Sampling and monitoring wood ants

Abstract

Wood ants ( Formica rufa group) are the ecological centre of many temperate and boreal forest ecosystems, with influence over ecosystem processes and other organisms. Owing to their dominance and keystone role, there are many reasons why it may be desirable or necessary to sample or monitor wood ants. Most field-based studies are based on exploring the relationships between red wood ants and their environment, be it the effects wood ants have on their surroundings via their nesting or foraging activities, or the effect a changing environment has on the ants. Given their keystone roles with the ecosystem, red wood ants can be useful indicators of ecosystem health, environmental degradation or restoration, or climate change (Torossian 1977b; Sorvari and Hakkarainen 2007b). With many species in Eurasia threatened and those in North America little understood, there is often simply a requirement to assess whether a species is present or not, or whether introductions or translocations have been successful. Unlike most other invertebrates, and indeed even other ant species, most red wood ants build conspicuous and long-lasting mound nests that facilitate their census. However, as for other ant species, this social living presents particular challenges for sampling and monitoring. Careful planning and the application of considered methods are needed to overcome these difficulties. This chapter provides an overview of the sampling methods and approaches that have been directly applied to wood ants, and the theory underpinning them. Where methods or approaches are ineffective or warrant further development, these are highlighted. The goal is to recommend a set of reliable and easy to use methods that can provide accurate and repeatable data, which are comparable between studies. The challenges of studying red wood ants Consideration of life cycle and seasonality Effective sampling or monitoring of wood ants presents considerable theoretical and practical problems. Wood ants are social insects which are patchily distributed and territorial. Moreover, there are seasonal patterns to the abundance and presence of certain castes. The queen (or queens) and some workers are present throughout the year, though not always visibly so. Males and particular stages of brood are present only for part of the year and this can depend on factors such as colony size and age, food availability and local environmental variables.