The science of howls: how wolves communicate
Posted on 11 March 2016
By Marshall Swearingen
BOZEMAN - A Montana State University researcher is part of a team that has found dialects in the howling behavior of wolves and other canid species.
Sara Waller, associate professor of philosophy in the College of Letters and Science, together with an interdisciplinary team from universities in India, Spain, the U.K. and U.S., has co-authored the paper "Disentangling canid howls across multiple species and subspecies: Structure in a complex communication channel," published recently in the journal Behavioural Processes.
The study takes a groundbreaking, quantitative approach to understanding canid howling, and has garnered media attention from NPR and other national news sources.
Researchers have long been able to identify local populations of canids, such as Yellowstone National Park's wolves, by their howls. But howling behavior varies significantly across those populations, as well across different species.
"This study is one of the first, larger attempts to sort though those local differences" and establish a more objective framework for understanding howling behavior, said Waller.
The researchers analyzed audio recordings of more than 2,000 howls from 13 canid species, including Mexican wolf, New Guinea singing dog, Golden jackal and the species of wolf that inhabits Yellowstone National Park. Waller contributed coyote howls recorded in Montana and other states.
The howls' pitch and other characteristics were quantified, and a computer algorithm was used to classify 21 unique "howl types." This allowed howl types to then be quantitatively compared among different species.
A major finding of the study is that howling behavior is consistent enough across local populations — but different enough across species — that it can be used to reliably identify those species.
"Just howls can tell us who is out there," said Waller.
The study is an outgrowth of the Cooperative Predator Vocalization Consortium, an international, collaborative group that Waller helped to launch in 2014 in order to research communication by animals that cooperatively hunt.
"Because I'm a philosopher, I work with the group on the big, broad questions," Waller said, including "how we can learn about the evolution of language."
Traditionally, philosophy has regarded language-based cognition as an exclusively human trait. But the study of canid howling is one of many ways in which that assumption is now being challenged.
"To collaboratively hunt, you have to have a lot of sophisticated cognition," including keeping track of the location of other canids in the pack and their proximity to the prey, said Waller. Complex howling behavior is similar in many ways to human language, she said, so the study of howling may provide insights into the fundamental processes by which language forms and operates.
"We're taking the training in philosophy and making it more broadly applicable," said Susan Cohen, chair of MSU’s Department of History, Philosophy and Religious Studies, adding that the department’s professors also collaborate on studies involving astrobiology and biomedical ethics. "Dr. Waller is well-known in her field for studying the way that different animal groups communicate among themselves, and how that affects how humans view them."
The study has implications for conservation. In Montana, where the predatory habits of wolves and coyotes sometimes put those animals in conflict with livestock growers, certain howl types could be recorded and played back in order to discourage the canids from inhabiting areas used by livestock, Waller said.
According to Waller, the study creates a foundation for future research exploring the implications of the diverse howling habits of canids. "It makes us ask bigger questions."