Whistle characteristics and daytime dive behavior in pantropical spotted dolphins (Stenella attenuata) in Hawai‘i measured using digital acoustic recording tags (DTAGs)

Abstract

This study characterizes daytime acoustic and dive behavior of pantropical spotted dolphins (Stenella attenuata) in Hawai'i using 14.58 h of data collected from five deployments of digital acoustic recording tags (DTAG3) in 2013. For each tagged animal, the number of whistles, foraging buzzes, dive profiles, and dive statistics were calculated. Start, end, minimum, and maximum frequencies, number of inflection points and duration were measured from 746 whistles. Whistles ranged in frequency from 9.7 6 2.8 to 19.8 6 4.2 kHz, had a mean duration of 0.7 6 0.5 s and a mean of 1.2 6 1.2 inflection points. Thirteen foraging buzzes were recorded across all tags. Mean dive depth and duration were 16 6 9 m and 1.9 6 1.0 min, respectively. Tagged animals spent the majority of time in the upper 10 m (76.9% 6 16.1%) of the water column. Both whistle frequency characteristics and dive statistics measured here were similar to previously reported values for spotted dolphins in Hawai'i. Shallow, short dive profiles combined with few foraging buzzes provide evidence that little spotted dolphin feeding behavior occurs during daytime hours. This work represents one of the first successful DTAG3 studies of small pelagic delphinids, providing rare insights into baseline bioacoustics and dive behavior.

Effects of duty cycles on passive acoustic monitoring of southern resident killer whale (Orcinus orca) occurrence and behavior

“…Therefore, when addressing research questions about fine-scale acoustic behavior, a preliminary study using continuous data should be conducted to assess the optimal duty cycle for that species in the study area. These recommendations also apply when considering subsampling of continuous recordings, such as those made with animal-borne tags (Silva et al, 2016) or towed hydrophone arrays (Rankin et al, 2008). Using duty cycles when recording passive acoustic data provides advantages in terms of allowing longer-term data collection and reducing the volume of data collected and analyzed; however, care must be taken when choosing duty cycle regimes.…”

Co‐evolution of cerebral and cerebellar expansion in cetaceans

“…We also repeated these analyses using diet breadth and latitude range (also from Fox et al, 2017) as a proxy for environmental heterogeneity, maximum dive time and two tonal traits, tonal range and tonal complexity (number of inflection points). Data on dive time were taken from Marino, Sol, Toren, and Lefebvre (2006), with additional and updated data from further studies (Argüelles et al, 2016;Barlow, Forney, Von, Saunder, & Urban-Ramirez, 1997;Ishii et al, 2017;Krutzikowsky & Mate, 2000;Miller, Shapiro, & Deecke, 2010;Minamikawa, Watanabe, & Iwasaki, 2013;Silva et al, 2016). Tonal data were taken from May-Collado, Agnarsson, and Wartzok (2007).…”

Successful suction‐cup tagging of a small delphinid species, Stenella attenuata: Insights into whistle characteristics

“…Recently, Silva et al . () presented whistle characteristics and daytime dive behavior recorded during the first successful deployment of DTAG3s on free‐swimming pantropical spotted dolphins ( Stenella attenuata ). Here, we use these DTAG3 data to further explore the whistle repertoire of pantropical spotted dolphins, by presenting visual categorizations of whistle contours, addressing evidence of repeated whistle types, and providing new data on individual call behaviors.…”

“…The process of selecting whistles for analyses was described in detail in Silva et al (2016). Briefly, acoustic data were initially analyzed in MATLAB (MathWorks, Natick, MA) using a toolbox designed for DTAG analysis (available at http://soundtags.st-andrews.ac.uk/dtags/dtag-3/).…”