Their individual voices help them as a herd.

At Wolverton Farm in New South Wales, Australia, 18 cows leaned into a microphone and testified. The herd, all Holstein-Friesian heifers (a Central European breed), were studied over a five-month period, and their testimony was recorded by acoustic biologists trying to understand how cows communicate—specifically, how their individual voices change depending on the situation at hand.

Now the research, published in the Nature journal Scientific Reports, has confirmed that each cow has a unique moo, and provided the first evidence that they maintain it in a variety of social contexts.

“In the dairy industry, we’re seeing increasing herd sizes,” but less attention being paid to individual animals, says Alexandra Green, a doctoral candidate at the University of Sydney and lead author of the paper. “We need to think of novel ways to look at their welfare.”

While animal vocalizations have been studied for decades, livestock are a relatively new subject. The vocal relationship between mother cows and their calves has been fairly well documented, but the unique voice of each animal in a herd—and how those voices function in a social setting—hasn’t received much study till now.

Green’s work looked at cow communication in five different contexts: when the heifers were in heat, when they were excited to eat, when they were denied food, when they were isolated from the herd but could see the other cows, and when they were isolated but couldn’t see the others.

“We found that their voices are individually distinct,” Green says. “But further to that, they’re able to maintain these individual characteristics across the contexts.”

New research confirms that cows have unique voices, which they use to express happiness, displeasure, and a range of other emotions. Courtesy Lynne Gardner / University of Sydney