Summary
Emerging technologies based on the detection of electro-magnetic energy
offer promising opportunities for sampling biodiversity. We exploit
their potential bye showing here how they can be used in bat point
counts - a novel method to sample flying bats - to overcome shortcomings
of traditional sampling methods, and to maximise sampling coverage and
taxonomic resolution of this elusive taxon with minimal sampling bias.
We conducted bat point counts with a sampling rig combining a thermal
scope to detect bats, an ultrasound recorder to obtain echolocation
calls, and a near-infrared camera to capture bat morphology. We
identified bats with the first dedicated identification key combining
acoustic and morphological features, and compared bat point counts to
the standard bat sampling methods of mist netting and automated
ultrasound recording in three oil palm plantation sites in Indonesia,
over nine survey nights. Based on rarefaction and extrapolation sampling
curves, we show that bat point counts were the most time-efficient and
effective method for sampling the oil palm species pool. Point counts
sampled species that tend to avoid nets and those that are not
echolocating, and thus cannot be detected acoustically. We identified
some bat sonotypes with near-infrared imagery, and bat point counts
revealed strong sampling biases in previous studies using capture-based
methods, suggesting similar biases in other regions might exist. While
capture-based methods allow to identify bats with absolute and internal
morphometry, and unattended ultrasound recorders can effectively sample
echolocating bats, bat point counts are a promising, and potentially
competitive new tool for sampling all flying bats without bias and
observing their behavior in the wild.
Short summary : Bat point counts are a modern, novel sampling
method combining thermal, ultrasonic, and near-infrared sensors. It
rivals and potentially out-performs mist-netting and passive acoustic
monitoring. We showcase the unique advantages of the method offers and
how it shines a new light on all types of flying bats.
Keywords : biodiversity sampling, Chiroptera, near-infrared,
point count, thermal, ultrasound