MONITORING AND ASSESSMENT OF WOLF-UNGULATE INTERACTIONS AND TRENDS WITHIN THE GREATER YELLOWSTONE ECOSYSTEM
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Ken Hamlin
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RESEARCH COMPONENTS
Methodology for Montana State University Wolf Monitoring Activities
We currently are intensively monitoring wolves and wolf predation on the
East Madison (EM), Gallatin
Canyon (GC), and Madison-Firehole
(MF) study sites. We are collaborating with the NPS and USFWS wolf restoration teams (Doug
Smith, Ed Bangs, Joe Fontaine), standardizing methodologies, coordinating field
efforts and sharing data. Wolf population data will be collected primarily by
the NPS/USFWS teams by maintaining a minimum of two VHF radio-equipped wolves in
all known packs to facilitate intensive aerial monitoring for determining pack
size, reproduction and territorial boundaries. Currently, USFWS captures wolves
by darting from a helicopter during early to mid-winter. This technique is
expensive, generally restricted to periods of adequate snow cover, and
constrained by limited availability of certified aircraft and pilots. Leg-hold
trapping, which is successfully used throughout North America, will be explored
as an alternative method for capturing wolves during the denning and rendezvous
periods.
If adequate numbers of wolves can be captured we also anticipate deploying 1-2 GPS collars in each of the study packs. The collars are designed to collect and store location data 12-18 times daily, with a programmed drop-off mechanism allowing the collars to be recovered for data retrieval without needing to handle animals a second time. A GPS collar was tested in the Taylor Peak pack during the winter of 2001 with excellent results. The GPS unit dropped off the wolf on the programmed date and was retrieved 3 days later on a forest trail. The unit had an 89% success rate, obtaining approximately 1100 locations, revealing the detailed movements of the pack throughout the time the collar was deployed. We anticipate programming GPS collars to be deployed for one-year periods, collecting location data as frequently as memory and battery capacity will permit. Such data will greatly facilitate our efforts to understand the potential influence of wolves on the distribution of elk as well as facilitate detection of kill sites.
| We will use ground telemetry techniques to estimate the number and location of wolves occupying the study area daily and to facilitate detecting fresh snow trails for tracking and locating kills. Radio signals from all collared wolves known to frequent the study area will be checked from roads daily, with periodic scans for other collared wolves associated with more distant packs. Approximate locations of each collared wolf will be acquired daily using ground-based triangulation employing a minimum of 3 azimuths (White and Garrott 1990). In order to locate wolf-killed prey, recent wolf trails in snow will be followed (Kolenosky 1972, Peterson et al. 1984, Huggard 1993). Attempts will be made to cover all wolf trails made in a 24-hour period to locate all kills. The vicinity of triangulated and aerial wolf locations and scavenger activity will be searched for tracks and kills when the wolves move from the area to assure research activities did not influence wolf behavior. To determine cause of death, necropsies will be performed on all ungulate carcasses discovered in the study area. Age of adult elk will be determined through cementum annuli analysis of incisor (I1 when possible) and/or canine teeth (Hamlin et al. 2000). To index body condition of all ungulates found dead, the fat level in bone marrow will be examined. We will saw through the middle of the femur and assess percent fat content (Harder and Kirkpatrick 1994), in 3 categories: (1) white and solid, (2) spotted pink—red solid, and (3) gelatinous (Cheatum 1949). |
Rose Jaffe radio-tracking wolves in Yellowstone using telemetry |
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Graduate student Justin Gude performing a necropsy on an elk |
The important parameters to be estimated from wolf tracking are predation rates (number of prey killed/100 wolf days) and total offtake (total number of prey animals killed by wolves). An estimated predation rate can be calculated using the estimated number of kills and the estimated number of wolf days of predation on each study site. For each day of 170-day annual field seasons, we will use all information available from ground and aerial telemetry, snow tracking, and opportunistic sightings of wolf sign to estimate the number of wolves present in the study system, referred to as ‘wolf days’. Not all kills are detected and the number of wolves on the study area cannot be known exactly. Therefore, we have developed a weighting scheme based on a subjective measure of observation efficiency to adjust the daily data on wolf days and number of kills to better estimate predation rates and offtake. Offtake, the number of elk killed by wolves, for the intensive winter-spring field season will be estimated by multiplying the estimated daily predation rate and the number of wolves in the study area that day (wolf days) and summing these values for the entire field season. |
Data from all wolves in the study area were used in the offtake estimation and subtracted from each estimated available prey type on the study area to estimate the proportion of the elk population killed by wolves according to species, sex, and age class. This analytical approach has been developed and refined by Bob Garrott, one of his graduate students (Rose Jaffe), and MSU statistics professor John Borkowski working with data collected over that past three years on the MF study site. The algorithms have been developed into an analytical program, which provides estimates of the predation rates and offtake an includes graphical displays of the seasonal patterns of these parameters.
Although the ground-based methodology will be our primary technique for locating kills on all three study sites, the NPS research team will continue their intensive aerial survey approach to detecting kills (known as ‘winter study’) for the wolf packs occupying portions of YNP (Chief Joseph, Nez Perce). During two 1-month periods each winter (mid-November through mid-December and March) the NPS team will locate each wolf pack via fixed wing aircraft. In an effort to observe hunting techniques and locate kills an attempt will be made to sight each pack and observe the animals continuously for a period of time if the wolves are determined to be traveling or hunting (Smith et al. 2000). Either an NPS or MSU ground-based team will attempt to visit each kill site detected from the air and record species, sex, relative condition and age of prey, and parts eaten. Outside these intensive sampling periods the NPS or FWS team will continue to locate all instrumented wolf packs in or near our study areas at approximately 10-15 day intervals.
Grizzly bears (Ursus arctos) may also prey on elk, but it does not appear that these losses will materially affect our study of wolf predation. It can be expected that grizzlies will take over wolf kills in the spring, and that some opportunistic killing of calves will occur. Our main demographic analyses will be based on rates of recruitment (spring calf-cow ratios) to the elk population aged 1 year and older. Calf predation by grizzly bears (and black bears, Ursus americanus) mainly occurs in the first few weeks of life (Singer et al. 1997), and is thus already incorporated in the existing baseline data on spring calf-cow ratios.
