An improved method of censusing deer in deciduous-coniferous forests

T.J. Floyd; L.D. Mech; M.E. Nelson

doi:10.2307/3800668

Home/Archive/USGS

USGS · 5221165

An improved method of censusing deer in deciduous-coniferous forests

T.J. Floyd·L.D. Mech·M.E. Nelson

View original source ↗Export metadata ↓

Abstract

Aerial censusing has been used to determine densities of many large mammals, including deer ( Odocoileus virginianus ) in agricultural areas or deciduous forests (Saugstad 1942, Morse 1946, Petrides 1953, Sanderson 1953, Berner pers. comm.). However, observability of deer from the air remains a problem in northern coniferous forests. LeResche and Rausch (1974) determined that even with the much larger and more observable moose ( Alces alces ) during ideal snow conditions, experienced observers counted only 68% of a known number of animals; inexperienced observers counted 43%. Caughley (1974) and Caughley et al. (1976) suggested that the best solution to the problem of observability in aerial censuses is to measure the magnitude of the biases that exist, and correct estimates accordingly. This paper describes an attempt to measure observability bias in an aerial census of deer in deciduous coniferous habitat and to produce an accurate estimate of numbers.

Explore related subjects

The Journal of Wildlife Management Article

Source-reported bounding extent: 43.500415° to 49.383079° latitude; -97.239209° to -89.489226° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

T.J. Floyd, L.D. Mech, M.E. Nelson. 1979. An improved method of censusing deer in deciduous-coniferous forests. https://doi.org/10.2307/3800668

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

A strategic method for expanding the Pacific Flyway Motus network

Understanding the movement and survival of birds of conservation concern during migration is critical for guiding conservation action. Unfortunately, the migratory life stage is understudied in many bird species because of the challenges of following such species over large distances, particularly those with small body sizes. One established method for tracking movement of small avian species is the Motus Wildlife Tracking System. This international collaborative network provides a powerful tool for tracking survival and movement, enabling estimation of parameters such as stopover duration, migratory connectivity, dispersal, and survival that are otherwise difficult to measure. While the Motus network is well established in eastern North America, coverage in the western part of the continent is limited, constraining sample sizes needed for robust demographic modeling. Expanding the Motus network is therefore a high priority for Pacific Flyway agencies. To date, methods for determining priority locations for new Motus receiving stations do not explicitly incorporate species occurrence. In collaboration with partners across the western United States and the Canadian Province of British Columbia, we used eBird data to prioritize strategic locations for new Motus receiving stations. We modeled multi-species co-occurrence, defined by abundance thresholds met in multiple weeks, using environmental and survey covariates while accounting for imperfect detection. Using occupancy model predictions, we identify high-use areas where new Motus stations are most likely to detect multiple species of interest. While the predictive maps provide a framework for strategically expanding the Motus network and supporting conservation of migratory stopover and wintering habitats in the Pacific Flyway, we also provide the analysis code and prediction output to support the expansion of Motus in additional regions.

Pacific flyway↗

USGS2025

Social composition of soft‐release groups is correlated with survival of translocated gopher tortoises

The social structure of translocated animal populations can have important effects on the survival and reproduction of translocated individuals for both solitary and social species. The gopher tortoise ( Gopherus polyphemus ) is a reptile of conservation concern that is currently experiencing high levels of mitigation translocation in Florida, USA. Individuals live in aggregations of burrows with frequent agonistic, courtship, and burrow-sharing interactions between residents. Given that exposure to many unfamiliar individuals may increase the frequency of aggressive interactions and social stress following translocation, we predicted that tortoises with greater numbers of familiar individuals co-translocated from the same origin site would have higher survival after translocation. To test this, we updated a recently published survival analysis of 2,822 translocated tortoises and 502 identified carcasses from a translocation site in the western Florida panhandle from 2006–2022. After controlling for simultaneous effects of soft-release enclosure identity, release season, release density, region of origin, sex, and size, adding the number of potentially familiar individuals improved model fit and showed increasing the number of familiars reduced the probability of being found dead. This effect was modulated by release density, being apparent only when density was high, suggesting a role for social interactions. This effect was also present only in the first few years after release, prior to the removal of soft-release enclosures preventing dispersal, and was similar in magnitude to previously identified effects of density, release season, and region of origin. We suggest that this effect may result from reduced aggressive interactions or social stress for tortoises with a greater number of familiar individuals in their release enclosures but cannot rule out the possibility of reduced novel pathogen exposure for individuals released with a greater number of individuals from the same source site or other factors that may be confounded with the size of translocated groups. Designing and implementing mitigation translocations to account for social composition of gopher tortoise groups could improve survival in release enclosures.

Florida↗

USGS2024

Density estimation using spatial capture-recapture analyses: Application to vaccination of prairie dogs against sylvatic plague

Prairie dogs are notoriously difficult to enumerate, with previously methods including visual counts, mark-resight, burrow counts, and catch per unit effort. Unlike those methods, spatial capture-recapture (SCR) analyses allow for formal estimation of density along with associated estimates of uncertainty, detection probability, and the size of the average area over which an individual was detected during the study period (referred to as an activity center). Using SCR analyses, we compared density estimates as part of a field trial evaluating the effectiveness of an oral sylvatic plague vaccine in black-tailed prairie dogs ( Cynomys ludovicianus ), Gunnison's prairie dogs ( C. gunnisoni ), white-tailed prairie dogs ( C. leucurus ), and Utah prairie dogs ( C. parvidens ) at 11 study areas in the western United States. The study was designed as a matched pairs analysis that included 27 individual paired plots (54 plots), each consisting of a plot treated with vaccine baits and a plot treated with placebo baits. Overall, we captured >3,000 individuals each year on these plots, and recapture rates ranged from 5–87%. For black-tailed prairie dogs, density estimates ranged from 2.7 individuals/ha (95% CI = 2.2–3.3/ha) to 77.3/ha (63.2–94.4/ha), and for Gunnison's prairie dogs, estimates ranged from 11.7/ha (10.6–12.8/ha) to 15.4/ha (14.4–16.7/ha). White-tailed prairie dogs were at their lowest density (3.3/ha, 95% CI = 2.9–3.8/ha) during the first year of the study and their highest density (14.5/ha; 13.5–15.6/ha) during the last year of the study. Utah prairie dog density estimates ranged from a low of 4.0/ha (95% CI = 3.55–4.6/ha) to a high of 20.8/ha (16.8–25.8/ha). Best-fitting models of prairie dog density indicated increasing patterns of density over time on most study plots, negative effects of plague, and positive effects of vaccination. Finally, we found low correlations between catch per unit effort estimates from previous published literature at these sites and our densities estimates. Spatial capture-recapture estimates allowed us to consistently compare treatment effects across space and time, although some exceptions are noted where we observed significant movement between plots within a pair (3 pairs) and when trapping effort between plots or years was not consistent.

Arizona, Colorado, Montana, South Dakota, Utah, Wy↗