Water vole survival survey in Carmarthenshire and Ceredigion
A six-month survey of water vole populations is aiming to help the protected species survive in mid and west Wales.
The Wildlife Trust of South and West Wales (WTSSW) says the creatures are in decline due to habitat loss and being eaten by American mink.
The survey follows several initiatives to boost water vole populations in the area during the last few years.
Populations in Ceredigion and Carmarthenshire will be investigated.
Water voles were once common in the UK but their numbers declined in the 1990s and by 2005, 90% had disappeared.
Last September a report by the Environment Agency and Wildlife Trusts said water vole numbers had declined by a fifth in the UK since 2011.
Conservationists say that habitat loss, predation by American mink, and changeable weather was to blame.
Nia Stephens, WTSSW's water vole officer, said: "To try to save this much loved species it is important to survey them, to monitor their populations and to work out what needs to be done to improve their chances of survival such as habitat management.
"It is very important we find out where the water voles are so that we can make sure that they and their habitats are protected.
"If any landowners know of water voles on their land we would be extremely grateful if they could contact us."
About 500 water voles were released in an area close to Llangorse lake, near Brecon, in 2011.
In 2010, two new ponds were built in the Parc-y-Llyn area of Aberystwyth to try to save the dwindling water vole population there.
Ms Stephens said she hoped the survey would lead to funding of a project to carry out habitat improvement work to protect the animal.