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Squamata · AnguidaeEntry 1,209 of 21,572
Slow Worm, Anguis fragilis

Reptilia · Squamata

Anguis fragilisLinnaeus, 1758

Slow Worm

Photograph by C. Oppermann, CC BY-SA, via iNaturalist

A day-active, meat-eating lizard from the Palearctic region, reaching 291 mm snout to vent.

Reptilia › Squamata › Anguidae › Anguis

Grows to
291mm
greatest recorded
Eats
Carnivorous
Active
Diurnal
Lives up to
54years
Body length across Anguidae

Longer than 94% of all species in Anguidae anyone has measured.

94% of 86 species are smaller6% larger
72 mmthe whole family, smallest to largest610 mm

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 72 to 610 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

48 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
2020
Population trend
Stable

The animal itself

Limbs
None
Venomous
No
Fangs
None
Longest recorded life
54years

Carey and Judge 2000, De Magalhaes & Costa 2009, Slavens and Slavens 1999, Wilson 2012: all 54 (captivity), "54?" (Petzold 2008), Hallmann & Griebeler 2015: 44.33, 30 in the wild, 54 in captivity (McInerny and Minting 2016), 30-35 in captivity (Dunayev and Orlova 202)

Preferred body temperature · chosen in a laboratory gradientmeasured
26.3°C
Body temperature when active · measured in the wild
24.25°C76 °F

mean body temperature of active individuals in nature

Body temp in the wild · mean, when active
22.1–26.4°C72–80 °F

body temperature of active animals in nature

Size

Length snout to vent · greatest recorded
291mm11.5 in

max 291 mm SVL (Feldman et al. 2016)

Length snout to vent · adult female mean
176.5mm7 in
Largest female · snout to vent
176.5mm7 in

snout-vent length; the source column mixes this with straight carapace length

Hatchling length · snout to vent
45.5mm1.75 in
Largest juvenile · snout to vent
47mm1.75 in
Body mass · greatestcomputed
79.72g2.8 oz

computed from length by a family-level allometric equation, not weighed

Body mass · a typical adult
11.66g0.41 oz

AnAge rates this record "acceptable"

Body mass at hatchingmeasured
0.54g0.02 oz

How it lives

Diet
Carnivorous

invertebrates (snails and earthworms mainly, to 95% of biomass, Corti and Cascio 2002, also Arthropods, see also Pedersen et al. 2009) and small vertebrates (e.g., Valakos et al. 2008: small lizards, newts and juveniles of its own species), "predominantly eating slugs, snails and earthworms, although spiders and insects are also taken (Luiselli 1992, Brown and Roberts 2008). Rarely, common lizards are consumed (Best 1965, Gleed-Owen 2012), and cannibalism has been observed (Campbell 1892b, Davies 1967)." McInerny and Minting 2016, slugs, earthworms and arthropods (Smith 1990), 70% mollusks, 30% arthropods (Barnagaud et al. 2020)

How it hunts
Active foraging

Mesquita et al. 2016

Active
Diurnal

Diurnal and Crepuscular (Corti and Cascio 2002, Valakos et al. 2008), Crepuscular, basking rare (Necas et al. 1997), Diurnal (e.g., Smith 1990)

Where it lives
Cryptic

Terrestrial, Cryptic / fossorial (Mesquita et al. 2016) / terrestrial (Barnagaud et al. 2020)

Habitat
Forest, Grassland, Shrubland
Biome
Temperate Broadleaf & Mixed Forests
Active season · months of the year
4–7months
Region
Palearctic
Mainland or island
Mainland
Highest it lives · above sea level
2740m

max 2400 (Hallmann & Griebeler 2015), max 2500 (Dunayev and Orlova 202)

Range size
2,517,277km²
Density
63–405per hectare
Home range · largest recorded
800m2

Breeding

Reproduction
Viviparous

(ovoviviparous (Stojanov et al. 2011)

Gestation or incubation
91days
Average clutch
9.48eggs
Eggs or young per clutch
2–28eggs

2-22 (Maso and Pijoan 2011), 2-12, mean 6.88 (Ferreiro and Galan 2004), 3-26 (Stojanov et al. 2011), mean 9 (Mesquita et al. 2016), mean 12.25 (Hallmann & Griebeler 2015), 3-17 (Patterson 1983), max 20, mean 8 (McInerny and Minting 2016), 1-18 mean 8 (Smith 1990), mean 11.5 (Barnagaud et al. 2020), 5-26 (Dunayev and Orlova 202)

Mean clutch
6.7–12.3eggs
Clutches in a year
0.75per year
Clutches a year
0.5–1per year
First breeds at
24–60months
Age at first breeding · female
1644days

Naming and history

Suborder
Sauria
Infraorder
Anguimoprha
Subspecies
No
Described by
Linnaeus
Moved to another genus · since it was first described
No
Described in
1758
Type locality
Sweden

Keeping one

3 ft 10 in × 3 ft 10 in × 2 ft 5 in(116 × 116 × 73 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 11.5 in (291 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 79 °F (26.3 °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.

10kJ per day

Worked out for an animal of 80 g, the heaviest recorded for Slow Worm — 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
  • — 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 in
  • — Lowest it lives · above sea level

Others in Anguidae

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). Anguis fragilis. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/anguis-fragilis

@misc{anguis_fragilis_2026,
  title  = {Anguis fragilis},
  author = {{The Reptile & Amphibian Encyclopedia}},
  year   = {2026},
  url    = {https://www.allanglescreatures.com/species/anguis-fragilis}
}

Sources

  1. Meiri, S. (2024). SquamBase — a database of squamate (Reptilia: Squamata) traits. Global Ecology and Biogeography. Public domain (CC0).
  2. AnAge, Human Ageing Genomic Resources (de Magalhães et al.), used under CC BY 3.0.
  3. Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
  4. Catalogue of Life (dataset 3LR), used under CC BY.