Demographics

• Present throughout most of the world with the exception of extremely cold regions
• Smallest bat (arguably the smallest extant mammal) is the Kitti’s hog-nosed bat (29-34mm in length, 15cm across the wings, 2-2.6g in mass)
• Largest bats are a few species of Pteropus (fruit bats or flying foxes) and the giant golden-crowned flying fox (up to 1.6kg and wingspan up to 1.7m)
• Different species select different habitats during different seasons, ranging from seasides to mountains and even deserts
  • Two basic requirements: Roosts (where they spend the day or hibernate) and places for foraging
  • Bat roosts can be found in hollows, crevices, foliage, and even human-made structures, and include ‘tents’ the bats construct by biting leaves (insert pic)

Diet

• About 70% are insectivores, most of the rest are frugivores (fruit eaters)
• • Few others feed on animals other than insects
  • 3 species of bats, known as vampire bats, feed on blood
• Each bat is able to consume 1/3 of its body weight in insects each night, and several hundred insects in a few hours
• A group of one thousand bats could eat four tons of insects each year
• If bats were to become extinct, the insect population is calculated to reach an alarmingly high number.

Behaviour

• Bats are nocturnal creatures; they hunt during the night, daytime spent grooming, resting or sleeping
• Bats can travel distances of up to 800km to hunt for food
• Large portion of bats migrate hundreds of kilometres to winter hibernation dens, some pass into torpor in cold weather, rousing and feeding when warm weather allows for insects to be active. Others retreat to caves for winter and hibernate in six months
• Bats rarely fly in the rain  as it interferes with echolocation and they are unable to locate food
• Social structures vary – some are solitary while others live in caves colonized by more than a million bats
  • Fission-fusion social structure among several species: ‘Fusion’ refers to a large numbers of bats that congregate in one roosting area, and ‘fission’ refers to the breaking up and mixing of subgroups, with individual bats switching roosts with others and often ending up in different trees with different roostmates
• Predators of bats include bat hawks and bat falcons

Reproduction

• Most bats have a breeding season – spring for species living in temperate climates
• 1-3 litters per season depending on the species and environmental condition (e.g. availability of food & roost sides)
• Females generally have one offspring at a time as mothers need to fly to feed while pregnant
• Female bats nurse their young until they are nearly adult-sized as young bats cannot forage on their own until their wings are fully developed
• Female bats use a variety of strategies to control the timing of pregnancy and the birth of their young to make delivery coincide with maximum food ability and other ecological factors (high local production of fruits & insects)
  • Delayed fertilisation: The sperm is stored in the reproductive tract several months after mating. Most often, mating occurs in fall & fertilisation only occurs the following spring
  • Delayed implantation: The egg is fertilised after mating but remains free in the reproductive tract until external conditions become favourable
  • Development of fetus delayed until conditions prevail (fertilized egg still given nutrients and oxygenated blood); Process can go on for a long period of time due to their advanced gas exchange system
• Young microbats become independent at 6-8 weeks and megabats at about 4 months (wings become large enough for flight)
• A single bat can live over 20 years but bat population growth is limited by the slow birth rate.