Blue-spotted salamander (Ambystoma laterale)
|Size||Length: 7.6 - 14 cm (2)|
- The blue-spotted salamander is named for the blue spots and flecks on its otherwise blackish body.
- The blue-spotted salamander spends most of its adult life living under logs, rocks or underground, usually only emerging to breed.
- The eggs of the blue-spotted salamander are laid in temporary ponds, where the larvae take two to three months to develop.
- The blue-spotted salamander often hybridises with closely related species, producing all-female hybrid populations.
The blue-spotted salamander is classified as Least Concern (LC) on the IUCN Red List (1).
A medium-sized North American salamander species, the blue-spotted salamander (Ambystoma laterale) is named for the blue spots and flecks along its sides, limbs and tail. These blue spots typically occur on a black to greyish-black background colour (2) (3) (4). The underside of the blue-spotted salamander’s body may be dark or may be paler than the upperparts, usually with some blue flecking and with a black area around the vent (2) (3).
The male and female blue-spotted salamander are similar in appearance, but the male is usually slightly larger than the female, with a longer, more flattened tail, and may also be more brightly coloured. During the breeding season, the male of this species can also be distinguished by its swollen vent (2) (4). Juvenile blue-spotted salamanders which have recently undergone metamorphosis often have yellowish rather than blue spotting, and may take several weeks to attain the adult colouration (2).
The aquatic larvae of the blue-spotted salamander can be quite variable in appearance. However, older individuals are usually dark brown to olive or grey above, sometimes with yellowish blotches on the back or a yellowish stripe down each side of the back. The underside of the body is lighter in colour and there are dark patches on the tail fins (2).
Like other Ambystoma species, the adult blue-spotted salamander is a rather stoutly built amphibian (5) with a broad head (4). This species can be confused with the closely related Jefferson salamander (Ambystoma jeffersonianum), but the blue-spotted salamander is generally smaller, darker and has more blue flecking on its body (2) (3) (4). However, the blue-spotted salamander commonly hybridises with the Jefferson salamander, and sometimes also with other species, to produce all-female populations of hybrids. The existence of these hybrids makes it difficult to identify these salamander species with certainty (2) (4).
The blue-spotted salamander has the most northerly range of any Ambystoma species (6), occurring across southern Canada and the north-eastern United States. Its range extends from Manitoba to the Gulf of Saint Lawrence in Canada, south through the Great Lakes basin to New England and New Jersey in the east, and to Minnesota and Iowa in the west (1) (2) (3) (6).
Several isolated populations of blue-spotted salamanders occur around the edges of this distribution (1) (6). Populations of hybrids between this species and the Jefferson salamander (A. jeffersonianum) are found over a large part of the south of the range (1) (2).
The blue-spotted salamander typically inhabits moist deciduous and coniferous forest with temporary ponds, often in areas with sandy or loamy soils (1) (2) (4) (6). However, this species can also occur in open fields, overgrown pastures and even gardens (1) (2).
Although it may show some tolerance to habitat disturbance, the blue-spotted salamander still requires wooded areas adjacent to small, fish-free ponds and other shallow water bodies that retain water into the summer (2) (4).
Members of the family to which the blue-spotted salamander belongs, the Ambystomatidae, are commonly known as ‘mole salamanders’ due to their predominantly underground existence (5). However, unlike its close relatives, which are found below ground for most of the year (4), the adult blue-spotted salamander is often found under logs, leaf litter or rocks, although it does also use burrows, including those of other animals (2) (6). This species may sometimes be seen in the open during rain showers (2).
The diet of the adult blue-spotted salamander includes a wide variety of small invertebrates, including insects, earthworms, snails, slugs, spiders and centipedes. Blue-spotted salamander larvae also feed on a range of invertebrates, taking aquatic insects and small crustaceans, and are also known to eat tadpoles (6).
The skin of the adult blue-spotted salamander contains glands, particularly on the tail, which produce a whitish, noxious substance. If threatened, the salamander may raise and wave its tail, and if further provoked it may lash it to deter the potential predator (2) (4). This behaviour also serves to draw attention to the tail, which can be regenerated if it is damaged during an attack (4).
The blue-spotted salamander breeds from around March to April (2) (3) (4), or slightly later in northern parts of its range (6), with breeding often being triggered by warm evening rains or rapid snow melt (2). At this time, the adult salamanders migrate towards suitable breeding ponds and begin courtship. The male blue-spotted salamander courts the female by nudging her with his snout, before grasping her behind the front legs and rubbing his chin on her head. Eventually, the male releases the female and deposits a packet of sperm, known as a spermatophore, in front of her. The female then moves over the spermatophore and takes up the sperm (2).
The female blue-spotted salamander lays her gelatinous eggs in small clumps on sticks, rocks or other debris in the bottom of the breeding pond (2) (3) (6). Each clump typically contains up to a dozen or so eggs, and the female usually lays around 225 to 300 eggs in total during the breeding season (2) (4) (6).
The eggs of the blue-spotted salamander hatch in around 3 to 5 weeks, depending on the water temperature (2) (6), and newly hatched larvae measure about 0.8 to 1.2 centimetres in length (2). The larvae of the blue-spotted salamander face many predators, including diving beetles, newts and tiger salamander (Ambystoma tigrinum) larvae (4), but those that survive metamorphose into adults around two to three months after hatching, typically between June and September (4) (6). After spending a week or so hiding beneath logs and stones at the water’s edge, the young salamanders migrate into the surrounding forest (4). The blue-spotted salamander is thought to reach maturity in about two years (2) (6).
Intriguingly, all-female hybrid salamander populations resulting from mating between blue-spotted salamanders and Jefferson salamanders (A. jeffersonianum) are able to reproduce by parthenogenesis, without needing genetic material from a male. These hybrids do mate with males of one of the parent species, but the genes of the male are only occasionally incorporated into the offspring (4) (6).
The blue-spotted salamander is a widespread amphibian and is not currently known to be undergoing any major declines (1). This species can be quite common in suitable habitat (2) (6) and shows some tolerance to human disturbance (2).
Although not globally threatened, the blue-spotted salamander may nevertheless face some localised threats in parts of its range. The main threat to this species is the loss and degradation of its forest habitats due to logging and road building (1) (2) (6). Acid rain may also be a potential threat to the blue-spotted salamander (1) (6), while the temporary ponds it requires for breeding are often altered by dredging, filling in, or by adding predatory fish (4).
Some of the all-female populations of hybrid blue-spotted salamanders have restricted ranges and may be vulnerable to extinction. However, the unusual genetics of these populations means that they do not fit the usual concept of a ‘species’, which is the concept around which conservation laws are generally based (6).
There are no specific conservation measures currently known to be in place for the blue-spotted salamander. This species would benefit from increased protection of its forest habitats (1).
The larvae of the blue-spotted salamander are believed to be significant predators of mosquito larvae, and may therefore play an important role in mosquito control (2) (4).
Find out more about the blue-spotted salamander and other amphibians:
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- Crustaceans: diverse group of animals with jointed limbs and a hard chitinous exoskeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Deciduous forest: forest consisting mainly of deciduous trees, which shed their leaves at the end of the growing season.
- Gland: an organ that makes and secretes substances used by the body.
- Hybrid: the offspring produced by parents of two different species or subspecies.
- Hybridisation: cross-breeding between two different species or subspecies.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Loam: a rich soil containing roughly equal proportions of clay, sand and organic matter.
- Metamorphosis: an abrupt physical change from the larval to the adult form.
- Parthenogenesis: the development of offspring from unfertilised eggs. The individuals that results are usually genetically identical to their mother.
- Spermatophore: a capsule or mass of sperm transferred from a male to a female during mating, for example in certain insects, arthropods and cephalopods (octopuses and squids).
IUCN Red List (August, 2013)
- Harding, J.H. (1997) Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press, Michigan.
AmphibiaWeb - Ambystoma laterale (August, 2013)
- Gibbs, J.P., Breisch, A.R., Ducey, P.K., Johnson, G., Behler, J.L. and Bothner, R.C. (2007) The Amphibians and Reptiles of New York State: Identification, Natural History, and Conservation. Oxford University Press, Oxford.
- Indiviglio, F. (2010) Newts and Salamanders. Barron’s Educational Series, New York.
- Lannoo, M. (Ed.) (2005) Amphibian Declines: The Conservation Status of United States Species. University of California Press, Berkeley, California.