Reptilia · Squamata
Heloderma suspectumCope, 1869
Gila Monster
Photograph by Blueag9, CC BY-SA, via Wikimedia Commons
A ground-dwelling, active by day or night, meat-eating lizard from the Nearctic region, reaching 362 mm snout to vent.
Also called Banded Gila Monster, Reticulate Gila Monster.
Reptilia › Squamata › Helodermatidae › Heloderma
- Grows to
- 362mm
- greatest recorded
- Eats
- Carnivorous
- Active
- Cathemeral
- Lives up to
- 48years
What is known
46 sourced facts, each taken from a named scientific dataset. How to read these.
Cited from a dataset unless a row is marked otherwise.
Standing in the world
- Still living
- Extant
- Conservation status
- Near Threatened
- Status assessed · the year the Red List last looked
- 2007
- Population trend
- Decreasing
The animal itself
- Limbs
- Four legs
- Venomous
- Yes
- Fangs
- None
- Longest recorded life
- 48years
- Preferred body temperature · chosen in a laboratory gradientmeasured
- 28.7–30.1°C84–86 °F
- Body temperature when active · measured in the wild
- 28.6°C83 °F
- Body temp in the wild · mean, when active
- 27.2–30°C81–86 °F
Carey and Judge 2000, De Magalhaes & Costa 2009, Stebbins and McGinnis 2012, see Bogert and Martin del Campo 1956, Beck 2005: 30 (captivity), TAUZ: an individual arrived as adult in 1974 or earlier (Arieh Landsman pers. Com.), Beck 2005: 19 in nature (p 113); Petzold 2008: 25, Murphy 2018 (to 20 years)
mean body temperature of active individuals in nature
body temperature of active animals in nature
Size
- Length snout to vent · greatest recorded
- 362mm14.5 in
- Length snout to vent · adult female mean
- 299.7mm12 in
- Largest female · snout to vent
- 299.7mm12 in
- Hatchling length · snout to vent
- 136.5mm5.25 in
- Largest juvenile · snout to vent
- 136.5mm5.25 in
- Body mass · greatestcomputed
- 975.3g2.2 lb
- Body mass · a typical adult
- 553.4g1.2 lb
- Body mass at hatchingmeasured
- 28.6g1 oz
max 362 mm SVL (Feldman et al. 2016)
snout-vent length; the source column mixes this with straight carapace length
computed from length by a family-level allometric equation, not weighed
AnAge rates this record "acceptable"
How it lives
- Diet
- Carnivorous
- How it hunts
- Active foraging
- Active
- Cathemeral
- Where it lives
- Terrestrial
- Habitat
- Desert, Forest, Shrubland
- Biome
- Deserts & Xeric Shrublands
- Active season · months of the year
- 7–12months
- Region
- Nearctic
- Mainland or island
- Mainland
- Highest it lives · above sea level
- 1950m
- Range size
- 345,299km²
- Density
- 0.08–0.14per hectare
vertebrates (tortoises, lagomorph young, squirrels, Beck 1990), eggs, Arthropods and carrion (see Bogert and Martin del Campo 1956), eggs and juvenile vertebrates and carrion (Rorabaugh and Lemos-Espinal 2016)
(e.g, Mesquita et al. 2016),(but infrequently, Beck 1990)
Cathemeral, mainly diurnal (Beck 1990, Jones and Lovich 2009), cathemeral (Rorabaugh and Lemos-Espinal 2016)
e.g., Mesquita et al. 2016
0-1950 (Rorabaugh and Lemos-Espinal 2016, Stebbins and McGinnis 2018)
Breeding
- Reproduction
- Oviparous
- Sex decided by
- Genes, ZW/ZZ
- Average clutch
- 5.35eggs
- Eggs or young per clutch
- 1–15eggs
- Mean clutch
- 5–5.7eggs
- Clutches in a year
- 0.75per year
- Clutches a year
- 0.5–1per year
- First breeds at
- 34months
4-7 (Stebbins and McGinnis 2012), 3-13 (Bogert and Martin del Campo 1956), 1-12, usually 4-6 (Ramirez Bautista and Arizmendi 2004), mean 5.7 (e.g., Mesquita et al. 2016), 2-12, mean 5.7 (Rorabaugh and Lemos-Espinal 2016), 2-12 (Stebbins and McGinnis 2018, Murphy 2018), 1-15 (Otsuka et al. 2020)
Naming and history
- Suborder
- Sauria
- Infraorder
- Anguimoprha
- Subspecies
- Heloderma suspectum cinctum BOGERT & MARTÍN DEL CAMPO 1956 Heloderma suspectum suspectum COPE 1869
- Described by
- Cope
- Moved to another genus · since it was first described
- No
- Described in
- 1869
- Type locality
- USA
Keeping one
4 ft 9 in × 4 ft 9 in × 3 ft(145 × 145 × 91 cm)
Minimum length × width × height, for one animal. Bigger is always better.
The standard sizes ground-dwelling species at 4 × 4 × 2.5 times snout-vent length.
Mindestanforderungen an die Haltung von Reptilien (Sachverständigengutachten), German Federal Ministry for Nutrition, Agriculture and Forestry, Animal Welfare Division, 10 January 1997. The standard states these floor areas are recommendations rather than binding limits.
From this animal’s own snout-vent length of 14.5 in (362 mm), at 4 × 4 × 2.5 times it, following the German federal welfare standard — how this is worked out.
In a laboratory thermal gradient this species settled at 84–86 °F (28.7–30.1 °C).
Preferred body temperature, recorded in a laboratory gradient where the animal could choose freely. A measurement of the animal, not a setting for a thermostat.
Feeding
A prey item should be no wider than the space between the animal's eyes.
Widely used across reptile husbandry references. The stated reason is that the gap approximates the width of the throat, so wider prey is associated with impaction. This is established practice, not a measurement.
89kJ per day
Worked out for an animal of 975 g, the heaviest recorded for Gila Monster — so it is the top of the range, not a figure for a particular animal. Weigh yours and the number will be lower.
An upper estimate, not a feeding target, and not veterinary advice. The equation covers only what an animal burns staying alive, so a growing, gravid or recovering animal needs more — and it was measured on wild animals, which move far more than one in an enclosure. Body condition and a vet who knows the species are what a feeding decision should rest on. Where this comes from.
Morphs
0 with peer-reviewed genetics behind them, 1 resting on breeder consensus. Most references present both with the same confidence.
- Population and bandingbreeder consensus
How the pink and black is arranged — broken and net-like in southern animals, more banded in northern ones. Follows the population rather than a gene.
Worth knowing. Gila monsters are venomous and a bite is medically serious; the animal grips and chews rather than striking and letting go. Many jurisdictions require a permit or forbid private keeping, and the species is protected in the states where it lives — Arizona protected it in 1952, the first venomous animal in the United States to be given legal protection.
Other inherited traits
Inherited characteristics and conditions recorded for this species. These are not morphs — nobody breeds for them.
- Sex determination1 reference
What nobody knows
These are not gaps in our research. No scientific dataset records them for this species — and saying so is information you cannot get from a reference that simply leaves a field out.
- — Length snout to vent · adult male mean
- — Length snout to vent · adult mean
- — Length nose to tail · greatest recorded
- — Female length · mean, nose to tail
- — Length nose to tail · adult male mean
- — Length nose to tail · adult mean
- — Largest male · snout to vent
- — Largest female · shell length
- — Largest male · shell length
- — Hatchling length · nose to tail
- — Largest juvenile · shell length
- — Egg length
- — Egg width
- — Body mass · adult female, mean
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How the young develop
- — Gestation or incubation
- — Hatchling length · smallest recorded
- — Hatchling length · largest recorded
- — Age at first breeding · female
- — Mature from · youngest recorded
- — Mature by · oldest recorded
- — Size at maturity · smallest recorded
- — Size at maturity · largest recorded
- — Colour on the back
- — Pattern on the back
- — Pupil
- — Red List criteria
- — Home range · largest recorded
- — Active in
- — Lowest it lives · above sea level
Others in Helodermatidae
Take this data
Everything on this page is available as data under CC BY 4.0 — use it freely, credit it, no permission needed.
This species as JSON · the whole dataset
Cite this page
The Reptile & Amphibian Encyclopedia (2026). Heloderma suspectum. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/heloderma-suspectum
@misc{heloderma_suspectum_2026,
title = {Heloderma suspectum},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/heloderma-suspectum}
}Sources
- Meiri, S. (2024). SquamBase — a database of squamate (Reptilia: Squamata) traits. Global Ecology and Biogeography. Public domain (CC0).
- Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
- Catalogue of Life (dataset 3LR), used under CC BY.
- AnAge, Human Ageing Genomic Resources (de Magalhães et al.), used under CC BY 3.0.