Climate change shrinks... whales

Nature has its own rules by which it tries to face challenges of all kinds. Gray whales in the Pacific Ocean have shrunk by 13% over two decades, according to a study that provides new clues to the effects of climate change on the marine mammals. The decline could have major repercussions on these whales' ability to reproduce and survive, and could also affect their food systems, scientists warn. In a study published in the journal Global Change Biology, researchers focused on a small group of about 200 gray whales in the northeastern Pacific Ocean. Considered the "sentinels of the ecosystem", these cetaceans stay close to the coasts and feed in shallower and warmer waters compared to other gray whale populations. Previous studies have shown that this group of whales, smaller and more delicate, are not in as good shape as other whale populations. "Currently, we know that their bodies have shrunk over the past 20 to 40 years, which is probably a precursor to a risk of population decline," Kevin Bierlich, co-author of the study, explained to AFP . The researchers analyzed drone footage from 2016-2022 of 130 whales whose age was estimated or known and found an average decrease of 13% in the length of adult whales between individuals born in 2000 and those born in 2020. the equivalent of a reduction of 1.65 meters in individuals with a length of 13 meters. The reduction is more pronounced in the case of females, which were usually larger than males, but which have now reached the same height as them. "Size is essential in the case of animals," emphasized Enrico Pirotta, researcher and lead author of the study. "It affects their behavior, psychology, life cycle and has cascading effects on the animals and the population of which they are a part", he explained. Reproduction is particularly affected as the chances of survival of smaller cubs may be lower. In addition, the study established a correlation between this decrease in length and the disruption of the ocean cycle caused by climate change, especially the currents that allow the development of plankton, the food of whales.