Ambystoma texanum

Geographic Range

Small-mouthed salamanders occupy a range from northeastern Ohio west into Missouri and eastern Nebraska. The northern edge of the range is southeast Michigan and the southern range goes through western Kentucky and Tennessee to the Gulf of Mexico. They even inhabit several islands in southern Lake Erie.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Ambystoma texanum are most numerous in lowland floodplain woodlands. They can tolerate some human disturbances, such as habitat fragmentation and farming. They can even live in an open prairie as long as there are breeding ponds free of fish. Small-mouthed salamanders are more versatile in their breeding requirements than other Ambystoma . They can breed in woodland vernal ponds, runoff ponds, flooded areas, river backwaters, and roadside ditches. Ambystoma texanum does not travel far from breeding ponds, so good habitat near the pond is important.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest

Physical Description

As its name suggests this species has a relatively small head with a blunt, short snout. The head tends to appear swollen behind the eyes and the lower jaw barely protrudes past the upper jaw. Coloration of the dorsum varies from pale gray to black. An irregular pattern of light blotches on the upper surface of specimen becoming darker on the sides and extending to the dark belly. During the breeding season small-mouthed salamanders may appear paler and have more conspicuous light markings. Adult length is normally between 11 and 17.8 cm (4.3 to 7 inches). Small-mouthed salamanders have 14 to 16 costal grooves. Males are smaller with longer and more compressed tails. Larvae usually have light bars or crossbands on an olive green or dark brown background. Near metamorphosis a dark pigment often obscures the light markings (Harding 1997).

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

• Sexual Dimorphism
• sexes shaped differently

Development

Larvae metamorphose to terrestrial salamanders in two to three months.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Courtship consists of groups of males bumping and nudging the females and each other. Males will move away from the group and deposit spermatophores on the substrate or on a stick or leaf. Females then "collect" the spermatophores (Harding 1997).

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

Ambystoma texanum breeds very early in the year. The migration to breeding ponds seems to be stimulated by just a few days of rain in late winter, frequently while ice still covers portions of the ponds. They tend to stay closer to breeding ponds in summer and late winter than other salamander species. A sibling species, A. barbouri , has a different reproductive strategy. The two species were formerly considered two races of A. texanum but now are classified as different species. Ambystoma barbouri , the "stream form," breeds in ephemeral headwater regions in contrast to A. texanum , the "pond form," which breeds in ephemeral lenthic habitats, including road side ditches, flooded areas and small ponds (Maureer and Sih 1996). Breeding begins four to five weeks later for A. texanum , which is an explosive breeder (Petranka 1984). A single female can produce 300 to 700 eggs annually, which are deposited in small loose gelatinous masses of 3 to 30 eggs. The eggs hatch in 3 to 8 weeks. The young mature to breeding size usually in their second year (Harding 1997). Size at maturity is 60 to 70 mm length from their snout to their vent (Lanoo, 2006).

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

Once a female deposits her eggs in the water, there is no further parental care.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning
  • protecting
    • female

Lifespan/Longevity

The lifespan of small-mouthed salamanders is not known.

Behavior

Members of the family Ambystomatidae are commonly called the mole salamanders because of their secretive underground lifestyle (Indiviglio 1997). When not breeding, A. texanum individuals tend to be hidden under rotting logs, rocks or leaf litter. They also make use of burrows dug by other animals including crayfish and small mammal burrows. An evening rain occasionally provokes them to emerge above ground (Harding 1997).

• Key Behaviors
• motile motile

Food Habits

Adult small-mouth salamanders eat insects, other arthropods, slugs, worms, and sometimes aquatic crustaceans. Larvae are generalist predators (Maurer and Shi 1996). They eat small aquatic invertebrates including Daphnia , isopod hatchlings and even larvae of their own or another species of Ambystoma (Harding 1997).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • molluscivore molluscivore
  • vermivore

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

Predation

Small-mouthed salamanders have concentrations of granular glands on the top of the tail. Salamanders confronted by potential enemies raise and undulate the tail and curl the head underneath the tail. This behavior is most often used when attacked by a snake. Larvae are preyed on by dragonfly larvae and tiger salamander larvae.

Ecosystem Roles

Small-mouthed salamanders are predators of small invertebrates and are preyed on by small to medium-sized predators, such as snakes, birds, and other salamanders. They are important members of healthy woodland and grassland communities. Small-mouthed salamanders are parasitized by some protozoan and helminth species, and by a cyclophyllidean cestode ( Cylindrotaenia americana ).

Economic Importance for Humans: Positive

Small-mouth salamanders eat slugs and worms and help keep pest species numbers down. In turn they are food for other animals.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

There are no negative impacts of small-mouthed salamanders on humans.

Conservation Status

Ambystoma texanum is common through much of its range. The success of small-mouthed salamanders is connected to their habitat tolerance. On the edges of their range, where numbers are low, management for this species would be beneficial--such as in Michigan, where it is listed as endangered. Management for A. texanum should be preservation of areas with known populations and maintenance of adjacent fish free ponds.

Other Comments

Ambystoma texanum hybridize with other Ambystoma species. Hybridization is most common in the areas south and west of Lake Erie.

Additional Links

AmphibiaWeb

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Kristi Roy (author), Michigan State University, James Harding (editor), Michigan State University.

References

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region . Ann Arbor, MI: University of Michigan Press.

Lannoo, M. 2006. "Ambystoma texanum" (On-line). Amphibiaweb. Accessed November 02, 2006 at http://www.amphibiaweb.org/cgi-bin/amphib_query?query_src=aw_search_index&table=amphib&special=one_record&where-genus=Ambystoma&where-species=texanum .

Maurer, E., A. Sih. 1996. Ephemeral Habits and Variation in Behavior and Life History: Comparisons of Sibling Salamander Species. Oikos , 76: 337-349.

McWilliams, S., M. Bachmann. 1989. Predatory Behavior of Larval Small-Mouthed Salamanders. Herpetologica , 45(4): 459-467.

Petranka, J. 1984. Breeding Migrations, Breeding Season, Clutch Size, and Oviposition of Stream-Breeding Ambystoma texanum. Journal of Herpetology , 18(2): 106-112.