylvania, the state Fish and Boat Commission, which is responsible for reptiles and amphibians, in 1993 approved regulations that limited collectors to taking one snake per year. Chris Urban, chief of the commissionís Natural Diversity Section, said some people believe the regulations stabilized the population, but said that was conjectural. The short answer on how the population is doing,we donít know.
That may change in the next few years. New research,some supported by the Department of Conservation and Natural Resourcesí Wild Resource Conservation Program,will shed light on the status of both rattlesnake species and how they can best be conserved. Surveys have been under way for several years on both species to determine whether snakes are still found in areas where they were known to exist historically.
Other studies have implanted transmitting devices in snakes, allowing biologists to use radio-telemetry to track their movements and identify important habitats for the snakes. Still other research has used DNA fingerprinting to help determine whether snake populations are becoming increasingly isolated from one another as new roads and development sprawl across the landscape.
A major concern is not just that numbers have declined, but new development is taking a bite out of rattlesnake habitat, bringing neighbors,many with a loathing of rattlesnakes,into the snakeís hunting and basking areas.
Fragmentation, Urban said, is a huge issue. Experience shows that snake dens quickly disappear as humans encroach. A backyard which once was a forest may be an attractive basking site for a snake that just dined on a few chipmunks. But when modern-day settlers see the snakes, Urban said, they run out and grab the hoe or shovel, and itís off with the head. Some people, if they find out there is a den nearby, go out and shoot every snake they see.
And, of course, the development brings more roads and more traffic,including people who use their vehicles as weapons against the reptiles. One of our snakes was recently hit on the road, Jellen said. Itís head was run over, and its tail was cut off. Somebody killed it, went back, got out their knife and cut off its rattles as a souvenir.
As development constricts habitat, and barriers are created to movement, biologists worry that the remaining snakes in some areas may become genetically isolated. Without being able to breed with outside snakes, their gene pool is limited, making them more susceptible to disease or other problems that may afflict the small populations in the future.
The degree that genetic isolation is a problem in the state is unclear. To find out, Lauretta Bushar, a geneticist at Arcadia University, has been doing DNA fingerprinting on timber rattlesnakes from different regions over the years as part of an effort supported by the WRCP.
She performs a type of DNA fingerprinting known as microsatellite analysis, which is used to study populations of a variety of threatened and endangered species around the world. Microsatellites are a class of genetic markers within the DNA of some species which are highly variable and can be used to distinguish individuals within a population.
Greater diversity among microsatellites within a region suggests greater gene flow among snake populations in that area. Fewer microsatellites means a population may have become isolated from other snakes. Itís been shown that in populations with really low genetic variability, there is increased susceptibility to disease, decreased fertility and increased abnormalities, and things like that, Bushar said.
So far, the studies show that timber rattlesnake populations in the large, unfragmented woodlands of northcentral Pennsylvania have the greatest genetic diversity. Sites on the eastern and southern edges of the state seem to have less genetic variability, and one population in Pike County seems remarkably different from the rest of the state,something that indicates it may have been isolated for a long period of time, or was possibly transplanted from somewhere else.
But Pennsylvaniaís populations generally look better than those from parts of New Jerseyís pine barrens where Bushar has also performed genetic analysis. They have found litters of snakes that are deformed, she said. So it is possible that some regions of the pine barrens are approaching a critical low level of genetic variation.
Urban said the genetics information can help identify areas that need special management. One of our interests in that type of project is we would like to establish management areas for different populations, if they exist, Urban said. We may manage them differently, just like certain game animals are managed.
On South Mountain near Michaux State Forest, named for the early French botanist who became a pioneer in forestry, some populations are considered so isolated that the commission has proposed a prohibition on the take of any timber rattlesnakes in the area. To protect timber rattlesnakes statewide, the commission recently proposed a prohibition on the collection of female snakes, and is proposing a size limit on collections to protect young snakes.
In Western Pennsylvania, massasaugas,the smallest rattlesnakes,are losing ground not only to development but to abandoned farmland. The snakes hunt in fields, but when overgrown by shrubs and saplings, these areas become largely unusable.
Historical records, going back as far as the late 1800s, show that Pennsylvania once had at least 19 massasauga populations spread over six counties. By 1978, that had declined to 11 populations in four counties, and it was listed as an endangered species in the state. By 1990, only eight populations in three counties were confirmed.
Over the past three years, Jellen has revisited those historic sites, and confirmed only four populations in two counties. Further, all those are isolated from one another. There has been no stopping the decline yet, he said. Immediate assistance is needed. That is what we are finding out with this study.
Not everyone agrees they are still disappearing. Urban believes the snakes may still be hanging on at additional locations, though perhaps at dangerously low levels. This species is one of the most cryptic herptiles that we have in Pennsylvania, he said. I think they are at more than four sites. They are just very hard to find.
Regardless, Urban said concerns about the massasauga are great enough that the commission has begun exploring property acquisition and easements to help the snake.
Habitat protection and management is the key to keeping the massasauga, according to Jellen. It hibernates in crayfish holes along streambanks, but it spends much of its life foraging in fields, where it preys upon mice, voles, shrews and other small mammals. Those habitats are in short supply. The amount of farmland is declining, and abandoned farms either revert to forest or are developed.
Only one of the four confirmed populations is considered stable, Jellen said. It is found at the DCNRís Jennings Environmental Education Center, where habitats are actively managed to help massasaugas, including the use of such brush clearing techniques as controlled burnings. Without that management over the past several decades, the massasauga would not be found there, Jellen said.
Promoting massasauga habitat on other properties can mean wading into brushy overgrowth with chainsaws and other gear to remove shrubs and saplings. Habitat management might also include removing perch sites used by raptors in the area. Of 25 massasauga snakes which Jellen tagged and tracked, six were eaten by hawks and owls. They seem to be a favored delicacy of some of the raptors. he said.
Worse, the snakes grabbed by the raptors were gravid,or pregnant,females. Youíre talking about a huge dent in your recruitment, Jellen said. It is a much bigger factor than what we had imagined it to be.
In addition to the three killed by cars, two were eaten by mammals. and one was lost to natural causes. In other words, nearly half died,a total surprise to Jellen. We had no way to expect we were going to lose this many snakes, he said.
Heavy mortality is a problem for both the massasauga and the timber rattlesnake because both take years to reach maturity, and females produce relatively low numbers of offspring, typically every other year.
Historically, snake populations could overcome natural pressures, but today they face the added burden not only of often-hostile humans, but the loss of habitat from roads and development. Humans and rattlesnakes have been at odds since the arrival of the first Europeans, who,having almost no experience with venomous snakes,were horrified by the rattling reptiles almost from the moment they set foot in the New World. (The latin name for the timber rattlesnake is Crotalus horridus.) Some Pennsylvania counties once even offered bounties on the snakes.
In fact, even in Michauxí day, when snakes were more plentiful, death by rattlesnake bite appears to have been rare. Pennsylvania rattlesnakes tend to be secretive and docile. They are more likely to hide or move away, if given the chance, than confront a human. Ironically, venom from snakes is also being used in research on treatments for hypertension, heart attacks and cancer.
They play an important role in ecosystems. Snakes, especially young ones, are prey for many species, such as raptors. Older snakes are themselves predators, helping to control the populations of rodents and other small animals.
They are to be respected, not feared, Urban said. They do have a value to the natural ecosystem.
The eastern massasauga is brownish gray to black on its back and sides with dark blotches running down the center of its back. It grows to 20-30 inches in length. The massasauga is found only in westcentral Pennsylvania. It lives in marshy areas or swamps with adjacent drier fields. Females mature in about two years. They give birth in mid to late summer to six to seven live young, each measuring 6-9 inches, every other year. The young are pale miniatures of the adults, save for a distinct yellow tail tip. Massasaugas mostly eat frogs and other amphibians, but will also prey on small rodents and birds.
Timber Rattlesnake The timber rattlesnake grows 36-54 inches long and is found in two color phases, the more common black (mostly dark brown and black) and rarer yellow, shown here, (black and brown crossbands on yellow). Both phases have a black tail. Completely black snakes are also found in some areas. Timber rattlesnakes are found in wooded hillsides in the mountainous areas of Pennsylvania. They prefer areas on southern slopes with rock outcrops to bask upon as well as fissures where they can hibernate. The female matures in the late summer of her 4th or 5th year. She gives birth, one year after breeding, to five to 17 live young, each 10-13 inches long. She breeds every two to three years, and in the intervening years eats to store sufficient fat for her year-long gestation, when it is believed that she consumes only rainwater. Timber rattlesnakes mostly eat mice and small rodents, but will also consume rabbits, birds, lizards and frogs. - From "Pennsylvania Amphibians & Reptiles"