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By Garry Rogers
Geographic Range
Ambystoma opacum, the marbled salamander is found throughout most of the eastern United States, from Massachusetts west to central Illinois, southeastern Missouri and Oklahoma and eastern Texas, south to the Gulf of Mexico and the Carolina coast. It is absent from peninsular Florida. Disjunct populations are found in eastern Missouri, central Illinois, in northwest Ohio/northeast Indiana, and along the southern edges of Lake Michigan and Lake Erie. (Petranka, 1998)
Habitat
Adult marbled salamanders live in damp woodlands, often close to ponds or streams. These salamanders are occasionally can be found around dry hillsides, but never far from a moist environment. (Flank, 1999; Petranka, 1998)
Unlike most other mole salamanders, this species does not breed in water. Adult marbled salamanders breed only in dried up pools, ponds, and ditches, and females lay their eggs under the leaves there. The eggs hatch after the ponds refill. (Petranka, 1998)
These animals are found in the following types of habitat:
temperate 
; terrestrial .
Terrestrial Biomes:
forest .
Aquatic Biomes:
temporary pools.
Physical Description
(3.54 to 4.21 in)
Ambystoma opacum is one of the smaller species in the Ambystomatidae family. It attains an adult length of approximately 9-10.7 cm (Conant and Collins 1998). It is sometimes called the banded salamander, because of its white or light gray crossbands across the head, back, and tail. Considered sexually dimorphic, males are smaller than females, and have silvery white crossbands. During the breeding season, the crossbands become very white and glands around the male's cloaca become swollen. Females are larger, and have silvery gray crossbands. (Petranka, 1998)
Some key physical features:
ectothermic ; heterothermic ; bilateral symmetry ; poisonous .
Sexual dimorphism: female larger, sexes colored or patterned differently.
Reproduction
Marbled salamanders breed once per year.
Breeding starts in the late summer in the northern part of the range, and extends into November in the southern part.
Unlike most others in this family, Ambystoma opacum has a very unusual reproductive strategy. Instead of breeding ponds or other permanent water sources, in spring months, the marbled salamander is a fall breeder, and breeds entirely on land.
After finding his mate, the male will court with the female, often moving in a circular fashion with her. The male will then proceed to undulate his tail, and raise his body. Following this, the male will deposit a spermatophore onto the ground. If interested, the female will then proceed to pick it up with her cloacal lips (Petranka 1998). After mating the female will venture off and select a small depression in the ground. This depression is usually a reduced pond, or dried bed of a ditch or temporary pond (Petranka 1998). The female will lay a clutch of between fifty and one hundred eggs. Once deposited the female will remain with them to keep them moist, until nests are flooded. As soon as the autumn rains come the eggs will hatch in the depression they were originally laid in. If rain never comes the eggs will remain dormant through the winter if temperatures do not fall too low, then hatch the following spring (Flank 1999).
Once hatched the gray colored larvae (1 cm) grow extremely quickly, eating primarily macrozooplankton. Large larvae, however, will eat amphibian larvae and eggs (Petranka 1998). The timing on metamorphosis depends on geographic location. Those that are found in the South can go through metamorphosis in as little as two months. Those in the northern climates generally take between eight to nine months (Petranka 1998). Young juveniles are approximately 5 cm, and attain sexual maturity in about 15 months, after metamorphosis (Flank 1999). (Flank, 1999; Petranka, 1998)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (internal ); oviparous .
Behavior
Ambystoma opacum is, for the most part, a solitary species, spending most of the time under leaf litter or underground (up to one meter). It is thought that species will defend burrows they inhabit against others of the same species. Occasionally, adults will share burrows with each other. Adults do, however, tend to be more aggressive towards each other when food is scarce (Petranka 1998). The only time species are in contact with one another is during the breeding season. Males will often arrive at potential sites about a week before the females (Petranka 1998). (Flank, 1999; Petranka, 1998)
Key behaviors:
terricolous; fossorial ; natatorial ; nocturnal ; motile ; migratory ; sedentary ; hibernation ; solitary .
Food Habits
Even with its small size, an adult Ambystoma opacum is a voracious, carnivorous predator, consuming large amounts of food. Small worms, insects, slugs, and even snails, make up its diet. Attracted to movement as well as odor, this species will not eat dead prey. (Flank, 1999)
Marbled salamander larvae are also active predators, and may be the dominant predators in their temporary ponds. They eat zooplankton (mainly copepods and cladocerans) when they first hatch, but add other prey to their diet as they grow, including larger crustaceans (isopods, fairy shrimp), aquatic insects, snails, oligochaete worms, and the larvae of amphibians, sometimes even other marbled salamanders. In woodland ponds larger larvae sometimes feed heavily on caterpillars that fall into the water. (Petranka, 1998)
Primary Diet:
carnivore (eats non-insect arthropods).
Animal Foods:
amphibians; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic or marine worms; aquatic crustaceans; zooplankton .
Predation
Marbled salamanders are preyed upon by various woodland predators (snakes, owls, raccoons, skunks, shrews, weasels).
Poison glands located on the tail provide a degree of protection. (Petranka, 1998)
Economic Importance for Humans: Positive
Marbled salamanders have no economic importance.
Conservation Status
IUCN Red List: [link]:
Least Concern.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
State of Michigan List: [link]:
Threatened.
This species is listed as threatened by the Michigan Department of Natural Resources (DNR). In other areas it is not considered threatened and can be locally common.
Declining populations in the Great Lakes region can be attributed to both declining habitat but more so the effects of widespread temperature cooling after a warmer postglacial climate brought them into the area.
For More Information
Find Ambystoma opacum information at
Contributors
Garry Rogers (author), Michigan State University.
James Harding 
(editor), Michigan State University. David Armitage (editor), Animal Diversity Web Staff.
