Listening In – Bats Recognize Echolocation Calls of Other Species

Bat echolocation calls evolved to optimize the information returning as echoes. Consequently, bats that forage or roost in similar habitats tend to evolve similar calls. Because echolocation calls emitted by one bat can readily be overheard by other bats in the area, the question is do bats eavesdrop on those calls to gain useful information on who is foraging nearby and where productive foraging sites are located?

In the last decade bat researchers discovered that some bat species can determine the sex and in some cases the individual identity of conspecific (members of the same species) calls (Kazial et al., 2008). Recently, in a series of detailed experiments, Schuchmann and Siermers (2010) tested whether bats of one species can recognize the calls of related species and use that information to their own advantage.

In this study, the researchers first tested whether four species of
horse-shoe bats (Figure 1) can discriminate between calls of their own species and those of sympatric, closely related and acoustically similar species (own-foreign experiment). More importantly, they also tested whether bats can distinguish between echolocation calls from different, acoustically similar species (foreign-foreign experiment).

rhinolophus
Figure 1. A horse-shoe bat Rhinolophus mehelyi in flight (From F. C. Robiller/Wikimedia)


Twenty four adult male
Rhinolopus euryale (Re) and 24 male R. mehelyi (Rm) were presented with four combinations of habituation signal followed by a test signal from either R. ferrumequinum (Rf), R. mehelyi (Rm), R. euryale (Re), and R. hipposideros (Rh).


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Figure 2. Behavioral data for the ability of Rhinolophus mehelyi bats to discriminate between echolocation calls of their own species and those of two other species of Rhinolophus (foreign). Black bars indicate the number of bats that discriminated between the habituation and test signals. (For details see Schuchmann and Siemers, 2010)

Figure 2 shows one set of data from these experiments. Here the first bar indicates that the bats did not discriminate when they were habituated and tested with playback calls from their own species. However, when the bats were habituated with their own species’ calls and tested with those of the other species in their community, all 48 bats were able to discriminate their own from “foreign” calls (
second bar). Further trials indicated that these bats were able to discriminate calls even when the “foreign” calls overlapped their own frequency band (third and fourth bars). Thus the bats appear to distinguish echolocation calls of their own species from those of other sympatric species in the same genus.

A second experiment also revealed that these bats distinguish among echolocation calls of different “foreign” species from the same local community (within the same genus).


References

Kazial, K.A., T.L. Kenny, and S.C. Burnett. 2008. Little brown bats (Myotis lucifugus) recognize individual identity of conspecifics using sonar calls. Ethology 114:469–478.

Schuchmann, M. and B.J. Siemers. 2010. Behavioral evidence for community-wide species discrimination from echolocation calls in bats.
The American Naturalist, 176:72-82.