Toads in a hole
Dave the natterjack is helping change the face of toad conservation. James Silvey from RSPB Mersehead explains.
The call of the wild
We head out onto the reserve at dusk carrying spot-lamps and wearing headtorches.
Just after sunset, the call begins: a long continuous churr that sounds like it would be more at home in the rainforest than the dunes of southern Scotland.
Natterjack toads are very loud. They are able to project their call up to two kilometres. But why?
Natterjacks differ from other toads and frogs, which tend to mate in the same ponds every year.
Natterjacks on the other hand, favour ‘ephemeral ponds’ - small ponds which form temporarily behind sand dunes during spring flooding. At the start of the breeding season, it’s the job of the males to track down these ponds. They then call out to the females to say, ‘Hey, they’re over here!’.
Working to give natterjacks a home means keeping their dune habitat healthy. A healthy dune system is one in which wind and tides shift the dunes around.
From one year to the next, the dune landscape should have the potential to look different, and the pools that form behind them in different positions.
This is important, because a long-established pond quickly fills with predators such as fish and dragonfly larvae, which find natterjack eggs and tadpoles delicious. For natterjacks, breeding in temporary ponds means breeding without fear of being eaten.
If, however, scrub plants such as hawthorn and buckthorn are allowed to colonise dunes, their roots fix them in place.
The shifting environment that is essential to healthy natterjack populations is lost. So we invest time and energy is clearing away the plants that might anchor dunes on the beach at Mersehead and make them less than ideal for natterjacks.
In the wake of the storm
But in 2014, the dunes shifted in a particularly unhelpful way. You may remember, this was the year of the worst winter storms on record. Ten-foot high sand dunes were washed away, and the natterjacks suddenly found their home floating far out in the Atlantic.
To make things even worse, the grassy area behind the dunes where the freshwater pools usually form became inundated with sea water – disastrous if you're a natterjack looking for somewhere to mate and lay eggs.
So we began a new project monitoring the natterjacks. We looked to see how much the storms had affected them, and to establish a population baseline that we could use to monitor their recovery in the coming years.
We’d already been surveying our natterjacks at Mersehead for 16 years, but we did this by counting the number of egg strings they laid in the artificial ponds we'd created for them. This method gives a figure that we can compare year to year and see whether the toads are doing better or worse.
But it doesn't give us an accurate number of the individual toads on the site. We'd also suspected for a while, after the number of strings in our artificial ponds had declined, that the toads had moved to naturally forming ponds elsewhere, so our figures had likely become innacurate.
Enter Dr Pete Minting. He did a PhD on natterjacks and now, as part of Amphibian and Reptile Conservation, he agreed to come and help us get a more accurate picture of our population.
Pete had previously used a new method of surveying natterjacks - taking a record of their markings and comparing them to build up an accurate picture of the individuals on a site. But he'd never used this method for a conservation project.
How do you fingerprint a toad
Each natterjack has a unique pattern of markings on their back -like a fingerprint.
Together with Pete, we set out over three nights during the breeding season, listening out for male natterjacks calling, and then carefully capturing them and photographing these unique patterns on each toad. Then came the clever part.
We fed the photos of the natterjacks into a computer programme that was initially created to help identify individual sand sharks and manta rays from their patterns. The same technique worked brilliantly with our toads.
We'd thought that the Mersehead population of natterjacks was around 50 individuals, but over the course of three night surveys, over three years, we were able to identify around 150 individual toads.
Our mate Dave
The computer programme gave each toad a code number, but there was one unusual natterjack that we gave a real name to.
All natterjacks have a pale yellow line that runs down their backs. But on this particular toad, the line had a bend in it, where it went round a large wart. This gave the line the shape of a letter ‘d’. So we named him Dave.
And we feel particularly affectionate about him, as we've captured him during all three years of surveying!
RSPB membership helps give natterjacks a home
It's thanks to people like you that we're able to create ideal habitat for natterjack toads at Mersehead, and to carry out pioneering conservation projects like this. Our members fuel everything we do through their support.
By joining the RSPB today, you can not only help keep Dave the natterjack and his young safe, you can give a home to thousands of species at sites across the UK, and even overseas, through our international conservation projects.