The otter used to be found in large parts of the Netherlands, but it has been hunted a lot because all predators had a premium because they were considered harmful. The otter’s fur also made a lot of money. Hunting was banned after World War II. But otters also disappeared in a different way. From the second half of the twentieth century, many otters disappeared due to the poor quality of the water. With the drowning of an otter in a fish trap in Friesland in 1988, it was assumed that this was the last otter and that they were extinct in the Netherlands. However, it was not long before attempts were made to reintroduce the otter.
Otters to almost five feet in length
An otter is a marten-like animal from the genus Lutra. He has swimming legs and a dark, dense, brown coat. The animal is found in many parts of Europe and Asia. An adult male otter can grow to between 80 and 140 centimeters long including its tail of 30 to 50 cm and reach a shoulder height of an average of 30 centimeters. Its weight varies between 5 and 12 kilos. Females measure between 60 and 70 centimeters in length with a tail length of 35 to 42 centimeters and weigh between 6 and 12 pounds.
Nocturnal animal that hides during the day
With its streamlined body, an otter is very well adapted to life in the water. Otters mainly live on fish smaller than 25 centimeters such as perch, carp, eel, pike and salmon. But it also eats anything it finds in the water such as amphibians, insects, crabs, rats, crayfish, water birds, vole and worms. To obtain sufficient food, an otter swims 3 to 10 kilometers per day and is mainly busy at night. During the day, they hide in sheltered places in reed beds, underground hollows and hollow trees with an entrance under water. The average age at which females give birth for the first time is 2 years. After a gestation period of 61 to 63 days, the young are born.
From polluted water to cleaner water and a better living environment
To a large extent, the discharge of pollutants into water became fatal for the otter in the twentieth century. Another factor was that many toxic pesticides were used in agriculture. However, due to the improvement of the living environment (cleaner water, better opportunities for fish migration and for spawning) there are again opportunities for the otter.
Poison
An otter lives as a predator of smaller animals that in turn live of even smaller animals. That way, the poison could eventually build up in the otter from one animal to another.
Water Framework Directive
But in 2000 the Water Framework Directive was published about measures that the responsible authorities must take to improve the quality of the water. The consequence of implementing that directive is that fish stocks have improved since 2000.
Living environment
It was also important that fish ladders were constructed in the rivers to counteract barriers to fish migration. Secondary channels were also constructed along the Rhine Branches to protect against high water, creating good spawning grounds for the fish.
Reintroduced after extinction
Only sixteen years after the declaration that the otters in the Netherlands were extinct, measures were taken to reintroduce the otters. Initially in Overijssel and later in Gelderland, Limburg and Friesland.
- 2002: In 2002 thirty otters from Eastern Europe and Germany were released in the De Weerribben-Wieden National Park in Overijssel. That park consists of a wetland area of 20,000 hectares. Several years after the release, otters have also been observed in the area.
- 2010: In 2010, the Otters in river land project was started to give the otters a good habitat and to make road and waterway intersections safe.
- 2011: In 2011, six otters were released in the De Alde Feanen nature park in the province of Friesland.
- 2014: In 2014, the World Wildlife Fund, together with Staatsbosbeheer, released a few otters in De Gelderse Poort nature reserve near Zevenaar.
Ecological corridors are necessary
The carrying capacity of a habitat mainly depends on the number of fish that are there and the length of the bank, because a male quickly needs 20 kilometers of bank for sufficient food. Because of these large living areas, the otter benefits greatly from good ecological connection zones. The otter is also helped by gangways or footpaths under bridges and by tunnels that have been built under roads.
Seek habitats with risks
In De Weerribben a male otter only needs a few square kilometers because there are many waterways with pet holes, pools and peat bogs. It does not allow other males within its habitat and has several females. Young male otters therefore have to find a new habitat elsewhere and are often run over by cars when they cross the road while wandering around at night. For example, cadavers have been found in the head of Overijssel and Friesland and also near Alphen aan de Rijn, Balkbrug, Doesburg, Raalte, Wierden and Zwolle. Relatively few females have been found in those cadavers because they are less fond of traveling.
Otters in zoos
If you really want to see an otter, it is better to go to a zoo instead of wandering around at night along riverbeds. In the Netherlands there are (in 2016) otters in a number of zoos.
- Aqua Zoo Friesland
- Amersfoort Animal Park
- Animal kingdom Europe
- Diergaarde Blijdorp
- GaiaPark Kerkrade Zoo
- Castle Park Born
- Nature Park Lelystad
- Wildlands Adventure Zoo Emmen
- Zoo Parc Overloon