Throwing coins at the critters was definitely not in their best interest. The October 7, 1946 SF Chronicle included an account of what killed one of the Academy's seals the previous year.
"It looks as if Oscar, Golden Gate Park's late great collector of coins, has left estate litigation in her wake. Oscar, who was a lady, swallowed coins thrown by a generous public for three years at the park's Academy of Sciences. Zinc chloride poisoning from wartime coins killed Oscar. In her stomach were found 514 pennies, 27 nickels, 8 dimes, 1 quarter, 1 Canadian penny, 1 streetcar token and 1 amusement token."
Readers of the time would have understood the reference to "zinc chloride," as all of the cents coined during 1943 were made from steel plated with zinc, and these coins were considered a nuisance all the way around. Zinc is quite toxic when ingested in quantity, as many a distressed mother of toddlers likewise learned. The problem abated after the war, when the zinc cents were withdrawn from circulation. Since 1982, however, our cents have been made of nearly pure zinc with just a thin coating of brass, so the hazard is now greater than ever.