Is climate change causing failed pregnancies in humpback whales?

Humpback whale breaching

A survey has found that the calving rate of humpback whales in the Gulf of St Lawrence off Canada has halved in the past 15 years. It is believed that this might be caused by warmer water due to climate change. This is because female humpback whales feed on herring and crustaceans and the population of these prey items are declining due to warmer waters. Therefore the females are not getting enough sustenance to enable them to accumulate the energy reserves required to maintain pregnancy or to feed newborn calves.

Humpback whale breaching

Humpback whale breaching. Image by ArtTower from Pixabay

The study was carried out by scientists at the University of St Andrews. They studied blubber samples and sightings of female humpback whales which enabled them to measure breeding success between 2004 and 2018.

They found that there was a decline from 40% of females having calves to 20% over the period. Since commercial whaling stopped in 1986 humpback whale numbers have increased particularly in the Southern Ocean.

The study was published in the journal Global Change Biology and the lead author, Joanna Kershaw, said that climate change is starting to affect the reproduction of the population of northern hemisphere humpback whales.

She said that, “It is possible that other, less well-studied populations are also experiencing declines and calving rates. Humpback whales and other top marine predators are sentinel species, so if there are significant changes at a population level it suggests that there are issues in their environment that are causing problems.”

It is now almost universally accepted that climate change truly does exist and that it is having a profound effect upon the natural world including the conservation of all species and in this instance the reproduction of humpback whales. Climate change is a human-generated major conservation issue.

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