The Constrictor Snakes of the Chicago Area
Nature Bulletin No. 693 November 10, 1962
Forest Preserve District of Cook County
Seymour Simon, President
David H. Thompson, Senior Naturalist
THE CONSTRICTOR SNAKES OF THE CHICAGO AREA
Snakes feed almost exclusively on other animals which they catch alive
and swallow whole. A few eat the eggs of birds or turtles but they rarely
touch anything that they find already dead. A snake's jaws are so
loosely joined and its throat so elastic that it is able to stretch around
prey large enough to form a big bulge in the stomach. The jaws with
their backward-slanting teeth are slowly 'walked ' over the victim, one
side at a time, like pulling a pillow case over a pillow.
Most kinds of snakes merely seize their prey and down it without any
further ado. In contrast, a poisonous snake, for instance a rattler, stabs a
rodent with its fangs and trails it until the venom takes effect. Still
others, called constrictors, grab their victims, flip coils around them,
and squeeze them to death. Four species with this feeding habit are
found in the Chicago area -- bull snake, black rat snake, milk snake and
These constrictors all have similar life histories. In early summer the
females lay a half dozen to two dozen elongate eggs with white leathery
shells. These are hidden under rocks, in rotten wood or in loose soil.
They hatch in late summer or early fall. The young escape by cutting
slits in the shell with an egg tooth on the tip of the snout -- like the egg
tooth on the beak of a young bird. They become sexually mature in their
second or third year but, unlike birds and mammals, they continue to
grow throughout life. They spend the winter in hibernation hidden away
below the frost line in burrows, under stumps, or deep in rock crevices.
The Bull Snake is Illinois' largest snake, sometimes reaching a length of
six feet or more. One of these in a farmer's barn is more valuable than
two or three cats for destroying rats and mice. In fields and woodlands
they catch ground squirrels, gophers and young rabbits, or rob birds'
nests both on the ground and in trees. One can consume a dozen duck
eggs or mice at a single meal; or it can live for months without any
food. A bull snake puts on a big show of ferocity when disturbed, but
that is all bluff. With the raised head weaving from side to side, and
pretending to strike, it hisses and snorts like an angry bull.
The Black Rat Snake also has the name Pilot Black Snake because it
once was supposed to warn rattlesnakes of danger. This large snake
spends much of its time climbing about in brush piles, bushes and trees
-- often 20 or 30 feet above ground. The upturned ends of its belly
plates enable it to hitch its way up smooth tree trunks and concrete
walls. When surprised, it habitually "freezes" in imitation of a broken
The Milk Snake, a medium-sized constrictor, is commonly found
around farm buildings where it hides during the day and prowls at night.
The superstition that it sucks milk from cows is absurd. Even supposing
that it did like milk and could suck, no cow would hold still for that
mouthful of needle-sharp teeth. Its diet is mostly mice and other snakes.
The milk snake does not make a good pet because it has a mean
disposition and is hard to feed. The King Snake, a downstate relative, is
famous for strangling and eating rattlesnakes.
The Fox Snake is a rather large serpent with a disagreeable "foxy" odor
when first captured. It hunts rodents, frogs, toads and salamanders on
the ground, or climbs for birds and their eggs. At the Little Red
Schoolhouse nature center, in recent years, two captive fox snakes have
laid eggs from which, after being exhibited 7 or 8 weeks, foot-long
young were hatched.
these constrictor snakes have a row of dark blotches down the
back and buzz the tips of their tails when alarmed, they are often
mistaken for rattlesnakes and ruthlessly destroyed. That is unfortunate.
They are useful.
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Update: June 2012