"Tiger sharks are one of the ocean's most iconic keystone species, helping maintain the balance and health of marine food webs." — #NatGeoExplorer Julia Saltzman (sciencewithsaltzy) "As a shark scientist, I track juvenile tiger sharks throughout South Florida to uncover the habitats these young sharks rely on during critical stages of their lives." — The National Geographic Society is celebrating America’s 250th anniversary by supporting the Explorers protecting the keystone species that have sustained communities for centuries. Keystone species define our country's wild spaces — and make them worth preserving.