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

 

Breeding season aggression is a potentially serious concern for owners of male green iguanas.  Spurred by reproductive hormones, mature males, even those which have been placid for years, may suddenly become dangerously aggressive.  This most often, although not necessarily, occurs in the late winter to early spring in the USA, so I thought that a word of caution might be in order at this time.

The Results of an Iguana Bite

If you are caught off-guard, an iguana attack can be quite severe.  A former coworker of mine, well-seasoned in reptile care, was surprised by an aggressive male who had been living without incident in the collection for over 10 years. The animal latched onto his throat and then fell to the floor, leaving a wound that required 18 stitches to close.

Timing and Indications of Sexual Maturity

Depending upon dietary and other factors, male green iguanas may reach sexually maturity as early as 18 months of age or as late as 7 years or more.  Unfortunately, the onset of aggression may be quite sudden, may not occur every year, and can last from 2 weeks to several months.  As you can see from the preceding story, animals may be even-tempered for many years before suddenly changing their behavior.

Males in breeding condition may exhibit a deepening of coloration in the orange-tinted areas of the head and body, and may head-bob and erect their crests.  Waxy secretions are usually present along the femoral pores, and dried semen is often found in their cages.  However, these changes do not always precede aggressive behaviors, so caution is always a necessity around large males.

Dealing With an Aggressive Iguana

A number of strategies for dealing with aggressive male iguanas have been proposed, with results varying widely.  I suggest that a plastic garbage can lid be held as a ready shield when working around aggressive males…a broom works well if the animal is at large in a room.  Fighting back with these tools may convince the animal to seek an easier target.  Avoiding close contact with the animal until the “mania” has passed, and keeping a shield at hand, are the safest options.  An alcohol-soaked rag (please see below) and, if possible, a helper, are very useful as well.

Some pet owners deflect aggression by providing their iguana with a towel to attack (or mate with!), while others keep the animal in a darkened room for 3-4 days to lessen the production of testosterone and other hormones.  Surgically neutering the animal is also an option, but the results of such have been mixed – in a significant number of cases the aggressive behavior remains largely unchanged.

If You Are Bitten

If you are bitten, do not pull your hand away.  Stabilize the animal so that it cannot thrash about and apply an alcohol-soaked rag to the lizard’s nostrils (avoid the eyes).  Liquor is fine to use (for the rag, not for drinking while working with your pet!) and should always be within reach during the breeding season.  Once the iguana releases its grip, secure it in its enclosure and call your doctor for instructions as to wound care.  Please do not neglect this step, as a tetanus shot or other care may be required, even for relatively minor wounds.

The Tail as a Weapon

The iguana that I am holding in the accompanying photo caused the cuts visible on my arm with a mere flick of his tail…the jaws are capable of doing much worse.  I came across him and the larger male (who, at 5’11” long, was the largest I encountered in the field) while working on anaconda research in Venezuela’s central llanos country.

Gravid Female Iguanas

Mature female iguanas often develop eggs as spring arrives.  Such will occur with or without the presence of a male, so be sure to watch even those animals which are housed alone.  Ideally, unmated females will resorb the eggs into their bodies, and have no need for nesting sites.  However, sometimes the eggs develop fully and, consequently, must be deposited.

Gravid (egg-bearing) female iguanas will usually cease feeding, or feed less vigorously, and will become very restless.  They often injure themselves by rubbing along cage walls and screening at this time, and they may attempt to dig through the cage floor.

Providing a Nest Site and Avoiding Egg Retention

Females without access to an appropriate nest site may retain their eggs, which will lead to potentially fatal health problems.  Provide gravid females with a large plastic container filled to a depth of 18-24 inches with moist top soil and moss.  Covering the container and warming the earth’s surface with a lamp may induce her to accept it as a nest site.  There are a number of other tricks you can try…please write in it you need further information.

Veterinary intervention may be required if the female refuses to lay her eggs.  In many cases, an injection of oxytosin is effective in causing the eggs to be expelled.

Further Reading

I’ve written about my experiences with wild green iguanas in another article on this blog.  Please see The Green Iguana on the Venezuelan Llanos.

An interesting article on iguana farming and conservation efforts in Belize is posted at http://www.thewildones.org/Belize/iguana.html.

 

Breeding Leopard Geckos (Eublepharis macularius) at Home: Determining the Sex of Your Pets

 

The ever popular leopard gecko is a good choice as an introduction to the breeding of lizards in captivity. Success, while not assured, is common…yet, these little fellows are so captivating that even zoos and well-experienced breeders continue to work with them.

Spring’s Effect
Leopard geckos are often brought into breeding readiness by the slight changes in temperature and day length that are evident even indoors. With the imminent arrival of spring (writing from southern NY I am happy to report hearing a song sparrow singing for the first time today!), I thought it a good time to discuss how female from male leopard geckos differ in appearance.

The Pores
Take a look at your pet’s vent, which is an opening, used for copulation and defecation, at the base of the lizard’s tail. Directly above the vent, between the rear legs, you will see a series of “V” shaped little bumps, which are known as pre-anal pores. These are large and readily visible in males and tiny and less-evident in females. The pores produce waxy secretions that are used by males to mark territories and, possibly, to attract females.

Hemipenes
Between the vent and the base of the tail, mature male geckos exhibit a pair of bulges. These bulges conceal the hemipenes, which are used during copulation to achieve internal fertilization. Male lizards and snakes have 2 hemipenes, and can use either, but only one at a time, when mating.

Practice!
You may need to look at a number of geckos, or reliable photographs, before being able to reliably distinguish males from females…but once you get the right “search image” the process becomes quite easy. Please remember that only mature animals – males of age 1 year or more, females generally of age 18 months or so – will exhibit noticeable sexual dimorphism (differences in appearance).

Further Reading
Please check out the book I’ve written on leopard gecko care and natural history at http://www.thatpetplace.com/pet/prod/240453/product.web.

 

 

 

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

Click here to view Part 1, Part 2 and Part 3 of this article. If you’re looking for information on Green Anole Natural History, click here.

Candidates for the Mixed-Species Terrarium

I have kept green anoles with 5 lined skinks, house geckos, brown anoles, green, gray and squirrel treefrogs, southern and spadefoot toads, DeKay’s (brown) snakes, various millipedes and land snails (…and water moccasins, but that was at the Bronx Zoo.  As they say “don’t try this at home“!).

I once established a group of green anoles in the upper half of a 300 gallon aquarium housing tropical fish – they take readily to such situations if provided ample branches and live plants upon which to climb.

Captive Longevity

Captive longevity approaches 10 years, but averages 5-7.

Handling

Green anoles are high strung and do not take well to handling.  They are fast moving and make long, seemingly reckless leaps, so be careful when opening their terrarium.  Let them see you open the enclosure, and do so slowly – in time, the anoles will move to safe, elevated locations as opposed to coming towards you.  They will, however, watch you closely and may take an opportunity to flee if you turn your back, so close the lid or door when reaching for tools, etc.  A small net might be useful to have on hand.  Green anoles shed their tails readily when grabbed forcibly.

Breeding

Please see also “Reproduction”, in Part I of this article, for notes on distinguishing the sexes.  Captive breeding has occurred spontaneously, but is most consistently achieved when the animals are exposed to cyclic changes in temperature, light and humidity levels.  Watch for young animals, as undetected eggs may hatch within the terrarium.

Green anoles originating from the northern portions of the range require longer and cooler “winters” than do those from the south.  In fact, southern-range animals are different, physiologically, from those in the north.  Experiments have shown that anoles living in south Florida are killed by the winter-time temperatures routinely tolerated by those native to northern Florida.  You can assume that pet trade animals are from the more southerly portions of the range (usually central/south Florida and Louisiana).

Cooling off periods of 60 days or so may stimulate reproduction.  Nighttime temperatures should be allowed to dip to 60-65 F for animals originating in the northern sections of the range, and 62-68 F for those from the south.  Daytime temperatures can rise to 81-83 F.  The daytime light cycle should gradually be reduced to 9-10 hours from the usual 12-14 (cover the cage during the day if it is located in a well-lit room).  Misting should be reduced to once daily.

Potted plants make ideal egg deposition sites.  Eggs incubated in vermiculite (1:1 vermiculite:water by weight) at 82-86 F will hatch in 32-46 days.

An interesting article on anole reproductive and social behavior, as well as a review of this species’ 100-year history as a laboratory animal, is posted at:

http://dels.nas.edu/ilar_n/ilarjournal/45_1/pdfs/v4501lovern.pdf

Please see Part I and Part II of this article for further information on Green Anole care. For Green Anole Natural History, Check out here.

Social Grouping

Keeping Several Males Together

Male anoles usually establish territories of at least 4 ft x 4 ft x 4 ft in captivity, so “one male only” is the rule in most home situations.   However, establishing 2 males in a suitably large enclosure is a worthwhile undertaking if at all possible.  If enough space is provided so that each can establish a territory, the males will display vigorously but will largely avoid physical contact (if crowded, the dominant animal will attack the other).  The presence of a competitor for female attentions may spur the males to breed as well.

 

Be sure to keep at least 3-4 females per male when attempting multi-male exhibits, as their presence may divert attention from aggressive displays and combat.  Another key to success lies in providing a complex environment filled with escape routes and sight barriers.  Vines, hanging plants and inter-twined branches will go a long way in increasing the effective size of your enclosure.

The Value of Smaller Pets and Zoo Animals

Observing anoles in colony-type situations will provide you with insights not possible in single-animal terrariums.  I have always preferred to keep smaller animals that could be well-provided for in captivity, as it is from these that we can truly get a feel for how life is conducted in the wild.

In a zoo or at home, one can more easily provide a “complete environment” for an anole than for an alligator.   Surrounded by creatures from all over the world during my years working for the Bronx Zoo, it was to those creatures most able to carry out a full range of behaviors that I was drawn.  I learned far more sitting in a greenhouse watching a colony of nearly “free-living” green anoles than I did in  front of multi-million dollar exhibits that, for all their good qualities, provided rhinos, bears, gorillas and other large mammals only a minimal replication of their wild habitats.

Female Dominance

Female green anoles will also establish a dominance hierarchy, based largely upon size. Those at the top may inhibit others from feeding and basking, so be sure to offer numerous basking and feeding opportunities and sight barriers.

 

Immature males are difficult to distinguish from females.  Watch smaller animals as they mature and remove any males, as these will be attacked by the adult male (please see Part I of this article for tips on distinguishing the sexes).

Compatible Species

Anoles, if given enough room, are ideally suited for community terrariums.  In the wild, they dwell in “edge habitats” (areas where 2 distinct habitat types meet) such as meadow-forest borders, and in the ecologically similar overgrown fields and gardens.  Habitat borders and edges usually support a greater variety of animals than do the interiors of either associated habitat.

The moderate temperatures and humidity levels favored by green anoles are suitable for a wide range of other interesting creatures.  It is often difficult to house amphibians and reptiles in the same enclosure, due to the great differences in their requirements, but green anoles uniquely span this gap.

Mixed-Species Considerations

When maintaining a mixed group of animal species, always provide more space than would be required for the same number of individuals in a single-species terrarium.  Be sure also to keep in mind the different feeding strategies of each.  For example, American toads will likely gobble up all non-climbing insects before anoles even begin to feed. On the other hand, anoles will leave no food for nocturnal hunters, such as green treefrogs, if all feeding is done during the day (the solution is to add a portion of the diet after the lights have gone out).