The US Navy continues to cover the oceans with tens of thousands of sonobuoys to monitor and detect submarine movement around the world. The DoD has allocated $178.5 million to buy an additional 136,000 sonobuoys.

About a meter-long, a typical sonobuoy device can be passive or active. The first type ‘listens’ to the noises produced by propellers of various kinds of vessels and pick out those made by a submarine. Active sonobuoys, sited in strategic points such as straits and harbors, can also sonar the water space around them to detect submarines.

The sonobuoys are usually positioned in designated areas from the air, typically by using SH-60F Seahawk helicopters.

“The United States Navy maintains a superior global Anti-Submarine Warfare (ASW) capability with the ability to detect, localize, identify, and track potential hostile submarines,” Global Security outlet said in 2011.

According to CNN, US sonobuoys are first and foremost aimed at tracking Russian submarines, over concerns they are “taking up positions near critical communication lines.”

US fears Russian subs near undersea cables may cut off communications - report https://t.co/yfw0Ql1HH3pic.twitter.com/xVMQQRZ76t — RT (@RT_com) October 27, 2015

Scientists say these sonar "intrusions" are proving deadly to marine wildlife, in particular whales. Sonar devices disrupt them and other sea mammals when nursing and feeding, which leads to injury or death of the animals who rely on sound to communicate and navigate, Elisa Allen, from People for the Ethical Treatment of Animals, told RT.

“Sonars can confuse and disorient them, terrify these animals,” Allen said. “Animals exposed to sonars have been known to rapidly change their depth in an attempt to escape the noise. This causes them to bleed from their ears and eyes,” she said, adding that whales and dolphins often beach themselves in their attempts to escape sonar.

198 pilot whales stranded on New Zealand beach http://t.co/MzVb2pTPhwpic.twitter.com/BCvJUs7ACw — RT (@RT_com) February 13, 2015

The lucrative $178,565,050 contract has been granted to ERAPSCO, a defense contractor in Columbia City, Indiana. Five types of sonobuoys are set to be delivered by October 2017.

ERAPSCO, a joint venture between the Sparton corporation and Ultra Electronics, has been producing military grade sonobuoys capable of detecting and classifying manmade objects traveling underwater since 1987.