Nature Today | Otter captured at new location in Amsterdam
The return of the otter in North Holland
Thanks to a successful reintroduction and improved water quality improvement, the otter has returned to the Netherlands a few years ago. The otter became extinct in the Netherlands in 1988 due to hunting, pollution, collisions and loss of attack. In 2002 a start was made with the reintroduction in the Weerribben-Wieden National Park. The otter population is now obtained at 450 animals. A success story!
After years of absence, an otter was captured in the Naardermeer in 2016. In the following years, a monitoring program was set up with twenty game cameras to track the otter in the Vechtplassen area. This research was conducted by the province of Noord-Holland and carried out in collaboration with Natuurmonumenten and volunteers from CaLutra, the otter and beaver working group of the Mammal Society.
Otters have been recorded several times in the Ankeveense Plassen and the Naardermeer. Sprains are also regularly found on the North Holland side of the Hollandse Brug in Muiderberg as part of the NEM Otter dispersal study. All these observations, supplemented by the dead otters found in the vicinity of Edam, already suggested that the otter would also show itself in the vicinity of Amsterdam. Still, the arrival of the otter was delayed.
The otter reached Amsterdam
In 2021, the presence of the otter has been proven several times in Amsterdam. For example, Steigerspoor is found on the loop and on the banks of the Diemer Pentagon, eaten fish and loss of footprints are detected. Only the otter hadn’t shown itself yet. After the first sprains were found by Stijn Nollen in the autumn of 2021, wildlife cameras were installed in consultation with the managers Vattenfall and Staatsbosbeheer. Success did not last long, because the otter had several times recorded on film and photo (see photo below).
This year sprains were found in the oral part of Waterland. The expectations were rightly high, because after placing wildlife cameras, an otter was found on the camera, as is comparable. The sprains found were collected and put in alcohol and will be examined for DNA in April on behalf of the province of Noord-Holland.
Bottlenecks
Now that there are more and more otters in North Holland, it is important that attention is also paid to hinder the otter’s survival. Traffic was the leading cause of death for otters. In 2019, no fewer than 150 dead otters were found, of which more than 85 percent were confirmed traffic victims. Fortunately, there are good opportunities to make safe passages under roads, so that otters and more are not hit. For example, in the planning of otters roads are already being adjusted according to the schedule, such as the ecopassage at the Maxi in Muiden. But there are still too many places where otters cannot safely cross.
Of course, good quality is important, with good water quality, healthy fish stocks and sufficient cover such as reed beds. Fish traps can also be a threat to the otter in the water, resulting in them drowning. Drowning can be prevented by using fish traps with a stop grid. That’s a frame that allows the fish to swim in, but the otters can’t.
The volunteers of CaLutra are committed to further mapping these in order to create a better and safer activity for the otter.
Text: Martijn Piek (CaLutra), Geert Timmermans & Edo Goverse
Photos: Geert Timmermans; Edo Goverse