The reindeer primarily used lichen as a food source. Lichen is a combination of a fungus and algae that live in a mutualistic relationship.
Lichen grows very slowly in Arctic regions such as this. World War II ended soon after the reindeer were introduced, so none of them were
actually hunted by the Coast Guard officers. The island was abandoned by humans, and the deer were left without any predators. In these
conditions, the population thrived.
• A biologist working for the US Fish and Wildlife Service began making regular visits to the island. In 1957 he counted 1350 reindeer. He
also noted that many of the lichen patches appeared trampled and barren.
• Graph the reindeer population from 1944-1963 and answer the questions on the back of the graph.
Year Population of Reindeer
1944 29
1945 37
1946 54
1947 81
1948 104
1949 139
1950 177
1951 240
1952 313
1953 398
1954 501
1955 630
1956 878
1957 1,350
1958 1,918
1959 2,840
1960 3,688
1961 4,040
1962 4,933
1963 6,000
1966 42 *
1967 0
1. Based on the graph, did the reindeer show exponential or logistic growth?
2. Why did the reindeer grow at this rate?
3. Based on the graph, what do you think the carrying capacity of this island was for reindeer? Explain your answer.
4. Why is it bad for a population to overshoot the carrying capacity of an ecosystem?
5. If the Coast Guard were to try this again on a similar island, what changes could they make to prevent the same outcome?
6. Critics of this story will argue that one of the factors that contributed to the population crash of the deer was a severe winter that
created snow too deep for many of the reindeer to dig for food. Does this mean the deer would not have experienced a dieback if not for the
blizzard? Does this new information change your perspective on this event?
*In 1966 the biologist returned to find only 42 reindeer in poor health, and the island was covered with 1,000’s of skeletons. Only 1 of the 42
was a male and he had some genetic abnormalities.