Polystyrene itself isn’t toxic but it degrades on exposure to UV light (the stomach acid and digestive enzymes of the animal probably does a number on it too), and when it breaks into microscopic particles it’s known to be toxic: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193629/
There’s also likely still traces of solvents, plasticizers or other additives that aren’t meant to be ingested, especially if the polystyrene wasn’t manufactured with food safety in mind.
Polystyrene itself isn’t toxic but it degrades on exposure to UV light (the stomach acid and digestive enzymes of the animal probably does a number on it too), and when it breaks into microscopic particles it’s known to be toxic: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193629/
There’s also likely still traces of solvents, plasticizers or other additives that aren’t meant to be ingested, especially if the polystyrene wasn’t manufactured with food safety in mind.
Shorter answer: yes, polystyrene is toxic.