Relative Performance and Practicality of Night Vision Aids and Naked Eye Counts for Emerging Bats

The Bat Conservation Trust’s Good Practice Guidelines now require the use of night vision aids for bat emergence surveys. In light of this, we compared the efficacy and efficiency of three bat emergence roost count methods: naked eye counts, infrared recording playback counts and thermal recording playback counts. Emergence surveys were performed at four soprano pipistrelle (Pipistrellus pygmaeus) maternity colonies across Scotland during the breeding season. The use of either night vision aid (thermal or infrared) significantly improved the rate of bat detection relative to the naked eye. However, when it was darkest (60–90 minutes after sunset), thermal outperformed infrared.