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European (Eurasian) Otter - Lutra lutra
European (Eurasian) Otter - Lutra lutra

[Image: 640px-Otter_in_Southwold.jpg]

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Subfamily: Lutrinae
Genus: Lutra
Species: Lutra lutra

The European otter, also known as the Eurasian otter, Eurasian river otter, Common otter and Old World otter, is a Eurasian member of the otter subfamily (Lutrinae), and is typical of freshwater otters.

The European otter is the most widely distributed otter species, its range including parts of Asia and Africa, as well as being spread across Europe. Though currently believed to be extinct in Liechtenstein, and Switzerland, they are now very common in Latvia, along the coast of Norway and across Great Britain, especially Shetland, where 12% of the UK breeding population exist. Ireland has the highest density of Eurasian otters in Europe. In Italy, they can be found in the Calore River area. These creatures live in South Korea, and are endangered.

In general, their varied and adaptable diets mean they may inhabit any unpolluted body of fresh water, including lakes, streams, rivers, and ponds, as long as the food supply is adequate. European otters may also live along the coast, in salt water, but require regular access to fresh water to clean their fur. When living in the sea, individuals of this species are sometimes referred to as "sea otters", but they should not be confused with the true sea otter, a North American species much more strongly adapted to a marine existence.

[Image: European_Otter_area.png]

The European otter is a typical species of the otter subfamily. Brown above and cream below, these long, slender creatures are well-equipped for their aquatic habits. This otter differs from the North American river otter by its shorter neck, broader visage, the greater space between the ears and its longer tail.[2] However, the European otter is the only otter in its range, so it cannot be confused for any other animal. Normally, this species is 57 to 95 cm (23-37 in) long, not counting a tail of 35-45 cm (14-18 in). The female is shorter than the male. The otter's average body weight is 7 to 12 kg (15.4-26.4 lbs), although occasionally a large old male may reach up to 17 kg (37 lbs). The record-sized specimen, reported by a reliable source but not verified, weighed over 24 kg (53 lbs).

European otters are strongly territorial, living alone for the most part. An individual's territory may vary between about one and 40 kilometres long (about one-half to 25 miles), with about 18 km (about 11 miles) being usual. The length of the territory depends on the density of food available and the width of the water suitable for hunting (it is shorter on coasts, where the available width is much wider, and longer on narrower rivers). The territories are only held against members of the same sex, so those of males and females may overlap. 

Hunting mainly takes place at night, while the day is usually spent in the European otter's holt (den) – usually a burrow or hollow tree on the riverbank which can sometimes only be entered from underwater. Though long thought to hunt using sight and touch only, evidence is emerging that they may also be able to smell underwater - possibly in a similar manner to the star-nosed mole.

The European otter's diet mainly consists of fish. During the winter and in colder environments, though, fish consumption is significantly lower, and the otters use other sources of food, including birds, insects, frogs, crustaceans and sometimes small mammals, including young beavers.

[Image: Otter%20picture2.jpg]
Mating takes place in water. Eurasian otters are nonseasonal breeders (males and females will breed at any time of the year) and it has been found that their mating season is most likely determined simply by the otters' reproductive maturity and physiological state. Female otters are sexually mature between 18 and 24 months old and the average age of first breeding is found to be 2.5 years old. Gestation for L. lutra is 60–64 days, litter weight when being compared to the female body mass is about 10%. After the gestation period one to four pups are born, which remain dependent on the mother for about 13 months. The male plays no direct role in parental care, although the territory of a female with her pups is usually entirely within that of the male.
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  • Claudiu Constantin Nicolaescu
Even wild mammals have regional dialects

December 13, 2017

[Image: evenwildmamm.jpg]
Credit: Cardiff University

Researchers from Cardiff University's Otter Project have discovered that genetically distinct populations of wild otters from across the UK have their own regional odours for communicating vital information to each other. The findings could have implications for wild mammal conservation efforts.

The study, which profiled chemical secretions from the Eurasian otter, suggests that genetically distinct populations of wild mammals have different odour dialects, which may have been driven by geographical separation. It also revealed that groups of otters with the most distinctive odour profiles were the most genetically diverse.

Dr Elizabeth Chadwick, from Cardiff University's School of Biosciences, said: "Many mammals have scent glands for leaving chemical messages that provide identifying information regarding sex and age. Our new research reveals that these odours might also reveal genetic differences..."

Chemical communication is essential for most mammal species and allows them to mark territory, identify other animals, attract a mate, and identify key information. Otters use a pair of anal glands in scent marking, and previous Otter Project research has shown that the odour of their secretions is associated with an otter's age, sex, reproductive status, and individual identity.

Dr Chadwick added: "Our findings raise some interesting questions. In the same way that people from London may not understand some of the verbal dialect of people from Cardiff, groups of otters with different odour dialects may not be able to pick up identifying information from each other.

[Image: 1-evenwildmamm.jpg]
Credit: Cardiff University

"Without further research, it is unclear how the otters interpret the chemical difference in secretions. If they don't 'like' or 'understand' unfamiliar scents these differences might hinder mixing - in the same way that people sometimes avoid those who are culturally different. On the other hand, genetic diversity makes individuals healthier – so being attracted to unfamiliar-smelling otters might be part of an evolutionary mechanism to avoid inbreeding, and drive genetic mixing.

"Given the evidence that difference in scent does reflect genetic differentiation, it is something that ought to be given more attention, for instance in species recovery programs and captive releases."

The research 'Odour dialects among wild mammals' is published in Scientific Reports.

Journal Reference:
Eleanor Freya Kean et al. Odour dialects among wild mammals, Scientific Reports (2017). DOI: 10.1038/s41598-017-12706-

Across multiple taxa, population structure and dynamics depend on effective signalling between individuals. Among mammals, chemical communication is arguably the most important sense, underpinning mate choice, parental care, territoriality and even disease transmission. There is a growing body of evidence that odours signal genetic information that may confer considerable benefits including inbreeding avoidance and nepotism. To date, however, there has been no clear evidence that odours encode population-level information in wild mammals. Here we demonstrate for the first time the existence of ‘odour dialects’ in genetically distinct mammalian subpopulations across a large geographical scale. We found that otters, Lutra lutra, from across the United Kingdom possess sex and biogeography-specific odours. Subpopulations with the most distinctive odour profiles are also the most genetically diverse but not the most genetically differentiated. Furthermore, geographic distance between individuals does not explain regional odour differences, refuting other potential explanations such as group odour sharing behaviour. Differences in the language of odours between subpopulations have the potential to affect individual interactions, which could impact reproduction and gene-flow.

Attached to this post:[Image: attach.png] Odour_dialects_among_wild_mammals.pdf (1.34 MB)
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  • Claudiu Constantin Nicolaescu
Are otters threatening amphibian populations?

Date: May 9, 2019
Source: Wiley

The Eurasian otter typically eats fish, but amphibians, which are in global decline, are also part of its diet, especially when fish are scarce. In a Mammal Reviewstudy, researchers identified bones of amphibians in otter faeces from southern Italy to determine which types of amphibians are typically eaten. They also reviewed 64 studies of otter diet.
In the 64 studies, an average of 12 percent of prey items taken by otters were amphibians. Predation of amphibians increased with longitude and was highest in the Alpine biogeographical region in winter and spring. Also, 28 amphibian species (35 percent of European species) were eaten by otters.
In their analyses from southern Italy, the investigators identified 355 individuals belonging to at least seven amphibian taxa. The investigators also concluded that when feeding on frogs and toads, otters are more likely to take the noisy males than the quieter females.
The findings suggest that amphibians are a more significant part of the otter's diet than commonly perceived. While this may constitute a threat to small populations of endemic amphibians, their global decline is also likely to have consequences for otter survival wherever fish resources have been depleted by overfishing and pollution.
"We knew that amphibians may represent a major food for otters in the Mediterranean area, but I admit we were amazed and impressed to discover how great the diversity of this resource could be," said corresponding author Dr. Alessandro Balestrieri, of the University of Milan, in Italy.

Story Source: Wiley. "Are otters threatening amphibian populations?." ScienceDaily. (accessed May 9, 2019).

Journal Reference:
  1. Giorgio Smiroldo, Andrea Villa, Paolo Tremolada, Pasquale Gariano, Alessandro Balestrieri, Massimo Delfino. Amphibians in Eurasian otter Lutra lutra diet: osteological identification unveils hidden prey richness and male‐biased predation on anurans. Mammal Review, 2019; DOI: 10.1111/mam.12155

  1. Amphibians form a major component of the diet of the otter Lutra lutra in several areas of its wide geographic range. Yet, amphibian remains are rarely identified to species level and therefore information on the diversity of this food resource is generally scarce.
  2. The aims of this study were: 1) to assess the overall pattern and trends in the use of amphibians as a resource by otters at the range scale, and 2) to highlight current knowledge on the diversity of amphibians taken as prey by otters. Additionally, we carried out osteological identification of amphibian remains in otter spraints (faeces) from southern Italy, with the aim of demonstrating how this method may improve our knowledge on predator–prey relationships.
  3. The frequency of occurrence of amphibians in 64 dietary studies averaged 12%. Predation of amphibians by otters increased with longitude and was the highest in the Alpine biogeographical region. Predation by otters was reported on 28 amphibian species (35% of European species). Peaks in their frequency of use were reported for all seasons, mostly in winter and spring. In southern Italy, we identified 355 individuals belonging to at least seven amphibian taxa (64% of available species; Rana italica, Rana dalmatina/italica, Pelophylax kl. bergeri/hispanicus, Hyla intermedia, Bufo bufo, Bufotes balearicus, and Lissotriton italicus), and pointed out male‐biased predation within the Order Anura (frogs).
  4. We conclude that the contribution of amphibians to the richness of the otter's prey community is far higher than commonly perceived, and that osteological analyses allow the detailed investigation of the feeding behaviour of this top predator of freshwater habitats.
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  • Claudiu Constantin Nicolaescu

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