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Movement characteristics of the Scarce Blue-tailed Damselfly, Ischnura pumilio


Katherine A. Allen, School of Biological Sciences, University of Liverpool, Liverpool, L69 7ZB, UK. E-mail:


Abstract.  1. The Scarce Blue-tailed Damselfly, Ischnura pumilio, is threatened in the UK and exists in small, transient colonies. Consequently, little is known about its dispersal characteristics. This study investigates movement in two contrasting habitats with the aim of informing conservation management on a landscape scale.

2. Mark-release-recapture studies were performed at an established colony in the New Forest and a smaller population in the Red River valley in southern England. A total of 2304 individuals was marked.

3. Ischnura pumilio was found to be exceptionally sedentary. Mean gross lifetime movement was 56 m and 43% of individuals moved <50 m in their lifetime. Movements over 150 m were very rare. Maximum lifetime movement was 1165 m. As such, I. pumilio is the most sedentary odonate studied in the UK to date.

4. Movement was inversely density dependent, which has important conservation implications if individuals attempt to emigrate from small populations because of low density. The presence of parasitic mites (Hydryphantes sp.) significantly increased movement distance.

5. Ischnura pumilio had a low dispersal probability compared to other damselflies. As the smallest British odonate, this is in keeping with the relationship between size and dispersal found across taxa.

6. Ischnura pumilio has been regarded as a ‘wandering opportunist’ due to its tendency to appear in locations far from known sites. However, this study suggests that long range movement rarely occurs from prime habitat that is maintained in an early successional stage. This has implications for the conservation of the species in the UK.