Spatio-temporal comparison of Pacific white-sided dolphin echolocation click types

Abstract

A comparison of temporal and geographical trends in different echolocation click types produced by Pacific white-sided dolphin Lagenorhynchus obliquidens can lead to insights into the significance of their usage by the dolphins. Using autonomous seafloor recording packages, the spatial, diel and seasonal patterns of Pacific white-sided dolphin echolocation click activity are described for 6 locations in the Southern California Bight. Click bouts of the 2 types of Pacific white-sided dolphin echolocation clicks are identified based on their unique spectral characteristics in long-term spectral averages. Type A clicks were detected on 317 of 1959 recording days and were heard at all 6 sites, with the majority of detections occurring at San Clemente Island and Point Conception. Type B clicks were detected on 130 recording days and were only heard at the 2 southern inshore sites. Significant diel patterns were evident for both click types: Type A click bouts were detected during more hours and with higher click rates at night than during the day, while Type B click bouts exhibited the opposite behavior, with greater activity during the day. At the southern sites, both click types exhibited a fall-winter peak in seasonal occurrence. At Point Conception, where only Type A was detected, peak occurrence was during spring. The described spatial and seasonal patterns support the hypothesis that click types are population-specific, while diel patterns suggest differences in prey preferences.

Risso’s and Pacific white-sided dolphin habitat modeling from passive acoustic monitoring

“…Off southern California, Risso's dolphins produce one species-specific click type with distinct spectral patterns, while Pacific white-sided dolphins produce 2 spectrally distinct click types, denoted types PWS A and PWS B (Soldevilla et al 2008(Soldevilla et al , 2010a. Spatial and temporal trends in PWS A and PWS B click occurrence support the hypothesis that these click types respectively represent the morphologically and genetically distinct northern and southern populations that overlap in the SCB (Walker et al 1986, Lux et al 1997, Soldevilla et al 2010b.…”

“…For these reasons, future studies should extend the spatial range of the study area to include more of, and extend beyond, the dolphins' known ranges. Differences in model explanatory power may reflect differences in prey preferences, as suggested by Soldevilla et al (2010b) for Pacific white-sided dolphin types based on differences in diel activity and spatial occurrence. Pacific whitesided dolphins are opportunistic foragers on variable prey types.…”

“…The 2 algorithms produced similar model fits for sea surface temperature (SST) and SST coefficient of variation (CV), which suggests that these interaction plots are valid for the S-Plus algorithm (Kruse 1989, Tynan 1997, Benson et al 2002 and expanding their range north during extended warm periods (Leatherwood et al 1980), while studies of northern Pacific white-sided dolphins indicate preference for cooler waters (Benson et al 2002, Becker 2007. The temperature difference between the 2 Pacific white-sided dolphin types reflects the southerly and northerly distribution of their echolocation activity and possibly population ranges (Soldevilla et al 2010b). Additionally, the seasonal variability described by Soldevilla et al (2010b) was incorporated into the models.…”

“…The temperature difference between the 2 Pacific white-sided dolphin types reflects the southerly and northerly distribution of their echolocation activity and possibly population ranges (Soldevilla et al 2010b). Additionally, the seasonal variability described by Soldevilla et al (2010b) was incorporated into the models. A positive relationship to the upwelling index was an important predictor for PWS B click detections, which seems counter-intuitive given the negative relationship to SST CV.…”

Spatio-temporal variation in click production rates of beaked whales: Implications for passive acoustic density estimation

“…Sound-recording tags mounted on 114 beaked whales are able to provide reliable click production rates specific to individuals because 115 clicks produced by the tagged animal contain low frequency energy that is absent in far-field 116 clicks from conspecifics (Johnson et al, 2009). Moreover, the clicks can be detected at ranges of 117 several kilometers in quiet conditions (Ward et al, 2008) and have a distinctive frequency Cue production rates can vary with context (e.g., Matthews et al, 2001) (Soldevilla et al, 2010b), based on data collected by autonomous bottom-mounted hydrophones.…”