Ratkings

I have just returned from a meeting in the local history society in the area of Copenhagen where I live. All very good fun, but as always, the interesting things happened afterwards. I started chatting to a 92 year old guy about strange animals, and as always, when I meet new people, asked him if he had seen any strange critters or heard stories about them. The answerwas no, but then he asked me, if I had heard about rat kings - those strange groups of rat, all stuck to each other by their entangled tails. I acknowledged that I knew what he was talking about, and then he started telling me about his childhood in Reersø, a smal peninsula on the west coast of the island of Zealand, where Copenhagen is located on the wet coast.
Apparently he and several of his friends knew how to make rat kings. At that time rats were common - brown as well as black rats - and it was considered almost a duty of any boy to kill and torment as many rats as possible. Every now and then they would catch a number of rats and tie their tails together, and have fun watching the animals trying to break free of each other. Sometimes they would get bored of their game and kill the animals with sticks or stones, but every now and then they would just leave them.
And in every case - or so he claimed - the rats just lived on, probably because the other rats fed them. In most cases they just ignored them, but in one case he told me he found one of these ratbundles in a cellar, caught them and decided to have a closer look. It turned out, that the string they had originally used, had rotted completely away, and the tails were just glued together by dirt, blood, foodremains, dried faeces and so on.
Could it be, that some rat kings are actually man made?