Nathusius’ Pipistrelle Bat (Pipistrellus nathusii)

The Nathusius’ Pipistrelle is a rare bat in the UK. It’s much rarer than the Common Pipistrelle and Soprano Pipistrelle. However, numbers have grown over recent years. It is a migratory species most often encountered in autumn. Although a few stay and breed in the UK.

What Do Nathusius’ Pipistrelles Look Like?

It is similar in appearance to the Common Pipistrelle and Soprano Pipistrelle. It has brownish-grey to deeper reddish-brown fur. The main differences are that it is a little bigger and the fur on its back is often longer with a shaggy appearance.

Their length ranges between 4.5-5.5 cm, boasting a wingspan of 22-25 cm. They weigh between 6-16 grams.

What Does Their Echolocation Sound Like?

Their echolocation calls are like those of the other Pipistrelles. However, their peak intensity call is lower between 36kHz and 40kHz. Their social calls are between 20kHz and 30kHz which is audible to some adults and children.

Do can definitely hear them with a bat detector.

Where Do They Live?

Found across Europe, their range extends from Ireland in the west to Russia in the east. They tend to stay in wetland habitats. In the UK, sightings are more common in the southeast.

Roosting Sites

During the warmer months, these bats form maternity colonies. Females come together to give birth and raise their young. Summer roosts are often found in tree holes, spaces between roof tiles, brickwork and bat boxes.

As temperatures drop, they seek out colder, more stable environments for hibernation. These sites include caves, mines, tree holes and sometimes cellars and basements.

During migration, they may roost in different places as they travel.

Preferred Habitats

The Nathusius’ Pipistrelle is an adaptive species and thrives in a range of habitats. These include;

1. Wetlands and water bodies: They provide a rich source of insects such as midges and mosquitos.
2. Woodlands and forest edges: Woodlands provide sheltered roosting sites and abundant insect prey. Especially in areas where woodlands transition to open spaces.
3. Grasslands and meadows: Especially those adjacent to water bodies or woodlands. They offer a bounty of flying insects, making them attractive hunting grounds.
4. Urban areas: Benefiting from urban rivers, canals, buildings and streetlights which attract insects.
5. Coastal areas: In some regions, they forage over salt marshes and coastal lagoons. Exploiting the rich insect fauna these habitats support.

What Do Nathusius’ Pipistrelles Eat?

Their diet consists of:

• Small flying insects
• Moths
• Midges
• Mosquitoes

Hunting Strategy

They forage along the edges of woodlands, water bodies, and open fields. These ‘edge habitats’ often have concentrated insect populations, providing rich hunting grounds.

Hawking is their primary hunting method. They often zigzag over water and scoop up insects using their wing or tail membrane. Then they transfer their catch to their mouth, all while still in flight.

How Do They Breed?

The primary mating season starts in the late summer and extends into the early autumn. However, there’s some variability based on geographical location and specific environmental conditions.

Swarming Behavior

Before mating, these bats often display a ‘swarming’ behaviour. Especially around underground sites like caves. Many males and females gather together in large groups. They engage in aerial displays and interact with each other. Experts believe this behaviour facilitates mate selection.

Mating Rituals

Male Nathusius’ Pipistrelles establish territories, known as ‘singing perches’. It is from these perches that they make complex vocal patterns to attract females. These vocalizations can vary in pitch and pattern, acting as unique mating calls.

Delayed Fertilization

After mating females store the male’s sperm in their reproductive tracts over winter. Actual fertilization takes place in the spring.

This ensures that pregnancy and lactation coincide with warmer weather and more food.

Gestation and Birth

Once fertilized in the spring, the gestation period lasts about 6 to 8 weeks. Females then give birth to a single pup, although they can sometimes birth twins. Birth typically takes place in maternal colonies. Where several females gather for collective rearing and protection.

Birth and Development

Pups are blind and hairless, fully dependent on their mother’s milk for nutrition. At night, mothers leave their pups in the roost and go out to find food. They come back sometimes to feed them.

As the pups grow, they begin to develop fur, and their eyes open. This is when they start to be more independent. By the age of three to four weeks, youngsters start practising their flight.

Maturity

By the end of their first year, they will have reached sexual maturity. As such, they can take part in the breeding cycle.

However, the life expectancy of many individuals in the wild is often limited. A significant proportion won’t survive their first year. Those that do can live for several years, with some records indicating a lifespan of up to a decade or more in the wild.

When and Where Do They Hibernate?

In the UK, Nathusius’ Pipistrelles will begin hibernation between late October and November.

Choosing Hibernation Sites

Bats are selective about where they hibernate. They need to ensure they remain undisturbed and protected from the elements:

• Caves and Mines: Many choose underground sites such as caves and abandoned mines. These places provide stable temperatures and high humidity, ideal conditions for hibernation. They tend to favour deep, cool, and moist sections of these sites.
• Tree Hollows and Crevices: Serve as hibernation spots. The thick bark and interior of a tree work well as insulation to keep a constant temperature.
• Buildings: Particularly older structures with lots of gaps or crevices. Basements, attics, and cellars can offer a quiet and stable environment for hibernation.

Hibernation Physiology

During hibernation, the Nathusius’ Pipistrelles significantly reduces its metabolic rate. This means they’re able to conserve energy. Their body temperature drops to almost the ambient temperature of their surroundings.

This torpid state allows the bat to survive for months without feeding.

Migration and Hibernation

Some populations of Nathusius’ Pipistrelles migrate before hibernating. They can fly long distances to find a good place to hibernate. Sometimes hundreds of kilometres away.

Emergence from Hibernation

As spring approaches and temperatures start to rise, they emerge out of hibernation. This awakening is a vulnerable time, as their fat reserves are almost all gone. They need to feed and replenish their energy as fast as possible. The resurgence of insects in warmer weather provides them with the necessary food.

Threats to Nathusius’ Pipistrelles

Despite being adept survivors, these bats face a myriad of threats. Most of which humans contribute to or exacerbate. These include;

Loss of Habitat

The rapid expansion of cities and urban areas has led to the loss of natural habitats. Forests, wetlands, and other natural spaces are often cleared for construction. As a result, bats lose essential roosting and hunting grounds.

Aggressive agriculture results in the removal of trees and hedgerows. These are also vital roosting sites for these bats.

Pesticides and Pollutants

Pesticide use on crops reduces the availability of insect prey. But they can also have a bioaccumulative effect. When bats eat insects contaminated with pesticides, toxins build up in their bodies. This can cause various health issues.

Water pollution also reduces the number of insects, especially in aquatic habitats.

Wind Turbines

Wind energy poses a significant threat to bat populations.

Bats are often attracted to wind turbines, which can lead to fatal collisions. Additionally, the pressure changes near turbine blades can cause barotrauma. This can often cause internal injuries in bats.

Disturbance of Roosting Sites

Human activities, like;

• Logging
• Building renovations, or
• Recreational ventures into caves and other roosting sites

Can disturb these bats, particularly during their breeding or hibernation periods. These can be fatal, especially during winter when they are in hibernation.

Climate Change

Changes in climate patterns can affect the distribution and amount of insect prey. Milder winters may also disrupt a bat’s hibernation patterns.

Climate change can lead to habitat shifts. These can force bats to adapt to new environments or face the risk of habitat loss.

Predation

While bats are excellent at evading predators, they still face threats from birds of prey. Domestic cats also pose a significant threat, especially to young or injured bats.

Disease

Bats, like all wild animals, are susceptible to various diseases. One notable disease affecting bats in Europe is White-Nose Syndrome.

The Nathusius’ Pipistrelle is not the primary victim of this disease. However, any spread or mutation can be a potential threat.

Conservation Status

The International Union for Conservation of Nature (IUCN) classes the Nathusius’ Pipistrelle as being of “Least Concern.” This means they are not in danger or vulnerable on a global scale. However, different regions may have different statuses. In some areas, these bats are in decline or under specific threats.

Conservation Efforts

Conservation efforts include;

Legal Protections

• Specific Laws: Many countries have established laws that explicitly protect bat species. For instance, in the UK, under the Wildlife and Countryside Act 1981. This makes it illegal to kill, injure, or handle bats, or even disturb roosts.
• International Agreements: International treaties and conventions, also exist. Like the Agreement on the Conservation of Populations of European Bats (EUROBATS). This aims to safeguard bats across countries by setting standardized protective measures.

Monitoring and Research

• Bat Monitoring Programs: Many countries have initiated bat monitoring programs. These involve regular surveys using bat detectors, which pick up ultrasonic calls. These programs help in estimating population sizes and health.
• Tagging and Tracking: Researchers can track movement patterns, feeding habits, and breeding locations. This data is invaluable in making conservation decisions.

Public Awareness

• Bat Walks: Organized bat walks encourage the public to go bat watching. This fosters appreciation and understanding.
• Educational Programs: Schools and community groups often host bat experts. They explain the vital role bats play in our ecosystem. They can dispel any myths and misconceptions people might have.

Creating Artificial Roosts

• Designing Bat-friendly Structures: When designing new buildings or renovating old ones, developers accommodate bat roosts.
• Bat Boxes: Placed in strategic locations, bat boxes provide a safe place to roost. The placement, height, and design are crucial for their success.

Habitat Restoration

• Afforestation: Planting native trees and restoring forests provides natural habitats for bats.
• Wetland Conservation: Wetlands are rich feeding grounds for many bat species. Conserving and restoring these areas ensures a steady food supply for bats.

Safeguarding Migration Routes

• Mitigating Wind Turbine Threats: Wind turbines pose a threat to migrating bats. Research is ongoing to find ways to reduce bat fatalities. This includes adjusting turbine operations during peak migration times.

Collaborative Efforts

• Bat Conservation Networks: Organizations like Bat Conservation International (BCI) and regional bat conservation trusts work together. They often pool resources, knowledge, and expertise.
• Citizen Science: Engaging the public in bat conservation. For example, reporting bat sightings or participating in surveys. This gets more people involved in conservation while gathering valuable data.

Addressing Key Threats

• Light Pollution: Research has shown that artificial lighting can disrupt bat behaviour. Efforts are being made to design outdoor lighting that minimizes its impact on bats.
• Pesticide Reduction: Pesticides reduce the number of insects. Encouraging organic farming and reducing pesticide use can ensure a steady food supply.

When and Where to See Nathusius’ Pipistrelles

In the UK, the best places to see them are in the southeast.

They are most active in late summer. Go for a walk near lakes and rivers at dusk. If you’re lucky, you might see them zig-zagging across the water as they hunt.