The discovery was made by ecologists from Hampshire & Isle of Wight Wildlife Trust. Over two consecutive days, ten male southern damselflies were recorded along a 675-metre stretch of the River Meon within the reserve. The first two individuals were spotted during a training exercise, prompting a return visit the following day to collect photographic evidence to support this discovery.
Tom Selby, Ecologist at Hampshire & Isle of Wight Wildlife Trust, said: "We weren't actually looking for southern damselflies when we made the discovery. While taking part in a team botany training exercise at the reserve, my colleague Jo and I happened to glance over a fence into the River Meon and spotted something familiar to us from survey work elsewhere in Hampshire, but that we weren’t expecting to see at St Clair’s. Fortunately, I had my close-focusing binoculars with me, which allowed me to get a good look and confirm the identification.”
The southern damselfly is a small but striking insect, with males displaying vivid blue and black markings. Larvae spend around two years underwater before emerging as adults during the summer months.
The southern damselfly is one of the UK's rarest damselflies and is listed as Vulnerable on the IUCN Red List. While Hampshire supports some of the country's strongest populations, its geographic distribution across the UK remains restricted to a relatively small number of suitable wetland habitats.
Dr Ben Rushbrook, Principal Ecologist at Hampshire & Isle of Wight Wildlife Trust, said: "This is an incredibly exciting discovery. Finding a species as rare as the southern damselfly here shows just how important it is that we continue restoring, protecting and connecting the places wildlife depends upon.”
While strong populations are known in the New Forest, and on the Rivers Itchen and Test, the southern damselfly is highly vulnerable because it depends on particular habitat conditions. Specifically, clean, well oxygenated and continually slow to moderate flowing water, in watercourses supporting shallow, silty marginal habitats with suitable plant species for egg-laying.
Ben adds: “To maintain the right habitat conditions for southern damselfly requires management, otherwise the watercourses they live on would ultimately become dominated by scrub and trees. Its presence in large numbers could therefore indicate healthy and sensitively managed rivers and wetlands. "
St Clair's Meadow Nature Reserve, managed by Hampshire & Isle of Wight Wildlife Trust, contains a species-rich floodplain meadow habitat alongside the internationally important River Meon chalk stream.
The discovery highlights the importance of safeguarding healthy rivers and wetlands across Hampshire. The Trust hopes further surveys will reveal more about the population and whether the southern damselfly is established elsewhere within the catchment.
The find underlines the importance of protecting Hampshire's globally rare chalk streams. Hampshire & Isle of Wight Wildlife Trust is calling for stronger protection for these internationally important habitats through its Save Our Chalk Streams campaign, which aims to tackle pollution, over-abstraction and habitat degradation affecting rivers across the county. Find out more here.
People wanting to learn more about the species can watch a short southern damselfly animation on Hampshire & Isle of Wight Wildlife Trust's website. The video, created as part of the Watercress and Winterbournes Landscape Partnership Scheme, funded by The National Lottery Heritage Fund, can be seen on the Trust website here.
The animation forms part of Chalk Stream Quest, a network of interactive walking trails across northern Hampshire designed to help people discover the wildlife and heritage of the county's internationally important chalk streams.
