Being catfished is never fun, but one animal takes deception to an entirely new level.
"Our paper shows that male superb lyrebirds regularly create a remarkable acoustic illusion of a flock of mobbing birds and, in so doing, create a complex but potent cue of a hidden predator," said lead author Anastasia Dalziell, a researcher in the Cornell Lab of Ornithology.
Some background — Male lyrebirds are infamous for their spot-on imitations.
In 2009, a clip from BBC's Planet Earth documentary series showcasing lyrebird vocalizations went viral. The video demonstrated how lyrebirds could pick up on nearby human sounds and eerily recreate them, from a camera shutter to a whirring chainsaw.
In order to lure female songbirds toward his colorful feathers, the male lyrebird also imitates the sounds of other bird species, such as the kookaburra. The male lyrebird's deception is so thoroughly convincing that he can even fool actual kookaburras.
But in this study, researchers wanted to focus on an even more deceptive vocalization the songbird produces during potential sexual encounters: an imitation of a flock of mobbing birds, which typically occurs when a predator is around — not during mating.
How they did it — Researchers first tested whether the male lyrebirds' vocal imitations were really that similar to a flock of mobbing birds.
According to the study, "mobbing flocks are formed when several individuals of the same or different species harass a predator."
The scientists tested this similarity using a field playback experiment. They observed the reactions of other birds to what the researchers labeled as the "D-song," which the scientists played through speakers. During the D-song, the male lyrebird dances by flipping his tail over his head, typically on a display mound where the male entices the female. He also mimics the complex vocalizations of the mobbing bird flock.
Several birds approached after hearing the D-song, suggesting the mimicry was successful.
Then came the more riveting part of the experiment. Researchers took recordings of the sexual encounters between male and female lyrebirds to better understand how mimicry played a role in copulation.
What's new — The findings from the field shocked the researchers.
"Astonishingly, males only mimic a mobbing flock in two contexts: when a potential mate tries to leave a displaying male without copulating, or during copulation itself," Dalziell said.
"These two moments are key to male reproductive success, suggesting that mimicking a mobbing flock is a crucial sexual behavior for males."
Notably, the males do not produce these fake vocalizations prior to sex, lending support to the idea that is more of a last-ditch effort to entice the females rather than a way to encourage them to view their colorful feathers prior to mating.
The researchers also found that there were no actual predators nearby during when the males mimicked the mobbing call, confirming that the mobbing call sounds are pure deception on the part of the male.
Why it matters — Scientists have often championed the sexual selection theory that Charles Darwin, the father of evolution, popularized.
As part of the sexual selection theory, Darwin offered up the idea that "taste for the beautiful" drives reproduction. For example, many male birds display prominent, colorful feathers, supposedly as a way to entice females to mate.
However, the researchers' findings actually support another competing idea: the sensory trap hypothesis. This is when "one sex uses deceptive mimicry to manipulate the opposite sex into mating," the study authors write.
The sensory trap hypothesis argues that complex sexual signals — such as the male lyrebird's imitations of a mobbing flock — occur as a result of "antagonistic co-evolution."
Here's how it works: Males imitate other species through their vocalizations to attract female songbirds.
The females, in turn, become more clever, adapting to the male's mimicry. This adaptation forces the males to produce ever-more-complex signals to trick the female into mating, leading to a tense situation that the researchers have dubbed a "coevolutionary arms race."
"In this way the elaboration of the complex avian vocalizations we call 'song' could be driven by sexual conflict, rather than a female’s preference for male extravagance," the study suggests.
The researchers also suggest these complex vocalizations could be an indication of higher-level cognitive functioning in lyrebirds, which exceeds the normal vocal learning found in most songbirds.
What's next — One particular aspect of the male lyrebird's behavior still puzzles the researchers.
Through their fieldwork, the scientists noticed that male lyrebirds would cover a female lyrebird's face, possibly as a way to prevent her from discovering the male's ruse.
That question — and others, like how this mimicry ultimately benefits male lyrebirds — still remains unanswered. To better understand the nature of this mimicry, researchers want to conduct further experiments to test females' response to mobbing flocks, "particularly in non-sexual contexts."
Researchers also suggest doing a cross-comparison of sexual mimicry across the animal kingdom.
For example, topi antelopes similarly raise "false alarm" calls when potential mates leave them. Likewise, Asian corn borer moths mimic the sounds of predatory bats, causing females to freeze up, giving the male the opportunity for sex.
For now, we can add this study to the ever-growing list of strange sexual behaviors that researchers have discovered — a Cyrano de Bergerac in reverse, mimicking danger in exchange for companionship.
Abstract: Darwin argued that females’ ‘‘taste for the beautiful’’ drives the evolution of male extravagance, but sexual selection theory also predicts that extravagant ornaments can arise from sexual conflict and deception. The sensory trap hypothesis posits that elaborate sexual signals can evolve via antagonistic coevolution whereby one sex uses deceptive mimicry to manipulate the opposite sex into mating. Here, the success of deceptive mimicry depends on whether it matches the receiver’s percept of the model, and so has little in common with concepts of aesthetic judgement and ‘‘beauty.’’ We report that during their song and dance displays,10 male superb lyrebirds (Menura novaehollandiae) create an elaborate acoustic illusion of a mixed-species mobbing flock. Acoustic analysis showed that males mimicked the mobbing alarm calls of multiple species calling together, enhancing the illusion by also vocally imitating the wingbeats of small birds. A playback experiment confirmed that this illusion was sufficient to fool avian receivers. Furthermore, males produced this mimicry only (1) when females attempted to exit male display arenas, and (2) during the lyrebirds’ unusually long copulation, suggesting that the mimicry aims to prevent females from prematurely terminating these crucial sexual interactions. Such deceptive behavior by males should select for perceptual acuity in females, prompting an inter-sexual co-evolutionary arms race between male mimetic accuracy and discrimination by females. In this way the elaboration of the complex avian vocalizations we call ‘‘song’’ could be driven by sexual conflict, rather than a female’s preference for male extravagance.