Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil.
Odontoceti emit broadband high-frequency clicks on echolocation for orientation or prey detection. In the Amazon Basin, two odontoceti species, boto (Amazon River dolphin, Inia geoffrensis) and tucuxi (Sotalia fluviatilis), live sympatrically. The acoustic characteristics of the echolocation clicks of free-ranging botos and tucuxis were measured with a hydrophone array consisting of a full-band and an acoustic event recorder (A-tag). The clicks of the two species were short-duration broadband signals. The apparent source level was 201 dB 1 μPa peak-to-peak at 1 m in the botos and 181 dB 1 μPa peak-to-peak at 1 m in the tucuxis, and the centroid frequency was 82.3 kHz in the botos and 93.1 kHz in the tucuxis. The high apparent source level and low centroid frequency are possibly due to the difference in body size or sound production organs, especially the nasal structure, the sound source of clicks in odontoceti.
National Research Institute of Fisheries Engineering, Fisheries Research Agency, 7620-7, Hasaki, Kamisu-shi, Ibaraki 314-0408, Japan.
Yukiko
Y
Yamamoto
National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
Tomonari
T
Akamatsu
Aquatic Mammals Laboratory (LMA), National Institute of Amazonian Research, Avenue André Araújo, 2.936, Petrópolis, Manaus, Amazonas 69067-375, Brasil.
Vera M F
VM
da Silva
Department of Marine Biology, Tokai University, 3-20-1 Orido, Shimizu, Shizuoka 424-8610, Japan.
Yayoi
Y
Yoshida
Wildlife Research Center of Kyoto University, 2-24 Tanaka-Sekiden-cho, Sakyo, Kyoto 606-8203, Japan.
Shiro
S
Kohshima
D000818:Animals; D049628:Body Size; D001938:Brazil; D004289:Dolphins / Q000033:anatomy & histology / Q000502:physiology*; D004455:Echolocation; D005260:Female; D006257:Head / Q000033:anatomy & histology; D008297:Male; D045483:Rivers; D013018:Sound Spectrography; D013045:Species Specificity