When my coworker's cat died, I covered her following shift, and put an announcement on the board* for the shift after that (which I couldn't cover.) The cat had been in declining health, and as I had an elderly cat myself, we'd actually discussed the possibility of covering shifts before the actual necessity.

*At that job, we'd either ask in person/by individual texts or write a general announcement on the whiteboard in the break room, and it doesn't usually make sense to come in just to write an announcement. (Also, the bosses had to approve, once you'd reached an agreement. I think that was mostly so we didn't have he-said-she-said about who was covering a specific shift.)