Name:________________ Per:____Gray Whale Population Date:_______________ Today, gray whales are protected by law, and tourists who view them at their breeding and calving grounds in Mexico, regard them as friendly. The whales seem to be curious about these tourists and frequently swim up to their boats and allow the visitors to touch their barnacle-covered backs. The experience is thrilling and many people believe the whales enjoy it, too. The gray whale has the reputation as another kind of fighter, a fighter against the forces that would bring about its extinction. The species has fought its way back from the brink of extinction on two occasions. Like other large whales, gray whales were commercially hunted and their numbers were reduced to just a few hundred at two different times. The eastern Pacific population of gray whales has made a remarkable recovery as a result of legal protection. In 1995, this population was removed from the endangered species list. Unfortunately, other species of whales have not been able to recover as quickly as the eastern gray and most remain highly endangered. The gray whale's range formerly included the coasts of both the Atlantic and Pacific Oceans. The Atlantic population had been hunted to extinction by the 1700s and in the early 1900s it seemed that the two Pacific populations (eastern and western) would follow. However, in the 1940s the species became protected by international agreement, and today the eastern Pacific population has recovered so much that it is no longer considered endangered (although it is still protected). Population estimates indicate that there are more than 20,000 gray whales in the eastern Pacific, approximately equal to estimates of the historic population. The eastern Pacific population of gray whales was removed from the endangered species list in 1995, but the western Pacific (Korean) population, which has not recovered at all, remains listed. The status of the western Pacific population is relatively unknown, but it is believed to be highly endangered and close to extinction. The gray whale is an interesting case study because one population is extinct, one is endangered, and one is recovered. The only animal known to prey on gray whales, other than humans, is the killer whale (Orcinus orca). However, an analysis of tooth scars on stranded gray whale carcasses indicates that these attacks frequently are not fatal. Although gray whales are protected throughout their range, they receive special attention at the breeding and calving grounds in Baja. In the 1970s, Mexico designated refuges in three of the four major lagoons the whales use. To prevent disturbance of the whales, boats are allowed to enter the lagoons only with a governments permit. The fact that gray whales congregate together in the winter for mating and calving has been partially responsible for both their difficulty and their recovery. In the 1800s, when commercial whalers discovered the calving lagoons, the concentration of whales in the shallow waters made their wholesale slaughter very easy. By the 1890s, the gray whale was almost extinct and most hunting stopped. In the 1920s, they were again commercially targeted, and once again, brought to the verge of extinction. There probably were only a few hundred individuals left when they were finally protected by international agreement in the 1940s. Since the 1940s, other protected whale species have languished near the verge of extinction, but the eastern gray whales' population has increased steadily. Some scientists believe gray whales have fared so much better than other species because, despite their low population numbers, they have no trouble finding mates because they gather in the small lagoons, the same factor that once made their slaughter so easy. Name:________________ Per:____Gray Whale Population 1760 19,000 1780 21,000 1800 20,000 1820 21,000 1840 9,000 1860 4,000 1880 2,000 1900 700 1920 1,500 1940 400 1950 450 1960 550 1970 700 1980 1,000 1990 1,500 2000 3,000 2010 11,000 2020 20,000 Date:_______________ Gray Whale Population 25,000 20,000 Gray Whale Population Year Whale Population 15,000 10,000 5,000 0 1760 1785 1810 1835 1860 1885 1910 1935 1960 1985 2010 2035 Time Data Analysis: 1. Draw a dotted line across your graph at the carrying capacity of grey whales and label it. 2. Label the year humans started hunting whales 3. Label the year laws were passed to protect the whales 4. Did the Grey whale population grow exponentially or logistically? (Circle one) 5. What conditions needed to exist for the population to grow in this way? 6. Assume that in the next 15 years grey whiles will again reach their caring capacity. Place a data point where the population will be at 2035. 7. Does this prediction in question 6 show logistic or exponential growth? (Circle one) 8. If grey whales feed on phytoplankton and krill, what seasons would they, migrate away from the polar waters? 9. Why would they migrate away from polar waters in this season? (Use the words limiting resource)? 10. What is the limiting resource in the tropical waters the Grey whales are migrate too?