Wild horse deaths in California sierra show a delicate ecosystem off balance

Heavy snow from a harsh winter buried food sources and forced the herd to starve or venture into new territories

East of Yosemite national park, Mono Lake is an ancient body of water, home to millions of brine shrimp and waterfowl and providing stunning views. It's also home to a herd of more than 500 wild horses that began arriving in the area around 2015.

This spring, as snowdrifts from a record-setting winter storm began to melt, officials were surprised to find the horses turning up dead.