That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

As mentioned in Part I of this article, tiger salamander larvae (Ambystoma tigrinum), run through with a hook while alive, are still used as fishing bait in some parts of the USA.  Last time we learned about the bait trade’s role in spreading a Chitrid fungus that is decimating amphibian populations worldwide, and in hastening the extinction of endangered tiger salamanders through hybridization.

Endangered but Legally Exploited

Despite the aforementioned environmental nightmares, the bait trade in tiger salamanders remains largely unregulated, resulting in infected animals being shipped from state to state.  This practice hastens the spread of already fast-moving pathogens and of non-native salamanders, as surveys have revealed that most people and bait shops release unused larvae into local waterways.

The situation is rendered all the more bizarre by the fact that these largest of all terrestrial salamanders are critically endangered in many areas.  In fact, several subspecies, including the Eastern tiger salamander (Ambystoma tigrinum tigrinum), are protected by individual states as endangered species!

Other Threats

Tiger salamanders also face serious threats from habitat loss, pollution and the introduction of game fish to breeding ponds.  Their use of two distinct habitats – aquatic and terrestrial – renders them especially vulnerable.

Protection, when offered, is often ineffective.  In New York State, for example, 75 feet of land around breeding ponds is closed to development – but research has shown that few if any adults live within that radius!

Tiger Salamanders in Captivity

Tiger salamanders make interesting and unusually responsive captives. Longevities exceed 30 years, but captive reproduction is still somewhat problematical.  They certainly deserve more attention from hobbyists …please write in for further information.

American Bullfrogs

American bullfrogs (Rana/Lithobates catesbeianus) have also recently been implicated in spreading amphibian diseases (New Scientist: May, 2009).  Researchers monitoring food markets in NYC and California discovered that 8% of the frogs being offered for sale carried ranavirus and nearly 70% were infected with Chytrid!

Further Reading

You can learn about the natural history of the eastern tiger salamander, and the steps being taken by the NYS DEC to prevent its extinction, at

http://www.dec.ny.gov/animals/7143.html.

The Organization Amphibian Ark has taken a leading role in Chytrid research.  Read about how this fungus has caused amphibian extinctions, and predictions for the future of the epidemic, at http://www.amphibianark.org/chytrid.htm.

Image referenced from Wikipedia and originally posted by Tigershrike.

Shocking as it may be to anyone with even a passing awareness of conservation issues, tiger salamander larvae (Ambystoma tigrinum) are still widely used as fishing bait throughout much of the USA.  Run through with hooks while alive, the 6-10 inch amphibians are wildly popular with anglers seeking bass, pickerel and other fishes.

Disease and the Bait Trade

Recently (April, 2009), biologists at the National Science Foundation announced that a significant percentage of larvae in the bait trade have tested positive for the deadly Chytrid fungus Batrachochytrium dendrobatidis.  This fungus has decimated amphibian populations on nearly every continent, and is responsible for the extinctions of local populations and, most likely, entire species.

Herpetologists are working feverishly to control its spread, but are as yet unable to understand why the fungus has become such a devastating problem in recent years.  Often, the only hope for amphibians in its path is captivity   – colleagues of mine recently collected an entire population of Panamanian golden frogs, but the long-term outlook is quite dim.

Virulent ranaviruses, which quickly kill many amphibians, have also been identified in larvae sold in bait shops in Arizona, Colorado and New Mexico.

Hybridization

As if the all this were not enough, the release of bait trade salamanders has resulted in the hybridization of critically endangered California tiger salamander populations (released barred tiger salamanders mated with the California subspecies).

Hybridization threatens survival by altering critical components of the genome.  For example, when various subspecies of ibex (mountain goats) were released together in Spain, the resulting hybrids gave birth during the winter, and the population became extinct.

Getting Involved

Partners for Reptile and Amphibian Conservation http://www.parcplace.org/, an organization of professional herpetologists and interested citizens, supports numerous research programs.  Please be in contact to learn more about this issue and their many interesting volunteer opportunities.

Next time I’ll discuss other threats to tiger salamanders, their conservation status, and problems regarding food market bullfrogs.  

Further Reading

Please see my book Newts and Salamanders  for information on the natural history and captive care of tiger salamanders and their relatives.

Image referenced from morguefile.