The Indiana University Axolotl Colony

Q. How big do axolotls get? A. Adult axolotls range from about 20 cm (8 in) to more than 30 cm (12 in) in length (including the tail). They usually weigh between 100 and 350 g (approx. 3.5 to 12.5 oz).

Q.How long do axolotls live?
A. Most of the axolotls in the Axolotl Colony are no more than six or eight years old, because we usually only continue to maintain animals that are still breeding. We have had animals in the colony as old as 12-15 years. I have been told of axolotls living as long as 25 years, but that cannot be typical. We do not know what their natural lifespan is in their natural habitat.

Q. What do axolotls eat?
A. Axolotls are carnivores. They eat water insects and insect larvae, small fish, worms, Daphnia, and similar small aquatic life. For more information read our Short Guide to Axolotl Husbandry.

Q. Please advise as per how much an axolotl should or should not eat.
A. How much an axolotl should eat or needs to eat depends on whether it is full grown or not. If it is still juvenile, it will eat a lot just so it can grow as fast as it can.

Some people have said that overfed axolotls may regurgitate part of their food, but in over a dozen years working with them, I have never seen this.

If the axolotl is eating all or most of the food it is offered, it is not getting too much. On the other hand if uneaten or partially eaten food is often left, reduce the amount given in each feeding.

As an axolotl finishes its growth, it needs less food. Its ok to skip a few days over a weekend. Typically adult axolotls only need to be fed two or three times a week.

An axolotl that has stopped eating altogether is probably sick.

Q. Are axolotls still found in the wild?
A. Yes, axolotls are still found in the small remnant that is left of their native lake: Lake Xochimilco, Mexico. Since this lake is now small in area and polluted, they are a threatened species (appendix 2, endangered species list).

Q. Are there any feral populations of axolotls?
A. I have never heard any reports of a feral population of Mexican axolotls, although I expect that in parts of the United States they would be able to handle the climatic conditions. I hypothesize that any axolotls that may have been released into suitable ponds in the States hybridized with local Tiger salamanders, if they survived, and were subsumed into that wild population.

Q. What is a water dog? Is it the same as an axolotl?
A. Water dog is a term often used for any larval or neotenic salamander, particularly tiger salamanders and close relatives, in North America. We try to restrict the word axolotl to the Mexican axolotl (Ambystoma mexicanum), but some people do use it for larval or neotenic tiger salamanders. One possible translation of the word "axolotl" (which comes from Nahuatl, the language of the Aztecs) is water dog.

Q. What are the differences between axolotls and tiger salamanders?
A. Mexican axolotls (Ambystoma mexicanum) and tiger salamanders (Ambystoma tigrinum) are closely related but distinct species. The Mexican axolotl is native to a single lake (formerly two adjoining lakes) in the Valley of Mexico--Lake Xochimilco. (The other lake, Lake Chalco, is no more.) Tiger salamanders are found throughout North America, including in Mexico. The Mexican axolotl is neotenic, probably exclusively, but they are not well studied in their natural habitat. Neotenic means that they retain certain larval features, most notably gills and tailfin, and are aquatic throughout their life. Neotenic animals attain sexual maturity and successfully reproduce in this "larval" form. They also undergo certain not so obvious changes as they mature. In particular, all adult (aquatic) Mexican axolotls have lungs, albeit rudimentary ones. Most tiger salamanders are not neotenic. They undergo "complete" metamorphosis, which means they lose all larval features, including the gills and tailfin, and are terrestrial as adults. Some tiger salamanders that inhabit certain cold-water mountain lakes in the western United States are also neotenic. However, if you take a Mexican axolotl away from its native lake, it continues in its neotenic state, but if you take one of these neotenic tiger salamanders away from its natural habitat, it is likely to become terrestrial. Therefore, although superficially similar, neoteny in the two species is different in nature. Finally, although WE use the word "axolotl" exclusively to refer to A. mexicanum, in common parlance the word is often used for any larval or neotenic Ambystomatid. Therefore if you wish to avoid ambiguity you should always specify MEXICAN axolotl.

Our Web site and our colony are concerned with the Mexican axolotl only.

Q. Do axolotls spend a lot of time foraging and moving around or swimming? How much activity is normal?
A. Axolotls typically spend most of their time relatively motionless on the bottom of their tank or bowl. If they have live food, they usually ambush it rather than chase it. Our pellet-fed axolotls do search the bottom of their containers to locate pellets. They arch their necks while doing this, suggesting that they may be using smell to locate the pellets. Sometimes axolotls surface to gulp air. (They have both lungs and gills.) They also flick their gills from time to time.

Q. Why do axolotls flick their gills?
A.Axolotls often "flick" their gills, moving them back and forth, while they are otherwise motionless on the bottom of their tank. Heather Eisthen found an inverse relationship between the amount of activity (e.g., swimming) and the frequency of gill movement. Probably they are moving CO2 saturated water away from the vicinity of their gills and bringing oxygenated water closer.

Q. Our axolotls gulp air frequently? Why do they? Does it indicate a problem?
A. All axolotls (except very young ones) have lungs, even though they are aquatic and have gills as well. Having both lungs and gills makes the axolotl a very versatile animal when it comes to gas exchange and enables the axolotl to survive in a relatively hypoxic environment. It is normal for any axolotl to gulp air from time to time, but if an axolotl gulps air very frequently, the behavior may indicate a problem.

Check:

Temperature. If it is too warm, less oxygen will be dissolved in the water, and an axolotl will gulp air more frequently.
pH. It should not be less than 6.5. Low pH can cause gill damage.
Ammonia. It is very important that ammonia levels be kept very low. Use an aquarium store test kit. The guidelines given for fish are okay for axolotls too. If ammonia is too high, do partial water changes frequently until it is brought under control.
Water flow. It should not be fast. Don't use a large power filter on a small tank. Slow circulation of water is ok.

Q. When I keep 2 or 3 animals together, inevitably somebody seems to lose gill branches or filaments. Is this due to "nipping" and to be expected, or is there a normal cycle of loss and regeneration? The gill-denuded animals seem to survive quite as well as the others. Do you have any experience with and/or comment on this?
A. Probably it's due to nipping, especially in the case of juvenile animals. Adults are less aggressive (or perhaps just not continuously hungry). Barring chomping, gills and filaments should be permanent (no cycle of loss and regeneration), though axolotls will regenerate them when they do happen to lose them. Illness can also lead to deterioration of the gills, as can poor water quality.

Q. How much light is appropriate for axolotls?
A.Very little is known about what might be axolotls preferences with regard to light and light intensity. If they are eating well and thriving under the room lighting conditions, and so long as the room is dark for a period of time each day, I see no problem. Light or no light, they like having someplace to hide.

We do know that changes in photoperiod are important for spawning. When days are getting shorter (even if artificially) they will not usually spawn, but lengthening the photoperiod apparently triggers more spawning behavior. The light may cause algae growth of course. Algae are not a problem for the axolotl and will actually keep the water cleaner.

Q. Is it better to house axolotls by themselves, or can several be together in the same tank?
A. Small larvae can be housed in groups, but they will tend to nip one another's toes, especially if food is not available all the time. We prefer to house juveniles individually to keep them from dining on one another. The juveniles never seem to grow at the same pace, and a larger axolotl will never hesitate to eat a smaller one. By the time they are about a year old, their growth slows, and they become less aggressive, so adults can easily be housed in groups. In one case, when two males were in a large aquarium with one female, one of the males did not thrive, so he was removed. All-male groups co-exist very well, but we find that we have more success getting spawns if we house adult males individually. Adult females can be housed together without affecting spawning.

Q. Can axolotls be safely housed in the same tank as South African clawed frogs (Xenopus laevis)?
A. I don't recommend putting an axolotl with a clawed frog. They can transmit disease to one another, plus I think it would stress them both.

Q. Can axolotls be safely housed in the same tank as fish?
A. Axolotls can be housed with fish that tolerate the same conditions, especially temperature. However, if the fish are smaller than the axolotl, the axolotl will eat the fish (or try to). Also, goldfish are often aggressive and will bite the axolotls gills. We have had axolotls coexist nicely with Plecostoma.

Q. We house axolotls for research purposes. Several of these have developed scoliosis. Some cases occur in the thoracic and lumbar regions but most appear in the base of the tail and cause severe deviation of the tail. Have you encountered this? Is this possibly a nutritional problem or could it be a genetic or developmental occurrence?
A. We have seen this, though not recently. A few might acquire the deformity while confined in their jelly coats before hatching, and there could be a genetic abnormality, but I think what you're seeing is probably nutritional, especially the thoracic and lumbar problems. It may indicate a calcium deficiency.

Q. Do healthy axolotls normally become agitated if one bangs on the side of its tank or from similar disturbances?
A. Axolotls do not normally become agitated by people banging or tapping on their bowls or tanks. It is often possible to stroke or move an axolotl around with your finger without it becoming disturbed. Axolotls accustomed to being fed by people are expectant rather than nervous when people are around.

Q. Two or three of the axolotls that we are using in class are floating at the tops of their tanks, listing to one side. Why is this?
A. Floating can be a symptom of illness. Perhaps gas produced by bacteria accumulates in the abdominal cavity and can't escape. Animals often float a bit because of a little air or gas that they cannot expel. They often float temporarily as well if they have just gulped air. I might keep an eye on a persistant floater, but if no other signs of illness are present, it is not a concern in itself. This is assuming that the animal is still completely underwater. Skin exposed to the air for an extended period of time will dry out and cause discomfort to the animal. Floaters may eat well, spawn normally, and otherwise behave normally. The list to the side is meaningless. Extreme cases (an animal that is upside down and can't right itself) are of more concern for obvious reasons, but even they may have little indication of disease. Rather than whether it floats are not, health should be judged by the condition and color of the skin and gills and by whether the animal eats regularly. You might try varying the diet of the animals. That might make floating less likely.

Q. How can I tell a male axolotl from a female axolotl?
A. You can distinguish adult male axolotls from females by their relatively straight bodies and large glands about the cloaca (vent). Mature females have round, plump bodies because they are filled with eggs, and they lack the conspicuous glands. Axolotls cannot be sexed until they are sexually mature, at about one year.

Q. When do axolotls become sexually mature?
A. Axolotls normally become sexually mature at about one year of age and about 20 cm or longer, nose to tailtip. Well-fed axolotls may mature earlier, and males often mature before females.

Q. How can I tell if an axolotl is metamorphosing?
A.Axolotls that are transforming to the terrestrial form resorb their gills and tailfin, and their eyes bulge out and develop lids. They abandon the habit of gulping air and begin to breathe through their nostrils. The color pattern may become more vivid and defined, and the skin becomes tougher and able to withstand drier conditions. Metamorphosing and metamorphosed axolotls also molt, shedding their skin in thin, black, translucent sheets. The complete transformation process takes a number of weeks. It may be several months before the last nubs of the gills are gone. Usually while metamorphosis is going on, the axolotl will stop eating or will eat very little. More information about terrestrial axolotls.

Q. What is the proper care for a metamorphosed animal?
A. Terrestrial Axolotls

Q. What can be done to cure a sick axolotl?
A. The first consideration when dealing with axolotl health problems is husbandry: How are the animals housed, what are they fed, how is the water kept clean etc.

If you have not already done so, check out our guide to axolotl care: http://www.indiana.edu/~axolotl/axolotls/shortguide/guide.html

Most pathogens to which axolotls are subject are opportunistic. The axolotl will not ordinarily succumb unless they are stressed. The stress could be acute or it could be chronic.

Typical sources of stress:

Too warm. Keep the axolotl at 16-20°C.
Water not clean. If the axolotl is in a bowl, change the water regularly. If the axolotl is in a filtered aquarium, make sure the ammonia level is low (preferably zero) and the pH is suitable (6.5-7.5 is best).
Water circulates too fast. Sometimes a large power filter on a small aquarium is a problem. The axolotl cannot maintain the protective qualities of its skin properly.
Food unsuitable or carries parasites. Bait minnows are no good because they carry a heavy parasite load. Aquarium-raised guppies or goldfish are okay. Earthworms (red worms, night crawlers) are fine. Various other foods are possible.

So what do you do if the axolotl is sick. First, understand that not everything is curable, and it is not possible to know whether a particular axolotl will recover even if the treatment is effective generally (considering the population as a whole).

Put a sick axolotl by itself in a clean glass bowl (e.g., a glass fish bowl). If possible put the bowl in a refrigerator or low temperature incubator (anywhere from 5-15°C). Low temperatures reduce the stress on the axolotl. You may, if external sores, cuts, or lesions are observed, put a few drops of mercurochrome in the water (tint the water pale orange) for a few days as a disinfectant or swab the wound directly with disinfectant. Do not put any compounds containing copper or manganese in the water.

The Richard Gordan lab (University of Manitoba) offers the following: We've had great luck treating skin infections and skin parasites, "fuzz" on the gills and apparent fungus in nip wounds, and red sores or skin irritations with Nitrofura - G, a compound of Furazolidine, methylene blue, and postassium dichromate available from most fish stores. We use it in the dosage recommended by the manufacturer. It goes in the water as a yellow powder that turns the water blue. The animals usually improve rather dramatically over three doses.

Consider using antibiotics.

Finally, BE PATIENT.
Axolotls are not cured overnight, ever.

Q. What antibiotics can be given to axolotls and what are the proper dosages?
A. The Axolotl Colony has used enrofloxacin (Baytril), amikacin, and gentamicin. All of these are powerful, broad-spectrum antibiotics. Amikacin and gentamicin are aminoglycosides, and enrofloxacin is a quinolone. In our experience, all are well tolerated by axolotls. We recommend that Tetracycline and related antibiotics be avoided because it is a strong skin irritant.

We give antibiotics by injection usually. We do not have good data on the efficaciousness of antibiotics added to the water. We use a dose of 5mg/kg body weight. We use a solution of 5mg/ml antibiotic in physiological saline and give a volume of .1 cc. The animal should get 3 shots of amikacin or gentamicin, each separated by 48 hours or 5-7 shots of enrofloxacin, each separated by 24 hours. We inject with a tuberculin, 25-gauge needle intraperitoneally, just in front of a hind leg, approximately parallel to the body and about midway between the dorsal and ventral surfaces: that is, dorsal to the bladder and ventral to the kidneys and too caudal to hit the liver or spleen.

It is possible that other antibiotics could be used, or that some antibiotics could be administered in water, but we do not have enough experience to recommend dosages of other antibiotics or other methods of delivery.

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