By Kelly Vowels, Yoko Tsukamoto, and Pattie Shelley

Many marine mammals are in danger of becoming extinct. There are two main causes of extinction- habitat loss and poaching. Habitat loss can be caused by oil spills, not only large spills but the every day spilling done by the average person. It can also be caused by pollution. Examples of pollution would be dumping of trash into the ocean, sewage runoff, and pollution caused by nuclear plants. The last cause would be competition. As the number decreases for a species, their ability to compete with other species and humans for food also decreases. They are not able to get enough food, or to keep their habitats. These habitats are being filled by other species. The other cause of extinction is poaching, which is the killing of the species for their fur, skin, or meat. In recent years people have began to take steps to stop these extinctions. But different marine mammals have different abilities to come back from near extinction. Examples of species abilities to recover are right whales, gray whales, northern elephant seals, and California sea otter.

Northern right whales are recognized both in the Atlantic and Pacific Oceans. About 800 years ago, before whaling started, the populations of northern right whales are estimated to have been at least 10,000 individuals each in the Atlantic and Pacific. As the whalers started to exploit these slow moving animals, their numbers started to decrease, and by the early 1900's, they were brought to near extinction (NMFS 1991). To avoid further depletion of northern right whale population, International Whaling Commission banned commercial whaling on right whales in 1946 (Duxbury and Duxbury 1994). In despite of such an effort, current populations are estimated to be only 300 in the Atlantic and as low as 100-200 to as high as 220-550 in Pacific (NMFS 1991, "Is Northern Right Whale On Path To Extinction?" 1999). Under present conditions, the population is headed for extinction in less than 200 years ("Right Whales More Closer To Extinction." 1999). Why?

There is no definite single factor reducing the population of northern right whale. They are at risk from competition for food with large number of other marine organisms, low reproduction rate, vessel interactions, entanglement in fish gear, and habitat degradation. Primal preys of northern right whale are copepods (Calanus spp.) and krill (Only Atlantic population feeds on krill very often). In the Gulf of Maine, which is one of the summer feeding ground for the Atlantic northern right whale, other planktovivorous fish occur in large numbers and may be at peak biomass levels. These fish such as sand lance, herring, Atlantic mackerel, river herrings, menhaden, basking sharks, as well as juveniles of many species of larger fishes could be significant competitors for northern right whales (NMFS 1991). There is also a speculation that Sei whales compete for the same food resources and their expanded number may be partly playing the roll in the depletion of northern right whales (Mitchell 1975 and Scarff 1986: cited in NMFS 1991).

A few studies have shown that the population growth rate of northern right whales is declining over years (Caswell et al.: cited in "Is Northern Right Whale On Path To Extinction?" 1999, Brown et al. 1994, NMFS 1991). National Marine Fisheries Service (1991) reports Gross Annual Reproductive Rate of north Atlantic right whale to be 0.048, meaning that only 4.8% of the first year calves as a proportion of the entire Atlantic population contributes in the estimation of anticipated population growth. This low GARR is mostly due to their small population, which may contain lower proportion of mature females. Unfortunately observed north Atlantic data is in line with this estimate (Brown et al. 1994, Kraus et al. 1985 and Knowlton and Kraus 1989: cited in NMFS 1991).

Northern right whales are slow moving and their behavior such as resting at the surface, surface courtship groups, surface skim feeding and tendency to feed closer to the shore makes them more vulnerable to be struck by ships and tangled in fishing gear. These behaviors continue sometimes for periods of an hour or more, and it makes them more susceptible to collisions with vessels. Between 1970 and 1990, 22% (6 deaths) was due to collisions with ships in North Atlantic. However, no ship collisions have been reported from the North Pacific. Little is known about North Pacific population since only a small portion of the coastal waters of western North America provides the habitat for right whales. Therefore, this data does not mean that the Pacific population is less threatened (NMFS 1991). The effects of disturbances such as noise from the ships are unknown. Watkins (1986: cited in NMFS 1991) reported that in the Cape Cod Bay, normally northern right whales did not respond to engine sounds or minor vessel maneuvering. However, cows with calves and single long-diving whales have been observed to be sensitive to the noise and to avoid vessels (Kraus and Mayo, unpubl. Data: cited in NMFS 1991) whereas during courtship and surface skim feeding, they seem unresponsive to the engine noise (Mayo et al. Pers. Comm.: cited in NMFS 1991). Therefore, their responses to ships apparently depend on the behavior in which they are engaged.

According to the New England Aquarium's photographic catalog, 58% of the catalogued northern Atlantic right whales have scars and injuries around the tail stock indicative of rope and net cuts. In Atlantic 3 whales are known to have died from entanglement during 1970-1991 (NMFS 1991). To reduce further mortality of northern right whale, new federal regulation was passed on April 1^st. The regulation requires gill netters and lobster boats to avoid certain types of gear, and place bans on fishing in some areas ("Is Northern Right Whale On Path To Extinction?" 1999, "Right Whales Move Closer To Extinction" 1999).

Of all the possible causes of northern right whale population reduction, habitat degradation may be the most important factor affecting the recovery of northern right whale. Some examples of habitat degradation are due to offshore oil and gas leasing, untreated waste water discharge into their feeding ground, and extensive dredging activities during the winter in the only known calving grounds (Wilmington, Savannah etc.). Sadly, when the Common wealth of Massachusetts, the U.S. Environmental Protection Agency, and the U.S. Army Corps of Engineers have designated dump sites for extend untreated waste water discharge pipes further offshore into bay waters for several municipalities around Cape cod Bays (feeding ground of north Atlantic right whale), no studies were conducted or planned to examine the effects of the proposed activities on northern right whale or the marine environment (NMFS 1991).

During the mid nineteenth century American whalers searched mainly for sperm and right whales. In 1857, Charles Scammon discovered a lagoon in Baja California where gray whales went to calve (Tutorial, 1995). Whalers then concentrated their killings to these shallow calving lagoons because the gray whales were easy prey. They could then get a full load of oil in only two to three months, where it usually took three to five years on a sperm whale voyage (Rice, 1986). Soon there were dozens of vessels working in lagoons, in stations along the shore, and intercepting the migrating whales. This caused rapid depletion of stocks. By the early nineteen hundreds the last whaling station closed down as the gray whales were nearly extinct.

The gray whales were left alone for awhile and their numbers slowly increased. The new threat was the modern whaling stations with steam powered boats and harpoon guns. Fortunately for the gray whales these faster boats could now hunt the larger, more profitable blue and humpback whales. Also these smaller gray whales were found only in the winter, so there was little effort to try to catch them in the rough winter weather (Rice,1986). The next real threat was the invention of the floating factory ship in 1925 (Tutorial, 1995). This allowed the whalers to move anywhere. They set up ships in the calving lagoons and they could also set up ships in the rough winter weather. The gray whale population again dropped dramatically, less than 2,000.

In 1946 the International Whaling Commission was formed (Tutorial,1995). In 1947 seventeen nations ratified the International Convention for the Regulation of Whaling. This forbids the killing of gray whales except by aborigines or by contracting governments (Rice,1986). The population substantially increased. From the years 1967 to 1980 the National Marine Fisheries Service counted the whales as they migrated past Monterey, California (Rice,1986). Now there is over 20,000 where before exploitation there was around 15,000. There has been recent popularity of the gray whales in California. There are cruises that allow people to observe and photograph migrating whales at close range in calving lagoons. Conservationists are concerned about the frequent disturbances, especially the mothers and their newborn calves (Rice,1986).

The eastern north Pacific (California) gray whale is the only whale population that, following severe depletion, has recovered to near original numbers (Rice,1986). A north Atlantic stock is now extinct and a north western (Korean) stock is very depleted (Fact Sheet,1996). Even with this high number of California gray whales some say not to be optimistic. There is a new highway being built that will affect lagoons and there is proposed oil drilling in these lagoons (Rice,1986). Such threats are sure to endanger the growing population of the gray whales.

Northern elephant seal is an example of a marine mammal that was once close to extinction. It migrates once a year along the western coast of North America. They migrate north to feed, since there are more fish in colder waters (Allen, 1972). Females migrate to north central Pacific, while males migrate to Alaska (Allen, 1972). They then migrate back south to give birth and mate on certain islands off Mexico and California. Because they breed on land, it’s easier to kill them. Sealers would get between the herd and the water (Delong). When the elephant seals charged, some would be shot, others hit with club, or some were lanced (DeLong). The main reason that they were killed was for their blubber, which was used to produce oil. This oil, which was once used to make lamp fuel, is still today used to make other things- glycerin, soaps, creams, lubricating oil, and margarine (Allen, 1972).

By 1892, only one small colony of northern elephant seals remained on Guadalupe Island off Baja California (DeLong). One expedition was taken that year and only nine individuals were seen on land, of which seven were killed to be used for specimens (DeLong).

In 1907, another expedition was taken and 40 individuals were counted (DeLong). The remoteness of this island is probably what saved the species from complete annihilation. Then in 1911, the Mexican government passed legislation for the complete protection for them (DeLong). The United Stated followed suit.

Today the population of northern elephant seals is about 100,000 individuals, and they breed on ten islands off Mexico and California (DeLong). Many of these islands were not historical colony locations (Allen, 1972). This means in earlier times some of these rookeries were not used in northern elephant seals. There are several reasons why northern elephant seals have maintained to come back from near extinction. One reason is the strong laws of U.S. and Mexico against hunting of northern elephant seals. Since they are found along these coast hunting of them is almost disappeared. This isn’t the case for southern elephant seals, which migrate along coasts where there are few regulations against hunting them (Allen, 1972). So there numbers are still decreasing. Another reason is the almost lack of "natural" predators. The reason this is is because of their large size. Northern elephant seals are the largest pinnipeds in the northern hemisphere, and are surpassed in size only by the southern elephant seal in the southern hemisphere (Allen, 1972). Also they dive depth so they can escape their main predators- killer whales and sharks, and they also can get unexploited food from deeper waters. Another reason they may be coming back is their regularity in breeding. Sine they mate on certain islands its easy for them to find mates.

California sea otter is another marine mammals that were once endanger of extinction. At one time their range was from Prince William Sounds, Alaska to Baja California (Martin, 1990). They were ruthlessly pursued for the richness of its fur since its discovery by the Russians in about the middle of the 18th century (Kenyon). Their fur is of prime quality in all seasons, because they have a prolonged molting (Kenyon). There is no thinning or massive shedding that is noticeable in any season. Their skins sold for as much as $1,000 apiece (Kenyon). They are easy to kill, because they remain at the surface near the coast. They were in several different ways. They were shot when near the surf. They were surrounded by a party of spearers in their boats, and when the otter got tired of diving they would kill it (Kenyon). They were also clubbed when they went on shore.

Today the Alaskan population of sea otters is thriving. There are about 125,000 to 200,000 otters in Alaska (Kenyon). The California sea otter is having more problems because of its small size, limited range, and possible environmental threats caused by increasing human activity. In the late 1970s and early 1980s, a gill net fishery within the sea otter’s habitat expanded and otters were caught and drowned in the meshes (Kenyon). Population declined to 1200-1400 otters (Kenyon). Because of this decline, California legislature passed a law prohibiting the use of gill nets within 90ft depth curve (Kenyon). This was since not enough, because many otters are still killed. California sea otter also competes with fishermen, making protecting them more difficult. Alaskan populations also compete with fisheries, but there are still extensive coastal areas of excellent sea otter habitat where there are still no commercial fishery (Kenyon). This is not the case in California. There was a plan to transplant to unoccupied habitats, but this was controversial because of competition with fisheries. Even if they could get passed the fisheries, transplants are expensive and hard to do. Sea otters need to groom themselves all the time, and if they can’t they will die from stress. So to transplant they need large areas with water and land for just one otter.

In conclusion, it was found that the best way to bring species back from near extinction is by regulation of laws against killing of them and protecting their habitat. This is difficult to do because of the cost and because many marine mammals are competing with fishermen. This competition makes it harder to convince people that protecting them is important. Many people only see the bottom line-money. If they would lose money to protect the species, they won’t do it. Also different species require different methods to protect them. Determining the best method for all is difficult to do. One method may work for one species, but not for another.

Allen, G.M. 1972. Extinct and vanishing mammals of the western hemisphere. New York:Cooper Square Publishers, Inc. p417, 459-462.

Brown, MW; Kraus, CD; Gaskin, De; White BN. 1994. Sexual composition and analysis of reproductive females in the North Atlantic right whale, Eubalaena glacialis population. Marine Mammal Science. 10: 253-265.

California Gray Whale Tutorial. Revised 1995. http://www.slocs.k12.ca.us/whale/whale5.html

DeLong, R.L. Northern elephant seal.

Duxbury, A.C; Duxbury, A.B. 1994. An introduction to the World's Oceans. 4^th ed. Dubuque: Wm.C. Brown. P 395-396.

Gray Whale American Cetacean Society Fact Sheet. Revised 1996. http://www.acsonline.org/factpack/graywhl.htm

"Is Northern Right Whale On Path To Extinction?" UniScience News Net, Inc. 19 Mar. 1999. 22 Sept. 1999 <http://unisci.com/stories/19991/0319995.htm>.

Kenyon, K.W. Sea otter.

Martin, G. 1990. Otter madness. Discover. v11. n7. p36-39.

National Marine Fisheries Service. 1991. Recovery Plan for the Northern Right Whale (Eubalaena glacialis). Prepared by the Right Whale Recovery Team for the National Marine Fisheries Service, Silver Spring, Maryland. p 1-86.

Rice, Dale W.1986. Gray Whale. Marine Mammals 2^nd Edition. Pacific Search Press: Seattle, Washington.

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