• A whale's tale: The story hidden in thei

    From ScienceDaily@1:317/3 to All on Mon Mar 21 22:30:44 2022
    A whale's tale: The story hidden in their mouths

    Date:
    March 21, 2022
    Source:
    University of New South Wales
    Summary:
    Baleen plates -- the signature bristle-like apparatus toothless
    whales use to feed -- reveal how these large aquatic mammals adapt
    to environmental changes over time.



    FULL STORY ========================================================================== Scientists from UNSW Sydney have uncovered the secrets locked in the
    jawlines of humpback and southern right whales. Baleen plates -- the
    signature bristle- like apparatus toothless whales use to feed -- reveal
    how these large aquatic mammals adapt to environmental changes over time.


    ========================================================================== Baleen from filter-feeding whales -- that is, the bristle-like structures toothless whales like the humpback and southern rights rely on to feed
    -- holds a chemical record of their feeding patterns, which can help researchers understand changes in the whales' movements and behaviours
    over time.

    Researchers have now shown how the changes in the dietary habits of whales going back almost 60 years correspond with changing climate cycles. The research, published in Frontiers in Marine Science, shows it's possible
    to link feeding patterns with climate conditions using whale baleen,
    which could help us understand how these large aquatic mammals may react
    to climate events in the future.

    "What is incredible is that all of this information about dietary and
    spatial patterns has been unlocked just through analysing plates in
    their mouths," says Adelaide Dedden, the lead author of the study and
    a PhD candidate at UNSW Science.

    In the study, the researchers compared the information stored in the
    baleen of humpback and right whales in the Pacific and Indian Ocean with environmental data to see whether their behaviours reflected changes in
    climate conditions over time.

    "We found that the same conditions -- the La Nin~a events -- that bring
    us these devastating floods are also not good for the humpbacks that
    migrate along the east coast of Australia," says UNSW Professor Tracey
    Rogers, marine ecologist and senior author of the study.



    ========================================================================== Using baleen samples from museum archives, strandings and previously
    published data from other studies they discovered humpback whales
    migrating along the east coast of Australia showed signs of poorer
    feeding opportunities during La Nin~a phases -- a large-scale climate
    cycle that drives food availability within the Southern Ocean.

    "Baleen whales are enormous and need huge amounts of food. This makes
    them vulnerable to changes in the environment, but this is also
    compounded by their survival strategy," Prof. Rogers says. "They
    fast for the long periods when they leave their productive feeding
    grounds to breed. That's why they're extremely susceptible to changes
    in ocean-atmospheric cycles as they can drive food availability."
    Whalebone whispers An animal the size of a whale isn't exactly easy to
    analyse in a lab environment. Instead, researchers can look at smaller
    hard tissues that keep a more detailed record of the animal's activity.

    For filter-feeding whales, the long, slender keratin plates that hang
    from their upper jaw known as baleen allow them to take in many small
    prey at one time -- but they also lay down chemical clues known as stable isotopes that give clues about their eating habits.



    ==========================================================================
    "As the baleen grows, biochemical signals from their food are
    trapped. Like the information on the pages in a book, they don't change
    with time," says Prof.

    Rogers. "These signals allow us to reconstruct the behaviour of the
    whales through time -- what they ate, and the general area they were at
    the time." The study found that the variability in the stable isotopes
    within baleen for the humpbacks matched the changes in climate cycles -- implying that the whales' feeding patterns change with climate-driven
    resource availability.

    "Oscillation patterns in isotopes assimilated along their baleen plates
    are known to reflect changes in the whale's physiology, but we also found
    links between this isotope variability and changes in the environment
    happening at the time," Ms Dedden says.

    Feast or famine Humpbacks spend their winter months in warm tropical
    waters to breed before travelling back to southern Antarctic waters
    during summer to feed. Amid this migration to the tropics, they're away
    from reliable food sources and must depend on their body's reserves and opportunistic prey off Australia to survive.

    "As filter feeders, they rely on big aggregations of krill because it
    is energetically costly for them to feed," Ms Dedden says.

    Antarctic krill need sea ice to thrive. Following La Nin~a phases, other research has found there is less sea ice concentration where these whales
    feed, meaning there are fewer krill for whales to consume and sustain
    them through their migration months.

    "[With] humpbacks from the east coast of Australia showing signs of
    reduced feeding following La Nin~a periods, it means they're potentially struggling to build up the energy reserves required during summer,"
    Ms Dedden says.

    Previous research found links between increased whale strandings on the Australian coast following La Nin~a years, which the researchers say
    can be attributed to less feeding success.

    "Our colleagues have shown humpbacks are leaner -- a sign they're
    experiencing poor feeding conditions -- and have a higher chance of
    stranding in the years following La Nin~a events," Prof. Rogers says.

    "With La Nin~a events predicted to increase in intensity and frequency,
    it unfortunately means these whales may continue to have more of these
    poorer feeding prospects, and we could see more strandings in the future." Hopes for the future While it's not clear waters for east coast humpbacks,
    the study found that humpbacks from the west coast of Australia who feed
    in the Indian Ocean showed increased feeding success during La Nin~a
    periods. In promising signs, the researchers also say their counterparts
    on the east coast are developing alternative feeding strategies in more temperate waters.

    "East coast humpbacks have shown signs of adapting to different
    feeding strategies in other known productive regions on their migration route...something that future research could look at," Ms Dedden says.

    The researchers hope to use the study's findings to develop models that
    can help predict whale behaviour in the future.

    "We've worked out patterns from the historical trends from the past,
    and now we can use those models to make predictions into the future to
    see what it might look like for our whales," Prof. Rogers says.

    "The information from the study will also be useful for managers now, to
    know ahead of time those years whales are likely to be more vulnerable so
    they can be prepared and, if needed, change their management strategies
    around whale entanglement and stranding." While humpback whales are no
    longer listed as endangered, climate change still poses a significant
    long-term threat to the species.

    Prof. Rogers says our actions today to address climate change will make
    a big difference for whale populations now and in the future, just like
    they will for us.

    "We need to act now while we still can," she says.

    "Acting on climate change now is good for whales but also for all of us."

    ========================================================================== Story Source: Materials provided by
    University_of_New_South_Wales. Original written by Ben Knight. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Adelaide V. Dedden and Tracey L. Rogers. Stable Isotope Oscillations
    in
    Whale Baleen Are Linked to Climate Cycles, Which May Reflect
    Changes in Feeding for Humpback and Southern Right Whales in
    the Southern Hemisphere. Frontiers in Marine Science, 2022 DOI:
    10.3389/ fmars.2022.832075 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220321103757.htm

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