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Ambystoma macrodactylum, Long-toed salamander

Page history last edited by PBworks 16 years, 6 months ago
Long-toed Salamander (Ambystoma Macrodactylum) 

 

Taxonomy (Phylogenetic clades)

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata   

Class: Amphibia

Order: Caudata

Family: Ambystomatidae

Genus: Ambystoma

Species: A. macrodactylum

Idaho subspecies: A. m. columbianum (Eastern or Central subspecies)

Idaho subspecies: A. m. krausei (Northern subspecies)

 

 

 

Two pictures (above) of an adult A. m. columbianum (Easten or Central subspecies). Photos by Gary Nafis

http://www.californiaherps.com/noncal/northwest/nwsalamanders/pages/a.m.columbianum.html

 

Two pictures (above) of an adult A. m. krausei (Northern subspecies). Photos by Henk Wallays  henk.wallays[AT]pandora.be.

http://calphotos.berkeley.edu/imgs/512x768/1111_1111/1111/5591.jpeg

 

Identification
Adults
Adult long-toed salamanders are typically terrestrial (except during breeding season) and are usually three to four inches long but have been recorded up to almost seven inches (snout to tail). The body color varies among subspecies brown to black or gray to green. The species is characterized by a yellow to green dorsal stripe running from snout to the tip of tail. Dorsal stripe usually has uneven edges and may possibly be separated into blotches. The northern subspecies usually has an even edged or irregularly indented stripe that is unbroken and has a width that is greater than that of the nostril width. In the Eastern or Central subspecies the dorsal stripe in thinner, unbroken and stripe is constant with parallel edges, reaching the nose and creating yellow color on the eyelids.
 
The ventral surface is usually characterized by blue to white speckles or flecks that tend to become more concentrated into a solid bluish-white color toward the ventral surface. The skin of the long-toed salamander is relatively smooth and the body shape is slender. The long-toed salamander is appropriately named based on the large digit on the hind legs in which the third toe (of four) is elongated. Other adults characteristics include; apparent costal grooves, lack parotid glands, tubercules of their feet (sometimes weakly developed), lack of both nasolabial grooves, and lack a pale patch on the ventral surface of their chin (the last two characteristics are also keys for determining long-toed salamanders from Couer d'Alene salamanders). Male species usually have longer overall bodies and limbs than do females.  
 
Larvae 
Color on the dorsal surface is usually uniform (tan to black) and larvae typically are less than two inches in length. Larvae have three sets of long feathery external gills and 9-13 gill rakers on the third arch. Dermal projections from the head of the larvae are thought to aid in balance of early larval stages. Larvae tend to begin to metamorphose to the adult form at two to four inches in length and at one to two years in age. After transformation juvenile forms tend to be aquatic though and may appear as an adult form lacking a brightly colored dorsal stripe but may have muted grayish dorsal stripe.
 

 

 

 

Pictures of long-toed salamander larvae, youngest to oldest presented top to bottom respectively. Photos by Gary Nafis

http://www.californiaherps.com/noncal/northwest/nwsalamanders/pages/a.m.columbianum.html

 

Eggs  
Eggs are pigmented, either laid in singles or in aggregates (in spherical or elongate shapes) from five to 100 in number. Eggs range in size but can be up to 2.5mm in diameter. Location of egg laying varies but can be found on submerged vegetation, woody debris, and rocks as well as on the substrate of the lake, pond, pool or slow moving stream. Females have been known to carry 85-400 eggs per reproducing year.
 

      

Pictures of lon-toed salamander egg mass. Photos by Henk Wallays 

http://calphotos.berkeley.edu/cgi/img_query?query_src=photos_fauna_com-Amphibian&enlarge=1111+1111+1111+4788

 

Distribution
The species in general is broadly distributed throughout most of northwestern North America. In Idaho long-toed salamanders are common in northern Idaho and can be found in central Idaho as well. The eastern or central subspecies occupies the western portion of the state while the northern subspecies occupies the eastern portion of the state. Long-toed salamanders occur in Idaho more than any other salamander.   

 

Long-Toed Salamander Range

Range map for log-toed salamanders with subspecies divisions.

Range map from: http://www.npwrc.usgs.gov/resource/herps/amphibid/species/ambymac.htm

 

Habitat 

Habitats are quite varied for the species and range from alpine conifer dominated forests (and oak woodlands)/sub-alpine areas to shrub/sagebrush steppe and even grasslands. Larval and aquatic juvenile forms can be found in lakes, ponds, pools, and wet meadows at a wide range of elevations. Terrestrial adults are commonly found in closed canopy/seral stage forests in near proximity to water (usually within 100 meters of water to retain moisture). Long-toed salamanders have been observed in active logging operation areas. Adults spend a disproportionately high amount of time in subterranean habitats consisting mostly of abandoned mammal burrows and depend on preformed burrows due the apparent lack of fossorial capabilities. Adults return (migrate) back to natal areas when sexually mature to breed. Little information is known about the over-wintering and torpor habitats of long-toed salamanders. Sexually mature adults tend to come out of hibernation as soon as snow melt begins and move or migrate to breeding areas. In lowland areas long-toed salamander individuals have been observed to be active all winter with no apparent hibernation period. 
 
Terrestrial adults and juveniles tend to move locally around home range and migrate outside of home ranges during the night time. Home Range size varies for different subspecies but generally male home range sizes are larger than that of their female counterparts (approximately 168 and 116 square meters respectively). Terrestrial juveniles tend to migrate further than terrestrial adults and may colonize new habitats. Terrestrial juveniles also tend to have a larger average home range sizes than adults (approximately 282 square meters). Migrations which were once thought to be only by way of wet corridors (near streams and rivers), consequently research in the past 15-20 years has shown that migrations paths can but do not always follow wet migration corridors. At low soil moisture levels terrestrial adults and juveniles have been observed in congregations, where individuals intertwine, which is (thought to be) a behavior that can be conducted to minimize moisture loss.

 

 

 

 

High mountain lakes of North Central Idaho where long-toed salamanders were present at time of survey. Photos by Tobyn Rhodes

 

Behavior

Long-toed salamanders become active after hibernation and prepare for breeding, apparently stimulated by the thawing of ground. Likewise decreases in temperature seem to be the indictor for the appropriate hibernation timing. Long-toed salamanders retain a carnivorous habit throughout their different life stages. Larvae are opportunistic feeders and tend to prey upon zooplankton, aquatic and terrestrial invertebrates using a sit and wait strategy. Larvae have been observed to be cannibalistic eating other long-toed salamander larvae as well as other tadpole species present. Larval prey size is positively correlated with increasing larvae body size. Older aquatic larvae tend to transition into an active foraging mode where prey is stalked. Terrestrial adults actively forage and eat a wide range of prey including terrestrial and aquatic invertebrates (insects/insect larvae, spiders, slugs, and earthworms). Adult males tend to feed at breeding locations while females do not, which is a possible reason for males loitering for longer times at breeding sites.
Predators of long-toed salamanders include; predaceous aquatic beetles, introduced and native fish (especially trout species), other salamander species, frogs, snakes (especially garter snakes), and bird species (kingfishers). Defense mechanisms associated with long-toed salamanders are numerous but avoidance of predators is most pronounced in the subterranean lifestyle of terrestrial adults. The aposematic coloring of the yellow dorsal stripe is likely used to warn predators of the adhesive/neurotoxin components that may cause a fowl taste or interrupt neurotransmission in predators. Long-toed salamanders may release chemical signal cues into their local environment to reiterate their toxic capabilities. Adults have been observed in coil and lash/undulate their tails to deter attack situations. Once attacked adults have been observed to vocalize in loud clicks and squeaks in attempts frighten predators and cause a release reaction.
Reproduction 
Long-toed salamanders utilize a wide range of breeding habitat including local seeps, slow moving portions of streams, ponds and pools (some ephemeral) at low elevations, and small to moderate sized lakes and wet meadows at high elevations. Egg deposition tends to occur in shallow areas with abundant vegetation, woody debris, even rocky areas with a silt substrate within the described habitats. The wide range in elevation of northern and central Idaho impact timing of the breeding season and clutch size. Populations above 7000 feet mostly breed in early to mid summer and produce smaller clutch sizes while populations below 7000 feet breed typically in spring time producing larger clutch sizes. As soon as snow melt occurs (and ground thaw begins) sexually mature individuals leave hibernation and winter burrows to migrate back to their natal pond to begin breeding (philopatry). Migration to breeding sites is usually less than 100 meters but migration of sexually mature adults have been recorded up to one-third of a mile. Males have been observed to frequently arrive at breeding ponds/areas and await the arrival of females (males also tend to spend on average more time at breeding sites than females).
Long-toed salamander mating begins by a receptive male approaching a possibly receptive female and rubbing the underside of his chin on top of the female's snout. The chin rubbing ritual allows the male to secrete a chemical signal (aphrodisiac) indicating the males readiness to mate to the possibly receptive female. If the female chooses to mate then the she will follow the male in a posture with her snout to his tail. The male will then deposit a spermataphore at a site of his choosing which the female will draw into her cloaca, internally fertilizing her eggs. After fertilization the female will deposit eggs in singles or in groups of 5 to 100. Young larvae will emerge in 1 to 3 weeks and length of larvae stage is determined by the elevation of the natal area. Natal areas at high elevations typically have long-toed salamanders with larval stages of one to two years but larval stages have been recorded of up to three years. Lower elevation natal sites usually have long-toed salamanders with larval stage of three to six months but have been recorded as short as 50 days.

 

Scientific Study of Highlight

Funk, WC, and Dunlap WW. 1999. Colonization of high elevation lakes by long-toed salamanders (Ambystoma macrodactylum) after the extinction of introduced trout populations. Canadian Journal of Zoology 77:1759-1767.

 

In the western North America amphibian populations are declining due to site specific factors, one of the most likely factors is the introduction predator and competitor species such as trout which have occurred throughout the west during the later portion of the 20th century. Funk and Dunlap surveyed high elevation lakes in the northern Bitterroot Mountains of Montana to determine if long-toed salamanders were present in lakes where introduced trout species had gone extinct and determine extinction and colonization rates for lakes that were never stocked. Data collected in 1997 and 1998 on 42 lakes were compared with data collected 1978, over that twenty year time period some lakes in the study area had experienced a cessation of trout stocking (in 1984) and some of those trout populations went extinct. Funk and Dunlap performed perimeter searches around lakes surveying lake littoral zones for evidence of salamander larvae. Snorkeling of littoral zones was also conducted to ensure the accuracy of visual encounter surveys.

 

The proportion of lakes that contained trout and salamander larvae was determined to be significantly lower than lakes that contained only salamanders. Thus, suggesting that trout presence does exclude salamander larvae form lakes. Salamanders had colonized 83% (5 of 6 lakes) of lakes were introduced trout had gone extinct the proportion. Overall salamander decline from lakes that had never undergone trout introductions was determined to not be occurring with two more fishless lakes being colonized by salamander larvae in 1997 and 1998 than had been in 1978. Thus, Funk and Dunlap's findings tend to agree that the fish tend to reduce larvae of long-toed salamanders especially in high elevation lakes where the larval stage is longer (perhaps two years) and at that individuals at the larval stage for longer periods of time tend to be susceptible to predation by fish for longer period of time (which generally holds true for all amphibians).

 

Long-toed salamander populations in the area were previously determined to have low dispersal rates from lakes considered to be source populations. Funk and Dunlap have shown evidence that despite the low dispersal rate long-toed salamanders recolonized lakes where trout had gone extinct in relatively short amount of time (20 years). Funk and Dunlap's data set did not allow them to determine whether newly or recolonized lakes where long-toed salamander larvae are present exhibit successful new populations. The newly colonized populations likely represent populations where probability of extinction of is likely higher than established populations (due to demographic stochasticity, and negative inbreeding effects that tend to effect small breeding population sizes). Funk and Dunlap have begun to explore the source sink dynamic between long-toed salamanders and empty habitat patches created by trout extinction but call for more research to be done to determine factors that effect colonization success.          

 

References

Alberta Online Encylopedia. 1999. Alberta, Naturally. Long-toed Salamander, Species at Risk. <http://www.abheritage.ca/abnature/speciesatrisk/salamander_intro.htm>. Accessed 2007 Sept 20.          

 

Amphibia Web. 2005. Ambystoma macrodactylum species info. <http://www.amphibiaweb.org/cgi-bin/amphib_query?query_src=aw_lists_genera_&table=amphib&where-genus=Ambystoma&where-species=macrodactylum>. Accessed 2007 Sept 21.

 

Hamning VK, Yanites HL, and Peterson NL. Characterization of adhesive and nuerotoxic components in skin granular gland secretions of Ambystoma tigrinum. Copeia 132(3):856-859

 

Idaho Digital Atlas. 1997. Long-toed salamanders key characteristics. <http://imnh.isu.edu/digitalatlas/bio/amph/urodela/amma/amma.htm>. Accessed 2007 Sept 21.

 

Montana Outdoors. 2000. Montana Outdoors Portrait: Long-toed salamanders. <http://fwp.mt.gov/mtoutdoors/HTML/articles/portraits/salamander.htm>. Accessed 2007 Sept 21.

 

Stebbins RC. Western reptiles and amphibians (field guide). New York (NY). p156-157, 450, 468 

 

Created By: Tobyn Rhodes, Biology 404, Herpetology, University of Idaho

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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