title: Low frequency narrow-band calls in bottlenose dolphins (Tursiops truncatus): signal properties, function, and conservation implications.
abstract: Dolphins routinely use sound for social purposes, foraging and navigating. These sounds are most commonly classified as whistles (tonal, frequency modulated, typical frequencies 5-10 kHz) or clicks (impulsed and mostly ultrasonic). However, some low frequency sounds have been documented in several species of dolphins. Low frequency sounds produced by bottlenose dolphins (Tursiops truncatus) were recorded in three locations along the Gulf of Mexico. Sounds were characterized as being tonal with low peak frequencies (mean = 990 Hz), short duration (mean = 0.069 s), highly harmonic, and being produced in trains. Sound duration, peak frequency and number of sounds in trains were not significantly different between Mississippi and the two West Florida sites, however, the time interval between sounds within trains in West Florida was significantly shorter than in Mississippi (t = -3.001, p = 0.011). The sounds were significantly correlated with groups engaging in social activity (F=8.323, p=0.005). The peak frequencies of these sounds were below what is normally thought of as the range of good hearing in bottlenose dolphins, and are likely subject to masking by boat noise.
authors.affiliation: University of South Florida, College of Marine Science, 140 7th Avenue South, St. Petersburg, Florida 33701, USA. psimard@mail.usf.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Simard
authors.forename: Natalija
authors.initials: N
authors.lastname: Lace
authors.forename: Shannon
authors.initials: S
authors.lastname: Gowans
authors.forename: Ester
authors.initials: E
authors.lastname: Quintana-Rizzo
authors.forename: Stan A
authors.initials: SA
authors.lastname: Kuczaj
authors.forename: Randall S
authors.initials: RS
authors.lastname: Wells
authors.forename: David A
authors.initials: DA
authors.lastname: Mann
mesh_terms: D000818:Animals; D001307:Auditory Perception; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D056727:Endangered Species; D004784:Environmental Monitoring / Q000379:methods; D009624:Noise, Transportation / Q000009:adverse effects; D010470:Perceptual Masking; D011156:Population Density; D012767:Ships; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013045:Species Specificity; D013997:Time Factors; D014828:Vocalization, Animal