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First published online October 5, 2007
Journal of Experimental Biology 210, 3661-3676 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003764

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Phonotactic walking paths of field crickets in closed-loop conditions and their simulation using a stochastic model

Natasha Mhatre and Rohini Balakrishnan^*

Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560012, India

View larger version (69K): [in this window] [in a new window]   Fig. 1. Phonotactic paths of females presented with songs at different baseline and relative SPL values (A: 0 dB; B, 3 dB; C, 6 dB; D, 9 dB). Paths in which the louder speaker was on the right were mirrored so that the louder speaker is always on the left. Paths were not mirrored at relative SPL d0dB.

View larger version (54K): [in this window] [in a new window]   Fig. 2. Path vectors describing phonotactic paths of females presented with calling songs at different baseline and relative SPL values. Path vectors in which the louder speaker was on the right were mirrored so that the louder speaker appears on the left i.e. at 90°. The mean of all path vectors is the central, shorter thick arrow and the two on either side reaching the edge of the polar plot mark the angular deviation around the mean. The polar plots are all uniformly scaled to unit length. Path vectors significantly oriented towards 90° are marked with an asterisk in the polar plot. All other vectors were found to be uniformly distributed.

View larger version (17K): [in this window] [in a new window]   Fig. 3. (A) Mean first angle change made by females presented with calling songs at different baseline and relative SPL values. A positive value indicates a turn towards the louder speaker. Error bars indicate the angular deviation around the mean. (B) The first angle change made by a female during a phonotaxis trial was significantly positively correlated with the direction of that path vector. Positive values indicate turns to the left and negative values indicate turns to the right. Points represent the responses of all females to all treatments (R2=0.32, P<0.01; females, N=64; paths, N=205).

View larger version (42K): [in this window] [in a new window]   Fig. 4. (A) The angle changes made by females during walking bouts plotted against the relative SPL perceived at the pause preceding each walking bout. Positive angle changes indicate a turn towards the louder side. The angle changes made by the females were not correlated with the inferred relative SPL (P=0.28; pauses, N=2493). (B) A cartoon describing stimulus angle and the angle change made by the female in response. The speaker marked `louder' is louder at the position of the female. (C) The stimulus angle at the pause was correlated with the following angle change (P<<0.01; pauses, N=2493). A positive angle in this plot indicates left and a negative angle indicates right. (D) The slope of the regression between stimulus angle and subsequent angle change increased with increasing baseline and relative SPL with a decrease at high relative SPL for some baseline SPL values.

View larger version (13K): [in this window] [in a new window]   Fig. 5. (A) Mean number and (B) mean duration of pauses within each path made by females when presented with calling songs at different baseline and relative SPL values. Values are means ± s.d. (N values are given in parentheses).

View larger version (21K): [in this window] [in a new window]   Fig. 6. (A,B) The number (A) and average duration (B) of pauses made by a female in a path was weakly correlated with its sinuosity. (C,D) The error angle (the difference between the mean direction of the path vector and the angle of the louder speaker at the release position) was uncorrelated with the number of pauses (C) and mean pause duration (D).

View larger version (12K): [in this window] [in a new window]   Fig. 7. (A) The cumulative absolute angle change made in a phonotactic path is plotted against the distance walked for all paths in the stimulus treatment 55 d9dB. Each point in the plot represents the pauses made by the female in serial order. Large angle changes occurred in the initial parts of the paths. In the later part, females walked further without greatly changing heading angle. (B) A frequency distribution of the distances at which the transition between the two walking behaviours occurred.

View larger version (15K): [in this window] [in a new window]   Fig. 8. A regression of the angle change made during a walking bout against the duration of that walking bout had a greater slope before (A) the transition than after (B). The slope of the regression between the distance walked in a walking bout against its duration was lower before the transition (C) than after (D).

View larger version (49K): [in this window] [in a new window]   Fig. 9. (A–D) Phonotactic paths (N=15) generated by the simulation under the same stimulus conditions of baseline and relative SPL that real females were exposed to (see Fig. 2). The louder speakers are on the left. All plots are uniformly scaled.

View larger version (18K): [in this window] [in a new window]   Fig. 10. Mean and ranges of the different path measures produced under different stimulus conditions by the simulation. (A) Mean direction, (B) angular deviation of path vectors, (C) sinuosity. The closed circles indicate the means; error bars indicate ±2 s.d.; open squares indicate the values measured for the real paths. Baseline SPLs (BSPL) are indicated at the top of the figure.

View larger version (7K): [in this window] [in a new window]   Fig. 11. The first angle changes made by virtual females in the simulation were significantly correlated with the direction of their path vectors. The points represent the responses of all females to all treatments (P<<0.01; paths, N=192).

View larger version (38K): [in this window] [in a new window]   Fig. 12. The phonotactic paths produced by (A) real females (N=40) and (B) by the simulation (N=40) in the outdoor phonotaxis experiment. The position and approximate size of the speakers are indicated by the rectangles. The directions of path vectors are depicted in the insets; the shorter, thick central arrow indicates the mean direction and two thick arrows on either side the angular deviation.

View larger version (35K): [in this window] [in a new window]   Fig. 13. Paths produced by virtual crickets, deafened in the (A) right ear and (B) left ear. The path vectors are reproduced as insets (N=5). For further explanation, see Fig. 12.

View larger version (13K): [in this window] [in a new window]   Fig. 14. (A,B) Mean direction of path vectors of `virtual females' with ears of increasing directionality at (A) 61 d6dB and (B) 61 d3dB. Positive angular values in A and B indicate turning towards the direction of the louder speaker. The inset in the centre shows the changing PAD curve at different values of directionality. (C,D) The mean angular deviations of the paths at the two stimulus conditions.