In her Aug. 7 column, Louisa Willcox of the Natural Resources Defense Council claimed that the Yellowstone grizzly bear population should be relisted under the federal Endangered Species Act in order to prevent the population from going into a "tailspin." She took issue with the National Wildlife Federation's position that supports delisting now that all of the recovery targets have been achieved.

NWF believes that the recovery and delisting in 2007 of the Yellowstone grizzly bear population is a great conservation success story for the ESA. This successful recovery effort demonstrates that the ESA can work to recover even occasionally problematic large carnivores that exist at low densities, have low reproductive rates and occupy large landscapes. The success in Yellowstone resulted from hard work and significant investment by federal and state agencies and some conservation groups. Belittling and denying this success reduces the likelihood that similar success will be achieved elsewhere.

No wildlife biologist familiar with the data disagrees that Yellowstone grizzlies have tripled their numbers since the early 1980s and that grizzlies now roam over thousands of square miles from which they were previously exterminated. The population has increased at

4.5 percent per year during 1987-2008 because mortality quotas were (and remain) intentionally set to be conservative.

Mortality and reproductive rates typically vary from year to year so biologists base targets on data from several years. Willcox, however, continues to express alarm based on data from a single year. For example, when the count of females with cubs declined to 31 in 2005 compared to the 49 counted in the previous year, she claimed the government was covering up a "crash" in the population. Knowledgeable biologists, however, were not alarmed and subsequent counts proved that no crash had occurred.

Following delisting, state and federal governments have committed more financial resources to protect and manage grizzlies in Yellowstone. Agencies now spend $1 million a year more on grizzly monitoring and conservation in the Yellowstone ecosystem and monitor a much larger area for mortalities and other parameters than before delisting.

The Yellowstone grizzly population is the most studied bear populations in the world. Each year more than 10 percent of the Yellowstone grizzly bears wear active radio collars so that reproduction, movements, physical condition, food use and food availability can be monitored. These monitoring activities are conducted and coordinated by the federal Interagency Grizzly Bear Study Team just as they were before delisting. Their findings are reported annually in online reports and also published in peer-reviewed scientific journals (see: www.nrmsc.usgs.gov/scienceigbst/pubs).

Going forward, there are certainly many challenges facing both grizzlies and the agencies that are responsible for managing them. Whitebark pine may be one such issue, although nobody knows for sure what will happen to this bear food source in Yellowstone. What is clear, however, is that grizzlies are a generalist species that eat a wide variety of foods, switch quickly between food, and live in almost any habitat where they aren't killed. Populations continue to grow in areas where whitebark pine is gone and, in Yellowstone, during the frequent years of white bark pine failure. Nothing could ever be delisted if the bar was set at a height to accommodate frenzied speculation about the future.

There was high incidental mortality to bears last year caused primarily by poorly trained hunters shooting bears. However, the state and federal management agencies have moved quickly to identify sources and locations of the mortalities and have already agreed on how best to reduce them (see www.igbconline.org/YellowstoneMortalityReportFinalv2.pdf). Maps of mortality indicates that mortalities are increasingly occurring in areas into which the growing population has expanded. The distribution of these mortalities provides no reason to be alarmed that the core population of grizzlies in Yellowstone is declining.

The purpose of the Endangered Species Act is to get species to the point where federal protection is no longer needed. Acknowledging successes when they occur promotes conservation and collaboration to achieve the next success story - and helps all of us ensure America's wildlife heritage is protected for generations to come.

Sterling Miller is a senior wildlife biologist with the National Wildlife Federation, and writes from Missoula.