In some circles, the swimming pigs of the Exumas are virtual celebrities. People put a visit to Big Major Cay, near Staniel Cay, where the pigs swim out to greet incoming boats (and hope for food) on their bucket lists. Over the years, the pigs have been written about in cruising guides, Forbes and Travel+Leisure; they’ve even been featured on The Today Show. But now about half the swimming pig population has turned up dead, and nobody seems to know why. Big Major Cay doesn’t have any human population, but it did have about 20 pigs and piglets. The Bahamas…