Finding footprints and signs of activity will tell you what’s happened on last night’s hunt, but once the animal vanishes into the tangled undergrowth the only way to track it is to stand and listen for a call. Not from the tiger itself, but an alarm call from potential prey alerting their fellow animals to the location of the predator. In this way, Webb and his crew could track the calls and therefore the tiger’s progress through the jungle. The team’s local guides would then be able to predict its path and where the tiger was likely to emerge.
Webb’s team found one of the most useful vocal indicators were langur monkeys, who amazingly use a barking alarm call for leopards and a different call for tigers. Chital deer, favourite prey of tigers, respond to the langur alarm call and begin a persistent barking of their own. One of the most defined calls to listen for when tracking is given by sambar deer, who make a guttural squeak when they become aware of a tiger in the vicinity. An explosion of alarm shouts from different animals that echoes around the jungle indicates that the tiger has been hunting.
Webb was also surprised at how vocal the tigers were themselves, calling to each other, growling during mating and roaring afterwards.
Humans have always had a desire to communicate with animals, but a wide vocal range is beneficial to other inter-species communication too. Learning new sounds means parrots, for instance, are able to change their vocalisation to blend in with new flocks and learning new sounds can also be a way of showing off brain power in a mating ritual. Beluga whales and dolphins learn hundreds of new vocalizations throughout their lives and orangutans and even elephants have been recorded appearing to imitate human speech.
Not all animals can do it, however; there are particular brain circuits that control the muscles for vocalizations, and only some animals have them. A set of over 50 genes showed a similar pattern of activity in the speech-control centres of several vocal learners, including humans, parrots, songbirds and hummingbirds. This means humans use the same genes to speak as songbirds use to sing. Animals that can’t learn new sounds, like chickens and macaques, don’t activate these genes in the same way,
As Webb puts it, it’s very exciting to home in on “monkey frequency” and use the animal’s calls to track the progress of another animal you cannot see. Rather than talking to the animals, as Dr Doolittle said, maybe we should focus on listening to them.
