\n<\/p>\n
After decades of recovery, southern right whales are showing signs of a climate-driven decline in breeding rates, which scientists say is a \u201cwarning signal\u201d about changes in the Southern Ocean.<\/p>\n
After being hunted to near extinction by commercial whaling in the 19th and 20th centuries, southern right whales remained endangered in Australia.<\/p>\n
But long-term monitoring has revealed a worrying slowdown in breeding rates since 2017. Instead of giving birth to a calf every three years, southern right whales have shifted to four-year or five-year cycles, says Dr Claire Charlton, a marine biologist and the director of Current Environmental.<\/p>\n
For more than three decades, scientists have used photo identification data collected at the Great Australian Bight to study the species, identifying individuals by unique patterns of a type of callus, called callosities, and tracking their migrations and breeding behaviour over time.<\/p>\n
Charlton, who leads the right whale program in the Great Australian Bight, says southern right whales are \u201cmagnificent animals\u201d \u2013 \u201cjust the sheer size of them, and the fact that they live for 150 years\u201d.<\/p>\n
<\/span>Southern right whales photographed at the head of the Great Australian Bight.<\/span> Photograph: Permit Number M26085-13\/Richard Twist\/Current Environmental<\/p>\n \u201cThey feed in Antarctic and sub-Antarctic waters during our summertime, and then migrate up to our coasts during winter,\u201d she said. \u201cThe whales come every year to breed, mate, rest and socialise.\u201d<\/p>\n Sign up: AU Breaking News email<\/p>\n The research, published in Scientific Reports, has linked the shift in breeding cycles to climate-driven changes in their foraging grounds in the Antarctic and sub-Antarctic.<\/p>\n \u201cWe know that the ocean is warming, the sea ice is melting, that causes other environmental changes,\u201d said Charlton, the study\u2019s lead author.<\/p>\n The paper analysed calving intervals over 35 years, revealing a correlation between breeding rates and sea ice extent, the prevalence of marine heatwaves, the availability of prey and other climate-driven changes.<\/p>\n The researchers said similar trends had been observed in southern right whale populations across South America and South Africa, with other krill-dependent predators also facing pressure from marine heatwaves and declining sea ice.<\/p>\n This was a \u201cwarning signal\u201d about how climate change was affecting marine life, Charlton said, which highlighted the urgent need for coordinated conservation efforts.<\/p>\n Whale scientist Vanessa Pirotta, who was not involved with the study, said long-term data was essential for understanding these long-lived animals, and how they might adapt to a changing environment.<\/p>\n \u201cWe need to continue to learn more about [southern right whales] given that we were responsible for so much of their loss and where their populations are right now,\u201d Pirotta said.<\/p>\n <\/span>When conditions get worse, mammals such as whales \u2018pull back on having as many babies\u2019 as having a baby is demanding.<\/span> Photograph: Permit Number M26085-13\/Richard Twist\/Current Environmental<\/p>\n Commercial whaling ceased in Australia in 1979 and was banned by the International Whaling Commission in the late 1980s. Driven to fewer than 300 animals, populations in Australia now range between 2,346 and 3,940 individuals, or about 16% to 26% of pre-whaling levels.<\/p>\n Southern rights were like \u201ctractors of the ocean\u201d, said Dr Peter Corkeron, a marine ecologist and adjunct senior research fellow at Griffith University, who was not involved in the study. To feed, the whales would seek out dense patches of zooplankton and \u201cgo back and forth like they\u2019re mowing the lawn\u201d.<\/p>\n The change in calving intervals was a sign that conditions in the Antarctic and sub-Antarctic weren\u2019t as good as they once were, he said.<\/p>\n \u201cAs mammals, the choice to have a baby is demanding,\u201d he said. \u201cIf a female wants to maximise her lifetime reproductive output, she has to balance having babies and living a long time. When conditions are getting worse, you pull back on having as many babies.\u201d<\/p>\n \u201cAnthropogenic climate disruption affects everything,\u201d Corkeron said. \u201cIt\u2019s just another message, if people choose to pay attention to it, that we\u2019ve got to do something about this.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" After decades of recovery, southern right whales are showing signs of a climate-driven decline in breeding rates, which scientists say is a \u201cwarning signal\u201d about changes in the Southern Ocean. After being hunted to near extinction by commercial whaling in the 19th and 20th centuries, southern right whales remained endangered in Australia. But long-term monitoring<\/p>\n","protected":false},"author":1,"featured_media":44252,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[50],"tags":[5189,186,187,1600,154,183,520,5265,9418,6493,312,4233,902],"class_list":{"0":"post-44251","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-birth","9":"tag-climate","10":"tag-crisis","11":"tag-fall","12":"tag-linked","13":"tag-raise","14":"tag-rates","15":"tag-researchers","16":"tag-signal","17":"tag-southern","18":"tag-warning","19":"tag-whale","20":"tag-whales"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/44251","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=44251"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/44251\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/44252"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=44251"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=44251"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=44251"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}