Northern Coal Skink
Eumeces anthracinus anthracinus
Tioga County, NY
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.
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.
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
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