north continental divide - grizzly bears - igbc

Northern Continental Divide Ecosystem

The Northern Continental Divide Ecosystem (NCDE) is situated in northwestern Montana, and includes Glacier National Park, parts of the Flathead and Blackfeet Indian Reservations, parts of 5 national forests (Flathead, Helena, Kootenai, Lewis and Clark and Lolo), Bureau of Land Management lands, and a significant amount of state and private lands. Also within this region are 4 wilderness areas (Bob Marshall, Mission Mountains, Great Bear and Scapegoat), one wilderness study area (Deep Creek north), and one scenic area (Ten Lakes). The most intensive recovery efforts have been focused within the Recovery Zone and, as the grizzly bear population has expanded, efforts have also expanded into a buffer area identified as Zone 1. Together, these zones make up the Demographic Monitoring Area, where the objective is continual occupancy by grizzly bears, facilitated by maintenance of compatible habitat conditions and population criteria. The DMA encompasses more than 16,000 square miles (or 42,000 square kilometers).

The NCDE is believed to have the largest population of grizzly bears in the lower 48 states. In 2004, a large-scale sampling of grizzly bear DNA using hair-traps and rub trees was conducted across about 12,000 square miles (31,000 square kilometers) within and surrounding the Recovery Zone. Based on mark-recapture analyses of the individuals identified in the sample, Kendall et al. (2009) estimated that 765 grizzly bears made their home in the NCDE (95% confidence interval was 715–831). Female bears were found throughout the study area, indicating a good reproductive potential for the species. More information on the Northern Divide Grizzly Bear Project can be found on the USGS website Northern Divide Grizzly Bear Project 2002-2008.

Concurrent with this DNA study, an interagency team of state, federal, and tribal members was established to monitor the survival and reproductive rates of radio-marked grizzly bears throughout the Demographic Monitoring Area, from which population trend could be estimated. Results of the first 5 years of monitoring (2004–2009) were published by Mace et al. (2012) and a comprehensive report of analyses for 2004–2014 will be published in 2016. Estimates of vital rates indicate the NCDE population grew approximately 2.3%/year during 2004–2014. Assuming an initial population size of 765 bears in 2004, this suggests the grizzly bear population was approximately 960 bears in 2014 (the upper and lower bounds of the 95th percentile of population size were 837–1,089). As of 2014, radio-telemetry locations and verified sightings also indicated that the Demographic Monitoring Area was fully occupied by reproductive females (with cubs, yearling, or 2-year-old offspring), and that the grizzly bear population has expanded far beyond the Recovery Zone and is currently distributed over at least 22,000 square miles (or 56,000 square kilometers). More information on NCDE Grizzly Bear Population Monitoring can be found on the Montana Fish, Wildlife & Parks website Grizzly Bear Population Monitoring.

The NCDE subcommittee meets biannually to coordinate grizzly bear recovery efforts throughout the ecosystem. Agencies include Montana Fish, Wildlife & Parks, US Fish & Wildlife Service, US Park Service, USDA Forest Service, USDA APHIS-Wildlife Services, US Geological Survey, US Bureau of Land Management, Blackfeet Tribe, and Confederate Salish and Kootenai Tribes.

You can find more information about the Northern Continental Divide Ecosystem on the US Fish and Wildlife Service’s Northern Continental Divide Ecosystem Grizzly Bear Recovery page. On this page you will find a link to the Federal Register announcement of the “Initiation of 5-Year Reviews of Seven Wildlife Species and Two Plant Species in the Mountain-Prairie Region.”

Northern Continental Divide Ecosystem Subcommittee