Developing artificial nest boxes for a large aquatic mammal

Nest boxes and other human-made constructions have been widely and successfully used as conservation tools to increase nest-availability for hollow-dependent fauna, especially birds and some small and medium mammals. This study applies, for the first time, this recovery technique to a large aquatic mammal, aiming to improve resting, birthing and nursing sites of endangered Saimaa ringed seals (Pusa hispida saimensis) by developing artificial nest boxes. This landlocked subspecies' breeding habitat is severely affected by climate change. Because of mild winters, sufficient ice and snow habitat for subnivean lairs is lacking. In this study, floating nest boxes were developed. It was found that free-ranging ringed seals accept nest boxes as sites for resting, birthing and nursing. Thirty-four boxes in total were offered during six successive breeding seasons. Almost half (47%) of the available boxes were used by seals, and two pups were born and reared in the boxes during the 6-year study. Our study indicates that this innovative technique can be a valuable tool for the Saimaa ringed seal conservation in the changing climate.