Seeing a humpback whale in Glacier Bay is an unforgettable experience for many visitors. The true giants of Glacier Bay's waters, these endangered animals are 40-50 feet (12-16 m) long and weigh over 35 tons (32,000 kg). The humpback is a baleen whale that migrates seasonally. Most Glacier Bay whales swim to Hawaii each winter to mate and give birth, a 2,500-mile (4,000 km) journey that takes about a month each way. These whales do not eat while they are wintering in the tropics. All spring, summer, and fall in Alaska, they gorge themselves on high-calorie small schooling fish such as capelin and herring.