---
title: "What the sources say about the Eurasian Otter | AnimalTracks.wiki"
description: "44 claims from the Eurasian Otter profile, each beside the words of the source that backs it."
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canonical: "https://animaltracks.wiki/animals/eurasian-otter/sources/"
---

# What the sources say about the Eurasian Otter (*Lutra lutra*)

> 44 claims from the Eurasian Otter profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Eurasian Otter](https://animaltracks.wiki/animals/eurasian-otter/)

## Lutra lutra (European otter). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Lutra_lutra/

| The page says | The source says |
| :--- | :--- |
| Whiskers that sense a fish moving through the water | They use their vibrissae (whiskers) as sensing organs underwater to monitor the movements of fishes and other prey. (note: tagline) |
| Rivers, lakes, coastal fjords, peat swamps and rice paddies across Europe, North Africa and Asia, as far as Japan and Indonesia | They inhabit rivers, lakes, streams, freshwater and peat swamp forests, ricefields, ocean shores, fjords, caves, and terrestrial habitats adjacent to waterways. (note: stats.habitat; ricefields -> rice paddies. Range portion (Europe, North Africa, Asia to Japan and Indonesia) is sdz-otter, same quote as the heading claim above) |
| Fish, crustaceans, amphibians, small mammals, birds, eggs, insects and worms | Lutra lutra individuals eat fish, crustaceans, clams, small mammals and amphibians, birds, eggs, insects, worms, and a small amount of vegetation. (note: stats.diet; clams and the small amount of vegetation dropped for brevity, not misrepresented) |
| track the movements of fish and other prey underwater | They use their vibrissae (whiskers) as sensing organs underwater to monitor the movements of fishes and other prey. (note: stats.superpower) |
| Rivers, lakes, coastal fjords, peat swamps and rice paddies count as home | They inhabit rivers, lakes, streams, freshwater and peat swamp forests, ricefields, ocean shores, fjords, caves, and terrestrial habitats adjacent to waterways. (note: ricefields -> rice paddies) |
| In a territory of 1 to 4 miles, each otter keeps fixed places for getting in and out of the water, rolling, sunbathing and sliding down "otter stairways" | In its territory of 1 to 4 miles, each river otter has fixed locations for getting into and out of the water, rolling, sunbathing, and sliding on "otter stairways". |
| and track the movements of fish underwater | They use their vibrissae (whiskers) as sensing organs underwater to monitor the movements of fishes and other prey. |
| It can dive for up to two minutes and is most active at dusk and during the night | River otters can dive for up to two minutes underwater and are most active at dusk and during the night. |
| Its catch list is long: fish, crustaceans, amphibians, small mammals, birds, eggs, insects and worms, about a kilogram of food a day | Lutra lutra individuals eat fish, crustaceans, clams, small mammals and amphibians, birds, eggs, insects, worms, and a small amount of vegetation ... River otters hunt and feed several times a day, consuming about 1kg of food daily. |
| Eurasian otters are basically solitary. Mates pair only briefly and mothers keep their young with them for a time, though loose groups of up to six sometimes turn up | Lutra lutra are basically solitary animals with only temporary pairing of mates or mothers with their young, although they are sometimes found in loosely knit groups of up to six animals. (note: temporary -> briefly / for a time) |
| They are vocal too, with basic calls for alarm, greeting and mating plus up to 12 others, from shrill whistles and yelps to high-pitched screams of distress | Lutra lutra are vocal, with basic calls of alarm, greeting, and mating as well as up to 12 other calls. The voice of L.lutra consists of short, shrill whistling, yelps, whimpers, and high pitched screams of distress. |
| Paired scent glands at the base of the tail give off a heavy, musky smell, and scent marks carry news of territory boundaries, identity and sexual state | River otters have paired scent glands at the base of their tail which give off a heavy, musky smell. Scent marking is a form of communication between otters about the territorial boundaries, identity, and sexual state of each otter. |
| With its whiskers. The vibrissae work as sensing organs underwater, picking up the movements of fish and other prey | They use their vibrissae (whiskers) as sensing organs underwater to monitor the movements of fishes and other prey. (note: faq 1) |
| An otter hunts and feeds several times a day and gets through about a kilogram of food daily | River otters hunt and feed several times a day, consuming about 1kg of food daily. (note: faq 1) |
| for an otter whose voice is short, shrill whistles and yelps | The voice of L.lutra consists of short, shrill whistling, yelps, whimpers, and high pitched screams of distress. (note: vibe.reason) |
| alarm, greeting and mating calls plus up to 12 others | Lutra lutra are vocal, with basic calls of alarm, greeting, and mating as well as up to 12 other calls. (note: vibe.reason) |

## Otter. San Diego Zoo Wildlife Alliance.

https://animals.sandiegozoo.org/animals/otter

| The page says | The source says |
| :--- | :--- |
| The World's Most Widespread Otter | The most widely distributed otter is the Eurasian otter, found throughout Europe, North Africa, and Asia to Japan and Indonesia. (note: heading) |
| a river range that stretches from Britain to Japan | The most widely distributed otter is the Eurasian otter, found throughout Europe, North Africa, and Asia to Japan and Indonesia. (note: tagline; Britain is inside the stated European range) |
| Vibrissae, whiskers above its lips, that detect changes in the water current and track the movements of fish and other prey underwater. | An otter's rounded nose has whiskers above the lips that detect water current changes as well as the presence of prey ... lurking in the water. (note: stats.superpower; general otter anatomy on the SDZ multi-species page; the fish-tracking half is ADW's Lutra lutra vibrissae line (next claim)) |
| The Eurasian otter (*Lutra lutra*) is the most widely distributed otter species, found across Europe, North Africa and Asia as far as Japan and Indonesia | The most widely distributed otter is the Eurasian otter, found throughout Europe, North Africa, and Asia to Japan and Indonesia. |
| Its vibrissae, whiskers above its lips, detect changes in the water current and the presence of prey | An otter's rounded nose has whiskers above the lips that detect water current changes as well as the presence of prey ... lurking in the water. |
| Eurasian otter males form a dominance hierarchy, and the highest-ranking ones hold, and mark, the best ranges | Eurasian otter males form a dominance hierarchy, with the highest-ranking individuals occupying the most favorable ranges and marking them accordingly. (note: names the Eurasian otter on the multi-species SDZ page) |

## AnAge entry for Lutra lutra. AnAge: The Animal Ageing and Longevity Database, Human Ageing Genomic Resources.

https://genomics.senescence.info/species/entry.php?species=Lutra_lutra

| The page says | The source says |
| :--- | :--- |
| The longevity record in captivity belongs to a female who lived to 18.2 years old | The longevity record in captivity belongs to a female that was 18.2 years of age when she died. (note: AnAge calls the older 22-year captivity figure (which ADW carries) unverified) |

## Otter (Lutra lutra). Woodland Trust.

https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/animals/mammals/otter/

| The page says | The source says |
| :--- | :--- |
| In the UK, otters weigh 7 to 11 kilograms and measure 94 to 155 centimetres from nose to tail, and males are larger on average | One of our largest mustelids, they weigh in at 7-11kg and measure 94cm-155cm from nose to tail. On average, males are larger than females. (note: UK scope kept (Woodland Trust is a UK page: 'our largest mustelids'). AnAge's single 6,750 g adult weight dropped so the two don't read as contradicting.) |
| Spraint is the name for otter droppings, left on rocks and logs close to the water as a way of communicating with other otters | otter droppings, known as spraints ... Left on rocks and logs close to the water, they are a method of communication with other otters. |
| The Woodland Trust calls the otter's return across the UK a conservation success story: by the 1950s, hunting, habitat destruction and chemicals in rivers had left it on the brink of extinction there | The return of the otter across the UK is a conservation success story. By the 1950s, the species was on the brink of extinction due to hunting, habitat destruction and chemicals leaching into watercourses. (note: current institution page (blog dates 2026) for the present-tense UK state) |

## Loy (2025). Lutra lutra. The IUCN Red List of Threatened Species 2025: e.T12419A227078232.

https://doi.org/10.2305/iucn.uk.2025-1.rlts.t12419a227078232.en

| The page says | The source says |
| :--- | :--- |
| Near Threatened | IUCN Red List category: Near Threatened (NT). Lutra lutra (Linnaeus, 1758), IUCN taxon 12419. (note: stats.conservationStatus, read through GBIF's copy of the Red List per docs/fact-check.md) |
| The IUCN Red List classes the Eurasian otter as Near Threatened | IUCN Red List category: Near Threatened (NT). Lutra lutra (Linnaeus, 1758), IUCN taxon 12419. (note: assessment year dropped: no cached text states it) |

## Jędrzejewska et al. (2001). Feeding habits of the otter and the American mink in Białowieża Primeval Forest (Poland) compared to other Eurasian populations. Ecography.

https://doi.org/10.1034/j.1600-0587.2001.240207.x

| The page says | The source says |
| :--- | :--- |
| On five woodland rivers in eastern Poland, fish made up 51% of what otters ate by weight in spring and summer but 40% in autumn and winter, when amphibians rose to 58% | were studied by scat analysis on five woodland rivers and streams in eastern Poland. Fish constituted 51% of food biomass consumed by otters in spring‐summer and 40% in autumn‐winter ... made up 34% of otters’ food biomass in spring‐summer and 58% in autumn‐winter (note: biomass -> by weight; the 34%/58% sentence's subject is 'Amphibians (mainly Rana temporaria ...)', split across lines in the cache) |

## Weber (1990). Seasonal exploitation of amphibians by otters (Lutra lutra) in north-east Scotland. Journal of Zoology.

https://doi.org/10.1111/j.1469-7998.1990.tb04740.x

| The page says | The source says |
| :--- | :--- |
| The mix shifts with season and place | The proportion of amphibians identified in otter droppings varies seasonally and according to the habitat. |
| In north-east Scotland in 1987, the share of amphibians in otter droppings varied with the season and the habitat, rising in late winter and spring while the amphibians were hibernating or spawning, and it tracked how many amphibians were available | The dietary importance of amphibians to otters was studied in north‐east Scotland in 1987. The proportion of amphibians identified in otter droppings varies seasonally and according to the habitat. The consumption of amphibians increases in late winter and spring while they are either hibernating or spawning ... There is a significant correlation between the availability of amphibians and their consumption by otters. (note: faq 3) |
| Common frogs made up 60.8% of the amphibian prey, common toads only 1.7% | The main amphibian species involved in the diet is the common frog, Rana temporaria (60.8%), while the common toad, Bufo bufo, represents only 1.7% of the amphibian prey. (note: faq 3) |

## Clavero, Prenda & Delibes (2003). Trophic diversity of the otter (Lutra lutra L.) in temperate and Mediterranean freshwater habitats. Journal of Biogeography.

https://doi.org/10.1046/j.1365-2699.2003.00865.x

| The page says | The source says |
| :--- | :--- |
| A review of 37 European diet studies found that otters in Mediterranean areas relied less on fish, and more on aquatic invertebrates and reptiles, than otters in temperate areas | Thirty‐seven otter diet studies were reviewed, twenty‐one from temperate and sixteen from Mediterranean areas ... Mediterranean otters behaved as more generalist predators than temperate ones, relying less on fish, and more on aquatic invertebrates and reptiles. (note: 37 = 'Thirty-seven' in the quote) |

## Brzeziński & Romanowski (2006). Experiments on sprainting activity of otters (Lutra lutra) in the Bieszczady Mountains, southeastern Poland. Mammalia.

https://doi.org/10.1515/mamm.2006.019

| The page says | The source says |
| :--- | :--- |
| Along 28 kilometres of the River San in south-eastern Poland, a three-week survey of both banks counted an average of 4.18 new spraints per kilometre per day, and the more of a stretch's banks were steep and rocky, the more spraints it collected | Consecutive surveys of otter spraints of both banks along a 28-km stretch of the River San showed an average of 4.18 deposited spraints/km per day during a 3-week pre-experimental period ... Spraint deposition was positively correlated with the proportion of steep and rocky riverbanks (note: south-eastern Poland is the paper's title (Bieszczady Mountains, southeastern Poland)) |
| On 28 km of the River San in south-eastern Poland, researchers cleared old spraints from 14 stretches of river | Consecutive surveys of otter spraints of both banks along a 28-km stretch of the River San ... in sections where otter spraints were removed (n=14) (note: faq 2; 28-km stretch is in the same abstract) |
| In the first week, sprainting on those stretches rose 1.6-fold, while on 14 untouched stretches it fell 1.5-fold | in sections where otter spraints were removed (n=14), sprainting intensity increased 1.6-fold, while in the control sections (n=14) the defecation ratio decreased 1.5-fold during the first week after removal. (note: faq 2) |
| Adding spraints from unfamiliar otters made no further difference | Placement of additional spraints of unfamiliar individuals on half the experimental sections did not stimulate otters to increase defecation on these sections compared to those where only old spraints were removed. (note: faq 2) |
| The otters make up for it | in sections where otter spraints were removed (n=14), sprainting intensity increased 1.6-fold (note: faq 2 lead) |

## Murk et al. (1998). Application of biomarkers for exposure and effect of polyhalogenated aromatic hydrocarbons in naturally exposed European otters (Lutra lutra). Environmental Toxicology and Pharmacology.

https://doi.org/10.1016/s1382-6689(98)00026-x

| The page says | The source says |
| :--- | :--- |
| A 1998 study named PCBs, industrial chemicals, as one of the major factors in the otter's serious decline over the previous decades | In the serious decline of European otters (Lutra lutra) over the last decades, polychlorinated biphenyls (PCBs) are considered to be one of the major factors. (note: 1998 is the reference's publication year; 'European otters' is the species name, not a region: 'across Europe' was cut) |
| A 1998 study counted PCBs among the major factors in the otter's serious decline | In the serious decline of European otters (Lutra lutra) over the last decades, polychlorinated biphenyls (PCBs) are considered to be one of the major factors. (note: 1998 is the reference's publication year; faq 4) |
| In wild otters, the more PCB a liver held, the less vitamin A it stored, and that went with more infectious disease | A strong negative correlation was found between hepatic vitamin A and polychlorinated biphenyl (PCB) concentrations expressed as TCDD-equivalents (TEQs), coinciding with a higher incidence of infectious diseases. (note: faq 4; 'naturally exposed' / 'feral otters' -> wild) |

## Fournier-Chambrillon et al. (2004). Evidence of secondary poisoning of free-ranging riparian mustelids by anticoagulant rodenticides in France: implications for conservation of European mink (Mustela lutreola). Journal of Wildlife Diseases.

https://doi.org/10.7589/0090-3558-40.4.688

| The page says | The source says |
| :--- | :--- |
| in mustelids collected in south-western France from 1990 to 2002, the rodenticide bromadiolone was found in the livers of two of eleven otters | concentrations of eight anticoagulant rodenticides were examined in livers from 122 carcasses of four species of free-ranging mustelids collected between 1990 and 2002 in southwestern France. Bromadiolone residue was found in all species and 9% of the sample (one of 31 European mink, three of 47 American mink [Mustela vison], five of 33 polecats [Mustela putorius], and two of 11 European otters [Lutra lutra]). (note: chlorophacinone was also found in one otter; the abstract doesn't say whether it was one of the two, so the count is bromadiolone only) |

## Harrington et al. (2009). The impact of native competitors on an alien invasive: temporal niche shifts to avoid interspecific aggression. Ecology.

https://doi.org/10.1890/08-0302.1

| The page says | The source says |
| :--- | :--- |
| In one area of southern England, otters and polecats were absent in the 1990s but back by the 2000s | We compared the relative abundance and the behavior of mink in the 1990s and in the 2000s in an area of southern England where both otters and polecats were absent in the 1990s but reappeared in the intervening years. |
| a 2009 study found the invasive American mink there had switched from mostly nocturnal to mostly daytime activity, which the researchers suggest may help it avoid them | We also found that mink were predominantly nocturnal in the 1990s (in the absence of competitors) but were predominantly diurnal in the 2000s (in the presence of competitors). We hypothesize that this temporal shift may be an avoidance mechanism (note: 2009 is the reference's publication year) |