Which of the following factors would be least likely to act as a density dependent limiting factor in a population of mice?

Step 1: Analyze the question We are asked which factor is least likely to be a density-dependent limiting factor. So we need to find the option whose effect does not depend on how crowded the population is.

Step 2: Understand the concept

• Density-dependent factors have a stronger effect as population density increases. Examples include competition for food, space and mates, disease, parasitism, predation, and accumulation of waste.
• Density-independent factors affect a population regardless of its size or density. These are mostly abiotic, such as climate, weather, floods, fire, drought, and temperature extremes.

Step 3: Evaluate each option

• A. Buildup of waste products: More mice produce more waste, so the problem worsens as density rises. This is density dependent.
• B. Predation: Predators find prey more easily when prey are plentiful and concentrated, so predation is generally density dependent.
• C. Parasitism: Parasites and diseases spread faster in crowded populations, so this is density dependent.
• D. Unfavourable climate: A cold snap, flood, or drought kills mice whether there are 10 or 10,000 of them. This is density independent.

Step 4: Answer Unfavourable climate is the least likely to be density dependent, so the correct option is D.

Exam tip: Remember this: "Biotic and crowding-related = density dependent; abiotic and weather-related = density independent." When you see climate, weather, fire, or natural disasters in the options, think density independent.