Should you encounter a herd of cows munching on a field of grass, you might very well hear them emit some emphatic “moos.” It’s hard for humans to decipher these cow calls, but a new study shows that our bovine buddies communicate using unique voices, which remain consistent across a range of emotional circumstances.
Previous research has shown that mothers and calves show individuality in their vocalizations, helping moms recognize babies’ calls, and vice versa. But Alexandra Green, a PhD student at the University of Sydney’s School of Life and Environmental Sciences, wondered whether cows also display unique voices in other aspects of their lives. So she headed to a free-range farm on the university’s campus, equipped with headphones and a shotgun mic.
Green spent five months hanging out with a herd of Holstein-Friesian heifers, capturing their moos and lows. “My friends and family think it’s a bit funny,” she tells Liam Mannix of the Sydney Morning Herald, “but they are really intrigued by the results. Not many people think about this, I guess.”
In total, Green and her colleagues recorded 333 high-frequency vocalizations from 13 heifers, none of which had been pregnant. The calls were collected during a number of different situations, like when the cows were in heat and when they were anticipating a tasty meal, which the researchers identified as “positive” contexts. Calls were also collected when the animals were denied food, when they were physically isolated from their fellow herd members, and when they were both physically and visually isolated from the rest of the herd, which the researchers identified as “negative” contexts.
Using acoustic analyses programs, the researchers determined that the cows maintained individual vocal cues, whether they were communicating arousal, excitement or distress. It is “highly likely,” the study authors write, that cows are able to recognize other members of their herd through these calls. Listening back to her recordings, even Green could pick up on differences in the vocalizations.
“I could definitely tell them apart,” she tells Mannix.
The researchers’ findings align with previous observations indicating that cows are profoundly social creatures, which live in herds with observable hierarchies, experience long-term effects when they are separated from their mothers at an early age, and even learn better when they have their buddies around. It makes sense, in other words, that the animals would use vocal cues to aid in recognition of other herd members.
“In one sense, it isn't surprising they assert their individual identity throughout their life and not just during mother-calf imprinting,” Green acknowledges. “But this is the first time we have been able to analyse voice to have conclusive evidence of this trait.”
The study also adds to our understanding of the richness of cows’ social and emotional lives, an important finding at a time when cow welfare is severely compromised by mass farming practices. Farmers could use cow vocalizations to detect the wellbeing of distinct cattle, the study authors say—but treating cows as individual creatures with unique needs is often not a priority of industry farms.
“In the dairy industry, we’re seeing increasing herd sizes,” Green tells Isaac Schultz of Atlas Obscura. “We need to think of novel ways to look at their welfare.”