}

Bat angler bat

2006/03/01 Imaz Amiano, Eneko - Elhuyar Zientziaren Komunikazioa Iturria: Elhuyar aldizkaria

We are used to seeing large groups of bats in documentaries that eat fruit or nectar. We also know vampires, three species of vampires in America. The European bats, for their part, are insectivores. But there is one who, even if from time to time, has a more rare diet, like the sinners of bats. Recently we have had knowledge of it.
Bat angler bat
01/03/2006 | Imaz Amiano, Eneko | Elhuyar Zientzia Komunikazioa

(Photo: J.R. Aihartza)
The patent bat ( Myotis capaccinii ) is the main protagonist. The Mediterranean lives on the shores of the sea and until recently was thought to eat insects trapped on the surface or near the water. However, in 2001 fish scales were identified in the feces of the patcino bat, and in 2003 a study was conducted to confirm the data J.R. of the department of Zoology and Animal Cell Biology of the UPV. Aiartza and his team in Denia (Valencia, Spain), Alicante.

Four bats were captured and studied their excrements: fish scales appeared in all of them, and also the vertebrae in some excrements. So bats ducks eat fish, but... By chance? Do they have common food? Casual? Do live fish fish fish or eat dead? Questions arose that required deeper research.

The research well was installed inside the tent, in Denia, Valencia.
J.R. Aihartza Aihartza

Holiday area with swimming pool

With the aim of knowing more about the fish farming of the pious bats, they prepared a research space on the mountain: a large camping shop with a well and endless food inside, and individual bedrooms for five bats, like a spa!

In the well were placed fishes of the species Gambusia holbrooki, of about 3 cm of length and about 0,25 grams. In addition, insects that are the typical food of the apple tree were also released inside the shop. In this scenario, at night, they released bats for 4.5 hours and recorded them in video with infrared light. At the end of the night, each bat was placed in his bedroom and collected his excrements to analyze them.

Patent bat with a fish in claws.
J.R. Aihartza Aihartza

The bats were released on several nights and each night more fish were placed at an ever lower depth. Thus, the first night 50 fish (33.3 units/m 2) were placed in the well with a depth of 2,5 cm. The bats touched 47 times the surface with little force, but they ignored neither the waves nor the dead fish. It should be taken into account that the eco-location of bats cannot detect submarine objects, but those of surface or out of water, although they did not show interest in the waves of fish or dead fish. The insects, on the other hand, were hunted from the surface of the water. Of course, no remains of fish appeared, either in the excrements or anywhere else within the tent.

During the second and third night the concentrations of fish increased and the depth of water decreased. Thus, the third night 600 fish (400 units/m 2) were placed in waters of a single centimeter depth. That night the behavior of bats changed: 6.268 water spins, often with much force, without paying attention to dead fish. They were trying to catch live fish and, as the video explained, at least two of them fled the clutches. Subsequently, in the demolitions of the bats, scales and fish bones were found, and in several areas of the tent appeared with bones, scales and six fish heads.

(Photo: J.R. Aihartza)

Therefore, J.R. confirmed that bats capture and eat live fish. Aiartza and his team. However, it might be thought that bats would learn something for the third night.

For this reason, as control, a second group of bats (four bats) was captured which were introduced in the shop at night, and in the well, 600 fish at a depth of one centimeter. Contact with water was much lower, 829 times due to stress after capture. But, at the same time, their cynegetic behavior was similar to that shown by the previous team: they beat the surface of water again and again, putting the claws down the water with force. After the hunting session, both in the ejections of the control group and in the tent of campaign, fish remains appeared again. Thus, they affirmed that bats, in their usual activity, noticed the presence of numerous fish and began fishing.

Not just fish

Bats capture the fish and eat it hanging in a rest area, always starting from the head.
J.R. Aihartza Aihartza

Analyzing the data and recordings of images from excrements (both of bats inside the shop and outside it between 2003 and 2005) and residues, the researchers have formulated a series of conclusions and hypotheses.

The patcino bat captures fish when its density is high and/or water is very superficial. In addition, all bats used in research have the same behavior for fishing, although bats have been captured in different places. In fact, this species of bat often catches insects from the surface of the water, flying parallel to the water and using ecolocation. However, if during this process a frequent contact occurs with the claws, the waters begin to be more intense and try to capture them using a more vertical approach to water.

Likewise, they have concluded that the fishing behavior is triggered randomly by the number of involuntary contacts with the fish along the insect hunt, since the submerged can not be detected or visible with the ecolocation.

On the other hand, according to the fish found, bats eat fish from the head. This means that bats know what to do when they catch a fish. Keep in mind that birds eating whole fish, for example, swallow fish from the head, scales, bones, and fins in the throat. However, fish are not the staple food of these bats throughout the year, since rarely appear remains in the ejections.

Thus, the researchers have represented a hypothetical scenario in order to explain this fishing behavior.

This time it has not fished.
J.R. Aihartza Aihartza

The pathetic bat lives around the Mediterranean Sea, where droughts are frequent in summer. These droughts often generate small pools of river, shallow and full of fish. And as the typical food of this species are the insects of the aquatic surface, it is very common to accidentally touch fish with claws, which, in evolution, would develop the capacity of exploitation of the fish, generating a specific behavior.

Thus, the patcino bat can exploit a very abundant resource in specific conditions, but quite common, in time and in space. This scenario coincides with the research carried out in Valencia.

However, the bat manzanal is not the only bat that feeds on fish. In fact, the species Myotis vivesi and Noctilio colinus live from eating fish. In addition, there are species that occasionally consume fish. For example, it has been mentioned that the bat Daubenton ( Myotis daubentonii ) has once caught some small fish, even though it is not fully demonstrated. The latter is a species that also lives in the Basque Country.

Others
Bats in the world...
Bats are animals created about 50 million years ago. They live all over the world, except in the icy zones of the poles and the high mountains and in the most arid deserts.
The bats of the world are divided into groups of megakeroptera and microcrirópteros, and belong to the group of the first the great bats that we see in the documentaries, which eat fruit and nectar, that inhabit the Tropics. Microciropters are much smaller and live all over the world.
In total, more than 1,100 species are identified. However, it would not be surprising that in the most distant and inaccessible places little studied more species appeared. In fact, in a Europe so studied, as that which until 6-7 years ago was the species Pipistrellus pipistrellus, it is now divided into P. pipistrellus and P. pygmaeus, based on genetic studies.
The size records of bats are not poplars: the smallest bat weighs less than 2 grams and has a south width of 12-13 cm. The largest is more than 1.5 kg and can reach 2 meters wide south.
...and in Euskal Herria
In Europe there are a total of 32 species and in Euskal Herria there are 24, all of them microciroptera.
Some live in bats, others in tree cracks; those who live in buildings are also numerous... All available and adequate refuges are exploited. And sometimes more than one. Horseshoe bats, for example, use cold caves to hibernate in winter, but temperate places for breeding. These temperate areas are often buildings.
Also the birds!
The belief that European bats are insectivores and, in addition to the fishing bats, we also have birds.
The night bat ( Nyctalus lasiopterus ) is one of the largest bats in Europe. It flies to high heights, trapping insects, in open zones and at high speed. But, in addition to insects, a bird also flies like a redhead; catch and eat.
The first indication of this behavior was curious. In a sampling, special nets were installed for the capture of bats in a well to capture the great night bats that came to drink. All of a sudden, a large night bat with txantxangorri feathers in the claws stuck to drinking on the net.
From this fact, it is confirmed that this species hunts and consumes birds in the air, especially in times of bird migration (spring and autumn). For this purpose, studies of isotopes of nitrogen and calcium have been carried out, among others. According to the data, during the migration of birds, the proportion of isotopes 13 C/ 12 C and 15 N/ 14 N in bats blood is very similar to that of small birds, indicative that the night bat is fed by small birds.
Imaz Amiano, Eneko
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