Do echolocation calls of wild colony-living Bechstein's bats (Myotis bechsteinii) provide individual-specific signatures?
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Social animals often use vocal communication signals that contain individual signatures. As bats emit echolocation calls several times per second to orient in space, these might seem ideal candidates for conveying the caller's individual identity as a free by-product. From a proximate perspective, however, coding of caller identity is hampered by the simple acoustic structure of echolocation signals, by their task-specific design and by propagation loss. We investigated the occurrence of individual signatures in echolocation calls in individually marked, free-living Bechstein's bats (Myotis bechsteinii) in a situation with defined social context in the field. The bats belonged to two different colonies, for both of which genetic data on relatedness structure was available. While our data clearly demonstrate situation specificity of call structure, the evidence for individual-specific signatures was relatively weak. We could not identify a robust and simple parameter that would convey the caller's identity despite the situation-specific call variability. Discriminant function analysis assigned calls to call sequences with good performance, but worsened drastically when tested with other sequences from the same bats. Therefore, we caution against concluding from a satisfactory discrimination performance with identical training and test sequences that individual bats can reliably be told apart by echolocation calls. At least the information contained in a single call sequence seems not to be sufficient for that purpose. Starting frequencies did give the best discrimination between individuals, and it was also this parameter that was correlated with genetic relatedness in one of our two study colonies. Echolocation calls could serve as an additional source of information for individual recognition in Bechstein's bats societies, while it is unlikely that a large number of individuals could be reliably identified in different situations based on echolocation alone.
KeywordsVocal signature Individual recognition Echolocation Vespertilionidae Relatedness
We received financial support from Swiss National Science Foundation (SNF, 31-59556.99, to GK) and the German Research Foundation (DFG Si 816/2-1, to BMS). We thank Karsten Reckardt and Nicolas Bansac for helping with the fieldwork, Claudia Böing for excellent technical assistance in call analysis and Ingrid Kaipf for preparing Fig. 3. Wolf Blanckenhorn, Peter Pilz and Kamran Safi are acknowledged for statistical advice. The latter and Brock Fenton, Martin Obrist and Marta Manser provided helpful comments on earlier versions of this manuscript. Comments by two anonymous reviewers and Gerald Wilkinson greatly helped to improve the manuscript. The study was conducted under licence from the nature conservancy department of the government of Lower Frankonia and complied with German laws.
- Biscardi S, Orprecio J, Fenton MB, Tsora A, Ratcliffe JM (2004) Data, sample sizes and statistics affect the recognition of species of bats by their echolocation calls. Acta Chiropt 6:347–363Google Scholar
- Boinski S (2000) Social manipulation within and between troops mediates primate group movement. In: Boinski S, Garber PA (eds) On the move. University of Chicago Press, Chicago and London, pp 421–469Google Scholar
- Burnett SC, Kazial KA, Masters WM (2001) Discriminating individual big brown bat (Eptesicus fuscus) sonar vocalizations in different recording situations. Bioacoustics 11:189–210Google Scholar
- Elsasser D (1995) Soziale Kommunikation bei der Bechsteinfledermaus (Myotis bechsteini) in einer freilebenden Wochenstubenkolonie. Unpublished diploma thesis at the University of Würzburg, GermanyGoogle Scholar
- Fenton MB (1985) Communication in the Chiroptera. Indiana University Press, BloomingtonGoogle Scholar
- Fenton MB (1990) The foraging behaviour and ecology of animal-eating bats. Can J Zool 68:411–422Google Scholar
- Goudet J (1995) FSTAT (version 1.2): a computer program to calculate F-statistics. J Hered 86:485–486Google Scholar
- Kerth G (1998) Sozialverhalten und genetische Populationsstruktur bei der Bechsteinfledermaus (Myotis bechsteini). Wissenschaft und Technik Verlag, BerlinGoogle Scholar
- Kerth G (2006) Relatedness, life history and social behavior in the long-lived Bechstein's bat (Myotis bechsteinii). In: Zubaid A, McCracken GF, Kunz TH (eds) Functional and evolutionary ecology of bats. Oxford University Press, pp 199–212Google Scholar
- Kerth G, König B (1996) Transponder and an infrared-videocamara as methods used in a field study on the social behaviour of Bechstein's bats (Myotis bechsteini). Myotis 34:27–34Google Scholar
- Milton K (2000) Quo vadis? Tactics of food search and group movement in primates and other animals. In: Boinski S, Garber PA (eds) On the move. University of Chicago Press, Chicago and London, pp 357–418Google Scholar
- Möhres FP (1967) Communicative characters of sonar signals in bats. In: Busnel R-G (ed) Animal sonar systems: biology and bionics. NATO Advanced Study Institute, Frascati, Italy, pp 939–945Google Scholar
- Neuweiler G (2003) Evolutionary aspects of bat echolocation. J Comp Physiol A 189:245–256Google Scholar
- Siemers BM (2005) The use of ultrasound in bats: echolocation and communication. In: Brown K (ed) Encyclopedia of language and linguistics (in press)Google Scholar
- Siemers BM, Swift SM (2005) Differences in sensory ecology contribute to resource partitioning in the bats Myotis bechsteinii and Myotis nattereri (Chiroptera: Vespertilionidae). Behav Ecol Sociobiol DOI 10.1007/s00265-005-0060-5 (in press)
- Staden D, Schnitzler H-U (1995) The echolocation and foraging behavior of Bechstein's bat (Myotis bechsteini). 10th international bat research conference, abstract, Boston, p 169Google Scholar
- Zar JH (1999) Biostatistical analysis (4th Edn.) Prentice Hall, New JerseyGoogle Scholar