Butterflies have wing tails that may be more than just elegant adornments. According to Science News, a new study suggests that they could be survival tools that help butterflies escape from birds that attack them.
Researchers observed that butterfly wing tails attract the attacking birds' attention, which is good since it keeps more vital body parts safer. It might also explain why they have evolved independently over time across moth and butterfly groups. Evolutionary biologist Ariane Chotard of the National Museum of Natural History in Paris said that it might explain why many butterflies have tails.
Birds Attack Butterfly Wing Tails
Chotard and colleagues wondered whether wing tails of butterflies were also a target of birds after observing that butterfly species with false head or eyespot patterns on their wings are more likely to receive attacks from predators.
In the study titled "Evidence of Attack Deflection Suggests Adaptive Evolution of Wing Tails in Butterflies," published in the Proceedings of the Royal Society B, the team reported collecting 138 sail swallowtail butterflies (Iphiclides podalirius) from the wild in Ariege, France in 2020.
Swallowtail butterflies are found throughout Eurasia and sport two black tails on hind wings with some blue spots that contrast the yellow striped color of the butterfly. Among the specimens they collected, 41% only had one wing tail and 82% had damaged tails, suggesting predators might be targeting those spindly parts.
They tested their hypothesis by keeping wild-caught songbirds called great tits (Parus major) and showing them a dummy butterfly made from real swallowtail wings to fake a body. They filmed the whole interaction and found that 43 out of 59 beak strikes were on the hind wings. Also, 23 of those strikes touched both tail and colored upper body parts of a hind wing more than any area of the body.
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Butterfly Wing Tails Are Like Lizard's Tails
The team also measured the amount of force needed to tear various sections of a swallowtail wing and found that wing tails have the most fragile veins and are the most delicate part of butterfly wings. It is most likely the part that easily breaks off when birds attack butterflies.
The findings suggest that swallowtail butterflies could deflect attacks from predators by breaking off their tails, and brittle extensions of their bodies. It is similar to how lizards sacrifice their detachable tails to hungry predators.
Although, the team has not yet checked whether there could be some disadvantages in losing one or two of the tails. Chotard said that they will still likely survive after escaping a predator, but perhaps it could affect their flight.
Science News previously reported that moth tails could also deflect attacks from echolocating bats. Both defense mechanisms of moths and butterflies with wing tails have provided them with a similar benefit against visual predators, says evolutionary biologist Juliette Rubin, who was not part of the study.
Rubin added that future studies would determine the survival benefits of wing tails to butterflies could be the next step for the researchers. Learning the answer to that question will be informative and help their conservation.
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