Warming Oceans May Be Decreasing Calving Rates in Whale Species

Southern Right Whales spotted near Hermanus in South Africa. (Photo: Olga Ernst via [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Southern_Right_Whales_(Hermanus).jpg), [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/deed.en))

Following centuries of commercial whaling that nearly eradicated them, southern right [whales](https://mymodernmet.com/puerto-madryn-argentina-whales-paolo-osta/) have gradually started to bounce back. Nevertheless, recent studies indicate that [climate change](https://mymodernmet.com/2025-earth-photo-awards/) could now be hindering this recovery. Researchers have found a correlation between rising ocean temperatures and a decrease in the number of calves produced by these massive marine creatures.

Southern right whales typically reproduce at a slow rate under standard circumstances, with females historically giving birth every three years. Lately, however, scientists have noted extended intervals between births. In some instances, mothers are now birthing calves approximately every four years.

Researchers speculate that this phenomenon might be linked to the warming waters of the Antarctic Ocean, where the whales spend a considerable amount of time foraging. These whales heavily depend on krill-like crustaceans that flourish in cold, nutrient-dense waters. As ocean temperatures rise and sea-ice distribution changes, krill populations may also be affected. When food becomes scarce, female whales might find it challenging to accumulate the energy reserves necessary for carrying and nursing their young.

This pattern was identified by analyzing decades of whale observations along the coastlines of Australia. By monitoring individual whales that return annually to the same calving grounds, scientists could track long-term trends in birth rates. Over time, the data illustrated a gradual increase in the time between calves.

Even though southern right whales are still on the mend from the period of industrial whaling, reduced reproduction rates could complicate their recovery. When species reproduce less often, population growth slows—regardless of adult whale survival. These findings underscore how climate change is impacting ocean ecosystems in intricate ways. Even species that have bounced back from former threats may encounter new obstacles as their surroundings continue to evolve.

Researchers investigating long-term whale populations discovered that female southern right whales are producing calves less frequently, possibly due to fluctuations in krill availability associated with climate change.

Photo: EjGarcia/[Depositphotos](https://depositphotos.com/)

While the species has regained numbers in many areas, researchers caution that prolonged reproduction cycles could hinder future efforts toward population recovery.

Photo: [email protected]/[Depositphotos](https://depositphotos.com/)

*Sources:* [Southern Right Whales Are Having Fewer Calves; Scientists Say a Warming Ocean Is to Blame](https://insideclimatenews.org/news/27022026/warming-ocean-southern-right-whales-fewer-calves/), [Southern right whales are having fewer calves: What this says about ocean health](https://phys.org/news/2025-10-southern-whales-calves-ocean-health.html), [Declining birth rates in southern right whales alarm researchers in new study](https://www.abc.net.au/news/2026-02-12/climate-change-driving-down-southern-right-whale-calving-numbers/106332214)

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