Cows Sound Different To Each Other, Whether We Hear It Or Not
For some time now, we have known that cows call others in two ways, either via low-frequency nasal vocalizations or orally by emitting high-frequency calls. While the former is typically used in close contact or lower distress situations (think mother-calf interactions), the latter, loud calls are vocalized for distant communication or times of higher arousal. While previous research has already shown that the subtle mother-offspring calls contain individual-identity information, the high-frequency vocalizations are far more enigmatic. Commercially farmed cows undergo numerous procedures during which the animals emit said calls, but our knowledge of what they mean is limited. In this study, a mixed group of researchers set off to shed some light on the matter and, hopefully, identify a new way the well-being of cows could be assessed non-invasively.
Examples of loud, oral calls are reported during heat, separation from calf, isolation from other cows, and in anticipation of feed. The researchers here proposed that the vocalizations likely contain information about the sender’s identity and emotional state. Advertising individuality in high-frequency calls would be biologically advantageous when cows are trying to get social support from other cows within their herd. In fact, previous research suggests that unique vocal cues remain stable in kittens and deer exposed to different emotionally arousing situations, giving merit to the claim that remaining identifiable could indeed be an advantage. Should this prove to be the case with cows as well, the knowledge of how to recognize the individual from afar could assist farmers and animal welfare professionals in animal welfare detection and maintenance.
The topic is of particular interest as different emotional experiences have been shown to influence the way voices sound. A growing body of research highlights vocal indicators of emotion in pigs, horses, and goats. The results of this study showed significant differences between the acoustic structures of high-frequency calls of 13 cows who’d been listened to, and their calls recorded. Further analyses showed that the animals maintained vocal individuality across both positive (feed is provided) and negative (feed is not provided) contexts. Impressively, the statistical model was able to identify the individuals correctly above 50% of the time just by “hearing” their calls, both in positive and negative states. This is the first study to show that cows maintain vocal identity cues across a variety of farming situations.
Although not many animal advocates will find it surprising that cows produce individual calls that should, in theory, be able to be recognized by one another, this finding does suggest that we might be able to call for more non-invasive measures to assess cow welfare on farms. A step further would be to check whether, besides individuality cues, the high-frequency calls also contain emotional indicators.