The spotted salamander (Ambystoma maculatum), a member of the mole salamander family (Ambystomatidae), is a fascinating amphibian species native to eastern North America. Recognizable by its distinctive coloration, the spotted salamander plays an important ecological role in its forest and aquatic habitats. This article delves into the diet, habitat, and other key aspects of the spotted salamander's life history.
Identification and Physical Characteristics
The spotted salamander, also known as the yellow-spotted salamander, typically measures between 15 and 25 cm (5.9-9.8 in) in length, including the tail. Females tend to be larger than males. Like other mole salamanders, it has a stout body and a wide snout, suited to its fossorial lifestyle. The spotted salamander's main color is black, but can sometimes be a bluish-black, dark gray, dark green, or even dark brown. Two uneven rows of yellowish-orange spots run from the top of the head (near the eyes) to the tip of the tail (dorso-lateral ranging). The spots near the top of its head are more orange, while the spots on the rest of its body are more yellow. The underside of the spotted salamander is slate gray and pink. Sexual dimorphism (physical differences between males and females) is displayed in the form of larger-bodied females having brighter-coloured spots. Males will have a larger portion of the dorsal surface covered in spots that are less bright.
Distribution
The spotted salamander's range extends across eastern regions of the United States and Canada. Specifically, it can be found from Texas to Nova Scotia, Canada. In Virginia, they inhabit most areas, except for the lower region of the Eastern Shore and the southeastern corner.
Habitat Preferences
During the majority of the year, spotted salamanders live in the shelter of leaves or burrows in deciduous forests. The spotted salamander prefers closed-canopy hardwood forests with heavy ground-layer vegetation because of their cooler microclimates and higher humidities. They spend considerable time underground during the warmer months and can sometimes be found under rotting logs or in humus during spring and fall. This species is fossorial, meaning it spends most of its life underground. Adults spend their lives in forested areas within a half mile of a vernal pool. They are often found in burrows dug by small mammals, only a few centimeters under the surface within the well-drained soil of the forest floor.
They are rarely seen above ground, except after rain, during foraging activities, or when breeding. They need areas with soil that is easy to burrow into. Spotted salamanders are not easy to spot among leaves. They are also only active at night.
Read also: Learn About Marbled Salamanders
Dietary Habits
Spotted salamanders are carnivores with a diet that includes a variety of invertebrates. They are opportunistic feeders, consuming anything smaller than themselves. The spotted salamander preys upon earthworms, slugs, snails, spiders, millipedes, centipedes, insects, algae and other invertebrates. They often prefer to feed on soft-bodied organisms such as earthworms, snails, and slugs. As larvae, they are usually light brown or greenish-yellow. They have small dark spots and are born with external gills. The spotted salamander larvae are aggressive predators and have been known to cannibalize others when food is scarce.
Breeding and Reproduction
Spotted salamanders typically breed in the spring, usually from March to April in the northern part of their range, January to February in the Great Smokies, and December to February in the South. They usually move to breeding ponds at night during the first rain after the winter thaw. Recent studies, however, indicate that temperature may be a more important factor than precipitation, as precipitation in winter months increase, yet salamanders do not migrate. Males arrive at the breeding ponds first.
Hundreds to thousands of salamanders may make the trip to their ponds for mating in just one night. Males will start a dance-like behavior called a liebsspiel, where afterward they lay down their spermatophore. This dance includes the salamanders circling around one another and putting their head's on one another's tail. Males will migrate at higher rates than females early in the migration season. This could be due to different responses to temperature between males and females. Mates usually breed in ponds when it is raining in the spring. The female lays one or more compact egg masses covered with a jelly-like substance. Each egg mass contains about 100 eggs. The egg masses stick to submerged branches and objects. Many salamanders may use the same attachment site and produce communal egg mass clusters. Egg masses consist of 30 to 250 individual eggs surrounded by a stiff gelatinous matrix. The masses range in diameter from 1 to 6 inches.
There is a unique polymorphism in the egg colors of this salamander as one variety has an outer layer of water-soluble protein creating clear egg clumps and the other lays eggs that contain a hydrophobic protein that makes their eggs an opaque cream color; this variation in egg color is thought to be a response to the nutrient levels in the water in attempt to mitigate predation from other amphibian larvae. The eggs hatch in one to two months, depending on the water temperature. Young larvae eat zooplankton and insect larvae and sometimes other spotted salamander larvae. They become salamanders in two to four months. The .5" larvae hatch about 6-8 weeks after egg deposition.
Eggs of A. maculatum can have a symbiotic relationship with the green alga Chlorococcum amblystomatis. A dense gelatinous matrix surrounds the eggs and prevents the eggs from drying out, but it inhibits oxygen diffusion (required for embryo development). C. amblystomatis provides increased oxygen and supplemental nutrition from fixed carbon products via photosynthesis and removes the embryo's nitrogenous waste (ammonia) in the egg capsule, aiding in the salamander's embryonic development and growth. The developing salamander thus metabolizes the oxygen, producing carbon dioxide (which then the alga consumes). Photosynthetic algae are present within the egg capsule of the developing salamander embryo, enhancing growth.
Read also: Feeding Habits of the Tiger Salamander
Defense Mechanisms
A. maculatum has several methods of defense, including hiding in burrows or leaf litter, autotomy of the tail, and a toxic milky liquid it excretes when perturbed. This secretion comes from large poison glands around the back and neck. To protect itself from predators the spotted salamander can detach it’s tail and regrow it when attacked and it can also secrete an off-white milky substance from its neck and back that is toxic when consumed and a mild skin irritant.
The spotted salamander, like other salamanders, shows great regenerative abilities: if a predator manages to dismember a part of a leg, tail, or even parts of the brain, head, or organs, the salamander can grow back a new one, although this takes a massive amount of energy. Like other members of the mole salamander family the spotted salamander can easily regrow legs, tails, organs, heads or even parts of their brains when damaged.
Movement and Migration
The spotted salamander is fossorial. It rarely comes above ground, except after a rain or for foraging and breeding. A. maculatum tend to follow the same path in their migration to and from their burrows and breeding pools. They accomplish their journey in conditions that lack visual cues, since it is usually during periods of cloud cover. Some studies show evidence of landmark learning and use of geotaxis in spotted salamanders. Researchers found that spotted salamanders can associate visual landmarks with food.
Conservation Status
At the moment the spotted salamander is a species of least concern, but herbicides, and habitat destruction do threaten populations of the species. Most spotted salamander (over 90%) died before they metamorphize and leave their pool because of predators, disease or simply the pool drying up.
Read also: The Hoxsey Diet
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