Dear colleagues,
On behalf of my co-authors, I'm happy to share our two new publications on Rice's whales from the Gulf of Mexico.
1. Melissa S. Soldevilla, Katrina Ternus, Ashley Cook, John A. Hildebrand, Kaitlin E. Frasier, Anthony Martinez, and Lance P. Garrison , "Acoustic localization, validation, and characterization of Rice's whale calls", The Journal of the Acoustical Society of America 151, 4264-4278 (2022) https://doi.org/10.1121/10.0011677
ABSTRACT: The recently named Rice's whale in the Gulf of
Mexico is one of the most endangered whales in the world, and improved
knowledge of spatiotemporal occurrence patterns is needed to support their
recovery and conservation. Passive acoustic monitoring methods for determining
spatiotemporal occurrence patterns require identifying the species' call
repertoire. Rice's whale call repertoire remains unvalidated though several
potential call types have been identified. This study uses sonobuoys and
passive acoustic tagging to validate the source of potential call types and to
characterize Rice's whale calls. During concurrent visual and acoustic surveys,
acoustic-directed approaches were conducted to obtain visual verifications of
sources of localized sounds. Of 28 acoustic-directed approaches, 79% led to
sightings of balaenopterid whales, of which 10 could
be positively identified to species as Rice's whales. Long-moan calls,
downsweep sequences, and tonal-sequences are attributed to Rice's whales based
on these matches, while anthropogenic sources are ruled out. A potential new
call type, the low-frequency downsweep sequence, is characterized from tagged
Rice's whale recordings. The validation and characterization of the Rice's
whale call repertoire provides foundational information needed to use passive
acoustic monitoring for better understanding and conservation of these
critically endangered whales.
2. Soldevilla, M.S., Debich, A.J., Garrison, L.P., Hildebrand, J.A., & Wiggins, S.M. (2022). Rice’s whales in the northwestern Gulf of Mexico: Call variation and occurrence beyond the known core habitat. Endangered Species Research, 48:155-174. https://doi.org/10.3354/esr01196
ABSTRACT: The endangered Rice’s whale Balaenoptera ricei, with fewer than 100 individuals remaining, is the only year-round resident baleen whale found in the Gulf of Mexico (GOM) and occurs primarily along the northeastern shelf break near De Soto Canyon. Historical whaling records and predictive density modeling suggest that these whales potentially could occur more broadly throughout the GOM. High levels of anthropogenic activities in the GOM, including oil and gas exploration and extraction, fisheries, shipping, and the unprecedented Deepwater Horizon oil spill, highlight the need to better understand the distribution, ecology, and threats to this small population to improve protection of these endangered whales. We used long-term passive acoustic recordings from the northwestern GOM shelf break to explore the extent of Rice’s whale distribution in the northern GOM and to evaluate whether they exhibit seasonal movements throughout this range. We describe 6 new stereotyped variants of Rice’s whale long-moan calls, found predominantly in the western GOM, that share distinctive features with typical eastern long-moans, including a 150 Hz starting tone, an approximately 100 Hz tail with amplitude modulation, and a long call duration ranging from 10 to 35 s. Western long-moan variants were detected at 3 northwestern sites, occurring sporadically throughout the year on as many as 16% of days at the westernmost site, and infrequently at an eastern core-habitat site. These results indicate that some whales persistently occur over a broader range in the GOM than previously understood, which is important to consider when designating critical habitat and assessing threats to this Critically Endangered species.
Please feel free to contact me with any questions.
Best wishes,
Melissa
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Melissa Soldevilla, PhDResearch Fishery Biologist
Marine Mammal & Turtle Division
NOAA Southeast Fisheries Science Center
75 Virginia Beach Drive
Miami, FL 33149