Whether they like them or fear them, people find snakes fascinating. Despite
being legless, snakes inhabit most environments on Earth that are ice free for
at least part of the year. Deserts, oceans, forests, grasslands, lakes, rivers,
marshes, mountains, farms, and cities - all are homes to some of the 2400 known
species of snakes. Only 17 species are found in Michigan, but they are an
important and conspicuous part of our state's fauna.
Adaptation and History
Snakes, along with the lizards, turtles, crocodiles, and alligators, are
reptiles. This means that they are lung breathing, back boned animals covered by
dry horny scales. Their young, hatched from shelled eggs or born alive, are
essentially miniature versions of their parents. Reptiles depend on the outside
environment for body heat, unlike birds and mammals which can produce heat
internally. Snakes differ from other reptiles in being legless and in
lacking both eyelids and external ear openings. Their eyes are covered by a
protective transparent scale, and they hear by picking up vibrations through
their skull and jaw bones. The constantly flicking forked tongue is used to
augment the sense of smell. Odor particles are picked up and deposited on a
special organ in the roof of the snake's mouth which then sends information to
the brain. This sense of smell assists the snake in finding food and identifying
potential mates or enemies. The tongue of a snake is never a "stinger" or
weapon.
Snakes evolved from lizard ancestors about 100 million years ago, late in the
Mesozoic Era (the "age of dinosaurs"). Some lizard groups today are still in the
process of becoming legless, and certain primitive snakes, like boas, still have
remnants of hind limb and hip bones in their bodies. Leglessness may be
beneficial in some environments, as when burrowing underground or moving through
thick vegetation. Snakes move with great agility, using from 200 to 400 pairs of
ribs connected in turn to muscles and the large belly scales. The specialized
backbones (vertebrae) allow free lateral movement, but restrict vertical
movement, and some tree climbing species can "lock" their vertebrae to assist in
bridging between branches. The internal organs are arranged to accommodate the
elongated body shape, and most snakes have only one fully-developed lung, the
other being small and degenerate.
Food Habits
All snakes are predators. The smaller Michigan snakes feed on invertebrates
such as worms, slugs, or insects. The larger species take larger prey, such as
frogs, rodents, birds, or other reptiles. (Preferred foods for each species are
noted in the individual accounts above.) Snakes must swallow their food whole.
This is possible due to flexible connections between many of their skull and jaw
bones and stretchable skin, allowing them to swallow prey items larger than
their heads.
Non venomous snakes have tiny, recurved teeth that are useful for holding and
swallowing prey. Venomous species have these recurved teeth, as well as enlarged
teeth for injecting poison. A rattlesnake's fangs are hollow and function like
hypodermic needles to conduct venom from special glands into the body of its
prey. Rattlesnake venom is a specialized form of saliva that not only kills
small food animals but also begins the digestive process. The amount of venom
injected in a bite varies, depending on the angle and force of the strike and
the supply of venom available. About 30% of rattler bites are "dry", which may
account for the reported successes of folk remedies and miracle "cures." Any
bite from Michigan's one poisonous species, the Eastern massasauga, should get
prompt medical attention.
Conversely, a bite from a non venomous snake can normally be treated as one
would a scratch or puncture wound, with ample precaution against infection.
(Simply leaving snakes alone and using care when walking in natural areas will
prevent nearly all bites - these creatures do not seek confrontation with humans
and accidental bites are rare.)
Behavior
Like nearly all reptiles, snakes adjust their body temperature by moving in
and out of warm or cool places. In Michigan, most snakes probably prefer a body
temperature of about 75 to 85 degrees F. Extended exposure to freezing
conditions would be fatal, and they pass the winter in a dormant state in
underground rodent burrows or other natural frost free shelters. Accessible
basements and houses with cracked foundations may also attract shelter seeking
snakes, often to the dismay of homeowners! The dry, scaly skin covering of
snakes has no insulating properties, but does protect them as they move over
rough or prickly terrain. The outer skin covering is shed and replaced several
times during the year, and shed skins are good clues to the presence of
secretive snakes.
Breeding
Snakes usually mate in early spring, with males finding females by following
their scent trails. Sometimes several males may court one female, and males of
some species may fight "push and shove" battles over a female. Fertilization is
internal. Although the majority of reptiles reproduce by laying shelled eggs,
many snakes give birth to babies that develop inside the mother's body. Of
Michigan's 17 snake species, 10 are live-bearing and 7 lay eggs. (Breeding
habits for each snake are noted in the species descriptions, above.)
Egg-laying usually occurs in early summer, with the eggs deposited in an
empty rodent burrow, in moist sand or soil, or under a log or stump. Most snakes
abandon their nests soon after the eggs are laid, but females sometimes coil
about the eggs for varying time periods. Hatching occurs in late summer or fall,
the baby snakes cutting their way through the leathery egg shell using a special
"egg tooth". Live-bearing snakes give birth about the same time in late summer.
The babies often emerge enclosed in a thin membrane which soon ruptures. There
is no parental care of the young, though they may remain near the female for
several hours.
Conservation
Snakes are undoubtedly the most misunderstood and feared of all animals in
the state. This prejudice begins in our early childhood as we watch television
programs and read stories that portray the snake as an evil and dangerous
adversary, to be routinely avoided or destroyed. These fears are reinforced by
watching a parent or friend react to a snake by either running from it or
killing it. Fortunately the negative attitudes are beginning to change as people
are exposed to environmental science programs at schools, nature centers,
museums, and camps, and favorable publicity in the media.
More people now accept snakes for what they are - fascinating members of
Michigan's wildlife community that, if given the chance, will avoid contact with
humans. The vast majority are harmless, and the venomous species can be
identified with minimal training and avoided with simple precautions when
visiting natural areas. Some species that consume rodent or insect pests are
beneficial to agriculture. All snakes play a role in the natural environment by
contributing to ecological systems as predators and prey. They can best be
conserved for the future by providing for their habitat needs and then simply
leaving them alone.
The State of Michigan has enacted legislation to provide for the
protection and regulation of native reptiles and Michigan recently amphibians.
Rare and declining species are now protected from persecution and exploitation,
and all species are affected by limits on numbers that can be taken or removed
from the wild. Shooting of snakes and other reptiles is prohibited. Anyone
wishing to take or study reptiles or amphibians (frogs, toads, salamanders) in
Michigan should contact the Department of Natural Resources Fisheries Division
for details and licensing requirements.
Michigan Species
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