Passage V

Four researchers performed the following experiment to investigate changes in snowshoe hare populations in a coniferous forest over an 8 yr period.

Experiment

The researchers selected a 10 km x 10 km study area. Twenty-five 1 km x 1 km plots were then mapped out within this study area, so that none of the plots was in direct contact with another plot. Each plot was then assigned to 1 of 5 treatments, as shown in Table 1.

Each plot was surveyed during the month of April and the population density of snowshoe hares, in hares/hectare, was calculated. A hectare is 10,000 m². Table 2 shows the average population density of the plots assigned to Treat­ment 1.

For each year, the researchers defined the population density ratio for a given treatment as being equal to the value of the following expression:

Figure 1 shows the population density ratio for Treat­ments 2-5.

Tables and figure adapted from Charles K. Krebs et al., "Impact of Food and Predation on the Snowshoe Hare Cycle." ©1995 by the American Association for the Advancement of Science.