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

Everyone associates the poison or “dart” frogs (Family Dendrobatidae) with skin toxins, but it is to the slow, seemingly benign newts and salamanders that we should really pay heed. In many cases their toxins are far more virulent and, unlike those of the poison frogs, they are produced internally and are not dependent upon diet for their existence (in other words, the toxins do not decline after a time in captivity, as is the case for poison frogs!).

One of Earth’s Most Toxic Creatures
Over 200 compounds, some of which are medically significant, have been isolated from newt and salamander skins. Western North America’s rough-skinned newt (Taricha granulosa) possesses what may very well be the salamander world’s most powerful secretions…a single adult packs enough to kill 25,000 mice. More than one person (usually male, drunk and involved in some sort of “initiation” or dare), has suffered fatal consequences after swallowing a rough-skinned newt.

Skin secretions entering tiny cuts have rendered researcher’s limbs numb for hours, and a scientist who rubbed his eyes after touching a “woodland salamander” (I cannot recall the species, but belonging to the red-backed/slimy salamander group) wandered about blind for nearly 3 days before being rescued.

Toxins vs. Eel
Although the California newt’s (Taricha torosa) toxins pale in comparison to those of its rough-skinned cousin, they are not to be trifled with. I kept a California newt with an American eel for 17 years. The eel, a voracious predator that would as soon latch onto my hand as anything else, never once molested its seemingly defenseless tank-mate.

Next time I’ll relate an encounter I generated as a foolish 13 year old working in a pet store, which clearly illustrates the toxicity of even the most familiar of North American newts.

Further Reading
You can read more about the natural history and toxicity of the rough-skinned newt at http://www.amphibiaweb.org/cgi/amphib_query?where-genus=Taricha&where-species=granulosa&account=amphibiaweb

California Newt Image referenced from Wikipedia Commons and originally posted by Justin Johnsen

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.

Lengthening days and warmer temperatures are beginning to register on amphibian pets nationwide, stirring long-dormant breeding urges.  Last week I was please to find that a 2 year old female axolotl (Ambystoma mexicanum) which I paired with an older male had produced eggs for the first time.  A week or so earlier a reader informed me of another spontaneous axolotl breeding.

Mexican axolotls are an ideal choice for the prospective amphibian breeder, and are becoming ever more popular each year.  With spring upon us, I thought I might pass along some photos of my pair and their eggs, along with a few tips.

The Aquarium and Filter

The eggs pictured here are set up in a PLA House Plastic Cage equipped with a Small World Filter.  PLA House Cages are available in 6 sizes, and their light weight allows for easy water changes.  I have found them indispensible in my collection, and always have a number on hand.

The Small World Filter is ideal for use with amphibian larvae, as the water return is directed upwards and so does hamper weak swimmers.  Sponge filters work equally well.  I use an air pump that provides just enough aeration to keep the eggs slightly in motion.

Providing Cover
Axolotl eggs are typically attached to plants or other structures, as seen in the accompanying photo.  Once they begin to hatch, I’ll add additional plants, nearly filling the tank so as to separate the larvae a bit and reduce cannibalism.  Plastic plants set in bases are very useful, as they provide shelter throughout the water column. The Cypress Mat  provides excellent cover on the bottom of the aquarium, where the larvae will be spending most of their time.

Feeding Axolotl Larvae
Finely chopped live blackworms form the basis of my diet for newly hatched larvae…a worm feeder lessens the likelihood of the worms clumping together (larvae often choke while trying to swallow large balls of worms).  A brine shrimp hatchery is also useful, and larvae can sometimes be induced to accept freeze dried daphnia and other invertebrates as well.

Further Reading
Pleased see my article Breeding Mexican Axolotls  for additional breeding recommendations.

Those who keep reptiles, especially turtles and lizards, are often of the opinion that amphibians make rather unresponsive pets.  True, a number of frogs and toads “come to life” at feeding time, but by and large amphibians are somewhat more retiring than are most reptiles.  This is especially true of the salamanders, many of which spend the vast majority of their lives in hiding.

A Beautifully-Colored and Responsive Salamander

The strikingly beautiful fire salamander is, however, a notable exception.  Native to cool, mossy woodlands in southwest Asia, much of Europe, and a small portion of northwestern Africa (a continent noted for its lack of salamanders), fire salamanders are as visually oriented as any turtle and eagerly anticipate regular feeding times.  Typically colored jet-black and mottled with bright orange or yellow, one subspecies, Salamandra salamandra fastuosa is largely bright yellow with bold black lines going down the body, legs, and tail (please see photo).

The many fire salamanders I have kept would, without exception, leave their retreats in anticipation of food when I approached their terrarium.  Most feed from the fingers or forceps and are not shy about moving about in broad daylight once they are acclimatized to captivity.  They even move differently than most salamanders – holding their bodies high off the group and “stomping about” in a very determined (and most “un-salamander-like”) manner. And, as you can see from the photo, their bold personalities also suit them well as “amphibian ambassadors” to budding herpetologists!

A Caution Concerning Temperature

Fire salamanders could very well be the ideal amphibian pet for reptile enthusiasts.  Their one drawback is a distinct sensitivity to warm temperatures…a cool basement or similar situation is pretty much a necessity for success with this species.  Although individuals hailing from certain populations are a bit more heat-tolerant than others, nearly all become stressed at temperatures over 72°F.

Breeding and Longevity in My Collection and Elsewhere

However, when properly cared for, fire salamanders are among the most long-lived of all amphibians, with the captive longevity record being just over 50 years.

I received the 2 individuals pictured together here as larvae 14 years ago – they have bred several times and show no signs of slowing down.  They do not lay eggs, but rather give birth to live larvae. Some populations, particularly those living at high elevations, give birth to fully formed little salamanders, skipping the larval stage completely.

How I Keep and Feed Fire Salamanders

I keep my fire salamanders in a basement where yearly temperatures range from 55-68F.

As you can see from the accompanying photo, they feed readily from plastic tongs.  This allows me to increase dietary variety through the use of canned invertebrates – snails are particularly favored.  Field research has shown land snails to be an important part of the natural diet in many regions, so I rely heavily upon these, especially during the winter when other foods are scarce.

I also use canned silkworms, live earthworms (50% of the diet), blackworms, crickets, mealworm beetles, waxworms, sow bugs and wild-caught insects (i.e. moths gathered with the aid of a Zoo Med Bug Napper).

Further Reading

You can learn more about this salamander’s natural history and the threats facing wild populations at http://amphibiaweb.org/cgi/amphib_query?where-genus=Salamandra&where-species=salamandra

Please see The Natural History of Axolotls and The Captive Care of Axolotls for further information on this fascinating captives.  Today I’ll finish up with a note on reproduction.

Inducing Reproduction

Adult axolotls are sexually dimorphic, with females being of a heavier build and having shorter and broader heads than males.  The cloaca of the male is noticeably swollen during the breeding season, and gravid females become very plump.

The natural change in day length and room temperature in temperate regions is often enough to stimulate reproduction.  Animals under my care in NY respond to natural variations in room temperature (they are housed in a cool basement) and possibly day-length (light enters through a ground level window).  Females generally lay from January through March, sometimes into April, at water temperatures of 55-60 F.

A sudden increase of water volume and a drop in water temperature seems to stimulate breeding even outside of the normal breeding season. Be careful, however, that females actually lay their eggs when artificial methods such as this are utilized. Retained eggs are a great concern among many captive amphibians, although I have not run into such with axolotls.

The Eggs

Please see the Natural History of Axolotls for details on courtship and mating.  Females have been observed to pick up several spermatophores during the night, although it is not clear all are from one or several males.  Eggs are attached to water plants or any other substrate within the tank. Plastic plants make ideal deposition sites (from a pet-keepers point of view!) as they are easily removed from the aquarium.

Axolotls are ravenous consumers of their own eggs, and few will survive if the adults are left in the same tank. At temperatures of 55 to 60°F, the eggs will hatch within two to three weeks. I generally provide them with mild aeration, just enough to keep the eggs slightly moving. Eggs deposited on plants and on floating objects seem to have a higher hatch rate than do those laid along the bottom of the aquarium, so be sure to provide suitable sites for your females.

Caring for Axolotl Larvae

The larvae lie motionless for a day or so after hatching, after which they become veritable eating machines.  They are best raised in a bare-bottomed plastic or glass aquarium.  Mild aeration via the return from a corner or sponge filter should be provided.  The young require daily feedings and very frequent water changes – after having raised 160 to adulthood at one point, I can vouch for this as being a labor-intensive but ultimately rewarding task.

I’ve found light plastic terrariums or sweater boxes that can be easily dumped and filled to be the method of choice when rearing large numbers of salamanders.  I’ve also used plastic wading pools, but unless you can arrange a way to drain and re-fill easily, these can be a bit un-wieldy to work with.  The extra room they provide does, however cut down on cannibalism.  Please see Captive Care of the Mexican Axolotl (Physical Environment, Feeding) for tips on setting up enclosures and feeding axolotl larvae.

The IUCN’s recommended conservation strategy for this species, as well as historical and natural history information, is posted at:

http://www.iucnredlist.org/details/1095