If researchers observe a high density of banana slugs after rain, which statement best captures the interpretation?

• A. The slug population increases only because of rainfall causing more births.
• B. It’s due to sampling bias, not real change.
• C. Increased moisture may raise true activity or detectability.
• D. Slugs migrate into the study area after rain.

Answer: (C)

When moisture is high, banana slugs become more active and easier to spot. Rain creates damp surfaces and encourages movement, feeding, and seeking shelter, so a survey conducted after rain is more likely to find and count more slugs even if the actual population size hasn’t changed. That makes the best interpretation that the observed higher density reflects increased activity or detectability, not an immediate rise in numbers.

Births or population growth take time and wouldn’t explain a sudden spike right after rain. A sampling bias explanation is less about the biology and more about measurement artifacts, but the direct effect of moisture on slugs’ behavior and visibility provides a clearer, more immediate reason for the observed change. Migration could contribute, but the simplest, most general explanation is that moisture boosts activity and detectability, leading to higher observed density.