Northern Coal Skink
Eumeces anthracinus anthracinus
Tioga County, NY
Species
In number of species, lizards are the most successful
reptiles in the world. There are over 3,500 species of lizard alive today.
Most of these are found in the warmer tropics and subtropical regions of
the globe, but many are found in a more temperate distribution. Lizards
are uncommon to rare in New York with 3 species of 2 families native to
the area. One other species of a third family, Lacertidae, has been introduced.
Lizards are characterized by a long body with four
legs and a tail. The skin is covered in scales. Unlike snakes, most lizards
have movable eyelids and external ear openings. Many people mistake lizards
for salamanders, but salamanders have slimy skins as compared to the dry
scale covered skins of lizards. The feet of lizards ends in a claw, unlike
the feet of salamanders.
All of the lizards in our area are largely insectivorous,
feeding mainly on hard bodied arthropod prey. Lizards do not chew
and thus their food must be swallowed whole. They grab their prey with
their jaws, not with their feet. Virtually any insect that fits into the
lizards mouth will be taken as food.
Terminology
Tail Autonomy
Lizards, especially the skinks, are well known for
their ability to "drop" their tails and regrow another one. This remarkable
ability, referred to as tail autonomy and regeneration, respectively, is
believed to have one important purpose- predator defense. Many lizards
have fracture planes in their muscle and skeletal structure. Fracture planes
are weak spots in the muscle and bone that allow separation of the tail
from the rest of the body when pressure is applied. The tail separates
and flails from side to side. This movement captures the predators attention
and the predator goes after the tail allowing the lizard to get away. Most
lizards have several fracture planes so that only one segment of the tail
will detach at a time. This is so that the defense can be used several
times.
The detached part of the tail will regrow in time,
but a regenerated portion is markedly different from the original with
differences in scalation and coloration. As a testament to the effectiveness
of this defense mechanism it is uncommon to find an adult skink with a
completely original tail. The ability to autonomize the tail and the nimbleness
of our lizards make them difficult animals to hold.
Reproduction
Mating in lizards occurs soon after the emergence
from hibernation. Sexual differences in many lizards are pronounced and
take the form of differences in coloration and structure. In the northeast
it is most pronounced in our skinks, the males often having orange coloration
on the head or chin. Courtship begins with a series of head bobs and head
rubbing and is usually initiated by the male. In other species (like the
Fence Lizard), the male climbs onto the back of the female and bites at
the loose skin on the back of the neck. The specifics vary depending on
the species. Mating occurs when the female is receptive, otherwise the
female will refuse the male's advances and no copulation will take place.
Like all squamates, fertilization occurs internally.
This is accomplished with the use of the hemipenes, a pair of structures
that the male keeps inverted inside of the rear of his tail. The hemipenes
are analogous to a pair of pants that have the legs sewed shut. A pair
of pants, when removed quickly will be inside out. This is the way that
the hemipenes are kept most of the time. When copulation is imminent, fluid
fills up one side of the hemipenes, analogous to one leg of the pants.
Only one side of the hemipenes is used at a time in copulation. It is introduced
to the female's cloaca where it deposits the sperm and copulation is finished.
It then returns to its original position inside of the tail of the male
lizard.
Hemipenes are very ornate structures with a number
of different ridges and crevices. These patterns are specific to a species
with all members of a species having the same number and placement of the
ridges. Hemipenis structure, then, can be used to compare different species
and discover the evolutionary relationships between them. This requires
specialized equipment and is only done by taxonomists and professional
herpetologists. It cannot be done in the field.
Most of the lizards in the world are oviparous,
although there are a few ovoviviparous forms. All of our lizards lay their
eggs in late spring to early summer. Many lizards excavate a nest to provide
a place to lay their eggs. These nests are little more than a shallow hole
in the ground. Some species bury their eggs, others do not. The skinks
are well known for guarding the eggs until hatching time, but the female
provides no other parental care.
Young lizards hatch in late summer and are fully
capable of fending for themselves.
Northern Coal Skink
Eumeces a. anthracinus
Tioga County, NY
Families
Lizards are in the Class Reptilia, Order Squamata, Suborder Lacertilia.
Most lizards require relatively warm temperatures to become active. As
a result the northeast is significantly lacking in lizard diversity. There
are 4 species of 3 families of lizards found in our area.
Family Phrynosomatidae- Spiny Lizards and Others
Family Lacertidae- Typical Old World Lizards
Family Scincidae- Skinks
