This study measured the population dynamics of coyotes in the grasslands and creosote shrublands of McKenzie Flats, Sevilleta National Wildlife Refuge. The study was begun in January, 1992, and continued quarterly each year. Coyotes were sampled via scat counts along the roads of McKenzie Flats during winter, spring, summer, and fall of each year. The entire road transect was 21.5 miles in length. Scat counts over a week period (number of scats/mile/day) in each season along the roads were used to calculate the densities of coyotes (number of coyotes per square kilometer). Results from 1992 to 2002 indicated that autumn was the peak density period of the year, with generally steady declines through the year until the following autumn. Coyote populations appeared to fluctuate seasonally, but remained relatively stable at 0.27 +/- 0.03 (SE) coyotes per km2 during summer periods (this likely represents the "breeding pair" density, during which coyote pairs have set up territories and are raising young, but the pups have not as yet joined the parents in foraging activities).
The purpose of the study was to assess the dynamics of coyote populations in the grasslands and creosote shrublands of the Sevilleta NWR. Coyotes are important predators and omnivores in these habitats, feeding on a wide variety of vertebrates, arthropods, and plants. Populations of prey species may be controlled to some extent by coyote predation, in which case coyotes may have significant influences on the biodiversity and species composition of the desert grassland ecosystem.
The scats were sampled along 21.5 miles of roadway that was broken up into four "legs" of varying lengths.
Leg A: Black Butte southward to Five Points (5.7 miles).
Leg B: Five Points eastward to the turnoff before Palo Duro Canyon (4.1 miles).
Leg C: Palo Duro turnoff northward to the old McKenzie Headquarters site (6.1 miles).
Leg D: McKenzie Headquarters site northwestward to Black Butte (5.6 miles).
Each scat was the unit of sample.
Frequency of Sampling:
Sampled one week per season, four seasons per year.
Variable, depending on scat abundance.
Knowlton, Frederick F. 1984. Feasibility of Assessing Coyote Abundance on Small Areas. Unpublished Report, 14 pp.
The number of scats deposited by coyotes per mile of roadway per day in a typical western basin-and-range landscape has been shown to be correlated with the absolute density of coyotes. Therefore, the objective was to measure the deposition rate of coyote scats on the roads of McKenzie Flats.
The process involved two samplings along the roads. The first sampling involved the "clearing" of scats from the 21.5 mile survey route, so as to initialize the roadway with zero scats. On the assigned day, the technician would drive an ATV slowly (less than 5 miles per hour) along the route. When a coyote scat was observed, the technician would stop and pick up the scat, placing it into a zip-lock plastic bag that was labeled with the date and the "leg" letter. Each "leg" was bagged separately. The odometer reading of the scat location was recorded on the data sheet. If more than one scat was observed at the same place, the number of scats was recorded as well. For health and safety, the technician wore gloves during this process, or used tongs or a small trowell to pick up the scats and place them into the bag. When using the ATV, the technician wore a safety helmet.
During the early sampling periods (1992 to 1993), prior to the acquisition of the ATV in 1994, scats were collected by two technicians in a pick-up truck. One technician would drive, and the other would ride on the engine hood above the bumper, and scan the road as the truck was driven slowly along the road. When a scat was observed, the driver would stop the truck while the rider would collect the scat. The same data were recorded as described above.
One week following the "road clearing" survey, a second collection took place. The scats were sampled in the same fashion as before, but each scat was placed individually in a labelled small zip-lock plastic bag. Again, odometer readings were taken at the point of collection. Multiple scats from the same location were placed in separate plastic bags.
The scats were then returned to the field station, and placed in freezers for preservation pending analysis of dietary items.
Density values were computed as numbers of individuals per square kilometer. According to F. Knowlton (see reference above), the relationship between absolute densities of coyotes (x-value, independent variable) and the number of scats per night per mile x 100 (y-value, dependent variable) is:
Y = 2.66 + 11.42X, r2 = 0.97, n = 8
Transforming this equation for computing densities of coyotes from numbers of scats for each "leg" of the survey, and converting these values to numbers of coyotes per square kilometer, the coyote density equations for each survey "leg" are as follows:
D = Density of coyotes/km2, N = Total Number of Scats Collected/Leg
after a 7-day period.
Leg A (5.7 miles): D = [0.2195(N) - 0.2329]/2.59
Leg B (4.1 miles): D = [0.3052(N) - 0.2329]/2.59
Leg C (6.1 miles): D = [0.2052(N) - 0.2329]/2.59
Leg D (5.6 miles): D = [0.2235(N) - 0.2329]/2.59
The samples (scats) were collected in winter, spring, summer, and fall, of each year. Scats were collected from the road once at the beginning of a collection period, and once at the end (usually, one week later) during each of these four seasons per year. Months of collection varied in some years, but generally the sampling was conducted in January, April, July, and October. The study began in January, 1992, and is continuing.