From The Journal of Wildlife Management (JWM)
Credit: TWS
Credit: TWS
Cruise Ships Make Seals Splash
pup-rearing, breeding, and molting—reacted to passing or approaching ships. The team found that once a ship came within 500 meters, seals were increasingly likely to flush into the water. At 200 meters, 77 percent of seals would enter the water. Flushing into the cold water of Alaska has significant implications for seal pup survival, the authors note. While pups normally spend approximately 40 percent of their time in the water, an increase to 50 percent could put them in an energy deficit. To prevent seals from having to expend extra energy, the authors say that cruise ship regulations must be updated.
By Hair or By Scat
believed to have become established. Additional studies from both SRS and Alabama point to fawns being an important food source for coyotes. Though the authors note that several of their “lines of evidence” are correlations and don’t prove causation, the observations warrant further research into the impact of coyotes on deer populations.
Close to one million visitors each summer take a cruise in Alaska. This cruise ship traffic, which has steadily increased since the 1980s, is disturbing harbor seals (Phoca vitulina), according to a report in JWM (v. 74/6). Researchers from NOAA’s National Marine Mammal Laboratory led by John Jansen took observations of harbor seals from the decks of cruise ships entering or leaving Alaska’s Disenchantment Bay from May to August 2002. They watched to see how adults and pups that were hauled out on ice on the tidewater glacial fjords—important habitat for
Research on reintroduced gray wolf (Canis lupus) populations in the northern Rocky Mountains has relied mainly on radio telemetry, a highly informative but invasive and expensive technique. Hoping to find a more efficient tool for long-term monitoring, a team led by Jennifer Stenglein of the University of Idaho tested the accuracy of wolf hair and scat genetic sampling in central Idaho over two years, reporting their results in JWM (v. 74/5). The team collected samples in areas they predicted to be wolf rendezvous sites based on vegetation, topography, and other characteristics. They then analyzed the DNA using microsatellite loci. The genetic analysis identified a total of 122 individual wolves, more than four and a half times the number of radio-collared wolves in the same area. Researchers only needed to “capture,” or obtain a sample from, the same wolf 1.7 times for an accurate population estimate. The authors note that randomly selecting just half to three-quarters of all likely rendezvous sites and sampling for DNA could reduce the time and costs of analysis while still producing an accurate population estimate.
Coyote Creep
It’s well known that coyote (Canis latrans) populations have expanded their range in recent decades, even reaching areas where they are not native, such as some parts of the southeastern U.S. In a commentary in JWM (v. 74/5), John Kilgo of the USDA Forest Service Southern Research Station and colleagues discuss several observations that suggest that coyotes may be the reason for declining white-tailed deer (Odocoileus virginianus) recruitment, or survival of fawns to adulthood, in the Southeast. An increase in coyote numbers in South Carolina between 1997 and 2006, for example, mirrors a decline in the estimated statewide deer population during the same period. Further studies at the Savannah River Site (SRS) have revealed that fawn-to-doe ratios dropped sharply from before 1990 to the late-1990s and early2000s—just when the coyote population at the site is © The Wildlife Society
Discouraging Perching
In wide open spaces like the sagebrush steppe of the Intermountain West, power lines provide raptors with attractive places to perch—which is bad news for prey. Some scientists suggest that power lines may be part of the reason that prey species like greater sage grouse (Centrocercus urophasianus) are in trouble. Researchers Steven Slater and Jeff Smith of HawkWatch International wanted to see if perching deterrents such as spikes on power-line structures could keep raptors away. At sites in southwestern Wyoming, they recorded raptor presence, behavior, and any nearby prey remains at power lines equipped with deterrent devices that had been erected two years prior. They also studied control sites where power lines lacked deterrent devices. Reporting in JWM (v. 74/5), they note that over the course of a year they observed raptors or ravens 13 times more often on power line structures without perch deterrents than on structures with intact deterrents. They also found 97 percent fewer single prey items and 87 percent fewer grouped prey items at the deterrent sites. The authors suggest that managers should consider the availability of other perches in the surrounding landscape, and weigh the considerable financial costs of installing perching deterrents, just one of many tools available to conserve threatened species.
See this department online at www.wildlife.org for a complete list of articles recommended by TWP’s Editorial Advisory Board.
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