Indeed I was surprised too. Ecosystems are quite different in large cities. Specialists did extensive counts of fauna in Paris. I'm not sure if anyone also studied who prey on who, in there.
Having thought about it, I wonder if it could be a common end for an adult frog:
- I see few frogs, no snake, rare herons, and so many rats.
- frogs must be an easy catch as they are so smaller and slower than rats.
I hesitated to post this. I'm glad you found it interesting.