'Whale-sized' Genetic Study, Largest Ever for Southern Hemisphere Humpbacks
15 years of research in the waters of the South Atlantic and Indian Oceans,
scientists from the Wildlife Conservation Society, the American Museum of
Natural History, and an international coalition of organizations have unveiled
the largest genetic study of humpback whale populations ever conducted in the
analyzing DNA samples from more than 1,500 whales, researchers can now peer
into the population dynamics and relatedness of Southern Hemisphere humpback
whales as never before, and help inform management decisions in the sometimes
politically charged realm of whale conservation.
results of the massive analysis appear in PLoS One, an interactive open-access
journal for scientific and medical research. Other contributors to the study
include: Columbia University; University of Pretoria;
Environment Society of Oman;
Instituto Baleia Jubarta and PURCS (Brazil);
University of Cape
Town; Marine and Coastal Management (South Africa); Faculdade de Biociências; Agence
Nationale des Parcs Nationaux (Gabon);
Association Megaptera (France); Université de La Rochelle (France).
whales are perhaps the most studied species of great whale in the Northern
Hemisphere, but many of the interactions among Southern Hemisphere populations
are still poorly understood,” said Dr. Howard Rosenbaum, Director of the
Wildlife Conservation Society’s Ocean Giants Program and lead author of
the study. “This research illustrates the vast potential of genetic
analyses to uncover the mysteries of how humpbacks travel and form populations
in the southern ocean basins.”
little is known about southern ocean basin humpbacks that researchers initially
used old whaling records for insights into whale population boundaries.
collected skin samples from 1,527 whales from fourteen sampling sites from the
Southwestern and Southeastern Atlantic Ocean, and the Southwestern and Northern Indian Oceans.
The populations are known as Breeding Stocks A (Southwest Atlantic Ocean), B
(Southeast Atlantic Ocean), C (Southwest Indian Ocean), and X (Northern Indian
Ocean), based on information amassed and designated by the International
Whaling Commission, including data from 19th and 20th
Centuries commercial whaling.
scientists collected samples from living whales with biopsy darts fired from
crossbows. The darts harmlessly bounce off the marine mammals as they surface
to breathe. Samples came also from skin which is continually sloughed off by
the animals and collected by the research teams.
collected, the samples were brought to the lab at the AMNH Sackler Institute
for Comparative Genomics and examined through a technique called polymerase
chain reaction (PCR), which “amplifies” specific regions of DNA which
then can be used to statistically inform researchers about gene flow between
populations. The research team specifically focused on mitochondrial DNA, which
is passed through maternal lines of a population, in order to measure
interchange between groups.
The findings so far have revealed:
highest rate of gene flow between populations is between whales that breed on
either side of the African continent (Breeding Stocks B and C), with an
estimated one or two reproductively active whales every year swimming from one
ocean to join whales in another breeding ground. Authors of the current study
previously identified the same individual whale in both Atlantic and Indian Ocean breeding grounds at different times, the
first recorded instance of a humpback whale traveling between these two oceans.
lower rate of gene flow between humpbacks breeding on opposite sides of the
Atlantic (one population along coastal Brazil
and the other along the coast of Southern Africa).
While no individual whales have been detected traveling across the Southern Atlantic to both breeding grounds, genetic
similarities reveal a slight degree of populations interacting. Interestingly,
an examination of humpback whale songs between the two populations are similar,
another hint at interchange between the two groups, most likely in the
whales’ feeding grounds in Antarctic waters.
Stock X, which inhabits the northern Indian Ocean off the Arabian
Peninsula, numbers fewer than 200 whales and is the most distinct
in terms of genetics and migratory behavior. Unlike the other humpback
populations, it is non-migratory and only distantly related to the nearest
group of humpbacks (which breed off Madagascar
and the eastern coast of Southern Africa). As
a small, insular group, the “X” population is unique and therefore
a conservation priority.
addition to examining the population boundaries of humpbacks in the Southern
Hemisphere, the study also gives scientists some insight into the mysterious
and mercurial nature of marine ecosystems, with currents, water depth, and
other unseen factors serving as shifting conduits and barriers between marine
populations and ecosystems.
interesting historical note, Rosenbaum and his co-authors used old whaling
records to guide their research on whale populations. One set of
charts—titled “The Distribution of Certain Whales as Shown by
Logbook Records from American Whale Ships”—was compiled by Charles
Townsend of the New York Zoological Society (now WCS) and recorded the
locations of more than 50,000 whale captures (including humpback whales)
between 1761-1920. According to the charts, many humpback whales were captured
in the Gulf of Guinea,
Southeastern African and northeastern Madagascar, the same locations
where humpbacks congregate today. “Townsend was attempting to identify
distribution and possible boundaries between whale populations or
‘breeding stocks,’” noted Rosenbaum. “We’re still
trying to answer the same question with molecular technology in concert with
whaling logbook records.”
the needs of humpbacks and other whale species can be challenging in terms of
direct observations of these animals in the wild. Molecular technology gives us
a window into the lives of whales that can help us understand the ecological
forces shaping their movements and distribution,” added Rosenbaum.
“We can also use our findings to inform management decisions for a
species that is only now beginning to recover from centuries of commercial
humpback whale is a baleen whale that grows up to approximately 50 feet in
length. The species has distinctively long pectoral fins and a head with knobs
on the top and lower jaw. The humpback is also known for its acrobatics (such
as full body breaching) and haunting songs, typically sung by males and
possibly a mating behavior. The slow-swimming species was hunted commercially
until the International Whaling Commission protected the species globally in
1966. Current estimates for humpback whale numbers are widely debated.
While they are recovering, total population sizes may only perhaps be a small
percent of the original global population.
study was generously supported by The Eppley Foundation For Research, Flora
Family Foundation, and Lenfest Ocean Program.
Stephen Sautner (1-718-220-3682; firstname.lastname@example.org)
John Delaney (1-718-220-3275; email@example.com)
Current humpback whale numbers are a fraction of the original
population, yet the threats faced by this magnificent species are not well
understood. Urge Congress to increase funding for critical conservation
programs that assist researchers and conservationists in studying and
protecting humpback whales and other global priority species. Take Action
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