Description: In our field trip to Dixie Plantation, Paul excitedly came across a cute little critter--the marbled salamander. He was found under a log, near water. Ambystoma opacum usually grow up to 3-5 inches long. They have stout, chubby bodies that are covered with bands of white on a dark dorsum color (usually black or brown). The salamander we found was especially chunky. Like most Ambystomatids, this salamander also possesses somewhat of a "beer belly" appearance. The torso part is especially round in appearance. The bands are only found on its dorsum and do not continue on to the venter. These bands are a sexually dimorphic trait, as males will generally possess white crossbands, where as females will possess a more gray/silvery colored on their crossbands. Juveniles do not posess bands at all, but are lightly flecked with white or gray colors. With the preceding notion, I personally think that the salamander we picked up was an adult male, as he had distinct milky white crossbands on a black dorsum.
Habitat: Marbled Salamanders are a local species. They are found in Southeastern USA but are lacking in Georgia, peninsular Florida and higher elevations of the Appalachian mountains. They can be found in low-lying floodplains to hillsides, under logs and other relatively moist habitats. They are not considered endangered in our state, as they can be found very commonly. These species are also a popular pet; keeping them under moistened paper towels can mimic the habitat they are naturally found in. The only place they are endangered is near the Great Lakes.
Reproduction/Life History: Marbled salamanders, like all other ambystomatids have a biphasic lifecycle. As mentioned above, they migrate to to wetlands to breed. An interesting fact that differentiates them from most other salamanders is that they are autumnal breeders--they breed in Autumn whereas, most salamanders breed during the winter time. Courtship behaviors are seen in this species. After locating a potential mate, the male will move in a circular fashion around the female. If the courtship is sustained long enough, the male undulates his tail raising his body, and deposits a spermatophore which is picked up the female's cloacal lips (Petranka 1998). When ready, female marbled salamanders lay about 30-100 eggs on land--under logs or leaf litter, away from predatory fish populations. They have often bred before they arrive to the nesting site. They are really cool in that they return to their natal nesting site. Uniparental care is found in this species. The female stays with her eggs until the rain triggers them to hatch; she also incubates them. The aquatic larvae take 2-10 months to undergo the metamorphosis that accompanies the biphasic lifecycle. Ambystomid larvae are characterized by broad heads, caudal fins and long filamentous gills.
Behavior: These guys are, for the most part, a solitary species that spend most of the time under leaf litter or underground. It is thought that these species may be territorial and defend their own burrows as they do have small home ranges (the largest maxing out to only a few meters). They communicate through chemosensory signals. The only time that these species is really in contact with each other is during the breeding season. They are fossorial species--meaning they spend most of their time burrowing underground. Their chunky bodies and shorter tails are characteristic of this type of lifestyle. They are predators that will prey on small worms, insects, some small crustaceans, slugs and even snails. An interesting fact about these marbled salamanders is that they will not eat dead prey, as they are attracted to movement and odor (Petranka 1998). On the other hand, they are hunted down by snakes, owls, raccoons, skunks and other woodland predators. These marbled salamanders possess poison glands in their tails to deter predators.
Field Trip: The field trip to Dixie plantation was a fun one! In addition to Ambystoma opacum, we found the southern slimy salamander, some anoles, and various species of toads. My favorite, however, was the marbled salamander because it was so cute! Thats why I decided to write about him. An interesting question arose when students started wondering whether this organism was black with white stripes or white with black stripes. The general consensus was that he was indeed black with white stripes, as his venter and his limbs were black. Zebras, however, still remain a mystery..!
Petranka, J. 1998. Salmanders of the United States and Canada. Smithsonian Institution Press.
