Dead what?

More than 80% of all crew members are wearing T-Shirts on board. Especially on a tug, we love to grease the big moving parts on board. So it is of hardly any use to wear fancy and expensive shirts. After more than 36 years at sea, I saw probably a million T-shirts, some of them with the most bizarre text and prints.
But this one is different, our a/b Joseph suddenly showed us his new T-Shirt. Every time I see it, the text is even more intriguing to me than the time before.
Dead Bulls? laying on their back with white bands around them?
I can't figure out what it means, do you?