When a wolf or dog howls, to us they might all sound the same. But researchers from the University of Cambridge have developed computer algorithms that have allowed them to analyze the howling from different species and subspecies of “canids” – which includes wolves, dogs, and jackals – and distilled them down to 21 different types. The way that these types are then mixed during a vocalization can then be used to identify the specific animal that's making them.
These distinct differences effectively amount to, the researchers say, a “vocal fingerprint” for each species. The study, published in the journal Behavioural Processes, looked at a total of 2,000 canid howls made by 13 species, recorded from both wild and captive individuals from around the world. They then ran them through the computer algorithms to determine and compare the modulation patterns in the howls, such as their pitch and fluctuation. From this, they determined that there were 21 separate howl types among the canids investigated. 
It was the frequency that each individual species, and even subspecies, made these types of howls that gave them away. For example, the timber wolf from the eastern U.S. uses low, flat howls, which is in contrast to the critically endangered red wolf from the southern U.S. which instead displays high, looping vocalizations. The researchers describe these differing combinations as contrasting dialects.
While some species’ howls were found to be very distinct, they also discovered that others were incredibly similar. The red wolf, for example, produced noises much like the coyote with which they share the same habitat. This, they claim, could help explain why the conservation efforts to save the red wolf have failed, if the animals are mistaking coyotes for their own kind and interbreeding. It could potentially also offer a solution: If conservationists can take advantage of subtle differences in calls between the two species, perhaps they could find a way to keep the two populations apart.
The hope is that by understanding the differences, it could allow scientists to better track and manage wild wolf populations. “We are currently working on research in Yellowstone National Park in the U.S. using multiple recording devices and triangulation technology to try and pick up howl sounds and location,” explains Dr. Arik Kershenbaum, who led the study. “In this way we might be able to tell whether certain calls relate to distance communication or pack warnings, for example.”
If they can work out the different meanings behind certain calls, this could aid in limiting conflict with predators, namely humans. For example, if they can work out what howls relate to territorial displays or marking, farmers might be able to play them in order to encourage wolf packs to stay clear of their land.
Image in text: The red wolf is considered critically endangered, in part because of hybridization with coyotes. Valarie/Flickr CC BY-NC-ND 2.0
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