To establish whether it's a mammal marking its territory, you need to goad the beast. So this evening, take a piss on your front wheel and note the splash pattern. In the morning you can see whether the other beast has responded to your territorial challenge.
last month I had the seal fail. I could smell the fluid, and it was all over the wheel and side of tyre.
If it's animal, once they've started it'll keep happening, as it's a teritorial thing.
Had it in my house with another cat using the cat flap, ruined a cabinet bottom before we spotted him.