To investigate why lesser false vampire bats (LFVBs) are more attracted to female katydids, researchers from the Indian Institute of Sciences (IISc) conducted a two-year study on the prey patterns of these bats.
The study involved the first radio-tracking research in India, where radio transmitters weighing 0.15g were attached to both male and female katydids also known as grasshoppers.
The team, from the IISc Center for Ecological Sciences, observed the pattern of these insects over two seasons between 2020 and 2021 in the village of Mala, located near Kudremukh National Park.
The Indian Institute of Science (IISc) conducted a research study, which was published in the journal Behavioral Ecology and Sociobiology, to explore why Lesser False Vampire Bats (LFVB) feed more on female katydids.
Study finds female katydids face predation risk
These tiny nocturnal insects, weighing between 4 and 6 grams, are difficult to observe due to their size, camouflage ability, and nocturnal behaviour.
Male katydids emit acoustic signals to attract females during mating season, which can attract the attention of eavesdropping predators such as insectivorous bats.
However, the females have to fly in response to the calls of the male to locate them, while the males can identify the females through tremors. The study found that female katydids move more frequently and farther than males, exposing them to more danger as they rely on camouflage to avoid predation.
Despite their larger size, bats feed on female katydids because they are easier to catch. Acoustic cues from male katydids are necessary to attract females, and females fly to answer the calls, which can provide them with a “wedding present” in the form of protein-rich food, motivating them to fly despite the risk.
The study sheds light on the decision-making process of both predator and prey and the evolution of a system in which males produce species-specific calls that only females of their species can understand.
Female katydids at higher risk of predation
Researchers at the Indian Institute of Science (IISc) Center for Ecological Sciences (CES) conducted a study to understand why female katydids are more attractive to little free-tailed bats (LFVBs) than males.
Kasturi Saha, a CES student and the first author of the study, said that LFVBs are insectivorous and that the team found more remains of female wings than males. They speculated that females might be larger and more nutritious, making them the bats’ preferred prey.
When the researchers presented free-flying male and female katydids from a group of whistlers to bats in a large outdoor cage, the bats approached both sexes with equal frequency. Other experiments related to tracking the movement of katydids using radio transmitters showed that females move 1.5 times more and 1.8 times farther than males, making them more vulnerable to predation by bats.
The study suggests that female katydids fly frequently and longer distances in search of mates and suitable places to lay eggs, putting them at greater risk of being hunted by bats.
Katydids and bats’ interaction studied
In a 2015 CES study, researchers found that Megaderma spasma bats consumed significantly higher amounts of female leafhoppers than males. The researchers wondered why this was, given that the males were able to call while the females were silent. Bats showed a 100% response to female katydid flight, but less than 50% response to male katydid calls.
In 2023, a study was conducted to determine which sex of katydids flew further or further, and whether the bats preferred to approach males or females.
The study was conducted in two parts, with the first part observing the movements of bats and katydids in an enclosure in the Mala village of Karnataka. The researchers found that the bats approached the male and female katydids equally, but the females displayed better escape strategies.
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