Ilkka Hanski and Small Mammals: from Shrew Metapopulations to Vole and Lemming Cycles

Abstract

Ilkka Hanski may be best known for his work on insect and metapopulation dynamics, but he also contributed significantly to small mammal research. In the early 1980s he became interested in shrew dynamics, energetics, and of course, shrew metapopulations. He aimed at understanding the population biological consequences of body size in different shrew species. Feeding habits and environmental stochasticity affect shrew species in profoundly different ways: due to their short survival time small species have high extinction rates but their dispersal and colonization capacity is high which enables them to survive as metapopulations. After Hansson and Henttonen reported the Fennoscandian gradients in vole dynamics in the mid-1980s, Hanski became interested in vole and lemming cycles. The first models on this were published with Henttonen and Hansson in 1991 where the roles of specialist and generalist predators were assessed. Later, the models were further developed with Korpimäki and Turchin, with model parametrization from Microtus biology and including both specialist mammalian predators as well as avian predators. A special case was the model with Henttonen on competing vole species with a shared predator (apparent competition), which was related to the long-term fading out of vole cycles in Finnish Lapland in the mid-1980s (which though returned in the early 2010s). Later Hanski became interested in the work of Sittler and Gilg in Greenland. Together they modelled the very simple vertebrate community and showed how stoats played a pivotal role in generating a population cycle in the collared lemming. In addition to these specific works, Hanski was leading collaborator in several reviews on small rodent cycles and predation. He intended to return to shrew biology, but that never realized. Hanski was a fearless field biologist, but he always aimed at understanding natural phenomena at more general, theoretical level.Ilkka Hanski: The legacy of a multifaceted ecologist

Patterns of diversity, species richness and community structure in West African savannah small mammals (rodents and shrews)

“…In addition, live trapping is usually time-consuming and not at all cost-effective, thus typically resulting in short-term studies especially in Afrotropical areas where the economic costs are an important constraint to the field research. Obviously, this is a minor problem in Europe or North America, where several long-term live trapping surveys have been made (e.g., Pucek et al 1993;Krebs 2009;Kataev 2012;Amori et al 2015;Henttonen et al 2017;Casula et al 2019). It is also important to remind that some species are behaviorally less likely to be trapped than others (e.g., Allan 2020).…”

Numerical response of a mammalian specialist predator to multiple prey dynamics in Mediterranean farmlands

“…Numerical response of weasels to fluctuations in abundance of prey Small mustelids are hypothesized to cause vole cycles in Fennoscandia, which is often presented as a ubiquitous explanation for such fluctuations elsewhere (Henttonen et al 2017). A key feature of classical weasel-vole cycle models is a 1-yr delay in the numerical response of weasels to prey abundance, reflecting a lower growth rate of weasels relative to their prey and the dependence of weasel reproduction and survival on prey abundance.…”

Transferability of biotic interactions: Temporal consistency of arctic plant–rodent relationships is poor

“…Above such productivity threshold, rodent abundance should become decoupled from food plant biomass as predators generally suppress rodent peak abundance below a K (Aunapuu et al., ; Oksanen, Fretwell, Arruda, & Niemelä, ). Yet, K is a parameter most often set as constant in models constructed to investigate conditions for rodent cycles to result from predator–prey or plant–herbivore interactions (Hanski, Henttonen, Korpimäki, Oksanen, & Turchin, ; Henttonen et al., ; Turchin & Batzli, ). It should also be noted that K is defined differently among different models and empirical studies (Chapman & Byron, ).…”