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What the sources say

Common European AdderVipera berus

Every figure, record and mechanism on the Common European Adder profile was written from a source, and this is the working table behind it: 50 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

Animal Diversity Web, University of Michigan

Vipera berus. Animal Diversity Web, University of Michigan.

The page saysWoodlands, moorlands, heathlands and wetlands
The source saysAdders can live in woodlands, moorlands, heathlands, and wetlands.Note: stats.habitat
The page saysSmall mammals such as voles, shrews and mice, plus small lizards, birds and frogs
The source saysincluding small mammals such as voles (Arvicolinae), shrews (Soricidae), and mice (Murinae), as well as small lizards, birds, and frogsNote: stats.diet
The page saysHinged fangs that fold against the roof of the mouth and inject venom
The source sayshave hinged fangs used to inject venom into their prey. Hinged fangs fold at the base to lie against the roof of the mouth.Note: stats.superpower
The page saysA newborn adder is about 16 to 18 centimeters long.
The source saysAt birth, Vipera berus individuals measure approximately 16 to 18 cm long.Note: body
The page sayssome can grow as long as 80
The source sayscan grow as long as 80 cmNote: body; 'the longest' paraphrases 'as long as'
The page saysMales generally weigh 50 to 70 grams, and females 80 to 100 grams.
The source saysThe mass of male adders generally ranges from 50 to 70 grams, while the mass of females ranges from 80 to 100 grams.Note: body
The page saysAdders hunt voles, shrews, mice, small lizards, birds and frogs.
The source saysincluding small mammals such as voles (Arvicolinae), shrews (Soricidae), and mice (Murinae), as well as small lizards, birds, and frogsNote: body
The page saysThey have hinged fangs, which fold against the roof of the mouth and inject venom.
The source sayshave hinged fangs used to inject venom into their prey. Hinged fangs fold at the base to lie against the roof of the mouth.Note: body
The page saysWhen two adders fight, both raise their bodies into the air, intertwine and try to wrestle each other to the ground. This is known as the "dance of the adders".
The source saysWhen two adders fight, both raise their bodies into the air and intertwine themselves in an attempt to wrestle one another to the ground. This method of fighting is known as the "dance of the adders".Note: body
The page saysVoles, shrews and mice are on the menu, along with small lizards, birds and frogs.
The source saysincluding small mammals such as voles (Arvicolinae), shrews (Soricidae), and mice (Murinae), as well as small lizards, birds, and frogsNote: FAQ 3
The page saysOne method is to wait in one place for prey to pass by, then strike out and inject venom.
The source saysAdders wait in one place for prey to pass by so they can strike out, using fangs to inject their prey with enough venom to be fatal.Note: FAQ 3
The page saysAnother is to go looking for food.
The source saysThe second technique involves actively seeking out prey.Note: FAQ 3
The page saysWhen two adders fight, both raise their bodies into the air, intertwine and try to wrestle each other to the ground, a contest known as the dance of the adders
The source saysWhen two adders fight, both raise their bodies into the air and intertwine themselves in an attempt to wrestle one another to the ground. This method of fighting is known as the "dance of the adders".Note: vibe.reason

Source
02

Amphibian and Reptile Conservation

Adder (Vipera berus). Amphibian and Reptile Conservation.

The page saysA zigzag-backed viper
The source saysThe adder is easily recognised by a dark, continuous 'zig-zag' stripe along its back.Note: tagline
The page saysThe common European adder, Vipera berus, is a rather stocky viper.
The source sayshave rather a stocky appearanceNote: body; viper per the family named in ARC 'most northerly member of the viper family'
The page saysA dark, continuous zig-zag stripe runs along its back, with a row of dark spots down each side.
The source saysa dark, continuous 'zig-zag' stripe along its back. There is also a row of dark spots along each side.Note: body
The page saysThe background color varies from grey-white in males to shades of brown or copper in females.
The source saysThe background colour varies from grey-white in the male to shades of brown or copper in the female.Note: body; US spelling
The page saysAdders typically live 5 to 10 years.
The source saysAdders typically live to 5-10 years.Note: body
The page saysIn Britain, adders like open habitats such as heathland, moorland, open woodland and sea cliffs.
The source saysAdders like open habitats such as heathland, moorland, open woodland and sea cliffsNote: body; ARC is a British page: its habitat line follows 'found throughout Britain'
The page saysThey are not found in Ireland.
The source saysIt is not found in Ireland.Note: body
The page saysIn Britain, adders hibernate from around October to February, depending on local conditions.
The source saysThey hibernate from around October to February, depending on local conditions.Note: body; ARC is a British page, and its qualifier is restored
The page saysbut its bites are very rarely fatal.
The source saysadder bites to humans or dogs are very rarely fatalNote: body
The page saysAmphibian and Reptile Conservation counts only around ten recorded deaths from adder bite in the last 100 years
The source saysThere are only around ten recorded cases of death from adder bite in the last 100 yearsNote: body; the source's own 'only'
The page sayssays most bites happen when the snake has been disturbed or deliberately antagonised.
The source saysmost bites occur when the snake has been disturbed or deliberately antagonisedNote: body
The page saysA bite is potentially serious, though.
The source saysThough potentially serious, adder bites to humans or dogs are very rarely fatalNote: body
The page saysAdders are protected by law in Great Britain, where it is illegal to intentionally kill or injure one.
The source saysAdders are protected by law in Great Britain. It is illegal to intentionally kill or injure addersNote: body
The page saysTypically five to ten years, according to Amphibian and Reptile Conservation.
The source saysAdders typically live to 5-10 years.Note: FAQ 4; reworded so it no longer copies the body sentence
The page saysdangerLevel: Deadly
The source saysThere are only around ten recorded cases of death from adder bite in the last 100 yearsNote: stats.dangerLevel; capability reading (#1273)

Source
03

AnAge: The Animal Ageing and Longevity Database, Build 15, Human Ageing Genomic Resources

AnAge entry for Vipera berus. AnAge: The Animal Ageing and Longevity Database, Build 15, Human Ageing Genomic Resources.

The page saysThe AnAge database lists a captive record of 19 years.
The source saysMaximum longevity 19 years (captivity)Note: body
The page saysweightKg: 0.279
The source saysAdult weight 279 gNote: battleStats.weightKg; AnAge average. ADW gives 50 to 100 g; both put it under Medium, which the name guess gave

Source
04

Owens et al. 2025

Owens et al. (2025). The genome sequence of the common adder, Vipera berus (Linnaeus, 1758). Wellcome Open Research.

The page saysis the only snake north of the Arctic Circle in Scandinavia
The source saysis the only snake to occur north of the Arctic Circle in ScandinaviaNote: tagline; same figure in the 2025 genome paper
The page sayslives from Britain to the Pacific
The source saysIt ranges from the United Kingdom, where it is the only venomous snake species, across Eurasia to the Pacific OceanNote: tagline
The page saysfrom the United Kingdom across Eurasia to the Pacific Ocean
The source saysIt ranges from the United Kingdom, where it is the only venomous snake species, across Eurasia to the Pacific OceanNote: stats.habitat
The page saysAdults typically reach about 50 to 60 centimeters
The source saysThe species typically attains an adult length of approximately 50–60 cmNote: body
The page saysFrom Britain to the Pacific
The source saysIt ranges from the United Kingdom, where it is the only venomous snake species, across Eurasia to the Pacific OceanNote: heading
The page saysAdders live across Eurasia, from the United Kingdom to the Pacific Ocean.
The source saysIt ranges from the United Kingdom, where it is the only venomous snake species, across Eurasia to the Pacific OceanNote: body
The page saysIn Scandinavia, the adder is the only snake found north of the Arctic Circle.
The source saysis the only snake to occur north of the Arctic Circle in ScandinaviaNote: body
The page saysThe adder is the only venomous snake in the United Kingdom
The source saysIt ranges from the United Kingdom, where it is the only venomous snake speciesNote: body
The page saysBites and the future
The source saysas few as 14 deaths in the last 150 yearsNote: heading
The page saysYes. A genome paper on the adder names it as the only venomous snake species in the United Kingdom.
The source saysIt ranges from the United Kingdom, where it is the only venomous snake speciesNote: FAQ 1
The page saysA genome paper puts UK bites at an estimated 50 to 100 a year, and the deaths at as few as 14 in 150 years.
The source saysAdder bites are uncommon with an estimated 50 to 100 bites occurring annually in the UK ( Coulson et al. , 2013 ) and as few as 14 deaths in the last 150 yearsNote: FAQ 2
The page saysas few as 14 in 150 years
The source saysas few as 14 deaths in the last 150 yearsNote: FAQ 2

Source
05

Wüster et al. 2004

Wüster et al. (2004). Do aposematism and Batesian mimicry require bright colours? A test, using European viper markings. Proceedings of the Royal Society of London. Series B: Biological Sciences.

The page saysThe zigzag test
The source saysmodels bearing the characteristic zigzag band of the adder (Vipera berus) are attacked significantly less frequently than plain modelsNote: heading
The page saysIn a field test, birds made 813 attacks on 12,636 Plasticine snake models.
The source saysthe analysis of 813 avian attacks on 12,636 Plasticine snake models in the fieldNote: blockquote
The page saysModels with the adder's zigzag band were attacked significantly less often than plain ones.
The source saysmodels bearing the characteristic zigzag band of the adder (Vipera berus) are attacked significantly less frequently than plain modelsNote: blockquote

Source
06

Karlson-Stiber, Salmonson & Persson 2006

Karlson-Stiber, Salmonson & Persson (2006). A nationwide study of Vipera berus bites during one year: epidemiology and morbidity of 231 cases. Clinical Toxicology.

The page saysIn Sweden in 1995, 231 people were treated in hospital for adder bites
The source saysA total of 231 inpatients were treated for V. berus bites in Sweden in 1995.Note: body
The page says13 percent of them had severe envenomation.
The source saysMaximum severity of envenomation was none in 11%, minor in 47%, moderate in 29%, and severe in 13% of the cases.Note: body

Source
07

Gardner et al. 2019

Gardner et al. (2019). Make the Adder Count: population trends from a citizen science survey of UK adders. Herpetological Journal.

The page saysdata from 260 sites in Make the Adder Count, a UK survey begun in 2005, confirmed a significant decline, on average, across sites with small populations.
The source saysMake the Adder Count began in 2005 as a national surveillance programme collecting standardised counts of adders lying-out after emerging from hibernation. 260 sites have contributed data, confirming a significant decline, on average, across sites with small populationsNote: body; Gardner et al. 2019, so the finding is dated by the reference

Source
08

Bowles et al. 2024

Bowles et al. (2024). Vipera berus. The IUCN Red List of Threatened Species 2024: e.T47756146A215261275.

The page saysLeast Concern
The source saysIUCN Red List category: Least Concern (LC).Note: stats.conservationStatus; GBIF copy of the Red List, taxon 47756146 (checked against the taxon id in the DOI)
The page saysThe IUCN Red List rates the species Least Concern.
The source saysIUCN Red List category: Least Concern (LC).Note: body

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.