How much do bats eat per night?

Bats are fascinating nocturnal creatures that play an important role in many ecosystems around the world. One of the most interesting facts about bats is how much they can eat in one night. The amount of food a bat consumes each night depends on the species, with some bats capable of eating over their entire body weight. Bats need to eat a lot to support their high metabolisms and energy requirements for flight.

How Many Insects Do Bats Eat Per Night?

Most bats are insectivores, which means they eat insects. An individual insectivorous bat can eat anywhere from 10% to 150% of its body weight in insects per night, though most eat about 20% to 30% of their weight.

For example, the big brown bat weighs around 0.5 ounces. It might eat around 0.1 ounces of insects in a night, or about 6 to 8 grams.

The Brazilian free-tailed bat is one of the most numerous mammals in North America. An adult weighs approximately 0.7 ounces and can eat over 30 grams of insects in a single foraging session.

Some key factors that determine how much bats eat at night:

  • Species – Some bats are larger and require more food.
  • Body size – Larger bats eat more insects.
  • Metabolism – Bats have very high metabolisms to support flight.
  • Availability of prey – More insects means bats can catch more food.
  • Weather conditions – Bats eat less on cold, wet nights when insect activity is low.
  • Pregnancy and lactation – Reproductive female bats have higher energy demands.

Exactly how many individual insects a bat consumes per night is hard to quantify. However, researchers estimate that an average insectivorous bat likely eats between 1,000 to 3,000 insects per night. A large colony with over 1 million bats may devour hundreds of millions of bugs in a single night!

How Many Mosquitoes Do Bats Eat?

Mosquitoes make up a substantial portion of many bat species’ diets. The overall percentage of mosquitoes in a bat’s diet depends on the abundance of mosquitoes relative to other insects in their habitat. However, mosquitoes seem to make up 5% to 20% of food for the average insect-eating bat.

Certain bat species specialize in eating mosquitoes. The spotted bat focuses on moths, but mosquitoes may account for up to a third of its prey. Other bats known to feast on mosquitoes include the little brown bat, Brazilian free-tailed bat, evening bat, and hoary bat.

Studies show that bats in an average colony can eat anywhere from 6,000 to 8,000 mosquito-sized insects in a night. Not all of these will be mosquitoes, but mosquitoes could make up 1,000 to 1,500 insects devoured per bat per night.

With such voracious appetites for mosquitoes, bats are invaluable in controlling mosquito populations and limiting the spread of the diseases mosquitoes carry. Just one small colony of big brown bats can eat enough adult mosquitoes to protect local humans from up to 33 million mosquito bits a year.

What Other Insects Do Bats Eat?

While mosquitoes make up part of most insectivorous bats’ diets, they also eat a wide assortment of other insects. Just a few groups of insects commonly eaten by bats include:

  • Moths
  • Beetles
  • Flies
  • Midges
  • Caddisflies
  • Ants
  • Crickets
  • Termites
  • Mayflies
  • Grasshoppers
  • Cicadas
  • Dragonflies
  • Dobsonflies
  • Lacewings
  • Stoneflies

Bats hunt by echolocation, so they are able to target whatever insects are most abundant each night. Agricultural pests like corn earworm moths, cucumber beetles, and June beetles also often end up eaten by bats.

Some bats are spiders and scorpion specialists, and others eat dung beetles. There are even a couple species that eat small vertebrates like frogs and fish. But the vast majority primarily eat insects and arachnids.

Do All Bats Eat Insects?

While the majority of bats worldwide are insectivores, not all bats eat insects. Frugivorous bats mainly eat fruit as their name implies, while nectar-feeding bats eat nectar and pollen. Sanguivorous bats feed on blood, either from mammals or birds. Carnivorous bats eat small vertebrates like frogs, fish, lizards, and even other bats.

Here is an overview of how much the major feeding groups of bats eat in a night:

  • Insectivorous bats – Eat 6,000 to 8,000 insect-sized prey per night
  • Frugivorous bats – Eat up to half their body weight in fruit per night
  • Nectar-feeding bats – Eat up to one and a half times their body weight in nectar per night
  • Sanguivorous bats – Consume roughly 15 to 30 milliliters of blood in a night
  • Carnivorous bats – Eat 10 to 20 grams of vertebrate prey per night

The feeding habits of bats allow them to take advantage of a wide diversity of food sources based on what is available in their particular ecosystem. Even insect-eating bats help pollinate certain plants and disperse seeds. Understanding how much and what bats eat helps shed light on their critical ecological roles.

How Do Bats Consume So Much Food?

The massive amount of prey bats consume per night is directly related to their high metabolisms. A bat’s resting heart rate is often 10 times faster than a typical land mammal’s heart rate. Their circulation and breathing rates are also much faster. This enables them to generate the power needed for flight. But it also means they burn through energy quickly and need to eat a lot to sustain their activity.

Here are some key reasons bats need so much food:

  • Flight is energetically expensive – Bats have high energy needs to stay airborne.
  • Small body size – With tiny bodies, bats need to eat more relative to their weight.
  • High metabolism – Their bodies work overtime even when resting.
  • Cold torpor – They need extra energy to raise their body temperature.
  • Long awake time – Most bats are awake all night hunting.
  • Lactation – Milk production has substantial energy requirements.

Bats also have adaptations to process all the food they eat, like rapid digestion rates and kidneys specialized to deal with large liquid intake. Their ability to eat on the wing while flying also optimizes their feeding. Bat researchers continue working to unravel the mysteries behind bats’ remarkable feeding habits.

Do Bats Always Eat This Much?

While bats have tremendous nightly appetites, the amount of food they eat per night can vary based on several factors:

  • Weather – Bats eat less on cold, rainy nights when prey is less active.
  • Stage of pregnancy – Pregnant bats eat more to support developing pups.
  • Nursing young – Lactating bats have higher energy needs.
  • Time of year – Less food may be available in colder months.
  • Habitat quality – More prey is available in optimal bat habitats.
  • Colony size – Competition in large colonies may limit food per bat.
  • Individual size – Larger bats require more insects.
  • Age – Juvenile bats have greater food needs.
  • Roosting – Bats use up less energy in warmer roosts.

The availability of prey is a major limiting factor on bat consumption. When insect supplies are low, bats may drop down to eating only 5% to 10% of their body weight per night to sustain themselves.

How Do Bats Find So Much Food?

Bats employ several key adaptations and strategies to locate sufficient food each night:

  • Echolocation – They use sonar to detect and track down flying insects.
  • Wingspan – Long narrow wings allow them to fly long distances.
  • Early emergence – They maximize hunting time by leaving roosts early.
  • Foraging in swarms – Swarming overwhelms insects’ defenses.
  • Nocturnality – They take advantage of the night insect buffet.
  • Large home ranges – They cover several miles every night.
  • Opportunism – They quickly adapt to exploit new prey sources.

Different bat species also employ various feeding strategies to optimize their insect-catching capabilities such as aerial hawking, gleaning, and trawling. Overall foraging time and success depends on predator avoidance by insects too. Despite the challenges, most bats are incredibly skilled at finding enough prey each night.

What Happens If Bats Don’t Eat Enough?

Bats can deplete their energy reserves fairly rapidly if they are unable to find enough food. Just a couple nights of poor feeding may negatively impact their health. Here are some effects on bats if adequate feeding does not occur:

  • Weight loss and starvation
  • Reduced energy and activity
  • Declines in metabolism, heart rate, and breathing rate
  • Torpor and hibernation
  • Decreased immunity and disease resistance
  • Poor body condition
  • Impaired brain function
  • Difficulty caring for pups
  • Higher mortality rates

Starving bats become desperate and may take more risks venturing out in daylight and approaching humans. They need food on a nightly basis to survive. Having a healthy, robust population of insects is key to supporting bats’ high metabolisms and food requirements.

How Does Weather Affect Bat Feeding?

Weather conditions have a significant impact on bat foraging activity and insect availability:

  • Temperature – Bats eat more on warmer nights when insect activity peaks.
  • Precipitation – Rain makes echolocation difficult and reduces insect flight.
  • Wind – Strong wind hinders bats’ flight control and pursuit of prey.
  • Cloud cover – Darker nights improve bat foraging success.
  • Time of year – Insect numbers are lower in winter.

Extreme weather like storms, cold snaps, heat waves, and droughts can all decrease the insect population and hinder bats’ ability to find food. Some bats migrate during such conditions while others lower their body temperatures and go into torpor to conserve energy.

How Does Roosting Help Bats Feed?

Roosts are an important resource for bats as places to rest, digest food, care for pups, socialize, and thermoregulate in between feeding bouts at night. Key roosting benefits include:

  • Conserves energy so more can be spent on foraging
  • Dark, enclosed spaces help digestion
  • Temperature and humidity can be regulated
  • Social networks facilitate information sharing about food sources
  • Safe place for lactating females and pups
  • Hibernacula enable hibernation to avoid cold winters with less prey

Disruptions to roosts due to urbanization, timber harvesting, and other human activities can cause roost abandonment. Loss of quality roosting habitat may impair bats’ abilities to rest and digest food, resulting in lower feeding rates.

Effects of Pesticides on Bat Feeding

Pesticide use has unintended consequences for bats’ ability to feed. Pesticides can:

  • Reduce insect prey populations and availability
  • Contaminate insects as food source
  • Accumulate in bat tissues causing illness
  • Increase energetic costs of detoxification
  • Impair echolocation disrupting hunting
  • Alter insect behavior making them harder to catch

One study found bats ate 84% less after an area was sprayed with pyrethroid pesticides. Bats unintentionally ingest toxins as they groom themselves after eating contaminated insects. Choosing integrated pest management approaches over widespread pesticide use can help conserve bat populations and the pest control services they provide.

Benefits of Healthy Bat Populations

Supporting large, robust bat populations has many benefits for ecosystems and humans:

  • Natural insect control reducing crop and forest pests
  • Lower risk of insect-borne illnesses like malaria, dengue fever, West Nile virus, and Lyme disease
  • Pollination and seed dispersal for many plants
  • Fertilization from accumulated bat guano
  • Indicators of habitat quality and biodiversity
  • Potential sources for medicines from compounds in their saliva and guano
  • Tourism opportunities to view bats
  • Enhanced understanding of sensory systems like echolocation

But providing sufficient habitat and food resources through insect conservation is crucial for bats’ success. Healthy bat populations can provide economically and ecologically valuable services. Their voracious appetites help regulate insect pests, benefiting ecosystems and humans alike. We should be grateful for bats’ remarkable consumption capabilities.


Bats are among the most prolific predators of night-flying insects, making them extremely valuable as natural pest control. To fuel flight and sustain their high metabolisms, insectivorous bats may eat over 1,000 insects equaling 20% to 30% of their body weight per night. Amounts vary by bat species and conditions. Mosquitoes comprise 5-20% of most bats’ diets. Besides insect control, bats’ big appetites promote plant pollination and seed dispersal. Supporting large bat populations through habitat protection and reduced pesticide use helps ecosystems and humans. Bats’ remarkable nightly consumption highlights their importance in nocturnal food webs.

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