People.
It used to be hunting. Now we're killing the whale's food (krill) with a combination of overfishing and warming the planet.
People catch about 200,000 tons of krill per year.
As if catching all the krill isn't bad enough, climate change is melting sea ice, which is where the krill's food lives. So, a warming ocean kills off marine algae, which means that krill numbers drop, which means that blue whale numbers drop.
Stupid People
there has been a decrease in blue whales because people keep killing them and people are pouting the water.
Think about it. God created whales and people are killing whales we are not only killing off his creation, we are disrupting the ecosystem.
they get the pleasure of drinking the whales blood!
Blue whales are so big that killing them "humanely" - meaning fast and painlessly - is difficult. Blue whales breed slowly, meaning that any hunting can easily reduce the population. Blue whales are probably quite intelligent as animals go, and may form long-lasting relationships with others of their species. Their upset when family members die may be comparable to ours. Blue whales are no longer actually needed for human consumption. Those items we used to get from whales can now be functionally replaced with materials from other sources.
Yes, I think it can. I heard that sharks had been killing them and blue whales are endangered so people aren't very impressed with the sharks.
Because people are killing them.
people litter,pullute and somtimes kill blue whales
For their body parts, as in blubber and meat to sell. People are trying to stop the people who are killing them. If you are still interested whatch whale wars on tv.
they use them for food or some people just like killing whales
Weel is true <3
They are endangered because the Japanese are killing them for their fins, which are used as a medical purpose.
Because we live in a messed up world...