Reptilia · Squamata
Xantusia riversianaCope, 1883
Island Night Lizard
Photograph by Sula Vanderplank, CC BY, via iNaturalist
A day-active, omnivorous lizard from the Nearctic region, reaching 117 mm snout to vent.
Once published as Klauberina riversiana — those names reach this page.
Reptilia › Squamata › Xantusiidae › Xantusia
- Grows to
- 117mm
- greatest recorded
- Eats
- Omnivorous
- Active
- Diurnal
- Lives up to
- 32.9years
Longer than 86% of all species in Xantusiidae anyone has measured.
The bar is the rank itself: its length is the share of the family this animal exceeds. The chart below is the family’s real spread, on a logarithmic scale because body length here runs from 36 to 153 mm. The solid rule is this animal. Every bar is a count of real species, and nothing on this figure is estimated.
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
- Least Concern
- Status assessed · the year the Red List last looked
- 2007
- Population trend
- Stable
The animal itself
- Limbs
- Four legs
- Venomous
- No
- Fangs
- None
- Longest recorded life
- 32.9years
- Preferred body temperature · chosen in a laboratory gradientmeasured
- 28.3°C
- Body temperature when active · measured in the wild
- 23.5°C74 °F
- Body temp in the wild · mean, when active
- 18.7–28.3°C66–83 °F
Carey and Judge 2000, De Magalhaes & Costa 2009, Slavens and Slavens 1999:1`3 and 11 months; Fellers et al. 1998: 11.3 known, calculated 32.9; Jones and Lovich 2009: 12 or more, Cruz-Saenz 2012: 32.9
mean body temperature of active individuals in nature
body temperature of active animals in nature
Size
- Length snout to vent · greatest recorded
- 117mm4.5 in
- Length snout to vent · adult female mean
- 83.2mm3.25 in
- Largest female · snout to vent
- 83.2mm3.25 in
- Hatchling length · snout to vent
- 32mm1.25 in
- Largest juvenile · snout to vent
- 32mm1.25 in
- Body mass · greatestcomputed
- 32.2g1.1 oz
- Body mass · a typical adult
- 14.66g0.52 oz
- Body mass at hatchingmeasured
- 1.5g0.05 oz
max 117 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
- Omnivorous
- How it hunts
- Sit and wait
- Active
- Diurnal
- Where it lives
- Saxicolous, terrestrial
- Habitat
- Rocky, Savanna, Shrubland
- Biome
- Mediterranean
- Region
- Nearctic
- Mainland or island
- Found only on islands
- Highest it lives · above sea level
- 610m
- Range size
- 208km²
- Density
- 1458–3213per hectare
- Home range · largest recorded
- 17.4m2
(20-100% plants, marine snails and arthropods, Brattstrom 1952), invertebrates and plants (Jones and Lovich 2009)/invertebrates blossoms, seeds, stems and leaves (Stebbins and McGinnis 2018)
e.g, Mesquita et al. 2016
actively humting in bright sunlight (Van Denburgh 1922) / diurnal (no night activity, Jones and Lovich 2009) / strictly diurnal (Fellers et al. 1998)/"occasionally exposed at daytime" and "active in daytime" (Stebbins and McGinnis 2018)
Leaf Litter/Saxicolous (Stebbins 2003)/terrestrial (Mesquita et al. 2016)
Breeding
- Reproduction
- Viviparous
- Gestation or incubation
- 98days
- Average clutch
- 4.4eggs
- Eggs or young per clutch
- 2–9eggs
- Mean clutch
- 3.3–5.5eggs
- Clutches in a year
- 0.75per year
- Clutches a year
- 0.5–1per year
- First breeds at
- 42–60months
2-6 (Stebbins and McGinnis 2012), 6-9 on San Nicolas, 4-6 on San Clemente, means 3.5-4.6 (Bezy and Goldberg 2015), mean 3.76 (Mesquita et al. 2016), 2-9 (Stebbins and McGinnis 2018)
Naming and history
- Suborder
- Sauria
- Infraorder
- Scincoidea
- Subspecies
- Xantusia riversiana reticulata SMITH 1946 Xantusia riversiana riversiana COPE 1883
- Described by
- Cope
- Moved to another genus · since it was first described
- No
- Described in
- 1883
- Type locality
- USA
Keeping one
18.5 in × 18.5 in × 11.5 in(47 × 47 × 29 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.
Lives on rock, so stable hard surfaces and basking ledges suit it.
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 4.5 in (117 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 83 °F (28.3 °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.
4kJ per day
Worked out for an animal of 32 g, the heaviest recorded for Island Night Lizard — 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.
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
- — 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
- — Sex decided by
- — Red List criteria
- — Active season · shortest recorded
- — Active season · longest recorded
- — Active in
- — Lowest it lives · above sea level
Others in Xantusiidae
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). Xantusia riversiana. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/xantusia-riversiana
@misc{xantusia_riversiana_2026,
title = {Xantusia riversiana},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/xantusia-riversiana}
}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.