Vanessa Lyn, Wilder Ashford Trainee Warden conducts an amphibian survey
Thursday 22nd March, Hothfield Heathlands
Spring has begun transforming the rolling farmlands and woodlands around Ashford, and renewed energy pulses through the veins of the landscape. The emergence of new seedlings and fresh foliage are easy enough to witness - but the yearly awakening of amphibians and reptiles is a subtler, less obvious event, unfolding quietly after dark. Typically, amphibians emerge as early as January on mild, wet evenings. The ancient doubleness of these animals, at home both on land and in water, is a relic of that prehistoric process when their (and our!) ancestors, lobe-finned fish, evolved the limbs needed to move themselves onto land. They went to all that effort - so it seems to me only fitting to drag ourselves out of our homes on the odd drizzly evening to say hello to their descendants, as they set off towards their favoured ponds again.
Occasionally, I manage to persuade some of our enthusiastic volunteers to become amateur herpetologists for a night, and have a go at amphibian surveying. So, a few weeks ago, a group of Kent Wildlife Trust’s Ashford volunteers gathered at dusk in the car park at Hothfield Heathlands. We wandered down the hill together to the bottom of the site, to the ponds across Extension B. This is a wet meadow habitat, dotted with several pools, thick with clusters of rushes. Many of our volunteers had never visited Hothfield at night before, and were struck by the different character the reserve takes on nocturnally. As we entered the meadow, our torches conjured a string of blue-green lights wavering in the darkness - which turned out to be eyeshine of Hothfield’s flock of Hebridean sheep, cautiously watching our group of unexpected visitors.
When it comes to the first survey of the year, it always seems to take a little while searching the shallows before you get your ‘eye in’, even for seasoned surveyers, but it wasn’t long before the volunteers were spotting newts, which can often be found lying still in the shallows at ponds’ edges. As ectotherms (animals which obtain heat from their surroundings), how fast they can flee the torchlight depends on how much warmth they’ve gained from their environment. We counted various newts, many of which were given away only by a quick swish of a ribbony tail.
And then, in the shallows nestled among the base of a clump of rushes, I came across a placid male great crested newt. I fished him out of the water (under licence), and popped him in a little photo tank, so we all got a good close look at his amazing mottled bright orange and black belly, and his dramatic serrated dorsal crest. He was so large he almost didn’t fit into the tank, which was designed for looking at tiny fish. One of our volunteers remarked on ‘his little hands!’, neatly summing up how striking the elements of shared morphology between we humans and our amphibian distant cousins; all tetrapods (four-limbed vertebrates) share variations on the same initial ‘blueprint’ in our limb structures. Many of the volunteers had never seen one of these eye-catching newts before – which made it even more stark to explain to them that this species is endangered in the UK – but finding them present in on our reserve is good news, and serves as crucial species occurrence data.
Next, after navigating a farm gate, stiles and very muddy paths, the group headed back through the woodland to the promisingly-named ‘newt sanctuary’, where several ponds sit at a section of the border between the woodland and the open heathland. In these several woodland edge ponds, we counted many more newts, belonging to the two common UK species – smooth newts and palmate newts. Will, our Ashford Warden, happily announced he’d found another great crested newt – a mature male again, but this time a late bloomer with a smaller, less defined crest. Male amphibians tend to arrive keen and early to breeding ponds, waiting patiently (sometimes for weeks!) for females to turn up. In the nearby large, deep dewpond, we weren’t expecting to see much, thanks to the brown, murky water. However, our torchlights revealed several male frogs lingering around the pond edges. Some were betrayed only by the wriggling away of their long, striated back legs. Others some bobbed still on the water’s surface, relaxed, and nonchalantly displaying their moonlight-white throats - a trait which attracts female frogs, which had obviously served its intended purpose, because we then found a large clump of frogspawn, too. Once breeding is done, male amphibians like to take things easy, sometimes staying in the pond for a little while after breeding, while females tend to leave the pond more promptly after laying their eggs. As well as amphibians, we found whirligigs, diving beetles, various alien-looking dragonfly larvae, and two mating water-scorpions.
In total, in addition to the two great crested newts, we managed to record nine common frogs, and 48 smooth or palmate newts (the latter two newt species are notoriously hard to distinguish from each other from a distance, without fishing them out of the water). Although surveying for amphibians is often interesting in itself as a chance to encounter all sorts of aquatic wildlife, it also has a more serious purpose. Measuring (however roughly) amphibian presence on reserves helps us estimate and monitor their populations, in a time when global amphibian populations have been plummeting over the past half-century. The causes of these declines are habitat loss, diseases (chytrid, for instance, has decimated many amphibian populations), and pollution. Amphibians have the remarkable feature of permeable skin, which lets them ‘breathe’ underwater through their skin, which absorbs oxygen from the water. The downside of this trait is that amphibians can absorb other substances present in water, including pollutants. This leaves them highly vulnerable to aquatic pollution like farmland agrochemical runoff, or road-surface run-off from road gritting. Faced with these pressures, protected areas like Hothfield Heathlands offer important havens for amphibians, ‘buffered’ from sources of pollution. It was a pleasure to show the volunteers that these animals are using Hothfield, and benefiting from the volunteer team’s tireless habitat management work. Our work to create leaky dams, and blocking water channels in the bog areas to slow water flow, can help filter out pollutants as well as prevent flooding further down the river course, in turn helping amphibians avoid exposure to polluted river water beyond the boundaries of the reserve. With our continued conservation efforts, Hothfield can continue to ease these pressures on amphibians for years to come.