Organic farming: Let bats fight for you


By Digital team | 3 June 2019
bats
Photo: Merlin D. Tuttle

These small mammals have a massive appetite for insects and can consume more than their body weight in a single night. They should be part of every integrated pest management system.

A colony of bats can devour more than a million insects a night. This makes them an invaluable partner in the management of false codling moth and Mediterranean fruit fly – pests that annually cause huge losses in fruit orchards across the world.

In spite of these benefits, bats often fall victim to eradication campaigns and human activities that interfere with their sleeping and eating patterns. Many species are declining in numbers, and some are on the endangered species list.

BIOLOGICAL FACTS

  • Bats usually move into caves, but will live in any small space, such as cracks in walls or beams.
  • Bats are very particular about where they live. They like heat and prefer houses that are about 4.5 m from the ground and close to a water source.
  • Research has found that it can take up to 3 years before a bat colony moves into a bat house, but it can be faster.
  • Farmers can smear the houses with the dung of local species to attract bats.
  • Houses have specific measurements and should have openings of about 1.8 cm wide.
  • They should be sealed, and not leak or lose heat. And they should be no wider than 2 cm.
  • The houses can be placed on poles or fastened to walls.
  • A wall system will provide better protection than roofs and cracks and would help to grow a colony at a fast rate.
  • Wall systems can be placed against an outside wall.
  • The Cape Serpentine bat species, for instance, hunts at a height of 1 m to 6 m.
  • The Egyptian Freetail species hunts from higher up.

In terms of reproduction, bats are the slowest mammals for their size, according to Merlin Tuttle’s book America’s Neighbourhood Bats. Most females raise 1 pup per year and some species don’t reproduce until they are 2 years old. The Cape Serpentine reproduces faster than the Egyptian Freetail and could raise up to 4 pups a year. Bats tend to live quite long – up to 30 years.

THE BENEFITS OF BATS

In some parts of the world it’s accepted that fruit farmers cannot afford to go without bats in pest management.
Pest management: Insect-eating bats’ primary source of food is flying night insects, many of which are considered to be pests. Pregnant bats can eat as much as their own body weight in a single night. Dung analysis confirmed that 60% of the bat’s diet consists of moths. Other insects consumed include leaf hoppers, water bugs, beetles, and basically anything that flies. Even so, it seems they don’t feed on beneficial insects.
Cut worms and boll worms have been found to be sensitive to bat colonies at a distance of up to 250 m from an orchard. In one study, a bat colony helped to reduce an eelworm-moth population by 95%. Infestation increased by 65% when the bat colony was moved 2 km away from the orchards.
Pollination: Bats that live off nectar have huge ecological and economic value. Fruit trees such as bananas, avocado pears, dates, figs, peaches, mangoes and cashew nuts can all be pollinated by bats.
Seed distribution: Bats are often called “tropical farmers” because of their ability to distribute seed over large distances and by doing so help to keep the rain forests going.

Also read: Bats are nature’s pest control agents

  • This article was written by Lucille Botha and first appeared in Farming SA.