Christine M. Gabriele

Migratory Timing of Humpback Whales ( Megaptera novaeangliae ) in the Central North Pacific Varies with Age, Sex and Reproductive Status

Humpback whales migrate seasonally between high-latitude summer feeding grounds and low-latitude winter breeding grounds. Identification photographs of humpback whales were collected in the Hawaiian Islands between 1977 and 1995, and sighting histories were compiled for individuals. Analyses revealed that (a) mean dates of first identification were significantly earlier for juveniles and females with no calf than for males and females with a calf off the Big Island, and significantly earlier for juveniles than for females with no calf, males and females with a calf off Maui; and (b) mean dates of last identification were significantly earlier for juveniles and females with no calf than for males and females with a calf off the Big Island, and significantly earlier for females with no calf than for males and females with a calf off Maui. A within-subjects comparison showed that the date of first identification tended to be later for individual females in the years when they had a calf than in the years during which they had no calf. It was concluded that (a) migratory timing varies as a function of age, sex and reproductive status, (b) migratory timing is intimately connected with reproductive success and (c) migratory timing has important consequences for our understanding of humpback whale behaviour on the winter grounds.

Summary of Reported Whale-Vessel Collisions in Alaskan Waters

Here we summarize 108 reported whale-vessel collisions in Alaska from 1978–2011, of which 25 are known to have resulted in the whales death. We found 89 definite and 19 possible/probable strikes based on standard criteria we created for this study. Most strikes involved humpback whales (86%) with six other species documented. Small vessel strikes were most common (<15 m, 60%), but medium (15–79 m, 27%) and large (≥80 m, 13%) vessels also struck whales. Among the 25 mortalities, vessel length was known in seven cases (190–294 m) and vessel speed was known in three cases (12–19 kn). In 36 cases, human injury or property damage resulted from the collision, and at least 15 people were thrown into the water. In 15 cases humpback whales struck anchored or drifting vessels, suggesting the whales did not detect the vessels. Documenting collisions in Alaska will remain challenging due to remoteness and resource limitations. For a better understanding of the factors contributing to lethal collisions, we recommend (1) systematic documentation of collisions, including vessel size and speed; (2) greater efforts to necropsy stranded whales; (3) using experienced teams focused on determining cause of death; (4) using standard criteria for validating collision reports, such as those presented in this paper.

Source levels and call parameters of harbor seal breeding vocalizations near a terrestrial haulout site in Glacier Bay National Park and Preserve

Source levels of harbor seal breeding vocalizations were estimated using a three-element planar hydrophone array near the Beardslee Islands in Glacier Bay National Park and Preserve, Alaska. The average source level for these calls was 144 dBRMS re 1 μPa at 1 m in the 40-500 Hz frequency band. Source level estimates ranged from 129 to 149 dBRMS re 1 μPa. Four call parameters, including minimum frequency, peak frequency, total duration, and pulse duration, were also measured. These measurements indicated that breeding vocalizations of harbor seals near the Beardslee Islands of Glacier Bay National Park are similar in duration (average total duration: 4.8 s, average pulse duration: 3.0 s) to previously reported values from other populations, but are 170-220 Hz lower in average minimum frequency (78 Hz).

Source levels and calling rates for humpback whale (Megaptera novaeangliae) non-song vocalizations in Glacier Bay Alaska

Marine resource managers in Glacier Bay National Park, Alaska, have been tasked with assessing the impact of vessel noise on marine mammal species. Humpback whales (Megaptera novaeangliae) are a highly vocal baleen whale that forage between spring and fall in Park waters. While calling rates and source levels for this species have been described on breeding grounds and migratory corridors, these fundamental acoustic parameters have not been thoroughly described on foraging grounds, and have never been empirically measured in the North Pacific. Using a three-element hydrophone array deployed in the Beardslee Island complex of Glacier Bay during the 2015 summer foraging season humpback whale “whup” and “growl” calls were localized and source levels were calculated. Array recordings were paired with shore based abundance estimates from the same period and calling rates (calls per whale per hour) were estimated. Known calling rates and source levels are essential for developing detection algorithms, masking m...

Some things never change: multi-decadal stability in humpback whale calling repertoire on Southeast Alaskan foraging grounds

Investigating long term trends in acoustic communication is essential for understanding the role of sound in social species. Humpback whales are an acoustically plastic species known for producing rapidly-evolving song and a suite of non-song vocalizations (“calls”) containing some call types that exhibit short-term stability. By comparing the earliest known acoustic recordings of humpback whales in Southeast Alaska (from the 1970’s) with recordings collected in the 1990’s, 2000’s, and 2010’s, we investigated the long-term repertoire stability of calls on Southeast Alaskan foraging grounds. Of the sixteen previously described humpback whale call types produced in Southeast Alaska, twelve were detected in both 1976 and 2012, indicating stability over a 36-year time period; eight call types were present in all four decades and every call type was present in at least three decades. We conclude that the conservation of call types at this temporal scale is indicative of multi-generational persistence and confirms that acoustic communication in humpback whales is comprised of some highly stable call elements in strong contrast to ever-changing song.

More of the same: allopatric humpback whale populations share acoustic repertoire

Background Humpback whales (Megaptera novaeangliae) are a widespread, vocal baleen whale best known for producing song, a complex, repetitive, geographically distinct acoustic signal sung by males, predominantly in a breeding context. Humpback whales worldwide also produce non-song vocalizations (“calls”) throughout their migratory range, some of which are stable across generations. Methods We looked for evidence that temporally stable call types are shared by two allopatric humpback whale populations while on their northern hemisphere foraging grounds in order to test the hypothesis that some calls, in strong contrast to song, are innate within the humpback whale acoustic repertoire. Results Despite being geographically and genetically distinct populations, humpback whales in Southeast Alaska (North Pacific Ocean) share at least five call types with conspecifics in Massachusetts Bay (North Atlantic Ocean). Discussion This study is the first to identify call types shared by allopatric populations, and provides evidence that some call types may be innate.

Underwater Acoustic Ecology Metrics in an Alaska Marine Protected Area Reveal Marine Mammal Communication Masking and Management Alternatives

Vessel-generated underwater noise can affect humpback whales, harbor seals and other marine mammals by decreasing the distance over which they can communicate and detect predators and prey. Emerging analytical methods allow marine protected area managers to use biologically relevant metrics to assess vessel noise in the dominant frequency bands used by each species. Glacier Bay National Park (GBNP) in Alaska controls summer visitation with daily quotas for vessels ranging from cruise ships to yachts and skiffs. Using empirical data (weather, AIS vessel tracks, marine mammal survey data and published behavioral parameters) we simulated the movements and acoustic environment of whales and seals on three days with differing amounts of vessel traffic and natural ambient noise. We modeled communication space (CS) to compare the area over which a vocalizing humpback whale or harbor seal could communicate with conspecifics in the current ambient noise environment (at 10-min intervals) relative to how far it could communicate under naturally quiet conditions, known as the reference ambient noise condition (RA). RA was approximated from the quietest 5th percentile noise statistics based on a year (2011) of continuous audio data from a hydrophone in GBNP, in the frequency bands of whale and seal sounds of interest: humpback “whup” calls (50-700 Hz, 143 dB re 1 µPa source level, SL); humpback song (224-708 Hz, 175 dB SL), and harbor seal roars (40-500 Hz, 144 dB SL). Results indicate that typical summer vessel traffic in GBNP causes substantial CS losses to singing whales (reduced by 13-28%), calling whales (18-51%) and roaring seals (32-61%), especially during daylight hours and even in the absence of cruise ships. Synchronizing the arrival and departure timing of cruise ships did not affect CS for singing whales, but restored 5 – 12% of lost CS for roaring seals and calling whales, respectively. Metrics and visualizations like these create a common currency to describe and explore methods to assess and mitigate anthropogenic noise. Important next steps toward facilitating effective conservation of the underwater sound environments will involve putting modeling tools in the hands of marine protected area managers for ongoing use.

Source levels of harbor seal underwater reproductive advertisement displays

Harbor seals (Phoca vitulina), along with the majority of other phocid species, mate underwater. During the breeding season, male harbor seals set up underwater territories and use acoustic cues, known as roars, to defend these areas against intruder males and possibly to attract females. Vocalizations are low in frequency, predominately around 60-100 Hz, with some broadband components reaching up to 5 kHz, and range from 4-10 seconds in duration. Previously, source levels of vocalizations have only been estimated. Here we present a method for measuring vocalizations to estimate source levels of harbor seal roars. We used a three-element hydrophone array in Glacier Bay National Park to record harbor seal vocalizations during the breeding season (June—July 2015). Using the array, we localized individual vocalizing animals and calculated source levels of calls in the 40-500 Hz range. Knowledge of source levels for vocalizations of harbor seals is important for understanding how anthropogenic forces, such as...