Anne E. Simonis

Species-specific beaked whale echolocation signals

Beaked whale echolocation signals are mostly frequency-modulated (FM) upsweep pulses and appear to be species specific. Evolutionary processes of niche separation may have driven differentiation of beaked whale signals used for spatial orientation and foraging. FM pulses of eight species of beaked whales were identified, as well as five distinct pulse types of unknown species, but presumed to be from beaked whales. Current evidence suggests these five distinct but unidentified FM pulse types are also species-specific and are each produced by a separate species. There may be a relationship between adult body length and center frequency with smaller whales producing higher frequency signals. This could be due to anatomical and physiological restraints or it could be an evolutionary adaption for detection of smaller prey for smaller whales with higher resolution using higher frequencies. The disadvantage of higher frequencies is a shorter detection range. Whales echolocating with the highest frequencies, or broadband, likely lower source level signals also use a higher repetition rate, which might compensate for the shorter detection range. Habitat modeling with acoustic detections should give further insights into how niches and prey may have shaped species-specific FM pulse types.

Spatio-temporal patterns of beaked whale echolocation signals in the North Pacific.

At least ten species of beaked whales inhabit the North Pacific, but little is known about their abundance, ecology, and behavior, as they are elusive and difficult to distinguish visually at sea. Six of these species produce known species-specific frequency modulated (FM) echolocation pulses: Baird’s, Blainville’s, Cuvier’s, Deraniyagala’s, Longman’s, and Stejneger’s beaked whales. Additionally, one described FM pulse (BWC) from Cross Seamount, Hawai’i, and three unknown FM pulse types (BW40, BW43, BW70) have been identified from almost 11 cumulative years of autonomous recordings at 24 sites throughout the North Pacific. Most sites had a dominant FM pulse type with other types being either absent or limited. There was not a strong seasonal influence on the occurrence of these signals at any site, but longer time series may reveal smaller, consistent fluctuations. Only the species producing BWC signals, detected throughout the Pacific Islands region, consistently showed a diel cycle with nocturnal foraging. By comparing stranding and sighting information with acoustic findings, we hypothesize that BWC signals are produced by ginkgo-toothed beaked whales. BW43 signal encounters were restricted to Southern California and may be produced by Perrin’s beaked whale, known only from Californian waters. BW70 signals were detected in the southern Gulf of California, which is prime habitat for Pygmy beaked whales. Hubb’s beaked whale may have produced the BW40 signals encountered off central and southern California; however, these signals were also recorded off Pearl and Hermes Reef and Wake Atoll, which are well south of their known range.

High-frequency modulated signals of killer whales (Orcinus orca) in the North Pacific

Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6-36.1 kHz and median duration ranged from 50-163 ms. Source levels were 185-193 dB peak-to-peak re: 1 μPa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals.

Diel and lunar variations of marine ambient sound in the North Pacific

Marine ambient sound was recorded on autonomous high-frequency acoustic recording packages (bandwidth 10 Hz to 100 kHz) during long term deployments at multiple sites across the North Pacific, from the high latitude Aleutian Islands to tropical Palmyra Atoll in depths of 600–1 000 m. Most intertropical but no temperate locations showed a distinct diel pattern in ambient sound. The soundscape at each location was unique, yet there was a similar recurring sound of unknown origin in lower latitude locations. This sound had a peak frequency around 3–5 kHz and was recorded only for several hours after sunset. Additionally, at some locations, a broadband acoustic signal with bandwidth up to 60 kHz was recorded at night with crepuscular peaks. Both sound patterns were lunar dependent with lower acoustic levels during full moon phases. Site-specific diel and seasonal acoustic patterns have been observed for various odontocete species. Correlations between odontocete presence and levels of ambient sound are invest...

Long-term monitoring of Physeteroidea (sperm whales, dwarf, and pygmy sperm whales) in the Central and Western Pacific

The superfamily Physeteroidea includes three extant species: the sperm whale (Physeter macrocephalus), the dwarf sperm whale (Kogia sima), and the pygmy sperm whale (K. breviceps). Despite extreme difference in size between the Kogia spp. and their large Physeter relative, all three share ecological and acoustic traits relating to their deep-diving behavior and high rates of acoustic activity. All three species can be found across the Central and Western Pacific ocean, an area that has been monitored using passive acoustics (High-frequency Acoustic Recording Packages, HARPs) for more than 10 years. We identified sperm whale and Kogia spp. signals in the long-term HARP records from 13 locations across the Central and Western Pacific ocean. A combination of automated tools and human analysis were used to record detection events of both types of signals. While sperm whales were found at all 13 locations, the Kogia species (which cannot yet be distinguished acoustically) were detected at approximately half of...

Mid-frequency active sonar and beaked whale acoustic activity in the Northern Mariana Islands

Mid-frequency active (MFA) sonar has been associated with multiple mass stranding events of beaked whales around the world. A recent increase in military training exercises in the Mariana Archipelago corresponds with the presence of MFA sonar in the surrounding waters. We provide a quantitative report on MFA sonar and beaked whale acoustic activity detected on two autonomous acoustic recording packages deployed near Saipan and Tinian from March 2010 through December 2013. There were no detections of MFA sonar at Saipan during the 5-month deployment in 2010. On August 21, 2011, MFA sonar was detected near Saipan concurrent with a stranding event involving two Cuvier’s beaked whales (Ziphius cavirostris). After one observed day of MFA sonar activity in Saipan and Tinian in 2011, observations increased to 1 month of ongoing activity at Saipan and nearly 3 months ongoing activity at Tinian in 2012. In 2013, MFA sonar events were observed during one day at Saipan and zero days at Tinian. Received levels, sound...

Beaked whale species occurrence in the central Pacific and their relation to oceanographic features

Mesoscale oceanographic features are a major force in structuring the marine environment through processes such as eddy-induced upwelling, and as such effect distribution and aggregation patterns of all organisms along the food chain. It has been shown that top pelagic predators such as cetaceans react to these environmental changes in different ways. We present analysis of frequency-modulated (FM) echolocation pulses of Cuvier’s beaked whale (Ziphius cavirostris), Blainville’s beaked whale (Mesoplodon densirostis), and an unknown beaked whale species producing FM pulse type “BWC,” possibly ginkgo-toothed beaked whale (M. ginkgodens), at five locations in the central Pacific. The recordings were collected at Pearl and Hermes Reef (Northwestern Hawaiian Islands), Kona (Main Hawaiian Islands), Wake Atoll, Tinian, and Saipan (Northern Mariana Islands) between 2008 and 2015, ranging from 4 to 8 years per site. All three beaked whale species were present at all sites in different proportions throughout the rec...

Temporal patterns in detections of sperm whales (Physeter macrocephalus) in the North Pacific Ocean based on long-term passive acoustic monitoring

Sperm whales (Physeter macrocephalus), a long-lived, cosmopolitan species, are well suited for long-term studies, and their high amplitude echolocation signals make them ideal for passive acoustic monitoring. NOAA’s Pacific Islands Fisheries Science Center has deployed High-frequency Acoustic Recording Packages (200 kHz sampling rate) at 13 deep-water locations across the central and western North Pacific Ocean since 2005. Recordings from all sites were manually analyzed for sperm whale signals, and temporal patterns were examined on multiple scales. There were sperm whale detections at all sites, although the rate of detection varied by location, with the highest rate at Wake Island (15% of samples), and the fewest detections at sites close to the equator (<1%). Only two locations (Saipan and Pearl and Hermes Reef) showed significant seasonal patterns, with more detections in the early spring and summer than in later summer or fall. There were no significant patterns relating to lunar cycles. Analysis of...