Reproduction

Reproduction

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Female depositing her eggs
  1. In the field

    So far no one has watched any copulation outside of the shelters of Heloderma. A single deposit of egg´s was documented and made public (Ref. 20). The accurate hatching time of youngsters is not known. The hatchlings (weight about 35 gms) are observed at the end of April up to early June. Eggs are laid in July/August and one can only speculate that hatching occurs in the late fall. The hatchling immediately starts hibernation without going up above the ground. The second theory postulates a developed embryo that remains inside the egg over winter and hatches in spring.

  2. In captivity

    Captive bred Heloderma become sexually active in their third year. Male individuals might need one season more for maturity. They have to reach a snout-vent length (SVL) of at least 22 cm for sexual maturity and females have to gain a SVL of 24 cm (Ref. 22). Imperative for a successful breeding is a hibernation of a minimum of three months at about 13°C average. Copulation occurs when mature follicles ("bloating" of the female) are present. Males have to supply fully mature sperm at the same time.

    Oviposition proceeds if the female is provided with an accepted and suitable site (Ref. 23). An average clutch of eggs consists of 4 to 5, at the best of conditions, the maximum is 7 eggs. The eggs are transferred as soon as possible to an incubator. Although the eggs have been removed the female forms a hill of sand above the deposting site. There she stays a few days to observe and to protect her supposed eggs.

    Females protecting their egg depositing sites

    Female protecting her egg depositing site Female protecting her egg depositing site Female protecting her egg depositing site Female protecting her egg depositing site

    Incubation time of the eggs varies from 134 - 155 days (five months!) depending on the incubation temperature (26 - 29°C). The embryo in the egg is connected with the yolk sack via the umbellical cord. Two to three weeks before hatching, the eggs normally start to dent and final hatching takes place within 48 hours. While hatching, the yolk sack is completely retracted into the abdomen. The yolk is going to be absorbed (Ref. 24,25,26,27,28,29,30).

    The cycle of reproduction is depicted in the following photographs.

    Copulation of two different pairs each with left and right hemipenis

    Copulation of two different pairs Copulation of two different pairs Copulation of two different pairs Copulation of two different pairs
      Video

    At the beginning of a mating season, males shed their hemipenisses. The male will hook a rear limb around her pelvis and position the tail under. This will align the male´s cloaca for introduction of one of the hemipenis's. Copulation lasts for about 2,5 hours.

    The exposed hemipenis attempting copulation The exposed hemipenis attempting copulation The exposed hemipenis attempting copulation Copulation
    The exposed hemipenis attempting copulation
    Selection of shedded hemipenis skins Excess sperm fluid shortly after copulation Excess sperm fluid shortly after copulation The exposed female cloaca
    Selection of shedded hemipenis skins Excess sperm fluid shortly after copulation The exposed female cloaca

    Females seem to prefer "certain" males. If the "chemistry" fits, copulation proceeds within half an hour. Sometimes a female is only susceptible after many hours of "molesting" and she may bite at the male.


    Demonstration of a complete cycle of reproduction including: copulation, pre-egg shed, oviposition and hatching of the offsprings.

    Mating, Copula Pre-egg shed Oviposition Eggs shortly before hatching -
    hatching of the offsprings hatching of the offsprings hatching of the offsprings hatching of the offsprings


    Candling of fertile eggs shortly after egg deposition Egg after 4 months of incubation: note the prominent blood vessels and embryonic shape Vitality check: Graph documentation of the embryonic heart beat rate (Avitronics, Buddy Digital Egg Monitor) Vitality check: Graph documentation of the embryonic heart beat rate (Avitronics, Buddy Digital Egg Monitor)
    Candling of fertile eggs shortly after egg deposition   Video
    Egg after 4 months of incubation: note the prominent blood vessels and embryonic shape    		 Vitality check: Graph documentation of the embryonic heart beat rate (Avitronics, Buddy Digital Egg Monitor)

    Difference in size of two hatchlings with two one year old specimens. Weight at hatching is about 35 grams and after one year about 380 grams.

    Difference in size after one year Difference in size after one year

  3. Cycle of reproduction

    Control of the cycle of reproduction using ultrasound and X-ray

    Developing follicles Developing follicles Egg in developement Egg in developement
    9.3.06 Developing follicles 9.3.06 Developing follicles 16.5.06 Egg in developement 16.5.06 Egg in developement
    no egg deposit in june 06 06-06-22 Egg to be reabsorbed 06-10-20 New follicles appear 06-10-20 X-ray did not detect eggs*
    no egg deposit in june 06 06-06-22
    Egg to be reabsorbed    		 06-10-20
    New follicles appear    		 06-10-20
    X-ray did not detect eggs*

    * Note the abundance of osteoderms as small white points

    Ultrasound with measurement of egg size about three weeks before oviposition.

    Measurement of egg size about three weeks before oviposition Measurement of egg size about three weeks before oviposition Measurement of egg size about three weeks before oviposition Measurement of egg size about three weeks before oviposition
    Measurement of egg size about three weeks before oviposition Measurement of egg size about three weeks before oviposition Measurement of egg size about three weeks before oviposition Measurement of egg size about three weeks before oviposition

  4. Combat

    Combat in Heloderma is a ritualized fight between two males at the time of courtship and mating. A dominant male out of this combat is often preferred to copulate by a nearby female (Ref. 31).

    Sequences of combat (in captivity)

    Combat between two males Combat between two males Combat between two males Combat between two males
      Video
    Combat between two males Combat between two males Combat between two males, a female gets attracted Combat between two males, a female gets attracted
      Video with sound   Video with sound   Video with sound   Video with sound

    The sequence of photographs and video animations demonstrate that a nearby female is interested in this to happen and can be seen interfering with the struggling males.

    Some sequences of a combat resemble positions of a male-female courtship. Nevertheless, if a male wants to achieve copulation, he may show a similar aggressive behavior. This may give the observer the possibility of confusion and misinterpretation about courtship and combat.

  5. Courtship

    To show the difference in combat and courtship, photographs and video animations as follows.

    Courtship Courtship Courtship Courtship
    Courtship  Video      
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