Reptiles
Massasauga
Sistrurus catenatus · also called eastern massasauga, swamp rattler, black snapper
Most of North America’s rattlesnakes are animals of dry country. The massasauga is a wetland snake, small and grey and easy to miss, with a rattle that sounds more like an insect than a warning. It is also one of the continent’s most quietly imperilled reptiles.
Overview
Sistrurus catenatus lives in the interior of North America, in wet prairies, fens, bogs, and marsh edges from southern Ontario west through the Great Lakes states. Adults are 60 to 75 cm, stout, grey with a row of large dark blotches. It is an ambush hunter of voles, mice, and shrews.
The buzz, and a different lineage
Its small, high-pitched rattle sounds like a bee or grasshopper from a few metres off. It belongs to the genus Sistrurus, not Crotalus, and has nine large head plates like a harmless colubrid rather than many small scales.
Winter underwater
It hibernates alone in crayfish burrows at or below the water table, where the ground stays above freezing without fully flooding — a narrow requirement that limits where it can live.
Status
Globally Least Concern but declining. The eastern massasauga is federally Threatened in the US and Endangered in Canada, after most of its wetland habitat was drained.
Massasauga: common questions
How dangerous is a massasauga bite?
A massasauga bite is a genuine medical emergency and needs hospital treatment, but deaths are extremely rare. The venom is potent, containing tissue-damaging and blood-affecting components, and a bite causes intense pain, swelling, and bruising. However, the massasauga is a small snake with short fangs and a small venom yield, it is very disinclined to bite, and it often delivers little or no venom in a defensive strike. Only a handful of deaths have ever been recorded, most from many decades ago and involving no treatment. With prompt care and, where needed, antivenom, the outlook is good. The snake's shyness means most people never realise one is there.
Why is the massasauga endangered when it is listed as Least Concern?
The two labels describe different scales. The IUCN assesses the species across its entire range, where enough populations survive, mostly in the west and southwest, for it to rank as Least Concern overall. But the eastern massasauga, the form found around the Great Lakes, has lost most of its habitat to the draining of wetlands for farming and development, and its remaining populations are small, isolated, and still declining from road deaths, persecution, and habitat fragmentation. On that basis it is federally Threatened in the United States and Endangered in Canada. A species can be secure globally and in serious trouble regionally at the same time.
What should I do if I find a massasauga?
Leave it alone and give it room. The massasauga is not aggressive and will almost always stay still or move away if it is not cornered or touched. Step back, keep pets and children away, and let it continue on its way; it is doing valuable work controlling rodents. Do not try to move, catch, or kill it. In most of its range it is legally protected, and killing one can carry a heavy penalty. If a snake is somewhere genuinely hazardous, such as inside a building, contact a licensed wildlife control officer or a local herpetological group rather than handling it yourself.
How is a massasauga different from a fox snake or a hognose snake?
Both harmless species are regularly killed by mistake for massasaugas because they share the blotched pattern and, in the case of the eastern hognose and the fox snake, will flatten the head, hiss, and vibrate the tail when threatened. The differences are clear. A massasauga has a true segmented rattle at the tip of the tail, vertical cat-like pupils, a distinct triangular head with a heat-sensing pit between eye and nostril, and a stout body. Fox snakes and hognose snakes have round pupils, no pit, no rattle, and a tail that simply tapers to a point. When unsure, keep your distance from any of them.