Here's something you don't see every day. This is the waxy plug that rests inside the ear canal of a humpback whale. It is about 8 inches (20cm) long. When a dead whale is examined in a process called a necropsy, this is one of the important parts that the biologists seek. By finding the earplug and counting the lines (“growth layers”) under a microscope, the whale’s age can be determined. There are only a few people in the world with the experience necessary to do this accurately. For decades, biologists were not certain whether humpback whales add a new line of growth every year or every other year. However, when the earplug from a whale that died in Glacier Bay in 2001 (and had been seen since the 1970s) was examined, this question was resolved once and for all. Humpback whales add a growth layer EVERY year, which means that we now know that most humpback whales live into their 60s. It also underscores the importance of long-term study of these animals whose environment is constantly changing. Photographer: Sean Neilson