Sewer Rats

Franoise Cooperman
From the March/April 1998 Rat & Mouse Gazette

It takes our eyes a moment to adjust from the bright light of outdoors. Eventually, the dim yellow work lights lining the walls make it possible for us to read the sign in front us: 'Because the sewer is currently undergoing maintenance, it is dry, so you won't have to wear any special equipment to visit it.' We look at each other for a moment, then head slowly down the dank, dimly lit passageway. "So this is what an old 19th century sewer is like, huh?" I thought to myself.

The entire long passageway is made of dark brick arches. Dim yellow lights connected by thick heavy cables light the way. From overhead comes a variety of sounds, the sounds of the city under which we walk... muffled hollers of people, barks of dogs, bells of trams... Looking up, I can even see a discarded bike lying on a gutter grate. We walk forward, deeper into the tunnel. Suddenly, I see something scamper out of the corner of my eye! RATS!!

But these aren't your everyday sewer rats. These rats are part of a zoo! Along with all the elephants, sea lions, and bears, the Noorder Dierenpark in Emmen (located in the northern part of the Netherlands) also has a very special "sewer rat" exhibit. The rather large exhibit, a recreation of a sewer system from the late 1800s (the sounds were just a tape recording!), was only just completed this summer in June.

Upon closer inspection, I can see that all the rats aren't actually running free, but are protected from their human visitors by large sheets of plexiglass (although, if one listens carefully, small peeps and squeaks can still be heard). Their "cage" runs along both sides of the main passageway, but I was unable to determine if the sides were connected by a passageway in the ceiling. In one section, it's even made up to look like an old storage room. On the walls are several very informative signs discussing things such as the different species of rats, how they live and reproduce, what they like to eat, and facts and fiction about diseases.

A wide variety of tubes, pipes, "roots" (actually just branches attached to the ceiling), and old shoes provide an ample playground. The rats seem extremely energetic and playful; during our time there we even saw two overly ambitious rats fall from the branches (both females, of course).

Water is also a source of entertainment. Every now and then, fresh water will "leak" out of a high "drain pipe", creating a thin waterfall and providing the rats with not only plenty to drink but also plenty to do. More than one rat had several minutes of fun scooping the water up in his or her paws to bathe or drink. Slowly the water creates a small puddle, giving the rats an exciting, changing environment as well as an opportunity to splash and play some more.

We were fortunate enough to witness feeding time. A caretaker entered the giant cage and tossed a variety of grains and fruit into the pack of antsy rats. One bold fellow almost took a piece of fruit from her hand, but changed his mind at the last minute and scampered away. Once she left, the rats attacked the food and we attacked her... with questions.

Were they really wild rats? According to her, they were all lab born and raised, but are as close to wild brown rats (Rattus norvegicus) as genetically possible. They all have clean, lovely brown coats and extremely long, slender tails. She believes they should live about four years but didn't know for certain since the exhibit was only a few months old.

How many rats are in the exhibit? About 90, she told us. Their numbers are kept in check because all the males are sterilized by way of a vasectomy, not by neutering. Neutering would effect their natural behavior, and the zoo hoped to learn a bit about how rats interacted with one another. This just said, we look over to see the fattest rat sitting directly on top of a piece of food so that no one else could get it. A smaller rat darts into a tiny pipe with a piece of food so that the bigger rats pursuing her can't follow. And everywhere rats are kicking with their back foot or hopping about trying to keep the best morsels of food for themselves. Their caretaker also remarked at how impressed she was at how fast they learned and adapted. Only just a month or so ago, they scattered like marbles when she would bring them food. Now they come up to her and almost take the food from her hand.

Where do they sleep? According to her, these rats have a very easy life. Every evening they are herded through the pipes in the wall to cushy, warm little nest boxes in the back room. They only play in the sewer part of the exhibit during zoo hours.

We make sure to return just as the zoo is about to close in order to witness the rats being herded off and the exhibit being cleaned. The same caretaker turns up the lights and makes a few loud noises, and the rats are mere blurs as they dart through the pipes to safety. I can see a few curious noses still sticking out and a couple inquisitive black eyes trying to get one last look from the other side, but the caretaker puts a quick end to that by shoving a couple bathroom plungers over the pipes.

With that, our day at the zoo comes to an end. We make sure to purchase a special book (available only in Dutch) all about rats and the exhibit at the gift shop on our way out. But if you are worried that you might not get to the Netherlands in the next year or two to see this great exhibit, rest assured; it isn't going anywhere soon. According to the book, there was an old sewer rat exhibit that closed in 1987, but there was so much demand from the public for it to return that this new one was built. Perhaps people were simply getting tired of seeing those "common" lions and tigers and wanted a truly special animal... and what animal is more special than a rat?