It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Friday, March 15, 2024
Shark-bitten orcas in the Northeastern Pacific could be a new population of killer whale
AN INFOGRAPHIC SHOWING THE DIFFERENCES BETWEEN THE THREE ORCA ECOTYPES THAT LIVE ALONG THE COASTS OF CALIFORNIA AND OREGON AND THE POTENTIAL UNIQUE POPULATION
UBC researchers believe a group of killer whales observed hunting marine mammals including sperm whales, as well as a sea turtle, in the open ocean off California and Oregon could be a new population.
Based on available evidence, the researchers posit in a new study published in Aquatic Mammalsthat the 49 orcas could belong to a subpopulation of transient killer whales or a unique oceanic population found in waters off the coast of California and Oregon.
“The open ocean is the largest habitat on our planet and observations of killer whales in the high seas are rare,” said first author Josh McInnes, a masters student in the UBC Institute for the Oceans and Fisheries (IOF).“In this case, we’re beginning to get a sense of killer whale movements in the open ocean and how their ecology and behaviour differs from populations inhabiting coastal areas.”
Three ecotypes of killer whale live along the coasts of California and Oregon: ‘residents’, ‘transients’, and ‘offshores’.
The unknown orcas have been spotted before but the new paper contains a weight of evidence gathered from nine encounters with 49 animals from 1997 to 2021, enough to form a solid hypothesis, the researchers said.
“It’s pretty unique to find a new population. It takes a long time to gather photos and observations to recognize that there’s something different about these killer whales,” said co-author Dr. Andrew Trites, IOF professor.
The 49 killer whales could not be matched with any known animals through photos or descriptions. “In one of the first encounters researchers had with a pod of these oceanic killer whales, they were observed taking on a herd of nine adult female sperm whales, eventually making off with one. It is the first time killer whales have been reported to attack sperm whales on the west coast,” said McInnes. “Other encounters include an attack on a pygmy sperm whale, predation on a northern elephant seal and Risso’s dolphin, and what appeared to be a post-meal lull after scavenging a leatherback turtle.”
Shark scars provide vital clue
A key clue to the new population’s presumed habitat range lies in cookiecutter shark bite scars observed on almost all of the orcas. This parasitic shark lives in the open ocean, meaning the new population primarily inhabit deep waters far from land.
The orcas also feature physical differences from the three main ecotypes, including in their dorsal fins and saddle patches—the grey or white patches by the fin. “While the sizes and shapes of the dorsal fins and saddle patches are similar to transient and offshore ecotypes, the shape of their fins varied, from pointed like transients to rounded like offshore killer whales,” said McInnes. “Their saddle patch patterns also differed, with some having large uniformly gray saddle patches and others having smooth narrow saddle patches similar to those seen in killer whales in tropical regions.”
Along with marine mammal stock assessment surveys, fishermen and passengers on an open-ocean birding expedition and whale-watching tour also provided observations of the unidentified killer whales, said Dr. Trites. Spotting the new population has become something of a hobby among fishermen, some of whom have bought cameras for their trips specifically to snap an encounter, the researchers said.
The researchers hope to document more sightings and gather more information, including acoustic data about the orcas’ calls and genetic information from DNA samples to further investigate how these killer whales may differ, or not, from already documented populations.
Groundbreaking study reveals extensive leatherback turtle activity along U.S. coastline
Study is the first to identify the U.S. Atlantic coast as a significant region of feeding grounds for endangered leatherbacks migrating along the east coast of the United States.
UNIVERSITY OF MIAMI ROSENSTIEL SCHOOL OF MARINE, ATMOSPHERIC, AND EARTH SCIENCE
IMAGE:
THE FIELD TEAM, MITCH RIDER, CHRIS SASSO, SAMIR PATEL, AND EMILY CHRISTIANSEN WITH A LEATHERBACK TURTLE.
A new study led by a team of marine scientists at the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science and the National Oceanic and Atmospheric Administration Southeast Fisheries Science Center, provides groundbreaking findings that offer insights on the migration and foraging patterns of leatherback sea turtles along the Northwest Atlantic shelf.
Scientists have known that leatherbacks commonly swim from the South and Mid-Atlantic Bights during the warmer months to reach feeding areas near New England and Nova Scotia, Canada where food is plentiful. They migrate southward again when water temperatures drop during the winter. But questions still remained about where the turtles went in between, and what they were doing along the way.
The study, published in the Journal Frontiers in Marine Science conducted over several years offers unique insights into the utilization of the U.S. coastline by these majestic creatures, challenging previous assumptions and emphasizing key conservation implications.
"Our findings signify a paradigm shift in understanding leatherback turtle behavior along the U.S. coastline,” said Mitchell Rider, a research scientist at the Rosenstiel School’s NOAA Cooperative Institute for Marine and Atmospheric Studies and a lead author of the study. “By highlighting key foraging grounds and migration patterns, we aim to inform targeted conservation strategies to safeguard the future of these magnificent creatures."
Where the Leatherbacks roam
The research involved the tagging and monitoring leatherback sea turtles (Dermochelys coriacea) off the coasts of Cape Cod, Massachusetts and Beaufort, North Carolina. Between 2017 through 2022 the team successfully tracked 52 leatherback sea turtles, using advanced satellite tags capable of recording location, depth, and temperature data. Applying the tags involves finding and capturing the leatherback turtles, which can weigh several hundred pounds—a challenging task. The scientists were able to track and learn where the turtles go and the behaviors they exhibit during their migrations.
The waters off Cape Cod and Nantucket promote a high abundance of jellyfish in the late summer and early fall, which the leatherbacks appear to be taking advantage of. The scientists observed some of the leatherbacks tagged along Nantucket Shoals, stayed in the area for weeks to months after tagging before migrating back south.
In the Mid-Atlantic Bight, the team inferred that there is food availability, given the high number of leatherbacks that displayed feeding-like behavior year after year. However, the team noted the lack of research on prey distributions in this area, and further observations for leatherbacks would benefit by returning to the site to deploy camera tags to determine what the leatherbacks are feeding on.
The South Atlantic Bight appears to support several stages of the migration cycle: nesting, post-nesting foraging, and overwintering. Not as many leatherbacks frequented this area, but the ones that were tracked displayed feeding-like behavior especially along the continental shelf ridge. Previous research in the area indicates that blooms of cannonball jellyfish occur nearshore in the South Atlantic Bight primarily during the spring, which coincides with leatherbacks overwintering and nesting stages of their migration cycle.
“Our study revealed a significantly higher utilization of the U.S. coastline by leatherbacks, particularly along regions of the Mid-Atlantic Bight, South Atlantic Bight, and Southern New England. These areas emerged as possible major foraging grounds for leatherbacks migrating along the United States coastline, with notable activity observed off the coast of North Carolina.
“A key finding was further defining the Mid-Atlantic Bight as a critical foraging ground for leatherbacks from past studies, identified through sophisticated behavioral analysis,” said Rider. “By incorporating diving metrics such as dive frequency and duration, the study provides a comprehensive understanding of leatherback behaviors that distinguishes between their migration and foraging activities.”
Furthermore, the study highlighted the vulnerability of leatherbacks to incidental capture by fisheries and vessel strikes, underscoring the urgent need for conservation efforts to mitigate these risks. With impending developments, particularly the construction of offshore wind farms in the Mid-Atlantic Bight and Southern New England regions, the findings serve as a relevant guide for conservation managers to minimize impacts on this endangered species.
This study titled, “Where the leatherbacks roam: movement behavior analyses reveal novel foraging locations along the Northwest Atlantic shelf,” was published on February 20, 2024 in the Journal Frontiers in Marine Science. The authors are Mitchell J. Rider1, Larissa Avens2, Heather L. Haas3, Joshua M. Hatch3, Samir H. Patel4, Christopher R. Sasso5.
Funding was provided by the United States Department of the Interior, Bureau of Ocean Energy Management through Interagency Agreements M14PG00005, M10PG00075, and M19PG00007 with the United States Department of the Commerce, National Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service (NMFS), Northeast Fisheries Science Center (NEFSC) and Southeast Fisheries Science Center (SEFSC). This paper is also the result of research funded by the NOAA’s National Centers for Coastal Ocean Science, Competitive Research Program to the NOAA Fisheries Northeast Fisheries Science Center (NEFSC).
1Rosenstiel School of Marine, Atmospheric, and Earth Science, University of Miami, Miami, FL, United States, 2Southeast Fisheries Science Center, National Oceanic & Atmospheric Administration (NOAA) Fisheries, Beaufort, NC, United States, 3Northeast Fisheries Science Center, National Oceanic & Atmospheric Administration (NOAA) Fisheries, Woods Hole, MA, United States, 4Coonamessett Farm Foundation, East Falmouth, MA, United States, 5Southeast Fisheries Science Center, National Oceanic & Atmospheric Administration (NOAA) Fisheries, Miami, FL, United States
About the University of Miami
The University of Miami is a private research university and academic health system with a distinct geographic capacity to connect institutions, individuals, and ideas across the hemisphere and around the world. The University’s vibrant and diverse academic community comprises 12 schools and colleges serving more than 17,000 undergraduate and graduate students in more than 180 majors and programs. Located within one of the most dynamic and multicultural cities in the world, the University is building new bridges across geographic, cultural, and intellectual borders, bringing a passion for scholarly excellence, a spirit of innovation, a respect for including and elevating diverse voices, and a commitment to tackling the challenges facing our world. Founded in the 1940’s, the Rosenstiel School of Marine, Atmospheric, and Earth Science has grown into one of the world’s premier marine and atmospheric research institutions. Offering dynamic interdisciplinary academics, the Rosenstiel School is dedicated to helping communities to better understand the planet, participating in the establishment of environmental policies, and aiding in the improvement of society and quality of life. www.earth.miami.edu.
A leatherback turtle swims away after being succesfully outfitted with an advanced satellite tag which records location, depth, and temperature data.
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