Ambystoma maculatum

Geographic Range

Spotted salamanders are found in eastern North America. Their range extends from Nova Scotia and the Gaspé Peninsula west to the northern shore of Lake Superior, and south to southern Georgia and eastern Texas. The spotted salamander is absent from most of southern New Jersey, the Prairie Peninsula in Illinois, eastern North Carolina, and the Delmarva Peninsula.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Adult spotted salamanders are most abundant in deciduous bottomland forests along rivers, but can be found in upland mixed or coniferous forests if the climate is sufficiently damp and there are ponds suitable for breeding. Adults are rarely seen because they spend most of their time hiding in leaf litter, under fallen wood, or in tunnels below ground.

Like most Ambystoma salamanders, spotted salamanders lay their eggs in fresh water, but only in ponds and pools that lack fish. They often use temporary vernal pools.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial
• freshwater freshwater

• Terrestrial Biomes
• forest forest

• Aquatic Biomes
• lakes and ponds
• temporary pools

Physical Description

Adult spotted salamanders are 15-25 cm in total length, and females tend to be larger than males. Compared to other salamanders, the body is stout with a broadly rounded snout. The sides of the head are often swollen at the back of the jaw. The legs are large and strong with four to five toes.

The background color of metamorphosed spotted salamanders can be black, dark brown, or dark grey, while the bottom half and under-surface of the limbs are a pale slate gray. On either side of the mid-dorsal line of the body are large, round, yellow or orange spots. The spots may vary in number from 24 to 45, and they are arranged in two irregular rows running along the sides from the head to the tail. Unspotted individuals do occur but are rare.

Spotted salamanders have poison glands in their skin, mostly on their backs and tails. These glands release a sticky white toxic liquid when the animal is threatened.

When they hatch, the larvae of this species are 12-17 mm long. Their dorsal surface is dull olive green, and they remain a dull greenish color until they transform into the adult form. The underside of larvae is nearly white, and tail is finely stippled or mottled, with dark pigment near the tip.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry
• poisonous poisonous

Development

Spotted salamanders go through several stages over their lifetime. Female salamanders lay their eggs under water, and the larvae that hatch from the eggs are aquatic, with gills for taking oxygen from the water, weak legs and a broad tail for swimming. Larvae feed and grow in the water, and then metamorphose into an juvenile form with lungs and strong legs. Juveniles live on land, and after 2-3 years they mature into adults that can reproduce.

This species has relatively long incubation time in comparison to other salamanders. It takes 4-7 weeks for the eggs to hatch, depending both the temperature of the water they are in, and whether the eggs are laid in shady or sunny areas.

Spotted salamander larvae are 12-13 mm long when they hatch, with feathery gills and only their front legs present

Larvae grow quickly and transform within 2 to 4 months after hatching. Average size after metamorphosis ranges between 27 and 60 mm, depending on the conditions in the pond. The yellow and orange spots are usually acquired within a week following transformation.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Spotted salamanders begin migration to breeding ponds at night, during the first rain following the thaw of snow. Males respond more quickly to the rain and move faster than do the females, therefore they arrive to the pool first. They also stay longer in the ponds than females do, probably to increase their chances of fertilizing more eggs each year. The number of males present in the breeding pools is greater than the number of females, so when the females arrive the males swim about vigorously, rubbing and nosing each other. Males produced blobs of sperm called spermatophores (up to 80 per male), and the females take these spermatophores into their bodies to fertilize their eggs. Each male may fertilize several females, and each female may take up spermatophores from several males.

Male spotted salamanders may compete with other males for the chance to fertilize females. They push other males away from females, produce as many spermatophores as they can, and sometimes cover other males' spermatophores with their own.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

It takes several years for spotted salamanders to become reproductively mature, and the time required is strongly affected by the climate where they live. In the warmer parts of their range they may be ready to breed in 2-3 years, but further north they males may take 5 or 6 years and females as many as seven years.

See the Behavior section for more details on breeding behavior.

Females lay compact egg masses that are attached to submerged objects. The egg mass is covered with thick, clear or milky-white jelly. Each female lays approximately 100-300 or more eggs per year, in several separate masses. Reported averages are about 200 eggs per female per year.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Male spotted salamanders provide no parental care. Females invest nutrients in provisioning their eggs with yolk and supplying them with protective layer of jelly. They also make an effort to lay the eggs in a suitable location, usually on submerged tree branches or aquatic plants. There is no further investment after the eggs are laid.

• Parental Investment
• pre-fertilization
  • provisioning

Lifespan/Longevity

Most spotted salamanders (more than 90%) die before they transform and leave their pond, either because their pond dries up, or they are killed by predators or disease. If they do survive and make it out of the pond, they typically live about 20 years in the wild, though some have been reported as old as 30. Their chance of survival from one year to the next is much much higher after they transform.

Behavior

Spotted salamander larvae hide in the litter at the bottom of the pond when they detect potential predators, but when not threatened by larger animals, they are aggressive predators themselves.

After they transform from aquatic larvae to the terrestrial adult form, spotted salamanders disperse from their ponds on rainy nights. They find refuge in animal burrows and under logs and rocks. Most live within 100 meters of their breeding pond, though a few have been found as far as 250m. This species is not believed to be a strong digger, mainly using existing burrows and crevices, though some may enlarge or modify the tunnels they find. Most hide within a few centimeters of the soil surface, but some have been found as deep as 1.3 meters below the surface of the soil.

When ready to breed, spotted salamanders try to return to the pond they hatched in, and even if another pond is closer they will try to go to their own pond. They are able to locate the pond even if moved hundreds of meters away. It is not known exactly how they do this, but chemical sense (smell and taste) are probably important. They often arrive and leave their pond at the same spot, and may follow the same path every time they breed.

Adult spotted salamanders are quite sedentary, only moving as far as necessary to find food and cool moist refuges underground. They only emerge from their burrows if they can't get enough food below ground, and then only on moist or rainy nights. They stay hidden if conditions are too cold, too warm, or too dry.

• Key Behaviors
• terricolous
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• migratory migratory
• sedentary sedentary
• hibernation hibernation
• aestivation
• solitary solitary

Home Range

Spotted salamanders tend to stay in an area of 8-15 square meters of forest floor. They respond aggressively to other spotted salamanders that they encounter in their burrows or feeding area, but it's not known if they maintain or mark a territory.

Communication and Perception

These salamanders locate prey by smell and sight. Their vision is probably best for detecting motion in low light. Sense of smell is important in orienting spotted salamanders to their burrows and to their home pond, as are visual and tactile information. It is believed that home pond odors are preferred compared with foreign pond odors.

During courtship, males nudge and rub females, probably communicating with both touch and smell. Females are attracted by the chemical scents given off by males in the water.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Salamander larvae are aggressive predators. They are generalists, eating whatever small animals they can catch. When they first hatch they feed mainly on small insects, and branchiopod crustaceans like Daphnia and fairy shrimp . As they get larger they take larger prey, including isopods , amphipods , larger insects, frog tadpoles, and other salamander larvae. In times of overcrowding, usually when the vernal pools start to dry up, spotted salamander larvae may become cannibalistic and attack members of their own species.

The adult spotted salamander uses its sticky tongue to catch food. Their diet consists mainly of forest floor invertebrates, including earthworms , snails and slugs , millipedes , centipedes , spiders , and a wide variety of insects . They sometimes also eat smaller salamanders, such as the red-backed salamander, Plethodon cinereus .

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
• planktivore planktivore

• Animal Foods
• amphibians
• insects
• terrestrial non-insect arthropods
• mollusks
• terrestrial worms
• aquatic or marine worms
• aquatic crustaceans
• zooplankton zooplankton

Predation

Spotted salamander defense begins immediately following laying of eggs. The eggs are laid in masses that are covered in a thick, firm, jelly, overcoat to protect against some predators (e.g. leeches and sunfish ) and from dehydration, should the egg mass be temporarily exposed by sinking water levels. There is a particular species of unicellular green alga ( Oophila ambystomatis ) that grows on and in the jelly. The algae provides extra oxygen to the developing embryos, and may help camouflage the egg mass as well.

Despite this protection, a number of predators eat spotted salamander eggs: adult newts , wood frog tadpoles , crayfish and some species of caddisfly (especially Ptilostomis postica and Banksiola dossuaria ) and midges in the genus ( Parachironomus ). These predators are so effective that in some years up to 90% of eggs may be killed before they hatch.

Spotted salamander larvae are also heavily preyed upon. Hatchlings are eaten by those aquatic creatures previously mentioned and also various aquatic insects, fish, wading birds, other Ambystoma species, and snakes. Hatchlings raised in laboratories often die from protozoan infections as well.

Adult spotted salamanders are preyed upon by larger animals, including skunks , raccoons , turtles, and snakes, especially garter snakes (genus Thamnophis ). Like many other salamanders, adult spotted salamanders secrete a milky toxin from glands on the back and tail for defense against predation. The bright spotting on these salamanders functions as a warning to predators of their toxic defense.

Adult spotted salamanders respond to attack by arching the body and sometimes butting with the head or lashing with the tail, probably to expose the predator to as much poison as possible. They sometimes bite, and individuals of all sizes may also make sounds when attacked.

• Anti-predator Adaptations
• aposematic aposematic

Ecosystem Roles

Spotted salamanders can be important to the community of species that live and breed in vernal pools, affecting the abundance and diversity of other species in the pools, especially other amphibians. Gray treefrogs ( Hyla chrysoscelis and Hyla versicolor ) avoid breeding in ponds with spotted salamanders in them, and depending on the timing and size of the other species present, spotted salamanders may reduce the population of other Ambystoma species in their pools.

Economic Importance for Humans: Positive

Spotted salamanders may help control insect pest species, including mosquitoes that breed in their ponds.

Economic Importance for Humans: Negative

There are no known adverse effects of Ambystoma maculatum on humans.

Conservation Status

The spotted salamander is still a fairly common species, but its populations are particular vulnerable because of their dependence on vernal pools for breeding. Acidic precipitation has a negative effect upon their embryos, and habitat destruction is a problem, especially as it isolates populations from each other. The species is rated "of Least Concern" by the IUCN, and is not listed by the U.S. Endangered Species Act, in the CITES appendices, or by the State of Michigan.

The spotted salamander is still a fairly common species, and it is not considered endangered. However, the species depends on vernal pools to survive and reproduce, and this habitat is threatened by acid rain and deforestation. The species is rated "of Least Concern" by the IUCN, and is not listed by the U.S. Endangered Species Act, in the CITES appendices, or by the State of Michigan.

Additional Links

AmphibiaWeb

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Lauren Pajerski (author, editor), Undergraduate Research Opportunity Program, University of Michigan, George Hammond (author, editor), Animal Diversity Web.

Nichol Stout (author), University of Michigan-Ann Arbor.

References

Bishop, C. 1943. Handbook of Salamanders . Ithaca, New York, USA: Comstock Publishing Co..

Blanchard, D. 1930. The stimulus to the breeding migration of the spotted salamander. The American Naturalist , 691: 154.

Conant, R. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America . Boston, Massachusetts, USA: Houghton Mifflin Company.

Frank, N., E. Ramus. 1995. A Complete Guide to Scientific and Common Names of Reptiles and Amphibians of the World . Pottsville, Pennsylvania, USA: N G Publishing, Incorporated.

Georgia Museum of Natural History, 2000. "Spotted Salamander, Ambystoma maculatum " (On-line). Georgia Wildlife Web. Accessed April 19, 2004 at http://museum.nhm.uga.edu/gawildlife/amphibians/caudata/ambystomatidae/amaculatum.html .

North American Reporting Center for Amphibian Malformations, 2003. "Spotted Salamander, Ambystoma maculatum" (On-line). Amphibian Identification Guide. Accessed January 08, 2004 at http://www.npwrc.usgs.gov/narcam/idguide/ambymacu.htm .

Petranka, J. 1998. Salamanders of the United States and Canada . Washington and London: Smithsonian Institution Press.

Pough, F. 1976. Acid precipitation and embryonic mortality of spotted salamanders, Ambystoma maculatum . Science , 192: 68-70.

Sexton, O., J. Bizer, D. Gayou, P. Freiling, M. Moutseous. 1986. Field studies of breeding Spotted Salamanders Ambystoma maculatum in Eastern Missouri. Contributions in Biology and Geology , 67: 1.

The Vernal Pool Association, 2004. "The Vernal Pool" (On-line). Accessed April 19, 2004 at http://www.vernalpool.org/vernal_1.htm .