title: Discrimination of fast click-series produced by tagged Risso's dolphins (Grampus griseus) for echolocation or communication.
abstract: Early studies that categorized odontocete pulsed sounds had few means of discriminating signals used for biosonar-based foraging from those used for communication. This capability to identify the function of sounds is important for understanding and interpreting behavior; it is also essential for monitoring and mitigating potential disturbance from human activities. Archival tags were placed on free-ranging Grampus griseus to quantify and discriminate between pulsed sounds used for echolocation-based foraging and those used for communication. Two types of rapid click-series pulsed sounds, buzzes and burst pulses, were identified as produced by the tagged dolphins and classified using a Gaussian mixture model based on their duration, association with jerk (i.e. rapid change of acceleration) and temporal association with click trains. Buzzes followed regular echolocation clicks and coincided with a strong jerk signal from accelerometers on the tag. They consisted of series averaging 359±210 clicks (mean±s.d.) with an increasing repetition rate and relatively low amplitude. Burst pulses consisted of relatively short click series averaging 45±54 clicks with decreasing repetition rate and longer inter-click interval that were less likely to be associated with regular echolocation and the jerk signal. These results suggest that the longer, relatively lower amplitude, jerk-associated buzzes are used in this species to capture prey, mostly during the bottom phase of foraging dives, as seen in other odontocetes. In contrast, the shorter, isolated burst pulses that are generally emitted by the dolphins while at or near the surface are used outside of a direct, known foraging context.
authors.affiliation: Sea Mammal Research Unit, School of Biology, University of St Andrews, St Andrews KY16 8LB, UK parranz@st-andrews.ac.uk.
authors.forename: P
authors.identifier: http://orcid.org/0000-0001-8998-5149
authors.initials: P
authors.lastname: Arranz
authors.affiliation: Centre for Research into Ecological and Environmental Modelling, School of Mathematics and Statistics, University of St Andrews, St Andrews KY16 9LZ, UK Department of Mathematics and Statistics, Calvin College, Grand Rapids, MI 49546, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: DeRuiter
authors.affiliation: Vertebrate Ecology Lab, Moss Landing Marine Laboratories, Moss Landing, CA 95039, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Stimpert
authors.affiliation: Sea Mammal Research Unit, School of Biology, University of St Andrews, St Andrews KY16 8LB, UK.
authors.forename: S
authors.initials: S
authors.lastname: Neves
authors.affiliation: Department of Fisheries and Wildlife, Mammal Institute, Hatfield Marine Science Center, Oregon State University, Newport, OR 97635, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Friedlaender
authors.affiliation: Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Goldbogen
authors.affiliation: Kelp Marine Research, Hoorn 1624 CJ, The Netherlands Institute of Biology, Leiden University, Leiden 2311, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: Visser
authors.affiliation: Cascadia Research Collective, Olympia, WA 98501, USA.
authors.forename: J
authors.initials: J
authors.lastname: Calambokidis
authors.affiliation: Southall Environmental Associates, Aptos, CA 95003, USA University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Southall
authors.affiliation: Sea Mammal Research Unit, School of Biology, University of St Andrews, St Andrews KY16 8LB, UK.
authors.forename: P L
authors.initials: PL
authors.lastname: Tyack
keywords: Biosonar; Burst pulse; Buzz; Foraging behavior; Jerk; Pulsed sound