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Tactile discrimination of textures by Florida manatees (Trichechus manatus latirostris)

Authors

  • Gordon B. Bauer ,

    Corresponding author
    1. Division of Social Sciences, New College of Florida, 5800 Bay Shore Road, SSC 102, Sarasota, Florida 34243, U.S.A. and Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, U.S.A.
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  • Joseph C. Gaspard III,

    1. Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, U.S.A. and Department of Physiological Sciences, Aquatic Animal Health Program, University of Florida, Gainesville, Florida 32611, U.S.A.
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  • Debborah E. Colbert ,

    1. Association of Zoos and Aquariums, 8403 Colesville Road, Suite 710, Silver Spring, Maryland 20910, U.S.A.
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  • Jennifer B. Leach ,

    1. SeaWorld, 500 SeaWorld Drive, San Diego, California 92109, U.S.A.
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  • Sarah A. Stamper ,

    1. Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, U.S.A.
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  • David Mann ,

    1. University of South Florida, College of Marine Science, 4202 E. Fowler Avenue, St. Petersburg, Florida 33620, U.S.A. and Mote Marine Laboratory and Aquarium, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, U.S.A.
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  • Roger Reep

    1. Department of Physiological Sciences, University of Florida, Gainesville, Florida 32611, U.S.A.
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(e-mail: bauer@ncf.edu).

Abstract

Two male Florida manatees (Trichechus manatus latirostris) demonstrated sensitive tactile discrimination in a two-alternative forced choice task, using a modified staircase method. Stimuli were acrylic plates with vertical gratings of ridges and grooves. The standard stimulus, present on every trial, had 2 mm gratings and the comparison stimuli had wider gratings. The blindfolded subjects were trained to demonstrate discrimination by pressing the target with wider gratings. Discrimination thresholds (75% correct) for the subjects were 2.05 mm and 2.15 mm, corresponding to Weber fractions of 0.025 and 0.075, respectively. These results indicate thresholds on similar stimuli comparable to humans (index finger tasks) and better than harbor seals, Phoca vitulina, and the closely related Antillean manatee, Trichechus manatus manatus. Memory for the tactile task was quite stable for both subjects, over 2 yr in the case of one of the subjects. Video analysis of responses indicated that bristle-like hairs, perioral bristles, and skin on the oral disk were involved in the discrimination response.

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