What can the Common Clubtail dragonfly tell us about the state of our freshwaters?

During Dragonfly Week (16­-23 July 2022) Freshwater Habitats Trust CEO Jeremy Biggs celebrates the Common Clubtail dragonfly and considers what this elusive species can tell us about the state of our water bodies.   

Despite its name, the Common Clubtail dragonfly (Gomphus vulgatissimus) is one of the Britain’s rare dragonflies and is classed as Near Threatened on the IUCN Red List. In recent years, it’s only been recorded in parts of southern England and Wales, including along the rivers Thames, Severn, Arun and Wye.

The Common Clubtail is notoriously difficult to spot but what do we know about the species and what can it tell us about our rivers and other freshwater habitats?

What do we know about the Common Clubtail?

Like all dragonflies, the Common Clubtail is an insect. In fact, dragonflies were among the first insects to evolve, with fossil records dating back around 300 million years to the Carboniferous period. The largest insect ever known was the Meganeuropsos permiana, a dragonfly that lived about 275 million years ago and had a wingspan of about 75 cm. Estimated to weigh more than 450 g, it was similar in size to a crow.

Today, according to the British Dragonfly Society’s latest State of Dragonflies report, there are 46 dragonfly and damselfly species in the UK. One of these is the Common Clubtail.

While it’s almost exclusively found on rivers in Britain, including the Thames, one of the two known UK pond breeding records of Common Clubtail came from the ponds we created at Pinkhill Meadow, near Oxford. Like other large dragonflies, the species can fly considerable distances and is known to travel up to 10 km from rivers.

One of the reasons why the Common Clubtail isn’t easy to find is that it spends most of its life – up to four years – as a larva, semi-submerged in sediment. In contrast, its adult life lasts for around two months.

Spotting and identifying the Common Clubtail

The Common Clubtail spends about 95% of its life in the water, as larvae. To have any chance of seeing an adult, you’d be looking between May and July, though it can be like looking for a needle in a haystack. The adults are believed to use tree canopies more than other dragonfly species, so sightings are often in wooded areas. Lone females then return to the water to lay their eggs.

Adults grow to 50mm in length and are black with yellow markings, which turn green on males. One distinguishing feature (though you’ll probably need a bit of luck to get close enough to see it) is that, in contrast with most dragonflies, the eyes of the Common Clubtail don’t meet at the top of the head. Instead, they’re located on the side of the head, which must give them an excellent field of vision.

There is another way to detect the presence of the Common Clubtail. You might be lucky enough to find the cast skin of an emerging adult: the exuvia. This can be identified by its flattened body and stout front legs, which help burrowing. With careful searching these are not too hard to find: this is one I recently found on the River Thames near Oxford.

Why the Common Clubtail is important to Oxfordshire

The Common Clubtail is one of the rare species that makes the Oxford area so special for freshwater wildlife. It’s a hotspot for many rare and threatened plant and animal species and that’s why it’s one of the Important Freshwater Landscapes we’re focusing on as we create the Freshwater Network.

Many of the current records of the Common Clubtail are from Oxfordshire. While there are many clean water bodies in the county, interestingly this species seems to be doing well on the River Thames, which we know is seriously polluted. All the freshwater plant species that are sensitive to pollutants have been wiped out along the Thames, so this suggests the Common Clubtail is at least fairly tolerant to nutrient pollution.

How threatened is the Common Clubtail dragonfly?

We’re concerned about the Common Clubtail because of its restricted distribution in Britain. The species is mainly found along the Thames and Severn and their tributaries and rivers that drain out of the Welsh hills. It’s only found in a few areas of the country and its Near Threatened status means we should keep a careful eye on it.

While many insects are declining, overall numbers of species of dragonflies and damselflies are increasing in Britain. This is the result of climate change bringing continental European species to the UK. At the same time, we are seeing a decline in some resident species, which is thought to be the result of habitat loss and pollution.

Following its Clubtail Count (2017-19), the British Dragonfly Society said it was “increasingly concerned” about the Common Clubtail’s status, with recordings suggesting its numbers could be declining.

We know that adults are emerging earlier due to climate change, but don’t yet know if this represents a threat or opportunity for the species.

Freshwater wildlife needs clean water to survive and we are concerned about the impacts of water pollution on the Common Clubtail. While it is likely that the decline in water quality is impacting on numbers, we don’t yet know what effect pollution in the Thames and other rivers is having on the species. In the UK’s standard RICT invertebrate pollution sensitivity index it scores eight (with ten being the most sensitive).

At the larval stage, it doesn’t tolerate gross pollution, such as caused by sewage discharges and toxic chemicals. On the other hand, the Common Clubtail does seem tolerant to serious nutrient pollution, which has almost wiped out sensitive water plants in the Thames.

Boat activity and dredging can also have an impact on submerged larvae, but we don’t yet have the data to know the effect on the Common Clubtail.

There is a lot to learn about how this species is responding to human impacts and environmental change and we need to find out as much as we can if we want to try and reverse the decline.

What we all can do to help

We need to know more about this elusive creature if we’re going to protect it. That means gathering more information on where it’s living to help us understand whether or not it’s declining. This is something everyone can get involved in.

Our species directory and information from the British Dragonfly Society will help you learn how to identify the Common Clubtail. Find out where you can report sightings in your local area on the British Dragonfly Society website.

We are planning to run some field survey training courses in 2023. We will announce details soon but in the meantime please get in touch if you’re interested in this.

Landowners can help by supporting freshwater habitat creation and protection. Clean, unpolluted water will help freshwater wildlife thrive – including the Common Clubtail dragonfly.

Important Freshwater Landscapes, like the area around Oxford, are special places because of the range of wildlife they support, including the Common Clubtail dragonfly. We want to keep them that way.

At Freshwater Habitats Trust, our conservation work is focused on supporting freshwater biodiversity. We’re working with landowners and large organisations to create and restore habitats on floodplains and lobbying policymakers on issues like freshwater pollution. Through projects like Building Oxfordshire’s Freshwater Network and Water Friendly Farming and our role as Catchment Host for the River Thame and Ock, and as part of the catchment partnership in the New Forest, we’re bringing life back to freshwater. That will help the Common Clubtail and many other rare and threatened freshwater species.

To protect freshwater wildlife, including the Common Clubtail dragonfly, support our work by making a donation or becoming a volunteer.