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

A recent article (Jan. 2009) in Physiological and Biochemical Zoology has shed light on why spitting cobras nearly always hit the eyes of whatever creature they are aiming for, be it secretary bird (a predator), gnu (a trample hazard) or person.

Perfect Aim Not Needed

Utilizing high speed photography and EMG tests, researchers established that the snakes contract their head and neck muscles just before ejecting venom.  The contractions rotate the head and jerk it sharply from side to side, so that the venom forms a complex geometric spray pattern as it approaches its target.  As long as aimed in the general direction of the face, the venom contacts the adversary’s eyes nearly 100% of the time.

Keeping Zookeepers on Their Toes

I have worked closely with several types of spitting cobras.  Like many Elapids (cobras and their relatives), they are alert and quick-moving, and seem, at least on the surface, to be quite intelligent.  These traits, combined with their ability to both bite and “spit”, renders them quite a handful in captivity, and they provide much fodder for zookeepers’ tales.

Perhaps He Thought They Needed Exercise?

In one very bizarre incident from my Bronx Zoo days, a visitor held his son up so that the child could kick in the glass of an exhibit housing 3 black-necked spitting cobras (Naja nigricollis)!  As might be expected, the breaking glass caused a great deal of agitation to both the snakes and some of the other visitors…I say “some of” because nearly as many people were pushing towards the exhibit as were running away (those wacky New Yorkers!).  Fortunately, all emerged unscathed, and the snakes were recovered quickly.

Cobra Hunting to Start the Day

Another zoo adventure began when, still bleary-eyed after a few mugs of espresso very early one spring morning, I discovered that 3 red spitting cobras (Naja pallida) had vacated their holding cage overnight.  The ancient plastic goggles I used around spitters were fine for exhibit work, but rendered me nearly blind in the dim, cluttered recesses of the reptile house’s basement and storage areas.  Lifting the goggles briefly to peek under something was terrifying, but so was leaving them on and seeing only unidentifiable shadows.

One colleague, goggles perched on his forehead, spied a snake and grabbed it with tongs, neglecting to lower the goggles in the excitement.  Fortunately, the trapped serpent vented its wrath by biting the tongs, and not by spitting at my partner’s face!  After a few sweaty, suspense-filled hours, all 3 snakes were re-captured…whereupon I ordered new goggles!

I’ve also had run-ins with the spitting cobra’s much larger relative, the king cobra…please see my article A Close Call With a King Cobra http://blogs.thatpetplace.com/thatreptileblog/2008/06/ for more cobra tales.

Image referenced from Wikipedia, first published by LA Dawson, and shared under the Creative Commons Share Alike-2.5 License.

Browsing the pages of Herpetologica and other journals over the years, I several times came across field studies indicating that certain populations of savannah monitors consumed diets composed entirely of invertebrates.  In certain seasons, the lizards gorged on either locusts or land snails exclusively for months on end.  When some captives fed largely upon rodents showed evidence of kidney and liver damage and intestinal impactions, articles in popular magazines began calling for insect-based diets.

Canned Diets

Savannah monitors may approach 5 feet in length, and thus an insect-based diet is difficult to arrange…thousands would be needed weekly in some cases.  Zoo Med’s Canned Tegu and Monitor Diet provides a handy solution.  Formulated with these lizards in mind, it is readily accepted by most individuals.

After reading the aforementioned articles, I took a moderate position as regarded the savannah monitors under my care in public collections, using canned food as 60-75% of the diet.  I supplemented the food of adults

once weekly with vitamin/mineral powder  and that of juveniles 3-4 times weekly.

Invertebrate and Vertebrate Food Items

The easiest way to supplement canned food without using mice is to establish a breeding colony of Madagascar hissing roaches (even the well-armored adults are readily accepted) and nightcrawlers.  Crayfish, if available to you, are a great monitor food.  Other useful food items are land snails (available in seafood markets), tomato hornworms, hard boiled eggs (in moderation, i.e. once monthly) and canned grasshoppers , silkworms  and snails.  Pink and fuzzy mice (these are preferable to adult mice and rats) may be offered every 10-14 days.

My Observations of Wild Black and White Tegus

My observations of black and white tegus in Venezuela leads me to believe that, at least in llanos habitat, these lizards consume far more large insects, turtle eggs and frogs than rodents.  Mammals are taken when available, mainly as carrion or unearthed rodent nests.

I have kept tegus for lengthy periods on rodent-based diets but now counsel more variety…I suggest feeding as described above, but with canned food comprising a smaller portion (i.e. 25-50%) of the diet, and rodents, preferably pink and fuzzy mice, being offered once weekly.  If your tegu will accept whole fish (i.e. large shiners), use these in place of mice.

An interesting article on savannah monitor natural history and diet in the wild is posted at http://www.mampam.com/index.php?option=com_content&task=view&id=36&Itemid=76

The Partnership for Amphibian and Reptile Conservation (http://www.parcplace.org/) presents a unique opportunity for hobbyists and others to work in the company of professional herpetologists.  The organization is unique and, in my opinion, far-sighted, in focusing on common as well as rare amphibians and reptiles.  Membership is open to all interested persons.

Working groups are established to address species native to each of 6 geographic regions in the USA, as well as in Canada and Mexico, and volunteers are always welcomed.  Current initiatives range from monitoring smooth green snake populations to assessing vernal pond habitats.

Frog and salamander enthusiasts can participate in the National Wildlife Federation’s “Project Frogwatch” (www.nwf.org/frogwatchUSA) or the North American Amphibian Monitoring Program (www.pwrc.usgs.gov/naamp).  Amphibian deformities, an increasingly common concern, can be reported at www.nbii.gov/portal/server.pt.

State wildlife agencies often support volunteer-based conservation initiatives.  Links to the individual agencies (they all have different names) of each state may be found at http://www.fishwildlife.org/ or on the PARK website noted above.

Check out: Captive Care of the Mexican Axolotl Ambystoma mexicanum – Part 1, for the first part of this article.

Feeding

Repto-min, trout chow or salmon chow serves well as a mainstay; alternate this with Hikari Massivore Delight or a pelleted cichlid food, freeze dried prawn, live blackworms, earthworms, minnows, shiners and guppies.  Axolotls will also take frozen clams, mussels and similar foods, but marine-derived items should not be used as a major part of the diet.

Although normally bottom feeders, well-habituated axolotls will rise to the surface to eat, and take readily to hand- feeding.  A finger waved before one will be grabbed and “swallowed”.

Finely-chopped blackworms (use a razor) are the best food to start off with when raising larvae; brine shrimp are also accepted, but growth with be faster for those consuming blackworms (and each other!).  Be aware that blackworms, even chopped pieces, clump together; larvae may choke trying to take down a large ball.  Be sure to swish the worms about the tank, and watch that they do not “find each other” after awhile.  A surface worm feeder that releases the worms individually will help relieve this problem.  I’ve not been able to induce axolotls under 2 inches in length to accept Repto-min or other dry foods, but others report success with very small individuals.

Social Groups

While not overly aggressive toward each other when un-crowded, the feeding of live food seems to stimulate a near frenzy, during which animals may bite the gills and toes of their tank-mates. Generally these grow back without problems, but a treatment with Aquarium Pharmaceuticals Stresscoat is a useful safety measure.

Axolotls housed together should be nearly the same size – even a difference of 25% is too great, as the larger animal will eventually bite off the gills and limbs of the smaller, possibly killing it.  Feeding injuries among similarly-sized animals are less severe – the loss of a toe or gill tip.

Losses are usually high when young animals are reared together, but can be lessened somewhat by the provision of dense cover (please see “Physical Environment”, above).

Captive Longevity

Captive longevity approaches 25 years.  Animals in my collection are still breeding at age 17.

Handling

It is best to usher an axolotl into a plastic container, as they may damage their delicate skins when thrashing about in a nylon net.  Axolotls may also be picked up by hand, but use caution as they tend to lie very still and then suddenly explode, and can easily propel themselves to the floor.  Handle only when necessary to move or examine an animal, and use wet hands and great care as the skin is quite injury-prone.

Miscellaneous

The axolotl’s long history as a laboratory animal has given rise to a wide variety of attractive color phases, including leucistic, black, albino, piebald and others.  The genetics of color inheritance in this species is quite interesting, and seems not to follow the “normal” rules…at least not as I learned them!  Recently, bio-engineered axolotls that glow fluorescent green have appeared in the trade.

Rearing axolotls in the lab differs in some respects from home care, but much of value is contained in the protocols of institutions maintaining large research colonies.  You can read about how it’s done at laboratories and universities all over the world at:

http://www.ambystoma.org/AGSC/suppleguide.pdf

Please see Natural History of the Axolotl for information on axolotls in their natural habitat.

I highly recommend the Mexican axolotl as an aquarium animal for both beginning and advanced hobbyists, and include them whenever possible in the zoo exhibits that I design.  Assuming that attention is paid to temperature and water quality (please see below), axolotls are hearty, long-lived and quite simple to breed.  They are also extremely responsive pets, taking readily to hand feeding and perfectly content to be out and about by day.

Enclosure

Axolotls are entirely aquatic, with an adult requiring an aquarium of approximately 10 gallons in size; 5-10 gallons more should be provided for each additional animal.

Axolotls also fare well in plastic terrariums or sweater boxes that are emptied and cleaned as opposed to filtered; this method is very useful when rearing large numbers of young.

Physical Environment

Axolotls are unusual among salamanders in not requiring a shelter, but the provision of such will help to alleviate aggression when groups are kept together.  They readily take up residence in plastic reptile caves, clay flower pots or PVC pipes.

The young enjoy consuming their brethren, and should be afforded as much opportunity to avoid each other as is possible.  Individual shelters are not effective in preventing this (among young animals) in group situations.  Rather, fill most of the aquarium’s water column with Penn Plax Baby Hideouts and other plastic aquarium plants.  Weight these down with plant ties to cover the base of the aquarium, and position tall plants so that they fill the vertical space as well.

Axolotls can be kept in bare-bottomed or planted tanks.  If gravel is used, it should be of a size that cannot be swallowed.  Small rocks ingested during feeding are often passed, but impactions can occur.  Live aquarium plants, if used, should be sturdy and well-rooted, or floating.

Light and Heat

A florescent bulb is best used for illumination, as it will not add significantly to water temperature.  Axolotls do not need a source of UVB light.

Axolotls are native to cool, high-altitude lakes, and do best at water temperatures of 62-70 F, with a dip to 50-52 F in winter, if possible.  People do keep them at warmer temperatures, but such leaves the salamanders susceptible to illness and fungal problems.  At temperatures above 75 F, Saprolegnia infection is not infrequent (this and certain bacterial infections usually cause the animals to float to the surface).  A cool basement is ideal for year-round maintenance.

Water Quality and Filtration

Axolotls are fairly tolerant of a wide variety of conditions, but should ideally be kept in soft water with a pH of 6.9-7.6.  Hard or acidic water can damage the gills.

Adequate filtration and frequent water changes are essential.  Axolotls have large appetites and excrete copious amounts of nitrogenous wastes (which are largely dissolved in water and not visible), and can quickly succumb to ammonia toxicity.  An ammonia test kit should always be on hand.

Canister, hanging or in-tank filters all have their place in axolotl aquariums, but each must be coupled with regular water changes.  Larvae are best kept in aquariums filtered with sponge or corner filters.  In all cases, filter outflow should be adjusted so as not to disturb the salamanders, as they are not strong swimmers and prefer still water.

Check out: Captive Care of the Mexican Axolotl Ambystoma mexicanum – Part 2, to read the rest of this article.