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1

Prey selection by Myotis myotis (Vespertilionidae) in a Mediterranean region

100%
Pereira M. J. R., Rebelo H., Rainho A., Palmeirim J. M.
Acta Chiropterologica
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2002
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tom 04
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nr 2
Seasonal variations in the diet composition and prey selection by Myotis myotis were studied in a Mediterranean region dominated by open stone oak woodlands, olive groves, and cereal steppes. The diet and food abundance were determined by faecal analysis and pitfall trapping, respectively. Overall, the diet (expressed as % frequency) was dominated by carabid beetles (Carabidae, 52%), crickets (Gryllidae, 43%), and spiders (Arachnida, 34%). Food was far more abundant in the spring than in the summer and autumn. The dietary composition varied significantly throughout the year. In the spring, it was dominated by carabids and crickets, and in the summer by spiders. These were then replaced by carabids, which became the most frequently eaten prey in autumn. The spring-summer switch to spiders coincided with a marked drop in food abundance. Some of the temporal variations in bats’ diet can be explained by parallel changes in prey abundance. In comparison to central European populations, our Mediterranean colony of M. myotis consumed much more crickets and spiders, which was balanced with a lower use of carabid beetles. Prey selection was tested using logistic regression models. The results suggest that, although carabids are the most consumed, crickets are preferred. Spiders seem to represent mostly a complement preyed upon at times of lower food abundance. It is not clear if the preference for crickets is simply due to their great conspicuousness, or to the choice based on energetic rewards or taste. Overall, our results are consistent with the predictions of the optimal foraging theory.
2

Critical times of the year for Myotis myotis, a temperate zone bat: roles of climate and food resources

100%
Zahn A., Rodrigues L., Rainho A., Palmeirim J. M.
Acta Chiropterologica
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2007
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tom 09
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nr 1
In highly seasonal temperate zones climate may cause fluctuations in the accessibility of prey for insectivorous bats. The main objective of this project was to evaluate if these fluctuations can result in resource bottlenecks that affect the body condition of a temperate zone bat — Myotis myotis. Seasonal changes in body condition followed different patterns in Portugal and Germany, which have different climates. In Germany bats use thermally better hibernacula, which allow them to minimize energy expenditure, but because of the longer winters they emerge from hibernation in poorer condition. Except during the hibernation period, food was always abundant in Germany, but the condition of the animals was poor when bad weather constrained foraging, particularly in early spring. In Portugal food was limiting during the long dry summer, and this affected the condition of the animals for several months. The conclusion that food resources can act as a limiting factor is relevant for conservation because, like other bat species, M. myotis forages mostly in agricultural and forestry habitats, and can be affected by practices that accentuate resource bottlenecks. Where necessary, the management of agroecosystems near colonies of M. myotis and of other threatened bats should aim at minimizing seasonal food bottlenecks.
3

Availability of Food for frugivorous bats in lowland Amazonia: The influence of flooding and river banks

100%
Marques J. T., Pereira M. J. R., Palmeirim J. M.
Acta Chiropterologica
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2012
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tom 14
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nr 1
In Neotropical forests fruits are key resources for a great diversity of vertebrates, including many frugivorous bats, but little is known about the factors that determine their availability. We studied forest inundation and river banks as determinants of the spatial variation in the availability of fruits for bats in lowland Amazonia. We sampled the bat assemblage composition, fruit availability, and bat diet in terra firme upland forest and in two types of flooded forest — várzea and igapó. Two distinct frugivore bat guilds were found in both terra firme and flooded forests: (1) canopy frugivores, feeding mainly on Ficus and Cecropia, and (2) understorey frugivores that feed mainly on Vismia and Piper. Fruits consumed by the canopy guild were more abundant in the flooded forests — particularly in the nutrient-rich várzea, but those dominating the understory guild diet were most abundant in terra firme. Availability of both fruit genera most consumed by the canopy guild was greater along river banks than in the forest matrix. For the understory guild, the greater abundance of Vismia along river banks was compensated for by a higher availability of Piper in the matrix. In conclusion, both factors influence the availability of fruits, although differently for the canopy and understory guilds. The resulting differences in fruit abundance may explain variations in bat assemblages of the different forest types. River banks play a particularly important role in providing food for bats of both guilds, but are under particularly heavy human pressure.
4

Foraging behaviour and habitat use by the European free-tailed bat Tadarida teniotis

88%
Marques J. T., Rainho A., Carapuco M., Oliveira P., Palmeirim J. M.
Acta Chiropterologica
|
2004
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tom 06
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nr 1
Autumnal foraging behaviour and habitat use by Tadarida teniotis were studied in Southern Portugal, using seventeen radio-marked individuals, followed over multiple nights from fixed and mobile stations. Tadarida teniotis proved to be a late emerger, leaving the roost about one hour after sunset and, in contrast to most insectivorous bat species, only had one foraging bout. These bouts were very long, lasting an average of 6 hours and 39 minutes. Bout duration was unrelated to climatic conditions and so probably determined by foraging success. In the early evening almost all bats were foraging, but this activity declined steadily through the night. They kept flying even during fairly cold nights, but did not leave the roost on the coldest nights, in which they probably remained in torpor. As predicted by its body mass and wing morphology, T. teniotis was found to be a strong flyer, reaching speeds of over 50 km/h, and flying for up to 10 hours without resting periods. The observed speeds were 2.5 times higher than the predicted maximum range speed, which may be possible due to peculiar adaptations to high-speed flight. On most nights bats flew straight to a previously identified feeding site, but on a few they made slower indirect flights, suggesting a search for profitable foraging areas. Upon arriving to a feeding site most bats remained there for the rest of the foraging trip. The median size of these sites was just over 100 ha. Several tracked bats used the same feeding area simultaneously. The range of the colony had a radius of over 30 km, but most feeding sites were concentrated in a mountainous region located about 5 km north of the roost. The studied bats foraged preferentially over forested areas, particularly pine and cork oak woodlands. They used both alluvial plains and the valleys of a mountainous area, but not its ridges. Our observations support the hypothesis that T. teniotis is an opportunistic forager, depending on temporary concentrations of prey, such as insect swarms.
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