Whales have excellent hearing.
When it comes to senses, hearing is the most important one to whales. The sense of smell isn't well-developed in whales, and there is debate about their sense of taste.
But in the underwater world where visibility is highly variable and sound travels far, good hearing is a necessity. Toothed whales use echolocation to find their food, which involves emitting sounds that bounce off whatever is in front of them, and interpreting those sounds to determine the object's distance, size, shape, and texture. Baleen whales probably don't use echolocation, but use sound to communicate over long distances and may also use sound to develop a sonic "map" of the ocean's features.
Whales live a long time.It is nearly impossible to tell the age of a whale just by looking at it, but there are other methods of aging whales. These include looking at ear plugs in baleen whales, which form growth layers (kind of like the rings in a tree), or the growth layers in the teeth of toothed whales. There is a newer technique that involves studying aspartic acid in the whale's eye, and is also related to growth layers formed in a whale's eye lens. The longest-living whale species is thought to be the bowhead whale, which may live to over 200 years old!
Whales give birth to one calf at a time.
Whales reproduce sexually, meaning it takes a male and a female to mate, which they do belly-to-belly. Other than that, there's not much known about the reproduction of many whale species. Despite all our studies of whales, reproduction in some species has never been observed.
After mating, the female is generally pregnant for about a year, after which she gives birth to one calf. There have been records of females with more than one fetus, but usually only one is born. Females nurse their calves - a baby blue whale may drink over 100 gallons of milk a day! Plus, they need to protect their calves from predators. So having only one calf allows the mother to focus all her energy on keeping that calf safe.
While the heyday of whaling ended awhile ago, whales are still hunted. The International Whaling Commission, which regulates whaling, allows whaling for aboriginal subsistence purposes, or scientific research.
Whaling occurs in some areas, but whales are threatened even more by ship strikes, entanglements in fishing gear, fisheries bycatch, and pollution.
Whale watching is a popular pastime along many coasts, including California, Hawaii and New England. Across the world, many countries have found that whales are more valuable for watching than hunting.
In some areas, you can even watch whales from land. This includes Hawaii, where humpback whales can be seen during the winter breeding season, or California, where gray whales can be seen as they pass along the coast during their spring and fall migrations. Watching whales can be an exhilarating adventure, and a chance to see some of the world's largest (and sometimes most endangered) species.