Words don’t come easy, but calls can be key

Talking animals are in the news, says Richard Collins

Wiki, a female orca in the Antibes Aquarium, can utter “hello”, “bye bye” and “Amy”, the name of her trainer, through her blow-hole. Killer whales copy each other’s sounds, so this is a case of mimicry, not conversation.

Wiki joins a handful of mammals able to reproduce human-like speech. In 1984, a captive beluga whale named Noc began imitating human voices. Beluga whales, “the canaries of the sea”, are renowned for mimicry. 

Another sea mammal, Hoover, the “talking seal” of the New England Aquarium, produced similar sounds, and Koshik, a domesticated Asian elephant in Thailand, also did so. Few mammals, however, are really strong on oratory; their vocal apparatus isn’t up to the job.

A schoolboy impersonating the teacher may be only slagging, but is the stand-up’s lampooning of politicians just harmless fun? What other subversive purposes does

mimicry serve? For one species of songbird, impersonating its neighbours can mean the difference between life and death.

The “flying predator call” is a quiet unobtrusive “seep” uttered by the birds in your garden. The sound is transmitted, across the species divide, when a hawk or falcon appears. It seems to be triggered automatically, like a burglar alarm. However, the findings of an Australian study suggest that, for one species, the alarm process is no mere knee-jerk reaction.

The brown thornbill is tiny songbird living in the woods and gardens of eastern Australia. During the nesting season, it runs the gauntlet of pied currawongs, magpie-like members of the crow family. Currawongs raid thornbill nests, eating eggs and chicks, but they don’t have it all its own way. They too have a lethal enemy; the goshawk. Constantly on the look-out for this big silent killer, currawongs eavesdrop on the calls of smaller birds; they listen out for the chorus of alarm calls produced when a goshawk appears.

Branislav Igic of the Australian National University used play-back recordings to study bird vocalisations in the Canberra Botanic Gardens. He found that, when a

currawong approaches, thornbills don’t just utter their own alarm calls, they mimic those of other species as well. This, apparently communal, response fools the currawong into thinking that a goshawk is on the prowl. The ruse won’t deter the currawong for long but it delays discovery of the nest, giving the chicks time to escape and hide. Recordings of mimicked alarm call choruses, played to

currawongs, kept them at bay for twice as long as ones where only thornbill predator calls were used.

But what goes on in a bird’s mind when it hears an alarm call? Is its response automatic, like that of a motion-sensitive security light? Toshitaka Suzuki, of Kyoto University, claims that the Japanese tit ‘can retrieve a visual image from specific alarm calls’. Somebody shouting ‘snake’ conjures up a mental picture of the reptile, especially if you happen to be walking barefoot in long tropical grass. Suzuki claims that birds have a similar ability.

When researchers moved a stick slowly, snakelike, up a tree trunk or along the ground, the tits in the vicinity, took no notice of it. However, if snake-specific alarm calls were played at the same time, the birds

immediately investigated the stick. They approached it closely. Spreading their wings and tail, they hovered over it. 

This, the researchers claim, shows that the calls conjure up the mental image of a snake. Our great tit is very closely related to the Japanese species. Can it too visualise danger from hearing warning calls?

T. Suzuki. Alarm calls evoke a visual search image of a predator in birds. PNAS. 2018.

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