A new study found that pacific coast grey whales have shrunk in length since 2000, adding to evidence that climate change and human activities are making marine mammals smaller.

Researchers from University of St Andrews in Scotland and Oregon State University of the United States focused on about 200 whales that are part of the wider Eastern North Pacific population of around 14,500.

By analyzing drone images taken from 2016 to 2022 of 130 individuals whose age was estimated or known, the scientists found a striking trend: a grey whale born in 2020 is likely to reach a full-grown adult length of approximately 1.65 meters less than one born in 2000.

This represents a significant 13 percent decrease in the total length of mature grey whales, which typically measure 11 meters to 12 meters in length.

It would be the equivalent of seeing the average height of an American woman plummeting from 162 centimeters to 142 centimeters over two decades.

Their diminished size could have big impacts on survival rates and reproductive success, according to research published in the journal Global Change Biology.

The study also found the trend was correlated with changes to the balance of "upwelling" and "relaxation" cycles of the ocean.