Human earwax, a sticky substance, accumulates many clues about the health of the host over time, as does whales giant earwax.
Figure 1: Measuring stress hormones in humpback whales is unusually difficult, so scientists are excited to find records of hormone levels in whale earwax.
For centuries, museum curators around the world have extracted large amounts of earwax from dead whales. Thanks to these earwaxes, scientists are now discovering how human activity has put pressure on whales over the past 150 years.
Stephen Trumble, a comparative physiologist at Baylor University, and his colleagues published the findings this month in the Journal Nature Communications.
It has been proved that human activities, from whaling to war to climate change, are tremendous stress-inducing factors that have a tremendous impact on whale behavior, even if we do not interact directly with them.
Each wax of a whale can be more than 50 centimeters long and weighs about 1 kilogram. It contains a lot of information about the whales living environment and clues about whales health. Moreover, because earwax accumulates in layers, similar to tree rings, researchers can obtain data on everything from pesticide contamination to reproductive cycles.
But trump and his colleagues are particularly keen to study whales response to human activities. One of the best ways is to measure hormone levels released by animals under pressure, such as cortisol.
It is very difficult to get long-term data on whale hormone levels. Tracking and sampling is virtually impossible in whales entire life. Whale whiskers used by whales to filter food contain information for about 10 years, but these animals usually live for 50 to 100 years, so this can only help us understand the limited information about whales.
On the other hand, whales earwax provides decades of data. However, Tran Bull said it is not easy to extract such information. Separation of the wax layer for analysis, each containing information about whale life for about six months, may require several days of careful work.
But the result is worth it. Its unprecedented to be able to combine stress factors with whale responses, especially throughout the life cycle, Trumble said.
Nick Kellar, a cetacean biologist at the National Oceanic and Atmospheric Administration (NOAA), agrees. This represents the best available science on the non-lethal effects of whaling and is a major advance in this field.
Figure 2: In the 20th century, baleen whales were badly hit by the whaling industry. Although they are on the verge of extinction, they are still the target of whalers.
War and global warming
In the new study, hormone data from 20 baleen whales, humpback whales and blue whales showed that whaling activities were closely related to whale pressure from the late 19th century to the 1970s, when legislation greatly reduced whaling activities. Tran Bull said, the result of our surprise is relevance.
Although researchers expect whaling to increase stress on whales, they did not anticipate that hormone levels would decrease as hunting decreased. These whales truly reflect their environment, and they are similar to danger warning, Trumble added.
But then there was another pressure factor, the global war. We suspect that during World War II, the increase in cortisol in whales may be the result of noise from aircraft, bombs, ships and so on, Trumble said.
After about 1970, especially after 1990, researchers found a worrying trend: cortisol levels also rose rapidly with the rise of water temperature. This shows that climate change has also put pressure on whale. Temperature rise can affect animals in many ways, from changing the location and number of prey to directly affecting their physiological function. Trumble said he and his colleagues are still working to reduce climate change factors that contribute to increased whale pressure. More research is needed, because the association with temperature is based on the wax found in 6 whale. In addition, Keira said he wanted to take into account other variables, such as the cause of animal death, because natural aging also affects hormone levels. But that does not mean there is no climate link between them. The best way to solve this problem is to study more whale earwax. Luckily, this is exactly what the trump plan is to do. He said they need to analyze dozens of samples of earwax. Source: NetEase science editor: Qiao Jun Jing _NBJ11279
After about 1970, especially after 1990, researchers found a worrying trend: cortisol levels also rose rapidly with the rise of water temperature. This shows that climate change has also put pressure on whale.
In addition, Keira said he wanted to take into account other variables, such as the cause of animal death, because natural aging also affects hormone levels. But that does not mean there is no climate link between them. The best way to solve this problem is to study more whale earwax. Luckily, this is exactly what the trump plan is to do. He said they need to analyze dozens of samples of earwax.