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First published online June 29, 2007
Journal of Experimental Biology 210, 2481-2488 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001909

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Acoustic feature recognition in the dogbane tiger moth, Cycnia tenera

James H. Fullard^1,*, John M. Ratcliffe² and Christopher G. Christie¹

¹ Department of Biology, University of Toronto at Mississauga, Mississauga, Canada, L5L 1C6
² Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA

View larger version (21K): [in this window] [in a new window]   Fig. 1. The tymbal phonoresponse of Cycnia tenera. (A) Oscillogram of one stimulus pulse in a pulse train and the tymbal sounds as a series of clicks within a single modulation cycle (Blest et al., 1963). (B) The habituation/generalization (H/G) paradigm. (Top) Initial stimulus pulse train and moth phonoresponse. (Middle) Tenth pulse train where the moth has completely habituated. (Bottom) Test pulse train stimulus showing lack of generalization in the moth's phonoresponse. (C) Measurements taken from one H/G trial. Responses were the number of tymbal modulation cycles per stimulus pulse train (normalized to the percentage change from initial response). Habituation was determined if the slope of a linear regression applied to the response decrease was significantly less than 0; lack of generalization (i.e. expressed stimuli discrimination) was determined from pooled habituated animals if the test stimulus response was significantly greater than the average of the last habituated responses.

View larger version (18K): [in this window] [in a new window]   Fig. 2. (A) Audiograms of C. tenera (N=5 males, 5 females), individuals as circles, gender medians as bold lines. (B) Habituation/generalization (H/G) trials of individual C. tenera (N=20). Values are means + 1 s.d., sample sizes in parentheses; no significant differences (P>0.05, paired-sample t-tests) exist in any of the trials.

View larger version (9K): [in this window] [in a new window]   Fig. 3. Habituation/generalization (H/G) trials of C. tenera (N=3–6) stimulus duration discrimination. 5–10, habituation pulse trains of pulse durations of 5 ms, test pulse train of pulse duration of 10 ms, equal and unequal duty cycles; 10–5, habituation pulse trains of pulse durations of 10 ms, test pulse train of pulse duration of 5 ms, equal and unequal duty cycles. Values are means + 1 s.d., sample sizes in parentheses; asterisks mark significant differences (P<0.05).

View larger version (10K): [in this window] [in a new window]   Fig. 4. Habituation/generalization (H/G) trials of C. tenera (N=18) to test responses after habituation to pulse trains of 5 ms pulses to different test duty cycles (increasing pulse duration, periods equal). Values are means + 1 s.d., sample sizes in parentheses; asterisks mark significant differences (P<0.05).

View larger version (23K): [in this window] [in a new window]   Fig. 5. (A) Threshold phonoresponse curves of C. tenera (N=9, for all graphs) to stimulus pulses of constant and variable duty cycles as a function of stimulus pulse periods. (Top) Pulse duration of 2 ms and variable duty cycles; (middle) constant duty cycle of 7% and variable pulse durations; (bottom) constant duty cycle of 20% and variable pulse durations. (B) Habituation/generalization (H/G) trials using equal duty cycles (7%) and search versus attack (terminal phase) echolocation pulse durations (15 and 1.5 ms, respectively) and periods (215 and 21.5 ms, respectively) played in normal and reversed sequence [simulations modelled after field recordings of wild Eptesicus fuscus hunting in an open area (Surlykke and Moss, 2000)]. Values are means + 1 s.d., sample sizes in parentheses.

View larger version (16K): [in this window] [in a new window]   Fig. 6. (A) Call parameters of a wild Eptesicus fuscus foraging in an open area as it attacks a flying insect [duration and instantaneous pulse period data computed from original data of Surlykke and Moss (Surlykke and Moss, 2000) with their definitions of echolocation phase]. (B) Expansion of the approach and terminal phases shown in A; points are marked where C. tenera's phonoresponse begins (B) and/or where it is most pronounced (*), as extrapolated from stimulus pulse periods described in the following studies: 1 (Fullard, 1984); 2 (Fullard et al., 1994); 3 (Ratcliffe and Fullard, 2005); 4 (Barber and Conner, 2006). For both graphs, duty cycles were computed from the original data.