Ambystoma mavortium, Barred Tiger Salamander

Ambystoma mavortium, Barred Tiger Salamander (Page by Roderick Sprague IV)


 Kingdom: Animalia

  Phylum: Chordata


    Subphylum: Vertebrata


      Class: Amphibia



         Order: Cadata

          Family: Ambystomatidae

           Genus: Ambystoma

            Species: A. mavortium

             Subspecies of Idaho*: A. m.  melanostictum and A.m. nebulosum



*There has been a recent change to the naming of species of the tiger salamanders. The eastern tiger salamander, Ambystoma tigrinum, which was the subspecies Ambystoma tigrinum trigrinum in the greater species has been elevated to its own species. What had been the other subspecies (A. t. diaboli, A. t. mavortium, A. t. melanostictum, A. t. nebulosum and A. t. stebbinsi) in A. tigrinum have been lumped into the new species A. mavortium. The subspecies have been dropped. Others have kept the subspecies intact within A. mavortium (A. mavortium diaboli, A.m. mavortium, A.m. melanostictum, A.m. nebulosum and A. m. stebbinsi) I am taking this approach as a convenient way of distinguishing the two distinct biotypes in Idaho.

(Highly modified map borrowed from )

A. t. melanostictum, the most common subspecies in Idaho(Picture also borrowed

from )

A. t. nebulosum, the subspecies from along the Utah border(Picture borrowed



The non-California (California has the endemic California tiger salamander Ambystoma californience) tiger salamanders of the western US, Abystoma mavortium are a heterogeneous bunch, consequently they have been spit into subspecies by some authors, but others argue we are dealing with a highly variable species that has a strong tendency to form local races. That the local races intergrade enough that we are simply are observing local samples from a continuum over its distribution. The individuals in the southwest corner of Idaho along the Utah border are distinct enough in form the tiger salamanders in the rest of the state that the author is calling them by their subspecies as a simple way to point out the differences. The tiger salamnders along the Idaho-Utah border fall into the description of the Arizona tiger salamander, Abystoma mavortium nebulosum while the tiger salamanders in the rest of the state fit the description of the barred tiger salamander subspecies Abystoma mavortium melanostictum. The Irschick, J. Duncan and Shaffer, H. Bradley paper, The Polytypic Species Revisited: Morphological Differentiation Among Tiger Salamanders looking at various morphological and DNA sequence characteristics seems to uphold the subspecies designations for the most part, most strongly with the gill raker (ridges found around the gill slits on the larvae and neotenic adults) numbers.



The range seems to include much of the west east of the Cascades and most of the mountainous west that is not so arid as to prevent them from migrating there and that has ponds and sometimes slow streams two feet (for breeding) or deeper devoid of fish, so you can see them in most any habitat. Altitude and latitude also play a role, in that in areas with cold enough winters to freeze ponds, they need deep ponds to avoid being killed by freezing if they cannot complete the lifecycle before the ponds freeze. The 59th parallel is the rough cutoff point between Abystoma mavortium and Ambystoma tigrinum. The range also extends up into Canada and down into Mexico. Some populations contain neotenic individuals, adults that are sexually mature without leaving the larval (“tadpole”) stage. Neoteny seems to be connected with harsh conditions outside the ponds and with low iodine levels in the environment. Some neotenic individuals can metamorphose in situations such as the pond drying up. Adults will find burrows of other animals or make their own to escape desiccation during the dry part of the year seeking damp soil. Sometimes they will congregate into piles to reduce the surface area exposed to air in burrows.


Mating takes place during the wet part of the year. In the cooler parts of its range, after the danger of freezing has passed in the spring. Males use tail nudging, nosing against the female’s tail to lead her away from the breeding congregations in the pond to try to get her safely far enough to take only his spermatophores, the sperm packets, into her vent, the opening at the end of the urinary and digestive tract. The male stimulates her to take up the spermatophore by tail fanning, waving his tail to send water carrying his pheromones to the female. Sometimes, another male will present his spermataphores to the female being courted by another male and successfully breed that way. Eggs are laid a few days after mating. The eggs are small gelatinous spheres roughly resembling frog eggs, but are laid singly or in elongate clusters on aquatic vegetation. The larvae take more than a year to develop into adults in cold or food poor environments. The adults can be as long as 20 cm, the neotenic adults being heavier than metamorphed adults.


Feeding is done with visual and presumably odor clues. The author had some as pets and found they ended up conditioned to take mealworms from his fingers. They captured the mealworms with their tongues, their mouths and tongues moving so rapidly, they made an entertaining light popping noise. They also would lunge forward if there was a short distance between them and the food the tongue would not cover. The larvae eat by opening the mouth to intake water while sometimes also lunging forward. The larvae and adults are carnivorous, eating mostly most any invertebrates big enough to notice and small enough to fit in the mouth. In some populations some larvae can develop into a cannibal morph with a large U shaped mouth for eating individuals of its own species!



The eyes are commonly studied in the lab as they are large for a salamander (though they look small relative to the size of the salmander) and have large cells, making microscopic observations easier than with other organisms. They are able to orient to the sun using polarized light detected by the eyes and pineal gland. They also use the detected light to set their circadian rhythm through the production of melatonin.


Ecologically, they are sensitive to a pH (how acid or alkaline on a scale that centers on 7 as neutral) less then 6, so acid rain can render breeding sites unusable. They can tolerate extremes in the higher natural alkaline pHs, though, so they tend to breed in alkaline desert bodies of water unsuitable for other species of amphibians.




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