Diving behaviour of American mink
Studying the behaviour of elusive animals like the American mink is extremely difficult and previous work has generally been limited to observations of field signs, laboratory studies of diving behaviour, or radio tracking (which provides information on space and habitat usage but not on the specific activities that are being performed).
Temperature-depth recorders (TDRs) allow very detailed data to be collected on free-living animals over a specified period of time. Although the size of such devices was previously limiting, successful technological advances in recent years mean that very small and precise TDRs can now be deployed on small-bodied, shallow-diving aquatic and semi-aquatic animals, like the American mink.
Data obtained from TDRs deployed on mink provide information on key activities such as hunting and diving and can thus shed light on their behavioural ecology, particularly foraging strategies and intraguild relationships.
In December 2005 we fitted the first datalogger onto a mink in the Upper Thames valley; we have since obtained 25 datasets from 19 individual mink. Initial analyses of a subset of this data showed that mink dive predominantly during the day and that although the number and duration of dives was hugely variable amongst individuals, some mink dived over 100 times a day, and for up to 60 second durations.
As part of a 3-year project on the diving behaviour of American mink, we are currently carrying out in-depth analyses of these data. The main objectives of this project are:
To validate the use of TDRs for describing activity patterns of semi-aquatic animals.
To examine mink diving behaviour and physiological capabilities in terms of dive duration, frequency, and pattern, at the level of individual dives and dive bouts.
To investigate differences in mink diving behaviour with respect to sex and season.
To investigate the shape of dive profiles and to determine whether dive success can be predicted from TDR data.
To model optimal foraging strategies for mink taking into account fishing vs. hunting on land, energetic bursts, and dive bouts depicting the exploitation of particular prey patches.
Mink are highly adaptable predators that consume a variety of aquatic and terrestrial prey and can occupy a range of habitats. Of particular interest is how mink might alter their foraging strategies in different habitats and climates, and in the presence or absence of mustelid competitors. In collaboration with the Laboratorio de Ecología de Predadores Tope (Laboratory of Top Predator Ecology) headed by Dr. Adrián Schiavini at the Centro Austral de Investigaciones Científicas (CADIC), we have initiated a new 2-year project investigating the diving behaviour of mink in Argentina. We also plan to extend this work to coastal habitats in Scotland and Iceland.
Prof Graeme Hays, Swansea University
Dr David Righton, CEFAS