SPERM WHALES

Whales are impressive animals.  The largest are said to be even larger than the largest dinosaurs.  My specialty deals with mostly very small animals, the invertebrates.  But the largest invertebrate, the giant squid, is a  food item for the sperm whale, the largest of the toothed whales.  During the time when sperm whales were relentlessly hunted for their oil, stomach analyses showed that squid were a major part of their diet.  Perhaps the most abundant squids in their diet were ammoniacal squid which live at great depths and retain high levels of ammonia compounds from their food.  The stored ammonia is thought to serve as a flotation device reducing the squid's need to swim to avoid sinking.

Longevity

Records of sperm whales from whaling days showed the average size was considerably larger than today.  Some of the largest males had deformed teeth suggested greater age than the largest sperm whales of today.  Tooth layering suggests the large ones in recent years approach one hundred years in age.  I think it may have been my search for long-lived animals triggered by my findings about extreme longevity in the deep sea (evolutioninsights 6/22/2013 post) that triggered my interest in sperm whales.

Deep diving

The large males dive deeper and stay down longer than any other mammal.  Perhaps the pressure is an additional factor in their ability to stay submerged for so long in addition to the known factors of high levels of myoglobin for oxygen storage in muscle and circulatory shifts to keep essential organs functioning.

The deep dives go into water only a few degrees above freezing in temperature.  The layer of blubber on the body not only insulates them from the cold, but because fat is much lighter than sea water it balances some of the weight of the heavier than sea water bones.  Much of the volume of the enormous head is filled with oil containing organs which counterbalances the weight of the bones of the skull and jaws.

Baleen whales

The blue whale is the largest whale and is one of the baleen whales that feed extensively on krill.  Krill are small crustaceans, but very numerous in some colder parts of the oceans.  Baleen is the filter on the whale's jaw that sifts out the krill from enormous quantities of water.  The blue whale may be able to select a layer of water where the krill are concentrated.  Some baleen whales are known to concentrate food organisms by circling a cluster until they are in a dense column that they can take much of into their enormous mouth cavity and filter them from the water.

Whales seem most closely related to some ancient hoofed mammals.  They branched off from our evolutionary line millions of years ago.  I will have one or two more posts on aspects of sperm whales not generally covered in discussions of their natural history.  One is their unusually important role in marine food chains, the other is an overlooked function of the oil storage organs in the head.

Joseph G. Engemann   August 29, 2013