To look up into the mountains and see the steam rolling from a mountain stream on a cold winters morning is a beautiful sight. However, to look out over the horizon and see the white spray of salt water coming from the blow of a huge hump-back whale is much more exciting sight and a whole lot warmer. I lived in the mountains of Colorado for most of my childhood. The first time I had the opportunity to see the ocean was on a vacation to California, when I was about 15 years old. It was even better than I had dreamed it would be. The different animals in the ocean, the color of the water, and the warm sand between my toes was probably what led me to come to the islands of Hawaii. When I first saw the hump-back whale I was amazed at their huge size and how they could breach out of the water so gracefully. It is as if they were trying to play or show off. So when we were asked to choose a favorite animal, I had no problem deciding on the hump-back whale.
The hump-back whale gets it’s name from the distinctive hump in front of the dorsal fin and from the way it raises it’s back high above water before diving. They are a member of the order Cetacea. This order is of aquatic mammals and the hump-back belongs to the suborder of the Mysticeti. The Mysticeti are the baleen whales which have three families and several species. The family in which the hump-back belongs is the Balaenopteridae, the true fin backed whale. The thing that separates this genus from the other fin-backed whales is the pectoral fins, which grow in lengths of about 5 meters (16.4 feet). This Genus is called Megaptera meaning great wing (Tinker 290). There was a controversy over the species name in the late nineteenth and early twentieth century. In 1932, Remington Kellogg finally settled the matter with Megatera Novaeangliae (Cousteau 84). The common English name is the hump-back whale.
The hump-back whale lives in both the Atlantic and the Pacific oceans. Since we live in the Pacific I’ll be discussing the hump-backs of the North Pacific. They migrate from North to South. In the months of July through September they gather in the Aleutian Islands, Bering Sea or the Chukchi Sea. They head south for the winter. They go to one of three areas: (1) Between the Bonin Islands, the Marianas Islands, the Ryukyu Islands and Taiwan; (2) The Hawaiian Islands, and (3) Along the coast of Mexico (Tinker 291).
One of the reasons these whales go North is for feeding. They have a short food chain compared to most mammals. Phytoplankton turns sunlight into energy and this energy is consumed by zooplankton. The zooplankton and phytoplankton are eaten by small fish. The whale in turn eats the fish. The chain is complete when waste products or dead whales decompose. They have a very short time frame in which they eat compared to the twelve months out of the year. They have not been seen feeding in Hawaii. It seems that they only feed during the summer months up north. During the fasting periods, in Hawaii, they survive on their blubber. They mix their diet with copepods, euphausiids (krill), and small fish, primarily herring and capelin. They are considered filter feeders, using baleen plates to filter out their food. They take huge amounts of water into their mouth using a gulping method and then when they push the water out, they put their tongue up so the water must pass through the baleens. The food becomes trapped and falls toward the rear of the mouth. The two gulping methods hump-back whales use are lunge feeding and bubble net feeding. Lunge feeding is used when food is abundant. The whale simply swims through the prey with it’s mouth open engulfing the prey. They can do this vertically, laterally or inverted. This is done toward the surface of the ocean. Bubble net feeding is used when the prey is less abundant. The whale dives below the prey and discharges bubbles from it’s blowhole. As the bubbles ascend they form a net that disorients the prey. Then the whale swims upward and fills his mouth with the net of fish and bubbles (Kaufman 55). Hump-backs have ventral grooves in their throat that expand allowing an enormous amount of water to be gulped. Hump-backs consume nearly a ton of food in a day’s time during their feeding season.
The hump-back whale’s stomach consists of three chambers and the duodenal ampulla much like a cows. The three stomachs are separate from each other. They have small and large intestines, a rectum, caecum and an anus. These organs are very similar and work much the same as in most mammals. The digestive glands of a whale are somewhat different. They do not have salivary glands that are functional. The liver is bilobed and the gall bladder is absent. The pancreas however resembles that of most other mammals (Tinker 63).
Mammals, which live in the sea, have a continued problem of dehydration. Hump-backs get water from the food they eat and during their fasting periods they get it from their blubber. However, the salinity in the whales bodily fluids is much higher than land mammals but it is still lower than the seawater. This creates a problem. They are in danger of losing too much water. In order to maintain a proper balance the whale passes large quantities of highly concentrated urine. The kidneys are specialized to do this. The feces also permit discharge of salt. However, few studies have been done on hump-back’s feces or urine (Kaufman 31).
As humans we can breathe either from our mouth or nose. This is not the case of the hump-back whale. The whale can neither inhale or exhale through their mouth. The nasal openings of a whale are known as the blowhole. There are two paired openings at the top of the head. The holes are closed and made water tight by two plugs (Tinker 65-68).
If you weighed ten elephants that would be the average weight of one hump-back whale. The male and female whale alike weigh between thirty and fifty tons. This weight will vary depending on the season. While fasting in Hawaii the weight will be much less. The calves are born in January and early February as a result from the previous years mating. They are born at approximately fourteen feet long and end up as long as sixty-two and a half feet with an average of fifty feet. The calf, a young hump-back, will drink one-hundred pounds of milk each day. This milk is very rich compared to domestic animals. The calf will begin to nurse soon after birth from two nipples located on either side of the vaginal slit. (Coustea 86). After birth they grow very fast. By March they more than double their weight and are ready to begin their migration north. They will wean in about five to seven months from birth.
Whales are not monogamous. Males have been seen romping and playing with females and it is thought that sometime during this romping and playing mating occurs. It has never been determined when. Over eleven to twelve months later, back in the same waters, the female gives birth. Usually they do not have calves each year, however, it is possible. The birth of twins has never been recorded however it is possible. Sexual maturity is as early as four years old for both sexes. They live for about thirty years but studies have shown they can live much longer. Using a “wax plug” system, much like the system of the rings of a tree, one whale was thought to have been fifty-eight years old before it died. (Balcom 15-19).The reproductive organs are located internally. The males penis is withdrawn into a slit. An erection of the penis is accomplished by a pair of muscles, much like that of cattle and horses. The females ovaries produce single celled eggs. When the egg is mature it is discharged into the fallopian tubes, a process known as ovulation. At this time if mating occurs and the egg is fertilized with sperm from the male the birth of a baby whale is on the way. (Kaufman 31-33).
Most mammals usually have five sense organs. The whale only has three. Touch, which is located in the skin, is the sense that can feel pain, heat, cold and vibration. They also have feelers called vibrissae. These feelers are very similar to whiskers on a domestic cat. The vibrissae are located in rows on the end of the lower jaw, on the sides of the lower jaw and on top of the head. Sight is the sense that allows the whale to see. The shape of the whales eyeball tend to make them far-sighted below the surface and near sighted above the surface. Since the eyes are located on either side of the head it makes it impossible for their visual fields to overlap, therefore, they do not have depth perception. Their auditory sense, or hearing, is very important because in the ocean the visibility is poor. Good hearing is used to help locate food, hear the approach of enemies, and communicate with each other. Their ears are gone and only a slit appears midway between the eye and the base of the flipper. The sense of smell and taste are not present like in most mammals (Tinker 81-85).
Due to the size of these enormous animals they have few predators. Man is their worst enemy. However, they do have confrontations with other whales. Some of the defenses used are, filling their mouth with water or air so to bluff the invader into thinking they are bigger than they are. As a second line of defense they will use the head and fins as weapons. They also use their huge body as a defense mechanism by positioning themselves between the invader, like a boat, and mother and calf. (Kaufman 93-115). A more subtle defense is countershading , where the top of the whale is dark which makes it harder to see from above looking down and the bottom is light so looking up it is hard to see against the lighter surface of the ocean.
Hump-backs produce a wide range of sounds. Often these sounds are long and complex that are repeated for hours. The first sounds were recorded here in Hawaii in 1952 by O.W. Schreiber on the basis of recordings collected at the U.S. Navy Sound Fixing and Ranging Station. One whale sung a song for fourteen hours without stopping. Since singing is done primarily during the mating season it is thought to serve a reproductive function. It has been shown that only the males sing this song. It may also attract females, scare away other males, or maintain the distance between singers. Males and females alike make other sounds which are associated with feeding and socially active groups (Kaufman 73-77).
The whales pectoral fins is not used for propulsion but to balance and steer. The tail or fluke is used to move this massive mammal through the water. The muscle caudal peduncle move the fluke in an up and down direction which propels the whale through the water (Tinker 55).
The worldwide population of humpbacks is estimated between ten thousand and fifteen thousand animals. This count is down from over one hundred and fifty thousand last century. (Dietz 39). Man has hunted the whale close to extinction. The good news is that we have bans against killing whales in most waters. Hopefully we did this in time to save them from extinction. It would be a true shame if my grandchildren could not enjoy these wonderful creatures.