K. Shawn Smallwood

A track count for estimating mountain lion Felis concolor californica population trend

Abstract Reliable estimates of status and population trend are critical for conservation of large terrestrial carnivores, but are usually lacking due to the high costs of sampling across large geographic areas. For detecting population trends of mountain lion Felis concolor californica, we evaluated counts of track sets on 48 randomly chosen quadrats in California. Each quadrat contained 33.8 km of transect on dusty, dirt roads, which were chosen by local wildlife biologists. A count of track sets by one person on all quadrats was more efficient than recording presence/absence by local survey teams. We estimated an efficient sample size of 44 quadrats in California after applying our data to a general formula for contagious distributions. This sample size can be reduced substantially by choosing new transect locations based on associations of tracks with topography and habitat. Tracks were most likely found on roads along 1st- and 2nd-order streams, on mountain slopes and knolls/peaks and in oak woodland and montane hardwood conifer forest. A changing mountain lion population can be detected with an inexpensive, periodic track survey and self-stratifying, non-parametric tests. Each track survey across California can be finished in 30 days. The many mountain lions and the variety of environmental conditions included at this extraordinarily large spatial scale permit estimates of: (1) trends among population strata in quadrats that are clustered according to typical number and age/sex class of track sets; (2) population size and demography after individuals are identified by their tracks, and after linear density on roads is calibrated from spatial density at intensive study, sites: and (3) spatio-temporal associations with bobcat Felis rufus, black bear Ursus americanus, coyote Canis latrans, and fox Vulpes vulpes and Urocyon cinereoargenteus.

A rigorous technique for identifying individual mountain lions Felis concolor by their tracks

Abstract We introduce a rigorous technique to make individual animal identification by tracks more objective than previously possible. With measurements from acetate tracings of two to six tracks from each rear foot of nine mountain lions Felis concolor, multiple-group discriminant analysis accurately grouped 100% and 92% of the tracks from the left and right rear feet, respectively. From bootstrap analyses we concluded that mountain lion track set discrimination was best achieved with the spread of the outer toes, heel width, and the midline width of the heel pad. After further research, this technique can be used to improve population studies of mountain lions and other large animals.

Site invasibility by exotic birds and mammals

Abstract Eradication of exotic species has been proposed to protect the integrity of nature reserves, but this can be a futile attack on symptoms without curing the causes of site invasibility—the susceptibility of a site to invasion by exotic species. More exotic bird and mammal species are found in California nature reserves that are surrounded by agriculture and human settlement, and that have suffered reduced richness of native mammal species. The chaparral ecotope contains 37 of the 41 exotic bird and mammal species in California, many of which are confined to large urban centers or residences. Farmland and settlements in the grassland ecotope support 17 of the wider-ranging exotic species. Site invasibility did not decrease with habitat area, but habitat fragmentation might lower biotic resistance in reserves by reducing mammal species richness and abundance after restricting dispersal. Reserve integrity can be best protected by landscape management that promotes native mammal species richness in and around reserves.

A Sustainable Agro-ecological Solution to Water Shortage in the North China Plain (Huabei Plain)

A highly seasonal rainfall pattern in the agriculturally productive region of Huabei Plain has been widely considered in China as a handicap to maximizing agricultural production. Enhancing this perception is the traditional policy of achieving provincial or regional self-sufficiency in grain production, which underlies Chinas production quotas. The Chinese government has decided to overcome this perceived handicap in order to meet the increasing water demands of urban populations and to achieving its grain quotas by constructing aqueducts to transport about 14 2 10 9 m 3 of water from the Dan Jiang Reservoir into the Huabei Plain. However, this engineering construction solution threatens the long-term market competitiveness of the region by driving up the cost of water relative to the value of the product, by taking too long to complete and by being unproven in its effectiveness. This solution also threatens the existing ecosystem by interfering with the natural hydrology, and it risks exacerbating the ongoing groundwater overdrafts that are contributing to the formation of numerous sinkholes and ground surface cracks in the region, as well as to the intrusion of sea water. A more certain, ecologically sound solution can be found in alternative agricultural practices and cropping systems. Reducing the winter wheat production by a relatively small acreage, combined with the increased use of water-saving irrigation systems, can more than replace the effectively usable 10 2 10 9 m 3 of water that the engineering construction project would transport via aqueducts. The recommended alternative cropping system would solve the water shortage problem immediately. This alternative would enable the government to allocate funds where they are more needed, such as to the clean-up of extensively polluted rivers and to ecological restoration, which bears on the sustainability of agriculture and food supply in China.

Interpreting puma ( Puma concolor ) population estimates for theory and management

Estimates of population size have been essential for ecological theory and wildlife management, but they depend on spatial scales of observation. Reported aspects of study and interpretive design were tested to see if they could explain variation in puma ( Puma concolor ) density. Comparison of puma studies revealed information shortfalls and possible confounding effects in research trends. Vegetation descriptions and other biological and physical aspects of the study site explained none of the 30-fold range of variation in puma density, nor did sampling and estimation methods and other aspects of study and interpretive design. Most (78%) of the variation in puma density estimates can be explained by the spatial extent of study area. Given the effect of scale, puma density estimates have been inappropriately extrapolated to larger geographic areas for management purposes. Due to spatial shifting of local population clusters, conventional density estimates cannot contribute to assessments of puma population trend without study at multiple sites over longer periods of time. Field studies would contribute more to knowledge of puma by spanning larger areas, a greater variety of land uses and habitats, and more of pumas range of distribution.

A rating system for potential exotic bird and mammal pests

Abstract Natural areas, natural resources, and agricultural production systems have been damaged by introduced species, and are jeopardized by future invasions. A rating system was developed to prioritize research and control efforts for preventing species invasions and eradicating established exotic pests. Four rating criteria were the species potential (1) to be introduced; (2) to establish; (3) to cause damage; and (4) to be controlled. Each species was rated independently for each criterion, and these ratings summed to provide a total score. The rating system was developed with 24 exotic bird and mammal species with well-known invasion and pest histories. We then rated the 14 bird and mammal species on the California Department of Food and Agriculture most unwanted exotic species list, and 10 other species. The rating system provided surprising objectivity for assessing the threat of species invasion and pest status. Of the 14 ‘most unwanted species’, four were rated as a low threat, and 13 of the 34 other rated species were recommended for this list. Certainly, this list should be lengthened. A quick-response apparatus was also developed to provide information on perceived exotic species threats. It consisted of a data base of expert contacts and citations on exotic pest species damage, biology, ecology, and control technology.

Scale domains of abundance amongst species of mammalian Carnivora

The spatial requirements of populations ought to be central to developing conservation strategies and ecological theory, but they are difficult to identify from the published collection of reported population estimates. Transforming population estimates into density and log values may have clouded recognition of the discontinuous relationship that exists between abundance estimates and the areas within which they were made. I used abundance estimates of terrestrial mammalian Carnivora to identify scale domains of abundance. In scale domain A, the study areas were too small to include all the individuals of the population, and abundance estimates increased propor-tionally with study area size. Scale domain B included high variation in abundance estimates, but these estimates no longer increased with increasing size of study area as they did in domain A. I refer to the smallest area in the scale domain B as the threshold area (the minimum area known to support a population of the particular species). The abundance in scale domain B averaged 52 individuals amongst all but three outlier species. Scale domains C and D were also identified, and included much larger study areas and substantially larger abundance estimates. The threshold area is the first empirically-derived representation of the minimum space used by populations of each species. However, nearly half of all carnivore abundance estimates were made in areas smaller than the threshold area, and only 4% could be used to represent transitions between scale domains B, C and D. The remainder varied within domains B, C and D due to variation in environmental conditions and research methods. Most comparisons of density between sites and between species have been made without considering whether the estimates represented the true population or some collection of individuals more or less abundant than the population. Threshold area can be used as a standard area against which to estimate and compare population density, in lieu of more appropriately comparing estimates of region-wide density, which generally do not yet exist. Also, threshold area could be predicted with reasonable error rates based on a typical species body mass, brain mass and home range size. Therefore, conservation biologists may now have a tool to identify the minimum habitat areas needed to conserve populations of carnivore species, and theoretical ecologists can relate ecological space at the population level to allometric variables.

Comparing pocket gopher (Thomomys bottae) density in alfalfa stands to assess management and conservation goals in northern California

Pocket gophers (Thomomys bottae) affect alfalfa (Medicago sativa L.) production in Yolo County, California, as well as the distribution of special status, rare species that either prey on gophers or use their burrows as habitat. Farming practices, as well as attributes of the landscape and of alfalfa fields, were compared to 134 estimates of gopher density among 35 alfalfa stands scattered throughout the County during 1992–1994. Gophers in alfalfa fields averaged only one-fourth the average density among published reports, and the range from low to high density was much smaller in alfalfa fields. Gopher density was greater at the field edge, especially during the first 2 years of stand production. Preference for the edge decreased by the third year of alfalfa production as gophers used the available space in the field interior. A stepwise multiple regression model could explain 73% of the variation in the 134 estimates of gopher density. This variation was explained by years since sowing of the alfalfa (standardized slope coefficient, β ≈ 0.52), annual frequency of flood irrigation (β ≈− 0.43), habitat area as a percentage of the landscape within a 500 m buffer around the field (β ≈ 0.31), season of the year (β ≈ 0.25), field size (β ≈− 0.20) and percentage of sand within the top soil layer (β ≈ 0.16). This model can be used to predict the distribution of special status species that depend on gophers, and can be used to guide conservation efforts by increasing the spatial extent of non-cultivated gopher habitat on suitable areas intervening alfalfa fields. Non-cultivated gopher habitat is currently rare in the valley portion of Yolo County. Gopher control failed to influence density to the magnitude sought by the alfalfa growers, and cessation of control would benefit both production and conservation goals in some alfalfa growing regions.