Insect Migrations Provide Food for Bats in the Pyrenees

Bats are fascinating animals that play important roles in ecosystems, such as pollinating plants, dispersing seeds, and controlling pests.

However, bats also face many threats, such as habitat loss, disease, and human persecution.

To better understand and protect these creatures, scientists need to study their behavior, ecology, and evolution.

One of the aspects that scientists are interested in is how bats interact with insect migrations.

Insect migrations are large-scale movements of insects across regions or continents, driven by factors, such as seasonality, climate change, and food availability.

Insect migrations can have significant impacts on ecosystems, agriculture, and human health.

A recent study by researchers from the University of Exeter has revealed new insights into how bats gather to feast as nocturnal insects fly through mountain passes in the Pyrenees each autumn.

The study showed that migrating insects are a vital food source for both migrating bats and those that live in the mountains.

It also provides the first ever evidence of migratory bats feeding on migratory insects while both are migrating.

How did the researchers study bat-insect interactions in the Pyrenees?

(Photo : NARINDER NANU/AFP via Getty Images)

The researchers conducted their study in the Pass of Bujaruelo, near Spain's border with France. The pass is a hotspot for a wide variety of insect species that fly south in the autumn

The migration of nocturnal insects happens over about two months each autumn, but varying weather conditions mean there are just three or four key nights each year when large numbers of insects fly through the pass.

The researchers used a combination of tools to monitor the bat and insect activity in the pass. They used acoustic detectors to record the echolocation calls of bats, which can be used to identify bat species and their behavior.

They also used radar to track the movement and density of insects flying through the pass, along with light traps to collect insect samples for identification and analysis.

The researchers collected data from 2019 to 2020, covering 36 nights during the autumn migration period. They analyzed the data to examine the relationship between bat activity and insect bioflow (the amount of biomass passing through a unit area per unit time).

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What did the researchers find out about bat-insect interactions in the Pyrenees?

The researchers identified seven bat species and 66 insect species (90% of which were moths) in the pass.

The most abundant bat species were common pipistrelle (Pipistrellus pipistrellus), soprano pipistrelle (Pipistrellus pygmaeus), Nathusius' pipistrelle (Pipistrellus nathusii), European free-tailed bat (Tadarida teniotis), and Leisler's bat (Nyctalus leisleri).

Meanwhile, the e most abundant insect species were cotton bollworm (Helicoverpa armigera), silver Y (Autographa gamma), rush veneer (Nomophila noctuella), death's head hawkmoth (Acherontia atropos), and turnip moth (Agrotis segetum).

The researchers found that bat activity was significantly correlated with insect bioflow.

On nights when large numbers of insects flew through the pass, activity of both migratory and residential bat species increased significantly.

This suggested that these nights are important moments for the bats to build and maintain their energy reserves.

There is also found evidence that migratory bats fed on migratory insects while both were migrating.

This is the first time that such a phenomenon has been documented. The researchers hypothesized that migratory bats may use the influx of insects as a "refueling station" to power their own journeys south.

What are the implications of the study for bat conservation and insect migration research?

The study has several implications for bat conservation and insect migration research.

First, it highlights the importance of major insect migrations as a vital food source for bats.

This means that any factors that affect insect migrations, such as climate change, light pollution, pesticides, and habitat loss, could also affect bat populations.

Therefore, it is essential to monitor and protect both insect and bat migrations across regions and continents.

Second, it reveals new information about the behavior and ecology of migratory bats. It shows that migratory bats can feed on migratory insects while both are migrating, which could have implications for their energy budget, navigation, and physiology.

It also shows that migratory bats can coexist and compete with residential bats in mountain passes, which could have implications for their population dynamics, community structure, and disease transmission.

Third, it demonstrates the potential of using acoustic, radar, and light trap methods to study bat-insect interactions in mountain passes.

These methods are relatively low-cost, non-invasive, and scalable, and can provide high-resolution data on the diversity, abundance, and movement of bats and insects.

These methods could be applied to other mountain passes or regions to compare and contrast the patterns and processes of bat-insect interactions.

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