“My father had an otter encounter, only in Zwolle-Zuid!”
After four otters swam in the canals of Zwolle last year, several videos appeared on social media last winter of otters swimming and hunting during the day in the middle of residential areas in Zwolle-Zuyd. so it is video About Paul van ‘t Veer’s father, who he shared via Twitter on January 1, 2022. And that’s “only in Zwolle-Zuid”, in a striking place and at a striking time. At about 10 a.m. on a weekday, this otter hunts in a Zwolle-Zuid mall. Ugly water but lots of fish!
These reports prompted Kalutra to investigate the use of otters for the urban area in Zwolle. The otter is known to be a shy and mainly nocturnal animal. So what does he do in the city during the day? And to what extent can a city provide a suitable habitat for an otter?
The research was conducted by Lidewij Disbergen, a part-time student in forest and nature management at Van Houl Larenstein University of Applied Sciences, under the supervision of Johan Spender, CaLutra Regional Otter Coordinator. Together with other Zwolle volunteers, they searched for new tracks for otters in the city. “I had to beat a little bit of searching under bridges for fascias in my neighborhood, in other words: searching for otter feces,” says Ledwig. “But soon I got into the routine here and the strange looks from the passersby were the cause of pleasant conversations about otters and nature in the city.”
life and death
Some very special events were also held during the study period. For example, a dead otter was found in Zwolle-South on March 30, 2022. An autopsy showed that this fox may have died of old age and that it had lost one of its eyes. Johan: “It’s very clear to think that this is a one-eyed otter that was very beautifully photographed by Jeroen Kloppenburg in the middle of Zwolle.” A second event also grabbed headlines in various media outlets. On June 11, small foxes were found in the marina in the center of the city. Ledwig: A captain saw him floating helplessly and called the animal ambulance. At the vet it turned out to be a small otter weighing 1.5 kilograms. Really small animal. He’s been taken care of at De Fûgelhelling Wildlife Sanctuary, given the bottle and is doing well.”
The habitat map can be compiled on the basis of all observations in recent years. The behavior of otters at these sites has also been described. This indicates that otters use the built-up area of Zwolle for a variety of life functions: to communicate via coils, to hunt and eat, to rest and move, perhaps even from birth to death. In addition, urban waters are used for migration to other areas. Lidewij: “When I began to associate observations at Overijssel, it became clear that Zwolle is at a somewhat crossroads of otters migration. Important routes along IJssel, Vecht, Zwarte Water and weteringen meet together in Zwolle.”
Opportunities and bottlenecks for urban otters
With the help of a literature study, the habitat requirements of urban otters with those of Zwolle have been described and compared. Ledwig: “The most important conclusion from this is that an otter can find more than enough food in the city, especially in winter. In addition, there are many possible resting places for otters, especially in rugged gardens and orchards, but also under bridges. However, bottlenecks can arise in places where 70 km of roads pass through otters territory and where non-restricted dog areas have been established along the water.In the long run, as in the whole of the Netherlands, they can shape water quality problem too.”
The extent to which human disruption forms a bottleneck is also questionable. “In Zwolle-Zuid, otters do not seem to have much problems with people, and have been observed regularly during the day during the winter period. However, in the middle, the crowds are much larger, particularly during events or in the summer months when many head people to the canals on a boat trip or on a picnic.”
The main obstacle to this research is the largely hidden life of the otters. It is doubtful whether observations from this study provide a complete picture of urban habitat use by otters. Therefore the main recommendation is to continue to monitor the activities and research of otters in the city in the coming years.
Text: Lidewij Disbergen and Johan Spinder, CaLutra, Mammal Society
Photos: Dierenambulance Zwolle (main photo: small otter taken by Dierenambulance Zwolle); Lidewij Disbergen