Shipping and pleasure vessel traffic has increased greatly along the British Columbia coast in the last 20 years. The increase in vessel traffic causes an increase of noise and physical disturbance in killer whale habitat. Short term effects have been documented in killer whale behaviour; however, long-term effects of chronic disturbance are still unknown.
Vessel disturbance primarily affects whales behaviourally, causing them to turn their attention away from activities like foraging, feeding, socializing and breeding to avoid the vessel. A study by Rob Williams and colleagues in 2006 investigated the activities of northern resident killer whales in the presence and absence of boats. They found that around vessels, killer whales reduced their time spent feeding and beach rubbing (an important social activity for northern resident killer whales). The reduction in feeding activity may have significant impacts on energy intake of these animals. When salmon are scarce, this may by particularly worrisome for resident killer whale survival.
Killer whales also face the danger of ship strikes and being hit by boat propellers from fast-moving vessels. Injury from any ship strike or propeller cuts can result in death of the individual whale hit and any offspring that may rely on that whale. In 2006, two resident killer whales were killed by suspected ship strike in British Columbia. ‘Fife’ (A60) was also hit by a boat, and luckily survived.
To reduce the impact of vessels on killer whales, the Be Whale Wise guidelines have been developed.
Increased vessel traffic also increases the underwater noise level. Killer whales rely heavily on sound to communicate and navigate. Underwater noise pollution from boats and other human activities has the potential to interfere with the whales’ ability to communicate with one another while foraging, or to mask echolocation signals the whales use to locate prey. Studies done in Washington have shown that southern resident killer whales will increase their call volume in response to boat noise. In 2008, Marla Holt and colleagues found that for every 1dB increase in underwater noise, killer whales try to compensate by increasing their sound by 1dB. However, increasing vocal output in reaction to increased noise could potentially have energetic costs, cause higher stress levels, or reduce the ability of individuals to communicate. At some level, background noise may completely mask communication and echolocation.
Other sources of noise pollution are:
- Seismic surveys for offshore oil and gas
- Marine industrial equipment like coastal oil rigs
- Military exercises like low frequency sonar
- Underwater construction like pile drivers
- Acoustic harassment devices used by fishermen to keep seals and sea lions away from their nets
Photo: Doug Sandilands
When boats get too close, they may disrupt the natural behaviour of killer whales.
Photo: Doug Sandilands
When boats are traveling at high speeds in the presence of whales, the threat of vessel strike increases.
Photo: Graeme Ellis
This young killer whale, A82, was likely struck by a vessel in 2006. It did not survive.
Increased vessel traffic causes increased underwater noise, compromising the ability of killer whales to find food and communicate.