Hobbies And Interests
Age
All multicellular animals have finite lifespans. Humpback whales enjoy a longer life than small mammals, but the massive aquatic creatures rarely live beyond the century mark. Whales that survive illness, predation, injury and whaling boats eventually succumb to old age. Determining a baleen whale's age presents a problem for researchers. While tooth wear gives a good indication of some species' ages, humpback whales have no teeth. Scientists ascertain a whale's age from its baleen growth; older whales may swim the world's oceans, but finding the animals' fragile baleen after death offers a challenge for researchers.
Illness
Multicellular parasites and unicellular pathogens afflict humpback whales just as they do other species. Nematode infestations may cause death directly or weaken a whale to the point that the animal can no longer feed or move freely. The whale starves to death if it cannot swim to find sufficient plankton and krill. Diseases from bacterial or amoebic pathogens can sicken a whale as well. "Whale lice," which are parasitic arthropods, attach themselves to the cetaceans' wounds and may contribute to scar tissue that limits mobility.
Predators
While no living creatures actively predate adult humpback whales that weigh up to 40 tons and grow to an average of 50 feet long, predatory sharks and killer whales will target immature humpback whales. Killer whales represent a particular danger to newborn humpback calves, as the predatory orcas hunt in packs that can distract the whale pod from its youngest and most vulnerable members. Cookie cutter sharks remove and eat plugs of skin from whales, leaving a means of entry for pathogenic microbes and parasites.
Injury
These mighty whales withstand the pressures of ocean depths and storms at sea, but even creatures as large as fully grown humpback whales can become injured. Collisions with ships or waves that unexpectedly dash the animals against rocky outcroppings can cause external or internal damage. While the animals' thick skins and ample layer of subcutaneous blubber prevent all but the most violent collisions from causing grave damage to them, small scrapes can become sites of infection.
Whaling
The whaling industry once filled vital industrial roles. Whales supplied lamps and lubricants with oil, perfumes with ambergris and manufactured goods with flexible baleen. Today, synthetic or vegetable versions of these products take the place of the things that whales once provided. A greatly reduced whaling industry still hunts these animals for food and research. Although whaling vessels more typically target smaller Minke and pilot whales, whalers will also pursue juvenile humpback whales.
Beaching
Whales' bodies have evolved for their aquatic environment. On land, the animals' vast bulk works against them and crushes their internal organs. Humpback whales that stray too close to land can become stranded. Researchers document whale beachings, but cannot always pinpoint a cause. Some whales have parasitic infections that may disorder their sense of direction, while others become ensnared in nets and wash ashore. While some whales withstand their terrestrial ordeal, others lack the strength to survive long enough for people to rescue them and return them to open waters.