Sunday, 11 November 2018

How porpoise sounds helped researchers test acoustic devices

by Sue Palminteri on 2 November 2018

A team of scientists used playbacks of recorded and artificial porpoise clicks to develop an adaptable method to assess the area in which acoustic monitoring devices can reliably detect these sounds

Researchers need to know how far away they can expect acoustic data loggers to capture the sounds of target animals to estimate the density of those animals from the recordings.

The cetacean data loggers could reliably detect the click signals up to nearly 200 meters (656 feet), which translated to a circular sampling area of 11 hectares (27 acres) per device.

The data logger algorithms could correctly classify the clicks as porpoise sounds only up to 72 meters (236 feet), representing a reliable sampling areas of just 1.6 hectares (4 acres) that could be used to estimate the density of a specific species, an issue affecting researchers working with more than one echolocating species.

An international team of scientists has developed a method to assess the detection area of acoustic monitoring devices.

These instruments, which can record the calls and other sounds of animals 24/7, have enhanced research on various cryptic yet vocal species, including batsbirds, frogs, bees, and tigers. Passive acoustic monitoring (PAM) units also work underwater to detect the presence or abundance of species such as whales and dolphins.

An acoustic device counts only those animals that vocalize within the range of its sound detectors, missing any animals that call beyond its reach. However, few studies have quantified the percentage of vocalizations in a given area that these devices actually capture.

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