Batting for food security
In the columns last week, I had dwelt upon the unheralded role played by small urban bats in controlling insects, mosquitoes and termites. Scientific research conducted outside of India has proved its role through evidence, but we are still obsessed with burly tigers and elephants, adorable dogs and pigeons.
Tens of millions of brown planthoppers, an insect pest on rice crops in South-East Asia, are consumed by wrinkle-lipped free-tailed bats (Chaerephon Plicatus) at night-time in Thailand. A seminal study conducted by Supawan Srilopan, Sara Bumrungsri and Sopark Jantarit of the Prince of Songkla University, Thailand, established that the bat was an important biological suppression agent of planthoppers.
Thai researchers analysed the diet of bats from two caves that differed in the percentage of surrounding land area occupied by rice fields (70% versus 22%). Bat fecal pellets were collected monthly for a year. A total of 720 pellets were analysed and the result revealed that bats daily fed on at least eight insect orders, including Coleoptera, Homoptera, Hemiptera, Diptera, Lepidoptera, Odonata, Hymenoptera and Orthoptera. It was found that Homopterans comprised greatest diet volume in the rice-growing season, whereas Coleopterans were most abundant in bat diet when rice fields were fallow. Moreover, most homopterans were identified as brown planthoppers, according to their research paper titled, ‘The Wrinkle-Lipped Free-Tailed Bat Feeds Mainly on Brown Planthoppers in Rice Fields of Central Thailand’.
“To the estimate relative numbers of brown planthoppers consumed each month, the number of genitalia of male brown planthoppers was counted. We recorded the greatest numbers of genitalia during rice-planting period, with an average of four genitalia per fecal pellet. Examining both the percent volume and percent frequency of each insect order in the diet of the bat revealed that the two study caves were no significantly different, even though the proportion of surrounding active rice fields was different. Our result suggests that tens of millions of brown planthoppers are consumed by this bat species each night,” Srilopan told this writer.
The field study corroborates the earlier hypothesis from 2014 put forward by researchers, Thomas Wangner, Kevin Darras, Sara Bumrungsri and Alexandra-Maria Klein, stating that the bat pest control contributes to food security in Thailand and that the sustainable production is critical to food security, especially in Asia, effective biocontrol of major rice pests such as White-Backed Planthopper is of eminent importance.
“In Thailand, this single species (wrinkle-lipped free-tailed bat) interaction may prevent rice loss of almost 2,900 tons per year, which translates into a national economic value of more than $1.2 million or rice meals for almost 26,200 people annually. Thus, bat population decline as currently observed in South-East Asia, will directly affect people by food and money. Functionally important populations, not just the rare and endangered species, should be included in conservation management of human-dominated landscapes,” was the prudence delivered for Asian governments by the researchers.
India is home to 125 species of bats, the majority being insectivorous. “All insectivore bats feed on insects of economic importance such as crop pests, moths, plant-sucking bugs, beetles, flies etc,” informs bat specialist, assistant professor Sumit Dookia of Guru Gobind Singh Indraprastha University, New Delhi.
But are Indian policy makers heeding the clarion calls of science and biodiverse sensitivities?