Breeding Mexican Axolotls – Ambystoma mexicanum


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:

Breeding East African (Kenyan and Egyptian) and Indian Sand Boas (Eryx colubrinus loveridgei, E c. colubrinus and E. johnii)


I’ve come across several of the 11 unique snake species known as sand boas, and have had the good fortune of working with breeding groups of an Asian and African species. Following are some remarks drawn from my notes and conversations with colleagues.

Indian Sand Boa

The Indian sand boa (2 possible subspecies) ranges widely through India and Pakistan.  Those I have kept have reproduced without a winter cooling period (this likely varies among the various populations).  It is a good deal larger than the more popularly kept Kenyan sand boa, sometimes reaching 40 inches in length.  Unfortunately, this impressive burrower is not commonly kept in the USA.


Males in breeding condition go off feed and actively search for females.    During courtship, the male attempts to unearth the female’s tail (she is generally below the sand when found) with his head.   His spurs stand out slightly from the body and are rubbed along the female’s back.  Copulation seems a quite awkward affair, with the male burrowing below the female and flipping more or less unto his back.

The Young

The young are born alive after a 4 month gestation period.  They are larger than those of related species, averaging 10-11.5 inches in length.  A bit of umbilical cord usually remains attached for a few days, after which time it dries up and falls off.

The young shed within 2 weeks of being born, after which most accept pink mice.  In common with other members of the genus, young Indian sand boas likely prey heavily upon small lizards in the wild.  “Scenting” pinkies with a lizard may encourage reluctant feeders.

East African Sand Boa (Kenyan and Egyptian)

The East African sand boa is frequently classified as two separate subspecies, the Egyptian and Kenyan, with the Kenyan being the more brightly colored race.  However, taxonomists disagree on this point, with some considering the entire species’ name invalid (please see reference below).

Their reproductive mode parallels that of the Indian sand boa, but breeding is more likely if they are subjected to a winter cooling period (70F ambient, with a warmer basking site and a drop in temperature to 65F at night).

Mating usually takes place in June-August, and the young, 4-18 in number, are born in October-December.  They are 5-8 inches in length at birth, and reach sexual maturity at approximately 2 years of age (at which time they are approximately 16 inches long).

Sand boa taxonomy is currently in flux; you can review the species currently accepted by the American Museum of Natural History at:

Caring for Reptiles and Amphibians: Useful Foods, Medications and other Products from the Aquarium Trade – Introduction and Feeding Accessories


The Influence of Hobby and Food-Species Research

As compared to the aquarium hobby, the keeping of reptiles and amphibians in captivity is a relatively new development.  Far more time and research has gone into the development of products designed for fish and aquatic invertebrates than is the case for herps, and we know a great deal more about keeping and breeding them in captivity.  Also, commercially valuable species such as salmon, tilapia, clams and shrimp have generated a great deal of husbandry-oriented research, much of which has found application in the aquarium hobby.

Fortunately, the needs of many amphibians and reptiles parallel, and in some cases closely match, those of certain fishes.  Many of the fine products designed for aquarists are therefore of great value to reptile and amphibian enthusiasts.

Keeping Amphibians and Fishes Together

The Aquarium Fish Dish  is a valuable tool for those keeping African clawed frogs and newts along with fishes.

Fishes that feed at the aquarium’s surface and mid-water level nearly always consume blackworms and other live foods, as well as sinking pellets, before resident amphibians are even aware that it’s feeding time.  Live food specialists, such as dwarf African clawed frogs, rarely do well with fish for this reason, despite otherwise co-existing well with many species and making for an interesting tank.  The Fish Dish allows you to specifically target bottom feeding amphibians in mixed-species aquariums.

Limiting Choke Hazards

I came upon the idea of using the Cone Worm Feeder many years ago when raising axolotl and red-spotted newt larvae.  I fed them largely upon live blackworms, which always clump together, even when finely chopped.  I found that larvae of both species sometimes choked to death while trying to swallow the tightly-packed worm balls.

The worm feeder dispenses live worms individually, and has proven very useful to me in raising a wide variety of salamander larvae.  I use it with adult salamanders as well, especially the smaller species such alpine newts.

Certain fish medications work well with amphibians…please see my article:

Methylene Blue As A Treatment for Aquatic Reptiles and Amphibians

Titanoboa cerrejonensis, the World’s Largest Snake: Extinct Anaconda-Like Serpent Believed to Have Reached 43 Feet in Length and 2,500 Pounds in Weight


Well, the name says it all – Titanoboa!

Snake-oriented web sites will be alive this week with news of the discovery of fossils belonging to a snake of unprecedented size.  Writing in the journal Nature, researchers from the Smithsonian Institute and the University of Florida note that Titanoboa was larger than the contrived serpent that “tries to eat Jennifer Lopez in the movie Anaconda” (Ms. Lopez and company appeared at the Bronx Zoo when that movie was in progress, seeking technical advice.  I was a reptile keeper at the time, but, sadly for me, the powers that be declined to become involved!).

Colombia‘s Anacondas…now and then

An artist’s rendition of the huge beast casts it much like a very large anaconda.  Indeed, the giant is believed to have kept to Colombia’s marshy areas, home to modern-day anacondas.  Titanoboa roamed Colombia during the Paleocene Epoch, just after the extinction of the dinosaurs (approximately 65 million years ago).

Chasing Today’s Giants

There is only one reasonably reliable account of a modern-day snake measuring over 30 feet in length.  A reward offered by the Bronx Zoo for another stood uncollected for nearly 100 years.

I’ve done my level best to find a record breaking anaconda, and I like to think that she is out there somewhere.  The largest anaconda that I came up with was just over 17 feet long and weighed in at 215 pounds – no Titanoboa, but then again not an easy animal to wrest from the muck of a Venezuelan swamp either.  For the full story and some photos of myself and others with that snake, please see my article Hunting Anacondas in the Venezuelan Llanos.


Scorpions in Captivity – An Overview of Popular Species – Part 1


Emperor ScorpionAs is true for tarantulas, reptile enthusiasts (myself included) are often interested in scorpions.  Today I would like to provide an overview of these most ancient of animals (they were likely the first creatures to leave the sea for a terrestrial existence), with specifics concerning some readily available species to follow next time.

Please Note:  All scorpions manufacture venom and are capable of delivering a painful sting. Human fatalities are rare but not unknown, and the venoms of many are relatively unstudied.  Also, an allergic reaction is always possible…during my years at the Bronx Zoo I was often in contact with scorpion researchers….some reported relatively severe reactions from species not known to be dangerously venomous.

Unfortunately, the trade in scorpions is not well-regulated, and highly venomous species do appear from time to time (I’ll relate a personal experience in Part II of this article).  Purchase scorpions only from reliable sources, and be sure you can identify the species you are considering.  That being said, some of those best-suited to captivity are not dangerous, and make fascinating terrarium subjects.  Please check the legalities of scorpion ownership before acquiring one, as such is regulated in some areas.

Do not grab scorpions by hand, despite what you may see others do.  To move a scorpion, use a long handled stainless steel hemostat to gently grasp the telson (“tail”).  A bit of foam rubber should be secured to the tips to prevent the scorpion from being injured. 


Scorpions are classified in the order Scorpionidae, and, along with spiders, ticks and mites, in the Class Arachnida.  Nearly 2,000 species have been described (as opposed to 40,000+ spiders), ranging in size from .3 to 8.5 inches in length.  The 4 inch long Cetrruroides gracilis is the largest species in the USA, while the South African flat rock scorpion (Hadogenes troglodytes) is the world’s longest and heaviest.

Range and Habitat

Scorpions are found in tropical, sub-tropical and (less commonly) temperate regions of all continents except Antarctica, and are absent from New Zealand.  Various species are adapted to live in deserts, open forests, grasslands, caves and rainforests.  Some are quite at home around people, and may be found in overgrown fields, agricultural areas, gardens, parks and even within homes.

A surprising number thrive in quite cold climates, ranging as far north as Canada and southern Illinois in North America.  A feral colony of a small African species, introduced in produce shipments, is established in southern England.  In the USA, scorpions reach their greatest diversity in the southwest, where 60+ species may be found.


All are predacious, with most consuming soft-bodied insects but some specializing in land snails, sowbugs and other scorpions.  Larger species may take frogs, lizards, shrews and other sizable animals on occasion.


All scorpions thus far studied give birth to live young, and a number are parthenogenic.  Females typically carry the soft, relatively defenseless young on their backs for a time.  Many species feed their offspring with shredded insects…in some the young are totally dependant upon their mothers for food and will perish if separated too quickly.

In contrast to most of their spider relatives, certain species, including the popularly kept emperor scorpion, are quite social and may be housed in colonies.


Scorpion venoms are not well-studied, but thought to be quite complex.  Some that have been analyzed have yielded compounds with potential medicinal value.  Most seem to be neurotoxic in nature, but cytotoxic varieties are known as well.

The larger scorpion species are generally not dangerous to people, while some of the very small ones have caused fatalities.  Most of the 25-30 species thought to be capable of delivering serious stings are classified within the Genera Centruroides, Androctonus and Tityus.  However, as we have limited knowledge of scorpions in general, all should be treated with caution.  As mentioned, the possibility of allergic reactions to even weak venoms is always a possibility.  In all cases, small, straw-colored scorpions from the Middle East and North Africa should be avoided.

Scorpions in Captivity

At least 15 species are well-established in captive breeding populations, and many others are regularly available.  Fortunately, one of the largest and most interesting, the emperor scorpion, is also quite benign.  It lives well in groups, and females are surprisingly attentive to their young.  Next time I’ll write about the care of this and other popular species.

A short introduction to scorpion ecology, along with a diagram of their body parts and photos of common species of the American Southwest, is posted at:

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