Hello Bioacoustics-L,
The following two articles can be downloaded by list subscribers at
http://www.uvm.edu/~bmitchel/Bioacoustics.html
Swan, David C. and James F. Hare. 2008. Signaler and receiver ages do
not affect responses to Richardson's ground squirrel alarm calls.
Journal of Mammalogy, 89(4):889-894.
Alarm calls alert receivers to the presence and/or nature of a predatory
threat. Studies of alarm communication in Richardson’s ground squirrels
(Spermophilus richardsonii) have focused on juvenile signalers and
receivers; however, adult and juvenile receivers may tailor their
response to alarm calls based on different underlying signal parameters
and attend differentially to alarm calls broadcast by adult versus
juvenile signalers. To examine the potential influence of signaler and
receiver age on the perception of response urgency, we presented
free-living juvenile and adult S. richardsonii with alarm calls produced
by juveniles and adults. Behavioral responses of call recipients were
videotaped and analyzed to determine the influence of signaler and
receiver age-class. No differences in vigilance response after juvenile-
and adult-produced calls were detected for either adult or juvenile
receivers. At the proximate level, the absence of any detectable
difference in the acoustic attributes of juvenile versus adult-produced
calls may account for the lack of differential response. The absence of
any age-dependent productional difference also is consistent with the
recently advanced notion of young concealing information regarding their
age in their alarm signals.
May-Collado, Laura J. and Douglas Wartzok. 2008. A comparison of
bottlenose dolphin whistles in the Atlantic Ocean: Factors promoting
whistle variation. Journal of Mammalogy, 89(5):1229-1240.
Whistles are narrowband, frequency-modulated sounds produced by many
cetaceans. Whistles are extensively studied in delphinids, where several
factors have been proposed to explain between- and within-species
variation. We examined factors associated with geographic variation in
whistles of common bottlenose dolphins (Tursiops truncatus) by assessing
the role of ambient noise, noise from boats, and sympatry with other
dolphin species, and reviewing and comparing whistle structure across
populations in the western and eastern Atlantic Ocean. Whistles of
adjacent populations differed, particularly in frequency parameters. A
combination of factors may contribute to microgeographic whistle
variation, including differences in ambient noise levels (dolphins
produced relatively higher frequency whistles in the noisiest habitat),
and differences in number of boats present (when multiple boats were
present, dolphins whistled with greater frequency modulation and
whistles were higher in maximum frequency and longer than when a single
boat was present). Whistles produced by adjacent populations were
relatively similar in structure. However, for clearly separated
populations, the distance between them did not relate directly to
whistle structure. We propose that plasticity in bottlenose dolphin
whistles facilitates adaptation to local and changing conditions of
their habitat, thus promoting variation between populations at different
geographic scales.
|