“Whooo goes there?!” Do owls know who is calling to them? A study on owl vocalization relative to population

Post based on: The assessment of biases in the acoustic discrimination of individuals Pavel Linhart (2017)

Owl live lives that are largely based on sound. This lets them have an almost omniscient view of the world around them. Being able to hear their world from a distance lets them stay in one location, allowing them to stay safely hidden while not having to fly around expending crucial energy to monitor their territories.

Pavel Linhart of the University of South Bohemia has studied many animal vocalizations to try and understand all the things they are able to communicate. Sound samples of animals are recorded, analyzed, and characteristics are removed with an algorithm to determine the contents of the animal’s message. These messages can contain body size, emotional states, and the identity of individuals among other things. Little Owls made a great species for Linhart to study. They live close together, do not migrate, and stay in a relatively small range, making them easy to work with.

The sounds are looked at by duration, frequency, and “colorations,” which seem to be small changes to basic calls. These differences can be analyzed and used to help determine both the number of individuals in a population, but also who those individuals are, with the goal being to allow individual monitoring through sound, basically being able to see the sounds of owl (or other animals) the way the owls themselves do; to know who is where and doing what.

One of the key takeaways from his research is that variations between individuals grow along with the density of the owl population. The conclusion drawn is there are benefits from having uniquely distinct sound signatures for individuals. Owls can communicate their presence to others and be identified as known owls, saving them the energy of investigating potential intruders to their territory. Owl calls do not change much over time, so even if they only encounter each other once a year for mating season, they can identify each other over great distance, year after year. There is also benefit to researchers, as it brings them closer to being able to use those same sounds to monitor individual animals using recorded sound.

To demonstrate some of the variations between individuals, Linhart has also published a Little Owl Match Game. There are 16 “cards,” each containing a recording of a Little Owl (and some simulated owls) for you to try to successfully match the calls as if you where the algorithm trying to match the sound to a known individual. You can play the game here.

In a related story, researcher Karla Bloem was studying Great Horned Owl calls when she met Baroque music specialist Marjon Savelsberg, who fell in love with the sounds of owl calls and became a virtual assistant volunteering to try to pick out individual owls by their vocalizations.

Her musical training made her very successful to pick out these individual variations between individual calls. She is now using her abilities to work with Eurasian Eagle Owls in her native Netherlands.