Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians
Abstract Accurate population size estimates are important information for sustainable wildlife management. The Romanian Carpathians harbor the largest brown bear (Ursus arctos) population in Europe, yet current management relies on estimates of density that lack statistical oversight and ignore unce...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2017-09-01
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| Series: | Ecology and Evolution |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/ece3.3177 |
| _version_ | 1818858755749576704 |
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| author | Viorel D. Popescu Ruben Iosif Mihai I. Pop Silviu Chiriac George Bouroș Brett J. Furnas |
| author_facet | Viorel D. Popescu Ruben Iosif Mihai I. Pop Silviu Chiriac George Bouroș Brett J. Furnas |
| author_sort | Viorel D. Popescu |
| collection | DOAJ |
| description | Abstract Accurate population size estimates are important information for sustainable wildlife management. The Romanian Carpathians harbor the largest brown bear (Ursus arctos) population in Europe, yet current management relies on estimates of density that lack statistical oversight and ignore uncertainty deriving from track surveys. In this study, we investigate an alternative approach to estimate brown bear density using sign surveys along transects within a novel integration of occupancy models and home range methods. We performed repeated surveys along 2‐km segments of forest roads during three distinct seasons: spring 2011, fall‐winter 2011, and spring 2012, within three game management units and a Natura 2000 site. We estimated bears abundances along transects using the number of unique tracks observed per survey occasion via N‐mixture hierarchical models, which account for imperfect detection. To obtain brown bear densities, we combined these abundances with the effective sampling area of the transects, that is, estimated as a function of the median (± bootstrapped SE) of the core home range (5.58 ± 1.08 km2) based on telemetry data from 17 bears tracked for 1‐month periods overlapping our surveys windows. Our analyses yielded average brown bear densities (and 95% confidence intervals) for the three seasons of: 11.5 (7.8–15.3), 11.3 (7.4–15.2), and 12.4 (8.6–16.3) individuals/100 km2. Across game management units, mean densities ranged between 7.5 and 14.8 individuals/100 km2. Our method incorporates multiple sources of uncertainty (e.g., effective sampling area, imperfect detection) to estimate brown bear density, but the inference fundamentally relies on unmarked individuals only. While useful as a temporary approach to monitor brown bears, we urge implementing DNA capture–recapture methods regionally to inform brown bear management and recommend increasing resources for GPS collars to improve estimates of effective sampling area. |
| first_indexed | 2024-12-19T09:01:20Z |
| format | Article |
| id | doaj.art-9eaeb515921247e6afdb44708e0dc56f |
| institution | Directory Open Access Journal |
| issn | 2045-7758 |
| language | English |
| last_indexed | 2024-12-19T09:01:20Z |
| publishDate | 2017-09-01 |
| publisher | Wiley |
| record_format | Article |
| series | Ecology and Evolution |
| spelling | doaj.art-9eaeb515921247e6afdb44708e0dc56f2022-12-21T20:28:28ZengWileyEcology and Evolution2045-77582017-09-017187134714410.1002/ece3.3177Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian CarpathiansViorel D. Popescu0Ruben Iosif1Mihai I. Pop2Silviu Chiriac3George Bouroș4Brett J. Furnas5Department of Biological Sciences Ohio University Athens OH USACentre for Environmental Research (CCMESI) University of Bucharest Bucharest RomaniaCentre for Environmental Research (CCMESI) University of Bucharest Bucharest RomaniaVrancea Environmental Protection Agency Focsani RomaniaAsociatia pentru Conservarea Diversitatii Biologice (ACDB) Focsani RomaniaCalifornia Department of Fish and Wildlife Wildlife Investigations Laboratory Rancho Cordova CA USAAbstract Accurate population size estimates are important information for sustainable wildlife management. The Romanian Carpathians harbor the largest brown bear (Ursus arctos) population in Europe, yet current management relies on estimates of density that lack statistical oversight and ignore uncertainty deriving from track surveys. In this study, we investigate an alternative approach to estimate brown bear density using sign surveys along transects within a novel integration of occupancy models and home range methods. We performed repeated surveys along 2‐km segments of forest roads during three distinct seasons: spring 2011, fall‐winter 2011, and spring 2012, within three game management units and a Natura 2000 site. We estimated bears abundances along transects using the number of unique tracks observed per survey occasion via N‐mixture hierarchical models, which account for imperfect detection. To obtain brown bear densities, we combined these abundances with the effective sampling area of the transects, that is, estimated as a function of the median (± bootstrapped SE) of the core home range (5.58 ± 1.08 km2) based on telemetry data from 17 bears tracked for 1‐month periods overlapping our surveys windows. Our analyses yielded average brown bear densities (and 95% confidence intervals) for the three seasons of: 11.5 (7.8–15.3), 11.3 (7.4–15.2), and 12.4 (8.6–16.3) individuals/100 km2. Across game management units, mean densities ranged between 7.5 and 14.8 individuals/100 km2. Our method incorporates multiple sources of uncertainty (e.g., effective sampling area, imperfect detection) to estimate brown bear density, but the inference fundamentally relies on unmarked individuals only. While useful as a temporary approach to monitor brown bears, we urge implementing DNA capture–recapture methods regionally to inform brown bear management and recommend increasing resources for GPS collars to improve estimates of effective sampling area.https://doi.org/10.1002/ece3.3177CarpathiansN‐mixture modelpopulation densityRomaniatrack surveyUrsus arctos |
| spellingShingle | Viorel D. Popescu Ruben Iosif Mihai I. Pop Silviu Chiriac George Bouroș Brett J. Furnas Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians Ecology and Evolution Carpathians N‐mixture model population density Romania track survey Ursus arctos |
| title | Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians |
| title_full | Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians |
| title_fullStr | Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians |
| title_full_unstemmed | Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians |
| title_short | Integrating sign surveys and telemetry data for estimating brown bear (Ursus arctos) density in the Romanian Carpathians |
| title_sort | integrating sign surveys and telemetry data for estimating brown bear ursus arctos density in the romanian carpathians |
| topic | Carpathians N‐mixture model population density Romania track survey Ursus arctos |
| url | https://doi.org/10.1002/ece3.3177 |
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