Passage I

Wood mice (a species of mammal) typically forage for food at night. Their foraging behavior can be affected by environmental factors, including the presence of moonlight and the presence of shelter (such as shrubs). Four students each proposed a hypothesis describing how the foraging behavior of wood mice is affected by the presence of moonlight and shelter. Then they conducted an experiment to test their hypotheses.

Student 1

Wood mice are more likely to forage when moonlight is absent than when moonlight is present. The absence of moonlight decreases the chance that a wood mouse will be captured by a predator. Therefore, the number of wood mouse visits to a foraging site will be greater during the new moon than during the full moon. Shelter has no effect on foraging behavior.

Student 2

Wood mice are more likely to forage at sites with shelter than at sites without shelter. The presence of shelter decreases the chance that a wood mouse will be captured by a predator. Therefore, the number of wood mouse visits to a foraging site will be greater when shelter is present than when shelter is absent. Moonlight has no effect on for­aging behavior.

Student 3

Wood mice are more likely to forage at sites with shelter than at sites without shelter, and they are more likely to forage when moonlight is absent than when moon­light is present. Both the presence of shelter and the absence of moonlight decrease the chance that a wood mouse will be captured by a predator. Therefore, the greatest number of wood mouse visits will be to foraging sites with shelter during the new moon.

Student 4

The foraging behavior of wood mice is not affected by the presence of shelter or moonlight. These factors do not affect the chance that a wood mouse will be captured by a predator. and therefore do not affect the number of wood mouse visits to a foraging site.

Experiment

Over the course of several months, the students counted the number of wood mouse visits to a foraging site with shelter and a foraging site without shelter during the new moon and during the full moon (see table).

Table adapted from Ramón Perea et al., “Moonlight and Shelter Cause Differential Seed Selection and Removal by Rodents.” ©2011 by The Association for the Study of Animal Behaviour.