Radio tracking study conducted by IISc reveals greater predation risk for female katydids

In order to find out what made katydids females more attractive to the bats, the researchers, apart from field observation, carried out experiments in a controlled environment to answer key research questions on predator-prey interactions

A whistler male with radio tag attached

A study conducted by the Indian Institute of Science researchers has revealed that female katydids (bush crickets) are at more risk than their male species and fall prey to their predator, the lesser false vampire bat.

In order to understand how katydids are hunted by their predator, a group of researchers led by Prof. Rohini Balakrishnan of the Centre for Ecological Sciences fitted tiny radio tags onto these insects and tracked their movement in the canopy.

They found that female katydids are at greater risk than males because the former are frequent fliers covering longer distances.

Prof. Balakrishnan and others in earlier studies had found that there were a lot more remnants of female wings than males at the roost of the bats, suggesting that they preferred to prey on female katydids.

In order to find out what made katydids females more attractive to the bats, the researchers, apart from field observation, carried out experiments in a controlled environment to answer key research questions on predator-prey interactions.

The lesser false vampire bat

“One possibility is that bats can detect females more easily since they are usually larger than males. Second, female katydids might be more nutritious than males and therefore preferred by bats. To test these possibilities, the researchers focused on a group of katydids called “whistlers”, in which females are almost double the size and weight of the males. They presented free-flying whistler females as well as males to bats in a large outdoor cage. Surprisingly, the bats approached both males and females with equal frequency. In fact, in this experimental setup, females escaped being captured more often than males. So, it was not the size or nutritive value of the females that increased the risk of their predation,” said IISc.

Then the researchers hit on a third possibility. Perhaps the females were flying out more often. To test this, the team glued tiny radio transmitters onto the backs of male and female katydids and tracked them as they flew across trees. What they found was that females tend to move 1.5 times more frequently and 1.8 times farther than males. This led them to conclude that flying more frequently and travelling longer distances across trees may put females at a higher risk of being hunted by bats than males.

This study was published in Behavioral Ecology and Sociobiology and is the first insect radio-tracking study in India.