Moose populations in North America are declining across much of their
southern distribution due to a combination of factors that include habitat loss,
predation, parasitism, disease, and heat stress. Factors contributing to the
decline of the Shiras subspecies of the Rocky Mountain states, Alces alces
shirasi, include habitat loss, degradation and natural succession; predation by
a number of large carnivores; and possible parasitism by winter ticks and
artery worm; however, the relative contribution of each is unknown.
Knowledge of population demographics serves as a critical baseline for
evaluating and understanding factors leading to population declines. Moose
are solitary animals that prefer densely vegetated habitats and are usually
present at low densities, which mean that collecting population data can be
challenging. Because traditional methods of studying moose that require
capture, radio-collaring, and aerial surveys are costly, sometimes produce
unreliable results, and are discouraged in some jurisdictions such as National
Parks, alternate methods, such as non-invasive sampling, are being
evaluated. While the use of such methods have been used in estimating
population parameters of free-ranging black-tailed deer, woodland caribou,
and mountain goats, this study will be the first to demonstrate its use for
moose.
In December 2013, we initiated a three-year northern Yellowstone National
Park (YNP) moose population study with the main objective to estimate
population abundance and vital statistics of northern YNP moose using noninvasive methods. To do so, we are systematically collecting fresh fecal
pellets from the extent of northern Yellowstone moose wintering range during
two distinct one-month sampling periods (early winter and late-winter).
We are extracting DNA from epithelial cells on the pellet surface in order to
determine gender and individual genotype using microsatellite analysis. Using
enzyme immunoassay, pellet progestagen hormone concentrations are
quantified to determine the pregnancy status of female moose for estimating
population pregnancy rates. Various pellet sample measurements including
average volume, width and length are being used to differentiation between calf,
yearling, and adult age classes. Program MARK capture-recapture modeling and
a robust design survey will be employed to generate estimates of population
abundance, and age- and gender-specific rates of apparent survival, recruitment,
and population change.
This study will provide important moose population demographic data for YNP,
Montana, and Wyoming biologists and managers, a relatively inexpensive yet
accurate method for long-term population monitoring, and a practical and
effective tool to support the management and conservation of moose throughout
the Greater Yellowstone Ecosystem.