Ship Noise Stresses Freshwater Fish
Wysocki, L.E. et. al. Ship noise and corisol secretion in European freshwater fishes. Biological Conservation 128:501-508. 2006
A striking study, confirming what many have suspected: exposure to noise significantly increases the secretion of stress hormones in fish. If this result is replicated for other species, it could dramatically shift the debate about ocean noise, because stress has been widely shown to make animals dramatically more suceptible to disease, toxins, and other health threats. The study at hand involved three freshwater fish (carp, gudgeon, perch) exposed to recordings of ships on the Danube and two Austrian lakes. The researchers measured the level of cortisol in the water before and after noise exposure. Cortisol is the primary stress-related hormone in fish and many other animals. After thirty minutes of exposure to the ship noise, secretions of cortisol roughly doubled, increasing from 80-120% depending on the species of fish. Interestingly, there was no increase in cortisol when the fish were exposed to a steady white noise as intense as the loudest boat sounds, suggesting that the variability of the ship noise is more important than the intensity.
Loons Change Song to Impress New Neighbors - Male loons change their calls only slightly from year to year when living on the same pond for many seasons. But when males relocated from one lake to another, as 10% to 15% do each year, researchers heard something different. Comparing calls from 13 males recorded before and after a territory switch, researchers found that 12 males changed their songs significantly. "It came as a shock," says Cornell'ls Charles Walcott. "At first I didn't believe a word of it." That begged the question of why the birds were changing their tunes. It turned out that new loons accentuated differences between their calls and that of their predecessors'. This may help ensure that potential rivals know that a new master of the lake has arrived, Walcott says. Ornithologist Donald Kroodsma of the University of Massachusetts at Amherst says that this study suggests that loons have richer social lives than once thought. "It requires the birds all really know each other," says Kroodsma. "We never give them enough credit for the knowledge they have of their fellow beings." Source: ScienceNow, 2/23/06 [READ ARTICLE] Cornell Press Release, 3/7/06 [READ PRESS RELEASE]
Autonomous Gliders Used for Acoustic Monitoring - For the first time, researchers have used autonomous underwater "gliders" as a platform for recording whale vocalizations. Previously, acoustic monitoring relied on hydrophones installed on bouys or the ocean floor, or deployed from ships. Scientists at the Woods Hole Oceanographic Institution (WHOI) have reported the first use of passive acoustic recorders in an ocean glider, a type of AUV (autonomous underwater vehicle) that looks like a large model airplane and can work in water depths to 1,000 meters (about 3,300 feet) or more. Gliders move both horizontally and vertically in the ocean and work around the clock in all weather conditions, typically up to a month or longer depending on the project. The vehicle carries a variety of high-resolution sensors to collect oceanographic measurements such as temperature, salinity, and fluorescence (a measure of phytoplankton abundance). Gliders also operate silently, which make them ideal for passive acoustics studies. Researchers say the gliders are a promising, cost-effective, and efficient alternative to long-term ship-based studies given ship costs in the thousands of dollars a day. Source: Eurekalert/WHOI Press Release, 2/21/06 [READ PRESS RELEASE] Seattle Post-Intelligencer, 3/4/06 [READ ARTICLE]
Helicopter Surveys Cause Minimal Disturbance to Seals, Penguins
Colin Southwell. Response behavior of seals and penguins to helicopter surveys over the pack ice off East Antarctica. Antarctic Science 17 (3), 328–334 (2005) [READ PAPER(PDF)]
Helicopter surveys are often used to monitor population levels of animals. In this study, researchers examined avoidance behavior, in response to the noise of the aircraft. They found that penguins moved more often and farther than seals, but that the distance moved seemed inconsequential. At close range (under 400m from the flight path), over half the penguins moved; the farthest any moved was 20m, but 90% moved less than 12m. Seals showed a similar extreme of movement, though 90% of those moving went less than 5m and far fewer responded: only about 20% moved at all, with another 25% exibiting an alert response without movement. Both animals showed some movement out to the limits of the test, 800m. While these results suggest that using aircraft for ocassional biological surveys is likely to not cause any dramatic impacts on populations, it also suggests that areas with high levels of aircraft traffic (eg, near villages, scientific outposts, common backcountry destinations, or industrial development) deserve to be examined for chronic modest behavioral disruption or increases in stress.
Right Whale Calls Changing in Industrialized Habitats
Parks, Clark, Tyack. Acoustic communication in the north atlantic right whale (Eubaleana glacialis) and potential impacts of noise. Presented at Ocean Science 2006 conference, January 2006.
Noting that the North Atlantic Right whale vocal repertoire is becoming better understood (sounds are used for making long-range contact, formation of social groupings, and reproductive advertisement), and that the whales live in a highly industrialized habitat, this study investigated changes in the whales' calls over time that may be in response to rising noise levels. On short time scales (minutes), both the fundamental and peak frequency of calls increase in the presence of elevated noise levels. On longer time scales (decades), the minimum and maximum frequency of a key whale call, the "upcall", have increased between the late 1950s and 2004; this increasing frequency has been gradually noted over decades. The North Atlantic Right whale upcalls are at a significantly higher frequency than the Southern Right whales' calls, which may be a result of differing ambient noise conditions in their environment. These results are significant, as they present evidence for a long-term, chronic behavioral change in the North Atlantic Right whale calling behavior that may be a result of increased levels of anthropogenic noise.
