Guide To How to Breed Tegus
This Guide How to Breed Tegus, focuses on the strategies one can use to breed this lizard. All the questions related to Tegus breeding and their courtship behavior are answered in this article.
Tegus are large lizards that can reach nearly five feet in length. They have a mottled black and white coloration that often is arranged into a banding pattern across the back and tail. Hatchlings display similar markings but typically have bright green heads. The green coloration fades after they reach about one month of age.
In both its native and introduced range, the Argentine black and white tegu is found in savannas and disturbed habitats such as forest clearings, roadsides, and fence rows. They are terrestrial lizards that rarely climb more than a few feet off the ground, but they are strong swimmers. Tegus can tolerate marine and freshwater habitats, such as flooded marshes.
During the winter months, tegus retreat into burrows while they undergo a hibernation-like period known as brumation.
Female tegus reach reproductive maturity after their second year of brumation or when they are about 12 inches long from the tip of the nose to the base of the tail. They lay an average of 35 eggs per year.
Females construct nests of dried vegetation, often at the base of trees, in clumps of tall grass or in burrows. Eggs incubate for approximately 60 days and require stable temperatures for successful hatching. After hatching, tegus grow quickly. Tegus may live up to 20 years.
How to Breed Tegus Lizards?
For breeding, you first need to have a sexually mature pair, or better yet a trio (one male and two females). Late juveniles and subadults can sometimes be sexed by visual examination of the cloacal region. A subadult male has visible spurs located on each side of the vent. Adult males also have enlarged jowls and are typically heavier bodied. The only way to positively identify the sexes is to have the tegus probed by a professional herp veterinarian.
As with most reptiles, tegus need a cooling or hibernation period for triggering breeding behavior. There have been reports of tegus breeding without it, but it is suggested to provide a hibernation period because this would be normal in their natural habitat. Feeding should be stopped 2 weeks before initiating the hibernation period.
This should coincide with the onset of winter in your area, regardless of whether the tegus are housed indoors or outdoors. Temperature and humidity should be dropped gradually over a 2-week period. Try to keep the temperature at 50°F (10°C).
Role of Temperature in Tegus Breeding:
Temperatures below 42°F (ca 6°C) would kill smaller species. Hibernation temperatures should be maintained for an average of 3 months or 5 months at the most. To end hibernation, reverse the process by gradually increasing temperature and humidity, and then resume feeding. Females should be fed heavily at this time, so they have enough fat reserves for egg production. Males often steal all the food, so it may be a good idea to feed the sexes separately.
Tegus normally copulate a month or two after coming out of hibernation. The courtship behavior of tegus is most interesting. The male performs a sort of marching-in place dance for the female, which is somewhat comical.
The male may also prod the female with his snout, and scratch at her sides. Coitus will soon follow and is sometimes a very violent act. Males housed together have been seen mounting each other to establish dominance.
Females have been known to dominate males by mock mounting prior to egg-laying, seemingly to let the males know that they want to be left alone. One male and one or two females can usually be housed together if the enclosure is large enough, but they should be separated at the first sign of aggression. It is recommended, putting the sexes together only for copulation, and only when you can watch them continuously.
The Best Time to Remove Male from the Nest:
The observant keeper will easily see when the gravid female tegu is ready to lay her eggs. She will usually stop eating 1–7 days before laying. As soon as this happens, provide the female with fresh nesting materials alfalfa hay, cypress mulch, or pine shavings and remove the male from the enclosure, as he may attempt to eat the eggs.
After the female builds a nest, she will lay 10–50 eggs. A female tegu may sit guard over her nest, but the eggs should be transferred to an incubator set at a temperature of 84°F (29°C). Hatching normally begins after 90 days of incubation.
Reproduction in Tegus:
Seasonal climate changes constraints to tegu activities, whether of a general type or specifically reproductive. In fact, the dormancy period, which stretches over five to six months, causes these activities to be circumscribed to spring and early summer.
The hatching of the small offspring, which signals the end of the reproductive phase, takes place towards the end of December and the beginning of January. From then onwards, the adult animals go through a phase of reproductive quiescence characterized by gonadal regression.
The reproductive activity of tegus comprises two clearly differentiated stages:
- Sexual interactions
- Nesting activities.
Depending on the type of behaviors that are predominantly recorded in these stages, they can be in turn divided into minor sub-stages.
Sexual Interactions Phase:
This stage encompasses all the interactions displayed by adults of the same and opposite sex, including territorial behaviors, courtship, and mating. These activities begin after hibernation, the end of which can be considered, for practical purposes, to coincide with the emergence of the animals from their shelters.
Territorial behavior is characteristic of tegu males and is aimed at marking certain physical spaces and establishing dominance over them. Males leave shelters before females and, after a few days of re-adaptation, they start to display a characteristic undulating dragging of their pelvis and hind limbs over the ground.
This movement produces friction on a set of structures located at the inner side of their thighs, called femoral glands, and the subsequent release of pheromones, specific substances that cause responses in individuals of the same sex, and possibly of the opposite sex as well.
The territory thus marked is defended with different intensity levels, including challenging, chases, and confrontations between the animals. Usually, pursuits consist of vertiginous races on four legs, though on rare occasion’s races on only the hind legs, and with a raised torso, can be observed.
The defiant attitude that precedes confrontations is expressed through characteristic postures and motions: head down, raised, and arched torso, and slow movements.
Such threats may cause fear in a contender, which thus assumes an evasive attitude, withdrawing from the confrontation with a lifted head and a straight back as a sign of meekness (interestingly, this is how females behave during courtship).
Conversely, an individual may react contendingly, which results in a fierce contest with the rivals persistently chasing one another in circles, while trying to grab the opponent by the neck and thrust it down onto the ground. Usually, clashes between similar-sized opponents are repeated with evident stubbornness.
The bites can cause different degrees of damage. On unfortunate occasions, a lizard might grasp one of the limbs or the tail of the opponent in its jaws and rotate over itself detaching them from the body.
This contraption constitutes an anti-predatory maneuver performed by many lizards, including tegus, to distract and free themselves from natural enemies. The loss of a portion of the tail has no important consequences for tegus, as it is later compensated by a regenerative process that restores it, at least rudimentarily.
Independently from the resulting physical traumas, combats affect sexual performance, so it is important to prevent and restrain them among the members of the breeding stocks.
Another event associated with male territorial behavior is the release of a whitish mucous substance through the copulatory organs or hemipenes. This substance of unknown function is produced in the form of slender strands called ‘seminal filaments.
On certain occasions, territorial behaviors are also observed in some females, which imitate males by aggressively reacting to the presence of other females. Seemingly, the territorial behaviors previously described do not set up any kind of long-lasting hierarchical organization. Indeed, tegus are predominantly polygamic and, during the sexual activity phase, males and females tend to copulate with different individuals.
Courtship and Mating:
The presence of females, which emerge from the shelters approximately a couple of weeks after males, marks the onset of courtship and mating rituals. Territorial behaviors become less intense and males progressively focus their attention on females, which they smell, chase after, and incite. Males start harassing females by softly biting their tails, to which they respond with brief escapes, lifting their heads, and erecting them back to show submission.
As stimulation increases, the chasing becomes more repetitive and bites gradually progress from the tail towards the neck of the female. At a more advanced stage, males attempt to mount females, while panting because of spasmodic movements of jaw muscles and scratch their backs with their hind legs.
Normally, courtship is rewarded with the mating event, during which the male keeps hold of the female’s neck with its front teeth in a delicate manner and curves its tail beneath that of the female.
This posture allows both cloacal regions to draw near one another, and the male is then ready to introduce its copulatory organs or hemipenes into the female genital tract.
Copulas are brief and last between thirty seconds to one minute, after which the individuals draw apart from each other. The male soon retracts its hemipenes and rubs its cloacal region against the ground, leaving some mucous material like the seminal filaments observed during territorial marking, but this time with no apparent shape.
Nesting activities involve fertilized female tegus exclusively, and they show complex maternal behaviors.
Characteristics of Gravid Females.
Effect of Mating on Ovulation.
After mating, tegu females exhibit evident changes in their conduct and anatomy, which anticipate imminent ovulation and subsequent oviposition. They turn aggressive and remain isolated, strongly rejecting new copula attempts.
In addition, after approximately 20 days between mating and ovulation, and because of accelerated ovule growth, their abdomens expand considerably. To a large extent, the increased growth of ovules (female gametes) is caused by the vitellogenic process, whereby they incorporate large amounts of nutrients as the yolk.
In results, the small precopulatory ovaries experience a 100-fold mass growth (from 4 to 400 g). The systematically observed relationship between mating and ovarian development suggests that a sexual stimulus (possibly copulation itself) might be involved in normal vitellogenesis onset, and thus in subsequent ovulation.
As a matter of fact, the sexual isolation of females led them to exhibit ovulatory cycles, accompanied by the degeneration (atresia) of the ovarian follicles (ovules and their corresponding envelopes). Though with a less uniform effect on vitellogenesis, lack of sexual intercourse sometimes resulted in the formation of large tumors that derived from ovarian follicles.
The annual reproductive capacity of female tegus under captive breeding has been documented. They may present regular oviposition cycles through several reproductive seasons, over five years or longer.
Notwithstanding that, such potential is not fully expressed and a variable proportion of individuals (up to 50%) do not go through ovulation and egg-laying processes after mating, showing infertile cycles (anovulatory ones). The cause for such reduced fertility in tegu females kept under our breeding conditions is still unknown, and thus constitutes a significant issue to be further investigated.
In this sense, the features of the calendar of tegu reproduction, which occurs without delay soon after dormancy, must be born in mind. That is why most parts of the plastic and energetic resources involved in reproduction comes from the previous season.
The lack of coincidence between feeding and reproduction is a frequent strategy of ectotherms called ‘capital breeding’, as opposed to ‘income breeding’ of endothermic species, in which resources are obtained simultaneously with reproduction.
This is an important aspect to consider in tegu reproductive management since the chances an adult female has for breeding will depend on the nutrition levels it acquired during the active phase before the hibernation period.
Nesting and Egg Laying:
In the wild, gravid females use an underground burrow to nest. A few days before oviposition, they drag weeds and other plant materials with their limbs. In captivity, as soon as females exhibit gravidity signs, they are taken to individual nesting enclosures provided with an incubation chamber.
With the supplied material (weed or dry grass), gravid females buildup a semi-spherical nest about 25 cm in diameter, which has a thick and smooth vegetable wall where they lay their eggs. Subsequently, they cover the nests with a layer of plant materials and earth. When they finish this task, they apparently urinate on the upper cover of the nest so that it keeps humid.
Finally, both the nest and the female that takes care of it remain hidden under a vegetable cover. It just takes a short time for eggs to descend through the oviduct (from ovulation to oviposition): possibly about 3 days.
At the time eggs are laid, the embryos have a very incipient development (primitive streak). These two aspects are important characteristics of a typically oviparous animal. Oviposition results in the laying of 20 to 45 whitish eggs, with an oval shape and a length of about 45 mm. Their shell is soft and resistant, but water permeable. Albumin is scarce or nonexistent; hence the yolk inside the eggs is practically in contact with the shell.
Incubation requires considerable maternal care. Once eggs have been laid, females will remain sitting on them with their bodies curled for quite long periods, and they will abandon this position only for basking and feeding.
Egg incubation lasts more than two months (70 days), during which the female defends her nest by decisively attacking eventual intruders. During this process, eggs absorb a considerable amount of water, so that when hatching is drawing near their shells show some facets and certain pigmentation they have acquired from the substrate.
Towards the end of the incubation phase, females begin spending more time outside the incubation chamber and start feeding more.
In most reptiles, climate factors seem to be the only determinants of the physical environment in which nests prosper. By contrast, tegus have a decisive share in this, as their incubating behaviors aim to generate suitable conditions for embryonal development. Indeed, forsaken nests will barely lead to hatching and offspring survival.
Maternal contribution appears to be predominantly (but not exclusively) aimed at regulating temperature and humidity conditions. Thus, we could observe that nests incubated by females kept an average temperature which was 5ºC higher than that of an empty incubation chamber.
Basking and the subsequent transference of accumulated heat seem to constitute the main nest heating mechanism. However, it is also possible that tegus might develop facultative endothermy in association with their reproductive activity, which is independent of basking.
In addition, it is possible to observe that the vegetable substrate in nests incubated by female tegus, in contrast to that in abandoned nests, is visibly wet and considerably decomposed. This increases its acidity throughout the incubation period (pH of 9 to 6).
These characteristics, together with the presence of uric acid secretions, suggest that urination plays a critical part in both substrate humidification and asepsis.
However, this type of ‘field incubation’ by females tends to lead to inconsistent hatching results. This is possibly due to various factors, such as climatic and edaphic ones, certain motherly behaviors, and even variable pertaining to human intervention, if we consider incubation chamber design.
Fortunately, unlike incubation by tegu females, artificial incubation experiences have been considerably successful.
Simple artificial incubation methods resulted in hatching rates close to 80%, which shows that this procedure may be a valid alternative in productive tegu breeding projects.
Besides, artificial incubation offers the interesting possibility of changing sex proportions inbred populations of several reptile species. In this respect, it has been demonstrated that thermic and hormonal egg treatments may play a significant role in determining sex ratio. Even though preliminary estimations about sex ratio in tegu hatchlings indicate a 50% contribution for each.
Hatching occurs in late spring or early summer. To rip through the eggshell, hatchlings use an ‘egg tooth’, which is a temporary small spike formed on the surface of the upper jaw. Hatchlings leave the nest through a common hole that the first new-born makes on the upper cover.
All hatchlings are born within approximately three days. They are 15 to 20-cm long, active, and independent, so much so that only two days after birth, they start seeking food. Indeed, they will have only three months to feed and store enough resources to be able to successfully endure the first, and probably the most dangerous, dormancy period.
A remarkable feature of nesting females, which is related to offspring survival, is that they lack cannibalistic behaviors, in contrast to other individuals.
Other Behaviours of Tegu Lizards:
During their active period, tegus display an additional set of behaviors that need to be considered for their successful captive breeding. Apart from engaging in basking and cooling activities as previously mentioned, they show cave digging and climbing habits.
Another behavior that they may present is cannibalism, particularly larger tegus eating small offspring (except for mother females, as previously stated). However, under captive breeding conditions, cannibalistic tendencies are prevented by routinely keeping animals separated according to age and size.
We should also mention the capacity of tegus to associate events: for instance, they link certain sounds (those when enclosures are opened or closed) with food provision, identify habitual farmworkers, and recognize shelters and preferential sites.
Tegu Lizard Breeding Facts
|Name of Lizard||Lifespan of Lizard||Clutch Size / Year||Sex %||Hatching / Incubator %||Average Price|
|Tegu||20 Years||Average 35 Eggs||50 %||80%||$200-$3000|