Hello Bioacoustics-L,
The following articles appeared in recent issues of the Journal of
Mammalogy, and list members can download copies at
http://www.uvm.edu/~bmitchel/Bioacoustics.html.
Matrosova, Vera A., Ilya A. Volodin, Elena V. Volodina, Nina A.
Vasilieva, and Alexandra A. Kochetkova. 2010. Between-year stability of
individual alarm calls in the yellow ground squirrel Spermophilus
fulvus. Journal of Mammalogy 91(3):620-627.
Abstract: Although individuality in alarm calls has been reported for
many ground-dwelling sciurids, the degree to which the vocal identity
encoded in alarm calls is stable with time has been studied only for a
single sciurid species. Thus, no comparable data are available. We
examined the retention of the vocal keys to individual identity after
hibernation in a natural colony of yellow ground squirrels (Spermophilus
fulvus), long-lived, obligate hibernating rodents that maintain stable
social groups for years. We recorded alarm calls in 2 subsequent years,
separated by hibernation, from 22 individually marked animals. All
individuals could be distinguished with high probability by their alarm
calls within a year. However, only 6 of the 22 animals kept their alarm
calls stable after hibernation. Sex, age, year of data collection, and
the distance that individuals moved between years did not have
significant effects on the retention of a stable alarm call structure
after hibernation. Given the low proportion of individuals with stable
alarm calls, vocal identity cannot be the only modality sufficient to
secure the recovery of personalized social relationships after
hibernation in the yellow ground squirrel.
Gillam, Erin H., Nickolay I. Hristov, Thomas H. Kunz, and Gary F.
McCracken. 2010. Echolocation behavior of Brazilian free-tailed bats
during dense emergence flights. Journal of Mammalogy 91(4): 967-975.
Abstract: Brazilian free-tailed bats (Tadarida brasiliensis) emerge from
cave roosts in dense columns in which adjacent bats are separated by
only small distances. We describe and quantify variation in the
structure of echolocation calls produced by these emerging bats and
determine if call structure changes in relation to the rate of emergence
measured using thermal infrared imaging. We recorded emergence calls at
2 roosts, 1 housing approximately 200,000 bats and the other
approximately 17,000 bats. We found that Brazilian free-tailed bats emit
distinct frequency-modulated (FMstart) and constant frequency (CFstart)
calls during emergence that are significantly different from
echolocation calls they emit while foraging. We propose that these calls
provide different information for orientation within the emergence
column. CFstart calls are very similar to social calls used by Brazilian
free-tailed bats, suggesting 2 potential functions for this call type.
The structure of both the FMstart and CFstart calls were not related to
the number of bats emerging from a roost, although significant
structural differences existed between sites. The differences between
sites could be associated with the spacing of bats during emergence,
because bats appeared to form tighter columns at the larger roost colony
compared to the smaller colony.
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