Female bushcrickets at higher predation risk, reveals radio-tracking study

A team of researchers at the Indian Institute of Science (IISc) has, in a recent study, established that female katydids (bushcrickets) are at a greater predation risk than males, possibly because they fly more frequently and cover longer distances.

The researchers, led by Rohini Balakrishnan, Professor at the Centre for Ecological Sciences (CES) in IISc, fitted tiny radio tags onto these insects and tracked their movement in the canopy to understand how they are hunted by their predator, the lesser false vampire bat.

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The study was published in the peer-reviewed scientific journal Behavioral Ecology and Sociobiology. Harish Prakash, postdoc at CES and an author of the paper, said this is India’s first insect radio tracking study.

Earlier studies done by Balakrishnan and others have found that lesser false vampire bats – native to south and southeast Asia – preferred to prey on female katydids though they are “usually silent” unlike the “conspicuous” males, IISc said in a statement.

The researchers followed two possibilities – females, usually larger than males, attracted more attention and female katydids could be more nutritious than males – that were discarded after an experiment with a group of katydids called “whistlers”.

Tracking movement

To test a third possibility, that the females could be flying out more often, the team glued tiny radio transmitters onto the backs of male and female katydids and tracked them as they flew across trees. They found that females tend to move 1.5 times more frequently and 1.8 times farther than males, leading the researchers to conclude that flying more frequently and traveling longer distances may put females at a higher risk.

“In systems where males produce conspicuous acoustic signals and females move silently, it has been assumed that males rather than females perform the higher-risk behaviours,” Balakrishnan said. Contrary to this view of risk-taking males and risk-averse females, the study shows that female katydids might be at greater risk of predation.

Kasturi Saha, PhD student at CES and corresponding author on the paper, suggested a possible reason for these frequent, long flights – “The females may move around in search of mates, as well as suitable egg-laying sites.”