Biodiversity

Studying small mammal population dynamics: advice to consider and pitfalls to avoid - a 60-year overview

Boonstra, R., Krebs, C. & Reid, D.

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This review synthesizes 60 years of research into small mammal populations, highlighting key lessons, common pitfalls, and the need for clear questions, solid study design, and reflection to guide future studies across 3,200+ species worldwide.

Key points

• Small mammals (<5 kg) make up the great majority of mammal species
• A significant number of small mammals play very influential roles (some keystones) in trophic webs
• Rarity is commonplace among small mammals, not necessarily because of human-induced threats, but often as a result of life history specialization and isolation
• Conservation of rare species, no matter the cause of their rarity, requires more focussed study. The experience of many decades of work on more common species can provide significant guidance.

Abstract

We consider what we and others have learned and the mistakes that we have made in the last 60 years of research on small mammal population dynamics. We consider all mammals <5 kg as small mammals, covering more than 3200 species including among others, mice, voles, lemmings, gerbils, guinea pigs, muskrats, shrews, squirrels, and hares, but not bats, in ecosystems globally. We start by emphasizing the necessity of posing a good question and what that means scientifically on one or more species or populations of small mammals. We consider the study design, the choice of the study area, the methods of population estimation, the necessity of measuring demographic parameters on births, deaths, and movements, the limitations of enclosure experiments, the problems faced by field experiments to test specific hypotheses, and the need to acquire social licence. By being self-critical we hope to encourage a new round of studies of small mammal populations that will avoid pitfalls, illuminate hypotheses not yet tested properly, and forge new directions.

Recommended citation

Boonstra, R., Krebs, C. & Reid, D. (2025). Studying small mammal population dynamics: advice to consider and pitfalls to avoid - a 60-year overview. Canadian Journal of Zoology. https://doi.org/10.1139/cjz-2024-0191