Carlos César Martínez-Rivera and H. Carl Gerhardt (2008): Advertisement-call
modification, male competition, and female preference in the bird-voiced
treefrog Hyla avivoca. Behav. Ecol Sociobiol. 63(2), 195-208.
Abstract: Senders and receivers influence dynamic characteristics of the
signals used for mate attraction over different time scales. On a
moment-to-moment basis, interactions among senders competing for a mate
influence dynamic characteristics, whereas the preferences of receivers of
the opposite gender exert an influence over evolutionary time. We observed
and recorded the calling patterns of the bird-voiced treefrog Hyla avivoca
to assess how the dynamic characters of calls vary during interactions among
groups of males in a chorus. This question was also addressed using playback
experiments with males. Playback experiments with females showed how changes
in dynamic call properties are likely to affect male mating success. Frogs
calling in pairs, groups, or in response to playbacks produced longer calls
than did isolated males. During call overlap, males often increased the
duration of the silent interval (gaps) between the pulses of their calls so
that the pulses of the calls of two neighbors interdigitated. This change
resulted in increased variability of pulse rate, a traditionally static
acoustic property; however, males also produced high proportions of
non-overlapped calls in which variability in pulse rate was low and had
species-typical values. Females preferred long calls to short- and
average-duration calls, and non-overlapped calls to overlapped calls. Given
a choice between pairs of overlapped calls, females preferred pairs in which
the proportion of overlap was low and pairs in which the pulses of such
calls interdigitated completely. The observed patterns of vocal competition
thus reflect the preferences of conspecific females, which have influenced
the evolution of the calling behavior of H. avivoca.
URL: http://www.springerlink.com/content/mw2418812k3k43n6/
For reprints please contact Carlos César Martínez-Rivera (Email:
Hannah M. ter Hofstede, John M. Ratcliffe and James H. Fullard (2008): The
effectiveness of katydid ( Neoconocephalus ensiger ) song cessation as
antipredator defence against the gleaning bat Myotis septentrionalis. Behav.
Ecol Sociobiol. 63(2), 217-226.
Abstract: Many nocturnal katydids (Orthoptera: Tettigoniidae) produce
intense calling songs, and some bat species use these songs to detect and
locate prey. One Nearctic katydid species, Neoconocephalus ensiger, ceases
or pauses singing in response to bat echolocation calls. We tested the
hypothesis that song cessation is an effective defence against gleaning bats
(i.e., bats that take prey from surfaces). We observed Myotis
septentrionalis, a sympatric bat species that uses prey-generated sounds
when gleaning, attack and feed on singing N. ensiger in an outdoor flight
room. These bats demonstrated a preference for the calling song of N.
ensiger over a novel cricket calling song when they were broadcast from a
speaker in the flight room. Bats attacked speakers broadcasting N. ensiger
calling song as long as the song was continuous and aborted their attack if
the sound stopped as they approached, regardless of whether a katydid was
present as a physical target on the speaker. Echolocation calls were
recorded during attacks and no significant differences were found between
continuous and interrupted song approaches for four call parameters,
suggesting that M. septentrionalis may not use echolocation to locate silent
prey. Therefore, song cessation by katydids in response to ultrasound is an
effective defence against gleaning bats.
URL: http://www.springerlink.com/content/638780067571007p/
For reprints please contact Hannah M. ter Hofstede (Email:
Kind regards
Sonja
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
Austria
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