Salty Water Threatens Natterjack Toad Recovery
Elevated salt levels in water may be hindering the recovery of one of the United Kingdom's rarest amphibians by rendering former breeding sites unsuitable for their survival, according to a recent study.
The natterjack toad is currently found in only a few locations across the UK.
In Scotland, its sole remaining habitats are situated along the Solway Coast, including the RSPB's Mersehead Reserve near Southerness.
Researchers discovered that water from former breeding sites in south-west Scotland exhibited salt concentrations linked to unsuccessful hatching, reduced growth, and altered development of the toads.
Research Details and Findings
The study was published in the academic journal Ichthyology and Herpetology and was led by Dr Frances Orton, an environmental biologist at Heriot-Watt University in Edinburgh.
"Natterjack toads have declined across the UK, not just in Scotland,"
"We wanted to find out why these tiny toads were surviving in the nature reserve in Dumfries and Galloway, but had disappeared from sites along that coast.
"We used anecdotal reports from farmers and local wildlife groups to identify former breeding ponds in Caerlaverock, Southerness and several farms."
The research team collected and analysed water samples from Mersehead, where the natterjack toad population persists, as well as from other sites.
They measured parameters including temperature, pH, and salinity, and exposed natterjack toad spawn to water from each location.
"Some of the former breeding sites had such a high level of salinity that no embryos survived to hatching.
Some weren't as lethally salty, but what we saw there was that the toads were much smaller.
That doesn't sound like a big deal, but when you're a frog, size really does matter. 95% of tadpoles are eaten by predators.
For the 5% that make it to the next stage of development, they need to be as big as possible for a chance at survival."
Implications for Conservation Efforts
Dr Orton noted that these findings could inform and improve conservation strategies aimed at increasing natterjack toad populations.
"Until now, a lot of natterjack toad restoration efforts have focused on improving terrestrial habitat, like clearing scrub or controlling vegetation,"
"That's still important, but now we know that unless the salinity of the water is tackled, the tiny toads will have no chance of survival."
The biologist emphasized the urgency of taking action.
"Amphibians are the fastest-declining vertebrate group globally,"
"They've been around for 350 million years, but now species like the natterjack toad are disappearing, quickly.
They play a huge ecological role as both predators and prey - they feed lots of animal species and, as gardeners will tell you, they eat lots of slugs and midges.
Natterjack toads are on the verge of extinction and it's vital we understand ways to protect and boost the populations that remain."
The research was conducted by Dr Orton and her team across seven sites in Dumfries and Galloway, with support from the Carnegie Trust and NatureScot.
