The role of ‘bats’ in pest control is a good topic to discuss as this has been the case recently Bat Appreciation Day 2024an ideal date to appreciate their usefulness and the need we have to care for, protect and preserve them.
The Miniopterus schreibersii is the most gregarious cave-dwelling bat in Europe and can form colonies of up to tens of thousands of individuals. In addition, it is a species with an important flight capability and its range can extend to more than 30 km from the refuge.
The San Cristóbal colony had between 3,000 and just over 7,000 troops during the entire study period. This colony is known to hunt with some frequency at least as far as the southern half of Doñana National Park.
bat colony
“This large colony can exist and sustain itself in an area so humanized by the characteristics of the species, namely an aerial hunter of open spaces,” says Carlos Ibáñez, researcher at the Doñana Biological Station. This means that it is not dependent on the type of plant substrate and also has a high movement capacity.
According to Ibáñez, although the medium is highly humanized, it is heterogeneous and will eventually offer sufficient alternative sources. Two-thirds of the area is devoted to a wide variety of agricultural crops, in addition to urbanized areas. The rest consists of patches of natural vegetation, including protected areas such as the Bahía de Cádiz Natural Park and the southern part of the Doñana National Park.
DNA metabarcoding analysis
The research is based on the metabarcoding analysis of the DNA of the remains of the prey in fecal samples of the bats. As a result, the scientific team identified just over 160 species of arthropods in the diet of these bats, 39 of which were identified as pest species.
Most of their food consisted of 24 species, 11 of which were pest species, mainly moths that, in the caterpillar state, attack various crops and forest masses (pine and holm oak forests or cork oak forests). These species also included the green stink bug, which attacks cotton and a wide range of fruits and vegetables.
In the diet of this bats Two prey items that are vectors of pathogens were also detected. One of these is the common mosquito, Culex pipiens, which, among other things, is a vector of the Nile fever virus, with cases of infection in humans in the area. The second is the cigarette bug, Neophilaenus campestris, a vector of the phytopathogenic bacterium Xylella fastidiosa, which is considered a serious global threat to agriculture in Europe.
Consumption of pests
The composition of the diet varies throughout the year, because there is a succession of peaks in the availability of different prey. In turn, the most commonly consumed insects are associated with different habitats and crops. This means that the bats They use the different habitats available to hunt and vary them over time. In this way the bats When foraging for food, they may target successive population explosions of pests that attack various crops or forests.
After identifying the species consumed by bats, The team quantified the colony’s consumption of pests, taking into account their daily intake, the size of the colony and the proportion of each prey species in the diet at any time.
In total, the colony had consumed a total of 1,610 kg of pest insects between May 11 and October 10. More than 90% corresponds to 10 species. To get an idea of what these numbers meant, the team focused on the specific case of the processionary caterpillar (Thaumetopoea pityocampa), a well-known pest typical of pine forests. The colony was closed between May 11 and October 10 bats had consumed a total of 1,610 kg of pest insects. More than 90% corresponds to 10 species
Doñana National Park
In the study area, pine forest covered only less than 3% of the land area used by the colony. Pine forests usually form small forests and even occupy gardens in urbanized areas. For example, the largest masses are found at more than 25 km in the Doñana National Park. The processionary caterpillar, in turn, has only one reproductive cycle per year, which implies that they are only available for a certain period of time.
In this area the maximum number of flights reaches between the second half of August and the first half of September. “In these weeks they were by far the most important prey, with appearances in more than 90% of the samples, despite the small area of the pine forest,” says Carlos Ibáñez.
“On these dates the colony reaches its maximum size with 7,200 individuals, partly due to the integration of the young that begin to fly independently in July, but also due to the integration of individuals from more distant refuges.” The population growth was probably related to the abundance of processionary caterpillars.
Procession arias
On these dates it was calculated that the colony consumes up to 6 kg of processionary caterpillars in one day. Since each moth weighs 0.1 gram, this means approximately 60,000 moths or images of processionaria. During the season they would eliminate approximately 173 kg of processionary caterpillars, equivalent to 1,730,000 moths. Since there are about 10,000 hectares of pine forest, they eliminate about 173 images/ha. It was estimated that the colony consumes up to 6 kg of processionary caterpillars in one day.
This colony is legally protected. M. schreibersii is a vulnerable species (CEEA) and the refuge is located in the Red Natura 2000 as ZEC (ES120030 Cuevas de la Mujer y de las Colmenas). “However, this does not guarantee its long-term conservation,” says researcher Carlos Ibáñez.
“Among the threats are the possible change of use of the enclave, the protection of the hollows where it spends the winter, such as the Hundidero-Gato and Motillas complexes, with increasing pressure from active tourist activities inside and the large number of wind farms. . in your vital area.” The role of ‘bats’ in the field of pest control. Updated text.