Aerial surveys adjusted by ground surveys to estimate area occupied by black‐tailed prairie dog colonies

Abstract

Aerial surveys using line‐intercept methods are one approach to estimate the extent of prairie dog colonies in a large geographic area. Although black‐tailed prairie dogs (Cynomys ludovicianus) construct conspicuous mounds at burrow openings, aerial observers have difficulty discriminating between areas with burrows occupied by prairie dogs (colonies) versus areas of uninhabited burrows (uninhabited colony sites). Consequently, aerial line‐intercept surveys may overestimate prairie dog colony extent unless adjusted by an on‐the‐ground inspection of a sample of intercepts. We compared aerial line‐intercept surveys conducted over 2 National Grasslands in Colorado, USA, with independent ground‐mapping of known black‐tailed prairie dog colonies. Aerial line‐intercepts adjusted by ground surveys using a single activity category adjustment overestimated colonies by ≥94% on the Comanche National Grassland and ≥58% on the Pawnee National Grassland. We present a ground‐survey technique that involves 1) visiting on the ground a subset of aerial intercepts classified as occupied colonies plus a subset of intercepts classified as uninhabited colony sites, and 2) based on these ground observations, recording the proportion of each aerial intercept that intersects a colony and the proportion that intersects an uninhabited colony site. Where line‐intercept techniques are applied to aerial surveys or remotely sensed imagery, this method can provide more accurate estimates of black‐tailed prairie dog abundance and trends. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Long‐Term Effects of Black‐Tailed Prairie Dogs on Livestock Grazing Distribution and Mass Gain

“…Beginning in 2008, we designated 4 pastures at CPER (2 130-ha and 2 390-ha pastures) containing active prairie dog colonies as areas where prairie dogs would be allowed to coexist with cattle. We mapped the boundaries of active black-tailed prairie dog colonies in these pastures during September or October each year during 2008-2019 following methods described by Sidle et al (2012). On the remainder of CPER (~5,360 ha), prairie dogs have been controlled annually since 2008 with rodenticides (implemented by the USDA Animal and Plant Health Inspection Service-Wildlife Services; Fig.…”

“…The CPER was created in 1937, and the first scientist to work there (D. F. Costello) wrote in his memoir ( ~ 1949; on file at CPER) “We have never made a complete list of the wildlife of the experimental range… The lone prairie dog in [pasture] 15‐W eventually died of ennui, or a coyote got him.” Prairie dogs remained extirpated from CPER from the 1940s through the 1980s, and then subsequently recolonized 4 locations on the property in the 1990s. Mapping of prairie dog colony boundaries began in 1997 using global positioning system (GPS) devices (Sidle et al 2012) with 6 documented colonies in 5 different pastures totaling 22 ha. Subsequent annual mapping showed that colonies expanded continuously for the next 9 years (Derner et al 2006), reaching a maximum of 961 ha in 2006.…”

“…Prairie dogs remained extirpated from CPER from the 1940s through the 1980s, and then subsequently recolonized 4 locations on the property in the 1990s. Mapping of prairie dog colony boundaries began in 1997 using global positioning system (GPS) devices (Sidle et al 2012) with 6 documented colonies in 5 different pastures totaling 22 ha. Subsequent annual mapping showed that colonies expanded continuously for the next 9 years (Derner et al 2006)…”

Testing for Thresholds in a Semiarid Grassland: The Influence of Prairie Dogs and Plague

“…The outermost boundaries of these colonies were mapped annually using global positioning system technology beginning in 1997 and continuing until 2011, with the exception that colonies were not mapped in 1998, 1999, or 2001. Mapping of colony boundaries followed methods described by Sidle et al (2012). Colony expansion primarily occurred during 2000-2006sizes were 8, 12, 18, and 31 ha in 2000and expanded to 129, 200, 244, and 245 ha, respectively, in 2006.…”

Combining Occurrence and Habitat Suitability Data Improve Conservation Guidance for the Giant Kangaroo Rat

“…Giant kangaroo rats are an ideal species for testing remote survey methods because they produce highly visible, distinct sign that indicates long‐term habitat quality, and they have a relatively small distribution. Though it may be difficult to survey entire ranges for species with larger distributions, this method is feasible for species that are visible in imagery (e.g., manatees [ Trichechus manatus ], Miller et al 1998; elephants [ Loxodonta africana ], Vermeulen et al 2013) or create conspicuous sign (e.g., beavers [ Castor canadensis ], Martin et al 2015; prairie dogs [ Cynomys ludovicianus ], Sidle et al 2012) over portions of their ranges. Projects can be scaled depending on need.…”