Abundance and population growth estimates for bare‐nosed wombats
Abstract Wildlife managers often rely on population estimates, but estimates can be challenging to obtain for geographically widespread species. Spotlight surveys provide abundance data for many species and, when conducted over wide spatial scales, have potential to provide population estimates of g...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2023-09-01
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| Series: | Ecology and Evolution |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/ece3.10465 |
| _version_ | 1797542919435976704 |
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| author | Wiebke Knoblauch Scott Carver Michael M. Driessen Rosemary Gales Shane A. Richards |
| author_facet | Wiebke Knoblauch Scott Carver Michael M. Driessen Rosemary Gales Shane A. Richards |
| author_sort | Wiebke Knoblauch |
| collection | DOAJ |
| description | Abstract Wildlife managers often rely on population estimates, but estimates can be challenging to obtain for geographically widespread species. Spotlight surveys provide abundance data for many species and, when conducted over wide spatial scales, have potential to provide population estimates of geographically widespread species. The bare‐nosed wombat (Vombatus ursinus) has a broad geographical range and is subject to spotlight surveys. We used 19 years (2002–2020) of annual spotlight surveys to provide the first estimates of population abundance for two of the three extant bare‐nosed wombat subspecies: V. u. ursinus on Flinders Island; and V. u. tasmaniensis on the Tasmanian mainland. Using distance sampling methods, we estimated annual rates of change and 2020 population sizes for both subspecies. Tasmanian mainland surveys included habitat data, which allowed us to also look for evidence of habitat associations for V. u. tasmaniensis. The average wombat density estimate was higher on Flinders Island (0.42 ha−1, 95% CI = 0.25–0.79) than on the Tasmanian mainland (0.11 ha−1, CI = 0.07–0.19) and both wombat subspecies increased over the 19‐year survey period with an estimated annual growth rate of 2.90% (CI = −1.7 to 7.3) on Flinders Island and 1.20% (CI = −1.1 to 2.9) on mainland Tasmania. Habitat associations for V. u. tasmaniensis were weak, possibly owing to survey design; however, we detected regional variation in density for this subspecies. We estimated the population size of V. u. ursinus to be 71,826 (CI = 43,913–136,761) on Flinders Island, which when combined with a previously published estimate of 2599 (CI = 2254–2858) from Maria Island, where the subspecies was introduced, provides a total population estimate. We also estimated 840,665 (CI = 531,104–1,201,547) V. u. tasmaniensis on mainland Tasmania. These estimates may be conservative, owing to individual heterogeneity in when wombats emerge from burrows. Although these two subspecies are not currently threatened, our population estimates provide an important reference when assessing their population status in the future, and demonstrate how spotlight surveys can be valuable to inform management of geographically widespread species. |
| first_indexed | 2024-03-10T13:37:21Z |
| format | Article |
| id | doaj.art-fab86c3ce39043e3bacb719b8afd3395 |
| institution | Directory Open Access Journal |
| issn | 2045-7758 |
| language | English |
| last_indexed | 2024-03-10T13:37:21Z |
| publishDate | 2023-09-01 |
| publisher | Wiley |
| record_format | Article |
| series | Ecology and Evolution |
| spelling | doaj.art-fab86c3ce39043e3bacb719b8afd33952023-11-21T07:26:25ZengWileyEcology and Evolution2045-77582023-09-01139n/an/a10.1002/ece3.10465Abundance and population growth estimates for bare‐nosed wombatsWiebke Knoblauch0Scott Carver1Michael M. Driessen2Rosemary Gales3Shane A. Richards4Department of Biological Sciences University of Tasmania Hobart Tasmania AustraliaDepartment of Biological Sciences University of Tasmania Hobart Tasmania AustraliaDepartment of Natural Resources and Environment Tasmania Hobart Tasmania AustraliaDepartment of Natural Resources and Environment Tasmania Hobart Tasmania AustraliaSchool of Natural Sciences University of Tasmania Hobart Tasmania AustraliaAbstract Wildlife managers often rely on population estimates, but estimates can be challenging to obtain for geographically widespread species. Spotlight surveys provide abundance data for many species and, when conducted over wide spatial scales, have potential to provide population estimates of geographically widespread species. The bare‐nosed wombat (Vombatus ursinus) has a broad geographical range and is subject to spotlight surveys. We used 19 years (2002–2020) of annual spotlight surveys to provide the first estimates of population abundance for two of the three extant bare‐nosed wombat subspecies: V. u. ursinus on Flinders Island; and V. u. tasmaniensis on the Tasmanian mainland. Using distance sampling methods, we estimated annual rates of change and 2020 population sizes for both subspecies. Tasmanian mainland surveys included habitat data, which allowed us to also look for evidence of habitat associations for V. u. tasmaniensis. The average wombat density estimate was higher on Flinders Island (0.42 ha−1, 95% CI = 0.25–0.79) than on the Tasmanian mainland (0.11 ha−1, CI = 0.07–0.19) and both wombat subspecies increased over the 19‐year survey period with an estimated annual growth rate of 2.90% (CI = −1.7 to 7.3) on Flinders Island and 1.20% (CI = −1.1 to 2.9) on mainland Tasmania. Habitat associations for V. u. tasmaniensis were weak, possibly owing to survey design; however, we detected regional variation in density for this subspecies. We estimated the population size of V. u. ursinus to be 71,826 (CI = 43,913–136,761) on Flinders Island, which when combined with a previously published estimate of 2599 (CI = 2254–2858) from Maria Island, where the subspecies was introduced, provides a total population estimate. We also estimated 840,665 (CI = 531,104–1,201,547) V. u. tasmaniensis on mainland Tasmania. These estimates may be conservative, owing to individual heterogeneity in when wombats emerge from burrows. Although these two subspecies are not currently threatened, our population estimates provide an important reference when assessing their population status in the future, and demonstrate how spotlight surveys can be valuable to inform management of geographically widespread species.https://doi.org/10.1002/ece3.10465bare‐nosed wombatdistance samplinggeographically widespread speciespopulation estimatespotlight survey |
| spellingShingle | Wiebke Knoblauch Scott Carver Michael M. Driessen Rosemary Gales Shane A. Richards Abundance and population growth estimates for bare‐nosed wombats Ecology and Evolution bare‐nosed wombat distance sampling geographically widespread species population estimate spotlight survey |
| title | Abundance and population growth estimates for bare‐nosed wombats |
| title_full | Abundance and population growth estimates for bare‐nosed wombats |
| title_fullStr | Abundance and population growth estimates for bare‐nosed wombats |
| title_full_unstemmed | Abundance and population growth estimates for bare‐nosed wombats |
| title_short | Abundance and population growth estimates for bare‐nosed wombats |
| title_sort | abundance and population growth estimates for bare nosed wombats |
| topic | bare‐nosed wombat distance sampling geographically widespread species population estimate spotlight survey |
| url | https://doi.org/10.1002/ece3.10465 |
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