BIOLOGY OF THE
BLUE-SPOTTED SALAMANDER

Basic Stuff about Salamanders

Salamanders are a large group (about 300 species worldwide) of tailed amphibians (Class Amphibia, Order: Caudata). They are "cold-blooded" animals, but unlike reptiles, do not bask to try and alter their internal temperatures. Their thin skins must remain moist (many species can draw oxygen in through their skin, and all draw moisture in through their skin), so most salamanders live reclusive lives, hiding under plant litter, rocks or fallen logs, and emerging only on moist nights. All salamanders are carnivorous, eating a wide range of insects and small invertebrates. Larger, aquatic salamanders may eat fish or other amphibians.

Most salamanders are terrestrial, forest dwelling species that return to water only to lay their eggs. Some species are fully aquatic (mudpuppies and hellbenders) and some spend part of their adult life on land, then return to the water (newts).

Salamanders hear by sensing vibrations in the ground. They have good eyesight and a good sense of smell. Unlike their relatives, the frogs and toads, they don't produce any sounds. Many species produce noxious or toxic skin secretions as a means of defense, and are often brightly coloured to announce their distastefulness or poisonous nature to predators. Salamanders shed their skin regularly, and almost invariably, eat it to recover the nutrients.

Description

The blue-spotted salamander (Ambystoma laterale) is a small critter. A large adult will only be about 12 cm long; 40% of that is tail, and its body is only about 1 cm wide. Coloration is shiny-black, like patent leather, with dusty blue spots, mainly on the sides and belly. It is a slimmer built and much smaller salamander than Manitoba's only other terrestrial species, the tiger salamander (Ambystoma tigrinum), which tends to be greenish-yellow with black blotches and stripes. Our other salamander, the mud puppy (Necturus maculosus) is aquatic, and never leaves the water.

Classification

The taxonomic classification of the blue-spotted salamander goes like this:

Name Derivation

Scientific: "Ambystoma", is from the Greek "Ambyx or Ambykos", referring to a cup or the rounded top of a cup; and, also from Greek, "stoma", meaning mouth. So, I guess "Ambystoma" refers to the rounded, cup-shaped mouth of this genus of salamanders.

"laterale" , from the Latin, "latus", for side or flank; or is it from the Latin, "later", meaning made of bricks? Sorry, couldn't figure that one out. My guess is the species name has something to do with the sides of the critter, but just what, I couldn't unearth. Maybe it's the prominent spots on the sides?

Common: The common name of this species, blue-spotted salamander, makes good sense. Its most striking feature is its blue spots.

Distribution

The blue-spotted salamander occurs in eastern central North America in a broad band stretching from the Atlantic provinces and northern New England, around the Great Lakes, and west as far as central Manitoba. It gets up to James Bay in northern Ontario, but all the sources I located suggested that the extent of its northward range has not been adequately defined.

In Manitoba, the species is found in the southeastern corner of our province, east of the Red River and as far north as the narrows of Lake Winnipeg (See map, salamander distribution in red). However, this is a very cryptic species, and one for which intensive inventory hasn't occurred. There will likely be extensions of its known range in this province for some time into the future. Any of you guys or gals up north ever come across a blue- spotted salamander? If so, let us know!

Habitat

This is a woodland species of salamander, that is probably restricted to areas of moist forest floor, near lakes, streams and wetlands; in areas with mixed forests (deciduous and coniferous trees together). It breeds in ephemeral, snow-melt ponds, like those used by wood frogs, and in small permanent ponds that are free of fish.

Populations

There are no estimates available of the population densities of the blue-spotted salamander. It is not a widely studied species, and its cryptic nature makes it very hard to find. Blue-spotted salamanders could use some serious study in this province. We really have no idea what shape their populations are in.

Life Cycle

Blue-spotted salamanders breed in early spring, April to mid-May, in small ponds. The adults emerge from winter hibernation (see below) and gather in the ponds. Most of the mating activity likely occurs at night. For most salamanders, the males use a combination of pheromones and visual displays to attract females into close proximity. The blue-spotted has a prolonged courtship where the male holds onto the female with his front legs and rubs his chin over her head. The male deposits a packet of sperm (a spermatophore) on the pond bottom, and tries to draw the female over top of it. She then picks it up with her cloaca (urogenital opening) and fertilizes her eggs internally.

Females lay their eggs (as many as 500) individually, or in small bunches, at the base of sticks, plants or rocks in the pond. The eggs take about a month to hatch. When they hatch the larvae have well developed eyes, mouths, external gills and a broad tail fin, so they can see, lunge and snap at the tiny aquatic animals they feed on, like daphnia, copepods or other invertebrates.

An egg with a larva ready to hatch.

A week-old larva.

As the larvae get older they look like tiny adult salamanders, except they have broad fins on their tails for swimming, and feathery, external gills. The front limbs emerge when they are about 2 weeks old, and the hind limbs are visible by 3 weeks old. Insect larvae and larger aquatic invertebrates are more important in their diet once they reach about 2 cm in length.

Larva at 3 cm.

They grow to about 3 cm in length, then transform into adult form and leave the pond, usually by late July to mid-August. (Some authors have suggested that the larvae transform when they are 5 cm, to as much as 8 cm long. Like other amphibians, the exact length of time required to reach a size where they can transform, and even the ultimate size they do transform at, will vary with food availability and other conditions.)

The danger of breeding in temporary ponds -
-sometimes they dry up!

They loose their external gills and tail fins, and gain their adult coloration before leaving the pond. I couldn't track down how long it takes for them to reach adult size, but considering they may have to increase their body mass by about 50 or 60 times to reach adult size, it probably takes at least a couple of years. How long they live for is anybody's guess, too.

Really weird stuff: "Boy salamander meets girl salamander, sperm fertilizes egg, new salamander grows up." That's the happy little story of how most salamanders, and most other animals reproduce. But it seems that sometimes Mother Nature gets tired of the same old, same old. So, to keep evolutionary biologists busy, and happy, she occasionally throws a monkey-wrench into things. Here's such a case. Enter, Tremblay's salamander (Ambystoma tremblayi). It occurs at the southern extent of the blue-spotted salamander's range. There are no male Tremblay's salamanders, they're all females. Not only that, they are triploid. That is, they have 3 sets of chromosomes, instead of the normal 2 that most animals, including we humans have. And they reproduce by parthenogenesis; the females lay eggs that do not need to be fertilized to start developing into a new embryo. They do, however, have to mate with a male blue-spotted salamander to stimulate their eggs to develop into embryos. (Still with me?) The triploid, all-female Tremblay's salamanders are sexual parasites on the blue-spotted salamanders. Male blue-spotted's waste their time and sperm on the Tremblay's, which are dependent on the presence of the former species to continue to exist.

How did such a situation come to be? It's thought to have resulted from hybridization of blue-spotted salamanders with another physically similar and closely related species, the Jefferson's Salamander (Ambystoma jeffersonianum). The range of these two species overlap in eastern North America, with the blue-spotted to the north and the Jefferson's to the south. It wasn't until 1964 that it was recognized that they were, in fact, separate species. Interbreeding, combined with incomplete meiosis (meiosis involves the separation of the chromosome pairs to produce egg and sperm cells) somehow resulted in the chance origin of not only the Tremblay's salamander, but also another species, the silvery salamander (Ambystoma platineum). Tremblay's has 3 sets of chromosomes, 2 from the blue-spotted and 1 from the Jefferson's; while the silvery has 2 sets from the Jefferson's and 1 from the blue-spotted. The silvery is a triploid all-female sexual parasite of the Jefferson's just as the Tremblay's is of the blue-spotted. And you thought everything in nature was so well ordered and sensible! Don't turn your back on Mother Nature!

Food

Like a lot of the other aspects of this species' biology, its food habits aren't well known. The adults are thought to eat various arthropods and soft bodied invertebrates such as slugs and earthworms. Isopods (pill-bugs) are another major food item. Reports of them eating isopods, land snails, slugs and worms suggest that their main feeding grounds are below the leaf litter in forests. Blue-spotted salamanders that I've kept in captivity would readily eat earthworms, but refused to touch any insects I gave them.

Habits

Activity: Blue-spotted salamanders are probably nocturnal foragers, to avoid the drying effects of the sun and daytime heat. They spend daylight hours under logs and rocks, or deep under the leaf litter. At night they come out, and search for worms and other invertebrates that are also more active on the forest floor at night. In spring and fall, when night-time temperatures dip down, it wouldn't surprise me to find out that they were more active during the daytime, especially on cloudy or wet days.

Defense: To look at it, you might think that a blue-spotted salamander would be at the mercy of many predators. Small, slow-moving, soft-bodied; how could such a critter defend itself? Actually, quite well, thank-you. Being small helps it hide under the forest litter, and under logs or rocks. This species' coloration helps it hide, too. The blue spots help to break up the outline of the salamander making it quite hard to see, should it ever venture out into the open. As to being slow-moving? Well, most of the time they are, but they can scoot along when they have to. They can move surprisingly fast, when prompted by danger (or when you're trying to photograph them!) and will quickly disappear from sight under something. And they have one other trick that's a last line of defense: a wriggly tail. When a blue- spotted salamander is disturbed by a predator, say a bird or some small mammal looking for a tasty snack, it holds its body still and wiggles its tail back and forth. This motion, and the sound it would make for a nocturnal predator, entices the predator to strike at the tail, instead of the more vital head or body of the salamander.

Gland's in the salamander's tail produce a milky, noxious liquid, that oozes out when it faces a threat. So, if a predator is persistent, it gets a mouthful of yucky tasting salamander tail, and most likely spits it out. The yucky stuff is also quite sticky and will foul the predators mouth with debris for a while, too, further distracting it from trying to eat the salamander. Two of 4 salamanders I caught one year had chunks missing from their tails, but were otherwise quite healthy. It would seem that this is a strategy that works.

Apparently blue-spotted salamanders will also adopt an aposematic display position with their tail held up and curved over their body when alarmed. Although I was never able to elicit this behaviour, this is a common technique among other toxic or noxious salamanders and newts to make sure a predators sees them and recognizes them as being distasteful before striking. That's what the term aposematic refers to. Prey animals can prevent a potentially damaging attack by being boldy coloured or acting in a way that gets them noticed, if they have some chemical defense or other special means to protect them. It's to the prey's benefit not to be attacked in the first place, and it's in the best interests of the predator not to try to eat something that's noxious or toxic. So, bold colouring and "warning" behaviours have evolved in species to ward off attacks, by advertising some serious protective mechanism. (This is why skunks are the colour they are, and why they raise their large tails and stamp around when you get too close to them. They're giving you fair warning!)

Overwintering: There is some controversy (raised by me) surrounding the overwintering strategy of this species. They are not freeze tolerant, like wood frogs and some other northern frog species, so they must hibernate somewhere that doesn't freeze. Some authorities suggest they go down abandoned small mammal burrows or other soil openings to below the frost line, and hibernate there. Yet they breed very early in the spring, around the same time as the freeze tolerant frogs. How could a small cold- blooded salamander detect the advent of spring deep under the earth? Remember, frost can penetrate several feet into the soil. My own personal theory is that, at least in Manitoba, they are overwintering in the other environment that is safe from freezing: the bottom of large ponds or other water bodies. In recent years I've only found blue-spotted salamanders in breeding ponds that were close to permanent water of some sort, and have never found them before the time when at least some leopard frogs were calling. Leopard frogs are not freeze tolerant and overwinter on pond or lake bottoms. In the coming years, I'll be watching closely to see if I can gather more evidence for my theory of blue-spotted salamander overwintering. I'd welcome advice, suggestions or further evidence to support my claims or the other, traditional view of how this species overwinters.

Care in Captivity

I've had good success keeping blue-spotted salamanders in captivity for periods up to a month or two. They're small, so you can keep them in a small aquarium. For spring-caught individuals, I set up an aquarium that is half water / half land, or that has a large island floating in shallow water. Early in spring the salamanders seem to prefer to be submerged in water most of the time. They even choose to eat under the water if given the choice. I've noticed that their preferences change as the season progresses. Later on they spend more and more time on the land in the aquarium, and ultimately avoid going into the water, so long as their is a moist surface to lie on. A summer-caught salamander should be kept in a terrarium with moist moss or gravel. If you put soil in, it will burrow under, make a mess, and you'll never see it. They like to hide under things, so a small cave or piece of bark in the aquarium is a good idea. And keep a secure lid on the aquarium. Salamanders walk up glass like you or I climb stairs!

Worms are readily eaten by captive blue-spotted's. I haven't been able to get them to eat any hard- bodied invertebrates or insects, but they do well on a worm a week.

If you're ever lucky enough to catch some salamander larvae, they can be raised quite easily in a small aquarium. Feeding them can be a bit tricky, as they require live food. The motion of their prey is a stimulus to attack. So, you have to have a source of tiny water animals: daphnia, copepods, insect larvae, etc. If you have a pond, lake or other wetland nearby, you can take a fine-meshed dip net and swirl it around to collect some of these tiny critters. Put them in a small jar and empty the contents into the aquarium. Another way of getting food items for the larvae is to take bunches of plants from a wetland and placing them in the aquarium. These will usually be covered in tiny animals that the larvae will eat. Change the plants every couple of days to keep a constant supply of food available. When you notice that the larvae are beginning to lose their gills and tail fins (this can happen rapidly, once they reach at least 3 cm in length), provide them with some land: a floating piece of wood or a rock sticking out of the water. When they are finished their transformation, release them back where you got them from.

As with any critter you remove from the wild, always let it go back at the same spot you found it, at an appropriate time of day. Don't release a salamander at high noon on a hot day! Wait for evening or a rainy day.

Final Thoughts

Blue-spotted salamanders are, in my opinion, incredibly beautiful little critters. They are hard to find and get hold of, but it is a worthwhile experience if you can. Their cryptic nature and nether-worldly existence makes them seem "exotic", but they are probably quite common in the woodlands of southeastern Manitoba. I'm concerned about how little we know about them, and how most people don't even realize they exist. Ignorance is not bliss, it is a recipe for extinction. We need to know more about all Manitoba's wildlife, so we can ensure that future generations will still be able to marvel at amazing critters like the blue-spotted salamander.

Acknowledgments

Some of the information contained in this article was drawn from the following sources.

The Reptiles and Amphibians of Manitoba. 1982. William B. Preston. Pub. by the Manitoba Museum of Man and Nature. Winnipeg, Mb., Canada. ISBN 0-920704-13-1

A Field Guide to the Reptiles and Amphibians of Eastern and Central North America - The Peterson Field Guide Series No. 12. 1975. Roger Conant. Pub. by Houghton Mifflin Co. Boston. ISBN 0-395- 19979-4.

Salamanders of the United States and Canada. 1998. James W. Petranka. Smithsonian Institution Press, Washington. 587 pp.