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1

Finding prey by associative learning in gleaning bats: experiments with a Natterer`s bat Myotis nattereri

100%
Siemers B. M.
Acta Chiropterologica
|
2001
|
tom 03
|
nr 2
I show that a Natterer's bat (Myotis nattereri) was operantly conditioned to echo cues from a large object; in this case a round bowl full of mealworms. In a subsequent choice experiment the bat preferred the empty, round bowl over an unknown, quadratic bowl filled with prey. I suggest that the quick but transient learning of cues indicating prey rich habitat patches might be adaptive for bats hunting in cluttered environments, where they can often not directly detect prey using echolocation. Therefore, it might be an additional foraging strategy of some gleaning bats to search for specific structural cues indicating a high probability of prey being present.
2

Calls of a bird-eater: the echolocation behaviour of the enigmatic greater noctule, Nyctalus lasiopterus

63%
Estok P., Siemers B. M.
Acta Chiropterologica
|
2009
|
tom 11
|
nr 2
The greater noctule (Nyctalus lasiopterus) is one of the rarest, least studied and the largest European bat. It feeds on large flying insects and also preys extensively on small night-migrating songbirds that it presumably intercepts at high altitude. The present study provides the first systematic account of echolocation behaviour and call design in the greater noctule. We documented variability in call duration from 1.4 to 25 ms and an associated strong variation in frequency parameters of echolocation calls. Greater noctules adapted call structure and repetition rate to the current perceptual task. In open space, they used calls with very low peak and terminal frequencies; generally below 15 kHz. We recorded echolocation calls from the sympatric — at least in Eastern Europe — smaller congener N. noctula. Our data suggest that acoustic separation of the two species is feasible. Therefore, acoustic monitoring could prove useful to survey distribution and habitat use of the enigmatic greater noctule. Using still lower call frequency than N. lasiopterus would yield larger detection ranges for large echolocation targets such as migratory birds for the greater noctule, while it might be constrained by the upper hearing threshold of passerines and thus the predator’s potential conspicuousness to its prey. However, in a within-genus comparison, allometric scaling explained the greater noctules’ call frequency to a very large extent, i.e., we found no evidence for specific adaptations of call frequency to bird hunting.
3

Effects of forearm bands on horseshoe bats (Chiroptera: Rhinolophidae)

51%
Dietz C., Dietz I., Ivanova T., Siemers B. M.
Acta Chiropterologica
|
2006
|
tom 08
|
nr 2
We assessed effects of forearm bands on three species of horseshoe bats (Rhinolophus ferrumequinum, R. euryale and R. mehelyi) marked for studies on regional movements and colony structure in Northern Bulgaria. Overall, more than 85% of the 580 recaptured individuals showed no negative impact of the banding. We had to note, however, slight or severe injuries in 7.6 and 6.4% of the bats, respectively. Injury rates varied greatly according to species and ring sizes. The use of the smaller of two tested ring sizes caused major injury rates of more than 60% of the recaptured R. mehelyi. But even in R. ferrumequinum, for which we obtained the largest sample size, and for which the recommended ring size is well-established, carefully fitted forearm bands caused injuries in 9.3% of the recaptures, an injury rate that is much higher than in most vespertilionid bat species. The main reason for the sensitivity of the horseshoe bats to ringing was that the ring rubbed raw the bats' propatagium; the resulting injuries led to growing scars and infections. We compare published and unpublished injury rates of 28 bat species with our results and discuss the use of alternative marking methods. We suggest that banding of horseshoe bats should be limited to well defined projects and only used if the study populations are in a good preservation condition and long term effects of the marking method can be monitored.
4

Horseshoe bats recognise the sex of conspecifics from their echolocation calls

51%
Schuchmann M., Puechmaille S. J., Siemers B. M.
Acta Chiropterologica
|
2012
|
tom 14
|
nr 1
Echolocation calls produced by bats contain information on the emitter that could be used in social interactions. Nevertheless, little is known about the whether such information actually is being used by bats. Here we tested the ability of two horseshoe bat species (Rhinolophus mehelyi and R. euryale; n = 20 each) to discriminate conspecific male from conspecific female echolocation calls and vice versa. Behavioural data from a habituation-discrimination paradigm revealed that both species were able to recognize the sex of conspecifics from their calls, providing evidence that cues on the sex of the emitter are encoded in echolocation signals. While our data support that the sex-specific acoustic cues are not (just) the horseshoe bats' constant-frequency call part, their nature remains enigmatic. This is the second study to show that bats can recognize the caller's gender from echolocation calls and the first to do so for ‘high-duty-cycle bats’; those that use calls with a prominent constant-frequency (CF) component.
5

Myotis daubentonii is able to catch small fish

51%
Siemers B. M., Dietz C., Nill D., Schnitzler H.-U.
Acta Chiropterologica
|
2001
|
tom 03
|
nr 1
We experimentally showed that Daubenton’s bat (Myotis daubentonii), a Palearctic vespertilionid species hunting for insects floating on or flying close to water surfaces, can take a small fish for prey if the fish penetrates a smooth water surface. The bat in our experiments was able to lift small fish and other big prey items out of the water by using its large feet. The bat readily fed on the fish we offered.
6

Fringe for foraging? Histology of the bristle-like hairs on the tail membrane of the gleaning bat, Myotis nattereri

51%
Czech N. U., Klauer G., Dehnhardt G., Siemers B. M.
Acta Chiropterologica
|
2008
|
tom 10
|
nr 2
Many bats are specialized to detect and capture arthropods from vegetation. As echoes from sitting arthropods and vegetation background overlap strongly, it is difficult for those bats to detect prey by echolocation alone. Within the largest genus of bats, Myotis, at least three species from different sub-clades show a characteristic fringe of hairs on the trailing edge of their uropatagium. All three species are capable of gleaning arthropods from vegetation with this tail membrane. Phylogenetic analyses strongly suggest that these specializations evolved convergently. Therefore, one can hypothesize that the hairs at the rim of the tail membrane have an important tactile and/or mechanical function for gleaning prey from substrate. To assess this question, we used light microscopic techniques to investigate the morphology and innervation of the bristle-like hair fringe, and for comparison, the structure of sensory mystacial vibrissae in Myotis nattereri. The results revealed that the fringe possesses two types of hair: larger guard hairs and smaller vellus hairs. Both hair types are well innervated underneath their sebaceous glands. They are encircled by a piloneural complex, which functions as a stretch and tension receptor. Although the bristle-like hairs are clearly not vibrissal follicle-sinus-complexes, their position, morphology and innervation strongly support a sensory function for prey detection and capture. An additional mechanical function, e.g., brushing prey off substrate, is plausible.
7

Conspicuous visual cues can help bats to find tree cavities

51%
Ruczynski I., Szarlik A., Siemers B. M.
Acta Chiropterologica
|
2011
|
tom 13
|
nr 2
In bats, vision plays a role in various contexts, particularly for long distance orientation and the detection of food. However, the extent to which vision is used is still poorly known. Here we test whether conspicuous visual cues increase the performance of the brown long-eared bat Plecotus auritus in an experimental paradigm based on tree hole discovery by bats. We used experimental logs with bark 'stripped off' (conspicuous bright area around entrance) and with bark 'not stripped off' to investigate whether there were differences in effectiveness of finding the entrances with or without light. Results indicate that the bats' effectiveness in finding the stripped entrances increased when light was provided. We suggest that the entrance was more visible due to high contrast between bark and wood. Our results indicate that visual cues could play a role in preselection of roost sites for this species.
8

Is species identity, sex, age or individual quality conveyed by echolocation call frequency in European horseshoe bats?

45%
Siemers B. M., Beedholm K., Dietz C., Dietz I., Ivanova T.
Acta Chiropterologica
|
2005
|
tom 07
|
nr 2
Horseshoe bats (Rhinolophus) use echolocation calls with a prominent part whose frequency is constant over time (CF) and matches the ‘acoustic fovea’ of the bats' hearing system. The present study on European Rhinolophus species investigates whether this CF component contains reliable information on species, sex, age class or quality (size and body condition) of the caller and could therefore have a communicative value. The resting frequencies (RF) were measured from stationary, handheld bats for the species Rhinolophus blasii, R. euryale, R. mehelyi and R. hipposideros (the latter with very low sample size) in Bulgaria, where they occur in sympatry. We recorded calls directly onto a laptop computer and used a specially designed analysis algorithm to achieve high and accurate frequency resolution. After silent periods, individuals ‘tuned in’ to their RFs always from lower frequencies, corroborating the recent finding that frequencies below RF might be used for auditory feedback control as well. Rhinolophus blasii could reliably be separated from its congeners by RF, while R. mehelyi overlapped strongly with both R. euryale and R. hipposideros. Only R. blasii showed sex and age differences in RF, albeit the overlap was large. Adult female R. blasii had higher RFs than both adult males and juvenile females. In R. blasii, RF was positively correlated with forearm length, body mass and body condition index; in R. mehelyi with body mass and body condition index. However, there was no correlation between RF and these body size parameters within a sex or age class for any of the species, suggesting that RF is not a reliable honest signal for intraspecific communication that would indicate the quality of a potential mate or competitor.
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