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?