Research ArticleNEUROSCIENCE

Integrating vision and echolocation for navigation and perception in bats

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Science Advances  26 Jun 2019:
Vol. 5, no. 6, eaaw6503
DOI: 10.1126/sciadv.aaw6503
  • Fig. 1 Bimodal and unimodal learning of shape using echolocation and vision.

    Learning curves of bats trained to discriminate between a prism and a cylinder under different sensory conditions. Inset shows front-bottom view of the two targets (the direction from which the bats approached) and top view of the experimental setup. For a more detailed setup, see Fig. 2B (the experiment had identical setup with different targets). The different colors depict different individuals. The red horizontal dashed line indicates chance level, while the gray dashed line indicates 75% success. (A) Training under conditions that allowed usage of both vision and echolocation. (B) Training using echolocation only. (C) Training using vision only. (D) Training with both vision and echolocation abolished. When using vision only (C), the bats immediately solved the discrimination task within one session. If there were other cues available, then the bats should have immediately solved the task in the other cues condition (D) as well. Therefore, we only trained the bats for several sessions under this condition. In all experimental conditions, bats performed one training session (with 24 trials on average) per day.

  • Fig. 2 Cross-modal recognition between echolocation and vision.

    Bats’ performance under complete darkness (black), dim light (white), and a control, which did not allow vision or echolocation (gray). In all three conditions, the bats received no reward (for either right or wrong decisions), thus preventing any learning. The letters on the x axis depict individual bats’ identifications (IDs). Performance was tested relative to chance level (dashed line). (A) Left: Results of the first round of cross-modal recognition experiment (dark, approximately 45 trials per bat; light and control, 20 trials per bat). Right: Top view of the experimental setup and front view of the targets (the direction from which the bats approached). (B) Left: The results of the second round (30 trials per bat per condition). Right: Top view of the experimental setup and front view of the targets (the direction from which the bats approached). *P < 0.05, **P < 0.01, ***P < 0.001.

  • Fig. 3 Sensory weighing of echolocation and vision in an orientation task.

    x-axis condition names: BR, black reflective; WR, white reflective; BNR, black nonreflective. (A) Top view of the setup of the experiment. (B) The percentage of bats flying toward the open versus the blocked arm when altering the visual or the acoustic characteristics of the wall blocking the blocked arm in three different light levels (~40 bats per condition). (C) The proportions of different behaviors of bats approaching the blocked arm when altering the acoustic reflectivity of the wall.

  • Table 1 Number of bats that participated in the study.

    In the bimodal learning and cross-modal recognition experiments, bats were trained to discriminate targets and were disqualified if they failed to reach 75% correct choice within reasonable time in the original training task (i.e., before any testing began). In the sensory weighing experiment, all bats that participated in the experiment were naïve and were flown once in the two-arm maze, except for in the “acoustic detection control” where bats were trained to detect a reflective wall. In the acoustic detection control, the bats were tested with either the right side of the two-arm maze blocked or the left side. The number of bats disqualified from each condition and the reason for disqualification are indicated. The numbers given for each condition are the numbers of participants after the removal of the disqualified bats.

    ExperimentNumber of bats
    Bimodal learning5 (same bats as round 2 in the cross-modal recognition; one of the bats was disqualified since it did not echolocate
    in light)
    Cross-modal recognitionRound 1: 4 (another 4 failed to reach the initial learning criterion)
    Round 2: 5 (another bat failed to reach the initial learning criterion)
    Sensory weighing conditions:Left blockedRight blockedNo. of disqualified
    No. of no
    echolocation
    No. of video
    malfunction
    No. of refuse to fly
    Black reflective wall (5 × 10−2 lux)20211052
    White reflective wall (5 × 10−2 lux)2020821
    Black reflective wall (2 × 10−3 lux)202042
    White reflective wall (2 × 10−3 lux)1919425
    Black reflective wall (3 × 10−5 lux)202032
    White reflective wall (3 × 10−5 lux)201848
    Black nonreflective wall (3 × 10−5 lux)6171
    Acoustic detection control (<10−7 lux)102 (failed to reach criterion)

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/6/eaaw6503/DC1

    Fig. S1. Spectra of the targets in the bimodal learning experiment.

    Fig. S2. The distribution of the bats’ angles relative to the targets.

    Fig. S3. Spectra of the targets in the cross-modal recognition experiment—round 1.

    Fig. S4. Spectra of the targets in the cross-modal recognition experiment—round 2.

    Reference (40)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Spectra of the targets in the bimodal learning experiment.
    • Fig. S2. The distribution of the bats’ angles relative to the targets.
    • Fig. S3. Spectra of the targets in the cross-modal recognition experiment—round 1.
    • Fig. S4. Spectra of the targets in the cross-modal recognition experiment—round 2.
    • Reference (40)

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