Toad numbers aren't growing because of salty water

The natterjack toad is one of the UK's rarest amphibians.

A new study has found that their survival and size is affected by salt levels in the water where they live.

Experts think this could help explain why their numbers aren't growing, with the water in some of the sites where they previously lived becoming unsuitable.

These toads are only found in a handful of locations, and their numbers could drop more if there aren't suitable grounds for them to breed on.

The project was led by Dr Frances Orton, an environmental biologist at Edinburgh's Heriot-Watt University.

"Natterjack toads have declined across the UK, not just in Scotland," she said.

"We wanted to find out why these tiny toads were able to live in the nature reserve in Dumfries and Galloway, but had disappeared from sites along that coast.

The study took samples at various sites to check their salt levels

The scientists found that the levels of salt in water was linked to failed hatching, smaller growth and altered development.

The research has been published in the academic journal Ichthyology and Herpetology.

Dr Orton said: "Until now, a lot of natterjack toad restoration efforts have focused on improving terrestrial habitat, like clearing scrub or controlling vegetation."

But it's now hoped that the findings could provide the first step towards reviving numbers.