title: Depth dependent variation of the echolocation pulse rate of bottlenose dolphins (Tursiops truncatus).
abstract: Trained odontocetes appear to have good control over the timing (pulse rate) of their echolocation clicks; however, there is comparatively little information about how free-ranging odontocetes modify their echolocation in relation to their environment. This study investigates echolocation pulse rate in 14 groups of free-ranging bottlenose dolphins (Tursiops truncatus) at a variety of depths (2.4-30.1 m) in the Gulf of Mexico. Linear regression models indicated a significant decrease in mean pulse rate with mean water depth. Pulse rates for most groups were multi-modal. Distance to target estimates were as high as 91.8 m, assuming that echolocation was produced at a maximal rate for the target distance. A 5.29-ms processing lag time was necessary to explain the pulse rate modes observed. Although echolocation is likely reverberation limited, these results support the hypotheses that free-ranging bottlenose dolphins in this area are adapting their echolocation signals for a variety of target detection and ranging purposes, and that the target distance is a function of water depth.
authors.affiliation: College of Marine Science, University of South Florida, 140 7th Avenue South, St Petersburg, Florida 33701, USA. psimard@mail.usf.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Simard
authors.forename: Ashley L
authors.initials: AL
authors.lastname: Hibbard
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: McCallister
authors.forename: Adam S
authors.initials: AS
authors.lastname: Frankel
authors.forename: David G
authors.initials: DG
authors.lastname: Zeddies
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Sisson
authors.forename: Shannon
authors.initials: S
authors.lastname: Gowans
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Forys
authors.forename: David A
authors.initials: DA
authors.lastname: Mann
mesh_terms: D000162:Acoustics; D000818:Animals; D000835:Animals, Wild; D001267:Atlantic Ocean; D050681:Bottle-Nosed Dolphin; D004455:Echolocation; D004777:Environment; D005431:Florida; D016018:Least-Squares Analysis; D016014:Linear Models; D013997:Time Factors