Crested geckos grow at their own rates. Most breeders estimate it takes 1 to 2 years for a baby to become an adult, with the average being around 18 months. This is not always the case. Sometimes, it appears that crested geckos hatched and reared in certain locations grow slower than others. There is speculation that fluctuations in humidity and temperature can affect growth rates as well. Usually, once a gecko hits around 10 or 12 grams, growth takes off until around 25 grams, during which time they grow quite quickly. Many breeders are frustrated by the fact that some geckos seem to “top out” at around 30 grams, which for females is not heavy enough to safely produce eggs for a season.
Generally, sexual maturity in reptiles is triggered more by overall body mass and less by age. Depending on the husbandry, reptiles in captivity reach sexual maturity earlier than in the wild – resulting in “young” adults. We as keepers place selective pressure on reptiles to breed faster, choosing the animals which mature at younger ages. Since growth generally slows at sexual maturity, the body stops putting resources into growth and diverts them into reproduction. There may be some risk that breeding early can stunt the overall growth, but in general, females bred at 35 especially can put on girth after breeding successfully if she is sufficiently “cooled” in the off-season. Young males in general tend to stay slim, perhaps because of the reproductive drive. There is no standard weight for a full grown crested gecko. Most reptiles tend to have indeterminate growth, meaning they grow constantly throughout their lives, although most crested geckos do not grow much after reproductive maturity. They can, however, put on extra weight with stored fat. That said, adult crested geckos are usually between 40 and 60 grams. Overweight geckos can suffer health problems and reduced fertility.
Baby crested geckos hatch out between 1.5 & 2 grams and are considered juveniles until they hit sexable weight, often at 16 grams. An adult crested gecko ranges from 35-55+ grams for females, while males are considered “adult” around 25 grams, when they are likely to successfully mate with a female. Larger females can often intimidate smaller males, and generally it’s always best to pair similarly sized animals to avoid bullying from either party.
Growth Rate Factors
The following are speculated factors in growth for crested geckos.
- Incubation length
Growth & Diet
Often, geckos fed in the “oldschool” method of babyfood and crickets seem to grow to sexual maturity (adulthood) around one year. This is probably a combination of increased feeding response, sugars (making them tend toward obesity) and protein. Live food and sugar are known to increase the feeding response. However, the danger is growing too quickly with too little nutrients, resulting in MBD, follicular stasis, and other health issues.
When feeding only Repashy CGD, crested geckos seem to reach adulthood around 2 years. 18 months is considered an acceptable time to breed if the gecko is up to weight (35+ grams).
Feeding insects is said to increase growth rates, but we have yet to determine whether it is the stimulus effect or the nutrient content of insects that contribute to the rise in growth rates. Some breeders have been experimenting with “bug slurries” to see if this affects development of their cresties.
Crested geckos kept at higher temperatures – but within the safety limits! – tend to grow more quickly. Our hatchlings grow much more steadily April – September. 75-78 degrees Fahrenheit, or slightly warmer than room temperature, seems to be optimal for the warm season. It is not known if there are any ill effects from keeping them at this range year-round, without a cool season.
Incubation Length & Hatch Weight
These factors also work with the age/size of the gecko. A tiny gecko can’t eat very much, has less overall mass and can dehydrate quickly, so hatchlings with a “head start” of higher hatch weight tend to gain more quickly. A long incubation period of around 80-100 days seems to produce larger, healthy hatchlings of around 2 grams. To obtain these incubation lengths, breeders can maintain the temperature of the incubator at ~70 degrees Fahrenheit. An “average” gecko is 1.5 grams at hatching; warm temperatures (~80)can hatch geckos at 1 gram or even less. Our data supports the conclusion that geckos hatched small grow more slowly than those that hatch larger, with the larger ones tending towards faster growth in comparison.
We’ve looked at our data from 2010 & 2011, and we don’t see a strong correlation between incubation lengths and size when the length of incubation falls between 60 and 90 days. The only pattern, and it’s not 100% accurate, is that the first hatchling from the first clutch of a season tends to be smallest or smaller than others.
Enclosure & Diet Changes
Many crested geckos will refuse to eat when settling into a new home, or after extensive changes to their enclosures. This generally only lasts for 2 weeks or so, but it is enough to impact growth for a short time. Try not to handle geckos too often; daily is generally too much for a young, skittish gecko. Once a week at cleaning is great. Some people have success rearing geckos communally in large enclosures. However, we noticed increased growth when we separated them into simple setups: individual 6-quart Sterilite tubs.
Additionally, a change in diet can cause the same response. CGD is preferred because it provides a consistent, complete and balanced food source that you can feed from the day you bring your new pet home.
Dehydration is a constant threat to reptiles in captivity. If not adequately hydrated, the gecko can become stressed and refuse food, and become less efficient at processing proteins. Chronic dehydration can also lead to renal disease, which further restricts growth and causes weight loss, among other symptoms. Another risk of low humidity is food (CGD) drying out, leaving geckos unable, but not necessarily unwilling, to eat.
According to the Merck Veterinary Manual:
In several species, reduced water availability has resulted in lowered growth rates without apparent changes in the physiologic status of the animals.
A humidifier to set the ambient room humidity to 50%, as well as large water dishes in the enclosures, can help combat dehydration! Also note that too high of humidity, combined with inadequate airflow, can lead to serious respiratory complications and death.
The size and growth history of the parents might also point to slow or rapid development of embryo and hatchlings. Careful record-keeping can shed some additional light into crested gecko growth rates!
Parasites such as pinworm have been identified as a possible cause in slow or no growth. Look for messy, smelly stools, and have a vet check a fecal sample to see if there is a need to treat for parasites with medication.
Length of photo-period may have an impact on growth and age of sexual maturity on many reptiles, even nocturnal ones like crested geckos. If the photoperiod contains more than 14 hours of light in a day, this could influence growth. It is known to encourage early sexual maturity in some frogs, but its effect on crested geckos is at this time uncertain.
It has been reported that some areas of the world tend to have differing growth rates! It may have something to do with the factors above: temperature & humidity fluctuations, photoperiod differences depending on latitude, etc. More reports are needed to determine the controlling factors of crested gecko growth across the US and the rest of the world.
Crested Gecko Growth Charts
Here is an example of growth rates of some of our crested geckos, recorded from the time we got them (notice the settling in period) and any drops in weight are from up-sizing them from a 6-qt tub to a larger enclosure.
This next example is from a group of hatchlings we purchased at around 2-3 grams. Housed communally in 20 gallon tanks, they did not grow very rapidly. However, once placed in 6-qt tubs, they began to settle in and start growing!
Regardless of the time it takes for geckos to grow and become an adult, as long as your gecko is eating and appears healthy, you have little to worry about. Cresties are a generally hardy reptile, and have a long lifespan of at least 15 years. If yours is taking a little longer to reach adult size (more than 24 months), review the factors above and consider slight changes in diet, temperature, humidity, and light cycle. Make sure your gecko is healthy and feeding primarily on Repashy Crested Gecko Diet, our top recommendation in commercial diets. Try to minimize stress and changes in their immediate environment; daily handling can also increase stress and reduce growth.