Dramatic decline of northern bat Eptesicus nilssonii in Sweden over 30 years
We monitored northern bat Eptesicus nilssonii (Keyserling & Blasius, 1839) acoustically along a 27 km road transect at weekly intervals in 1988, 1989 and 1990, and again in 2016 and 2017. The methodology of data collection and the transect were the same throughout, except that the insect-attracting mercury-vapour street-lights along parts of the road were replaced by sodium lights between the