34 results on '"Chandler, Richard"'
Search Results
2. Ecological filtering shapes the impacts of agricultural deforestation on biodiversity
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Hua, Fangyuan, Wang, Weiyi, Nakagawa, Shinichi, Liu, Shuangqi, Miao, Xinran, Yu, Le, Du, Zhenrong, Abrahamczyk, Stefan, Arias-Sosa, Luis Alejandro, Buda, Kinga, Budka, Michał, Carrière, Stéphanie M., Chandler, Richard B., Chiatante, Gianpasquale, Chiawo, David O., Cresswell, Will, Echeverri, Alejandra, Goodale, Eben, Huang, Guohualing, Hulme, Mark F., Hutto, Richard L., Imboma, Titus S., Jarrett, Crinan, Jiang, Zhigang, Kati, Vassiliki I., King, David I., Kmecl, Primož, Li, Na, Lövei, Gábor L., Macchi, Leandro, MacGregor-Fors, Ian, Martin, Emily A., Mira, António, Morelli, Federico, Ortega-Álvarez, Rubén, Quan, Rui-Chang, Salgueiro, Pedro A., Santos, Sara M., Shahabuddin, Ghazala, Socolar, Jacob B., Soh, Malcolm C. K., Sreekar, Rachakonda, Srinivasan, Umesh, Wilcove, David S., Yamaura, Yuichi, Zhou, Liping, and Elsen, Paul R.
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- 2024
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3. Modeling abundance, distribution, movement and space use with camera and telemetry data
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Chandler, Richard B., Crawford, Daniel A., Garrison, Elina P., Miller, Karl V., and Cherry, Michael J.
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- 2022
4. An integrated path for spatial capture–recapture and animal movement modeling
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McClintock, Brett T., Abrahms, Briana, Chandler, Richard B., Conn, Paul B., Converse, Sarah J., Emmet, Robert L., Gardner, Beth, Hostetter, Nathan J., and Johnson, Devin S.
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- 2022
5. Distance sampling and spatial capture-recapture for estimating density of Northern Bobwhite
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Nolan, Victoria, Wilhite, Nathan, Howell, Paige E., Chandler, Richard B., Ingram, Dallas, Yeiser, John M., Scott, Chris, and Martin, James A.
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- 2023
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6. Monitoring partially marked populations using camera and telemetry data
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Margenau, Lydia L. S., Cherry, Michael J., Miller, Karl V., Garrison, Elina P., and Chandler, Richard B.
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- 2022
7. Individual‐level biotic interactions and species distribution models.
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Gaya, Heather E. and Chandler, Richard B.
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SPECIES distribution , *POINT processes , *CLIMATE change , *MARKOV processes , *WARBLERS , *SPATIAL variation - Abstract
Aim: Accounting for biotic interactions in species distribution models is complicated by the fact that interactions occur at the individual‐level at unknown spatial scales. Standard approaches that ignore individual‐level interactions and focus on aggregate scales are subject to the modifiable aerial unit problem (MAUP) in which incorrect inferences may arise about the sign and magnitude of interspecific effects. Location: Global (simulation) and North Carolina, United States (case study). Taxon: None (simulation) and Aves (case study). Methods: We present a hierarchical species distribution model that includes a Markov point process in which the locations of individuals of one species are modelled as a function of both abiotic variables and the locations of individuals of another species. We applied the model to spatial capture‐recapture (SCR) data on two ecologically similar songbird species—hooded warbler (Setophaga citrina) and black‐throated blue warbler (Setophaga caerulescens)—that segregate over a climate gradient in the southern Appalachian Mountains, USA. Results: A simulation study indicated that the model can identify the effects of environmental variation and biotic interactions on co‐occurring species distributions. In the case study, there were strong and opposing effects of climate on spatial variation in population densities, but spatial competition did not influence the two species' distributions. Main Conclusions: Unlike existing species distribution models, the framework proposed here overcomes the MAUP and can be used to investigate how population‐level patterns emerge from individual‐level processes, while also allowing for inference on the spatial scale of biotic interactions. Our finding of minimal spatial competition between black‐throated blue warbler and hooded warbler adds to the growing body of literature suggesting that abiotic factors may be more important than competition at low‐latitude range margins. The model can be extended to accommodate count data and binary data in addition to SCR data. [ABSTRACT FROM AUTHOR]
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- 2024
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8. Measuring the benefit of a defensive trait: Vigilance and survival probability.
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Ellsworth, William H., Peacor, Scott D., Chandler, Richard B., Conner, L. Mike, Garrison, Elina P., Miller, Karl V., and Cherry, Michael J.
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PUMAS ,FORAGING behavior ,BIOLOGICAL fitness ,PREDATION ,PREDATORY animals ,PROBABILITY theory - Abstract
Defensive traits are hypothesized to benefit prey by reducing predation risk from a focal predator but come at a cost to the fitness of the prey. Variation in the expression of defensive traits is seen among individuals within the same population, and in the same individual in response to changes in the environment (i.e., phenotypically plastic responses). It is the relative magnitude of the cost and benefit of the defensive trait that underlies the defensive trait expression and its consequences to the community. However, whereas the cost has received much attention in ecological research, the benefit is seldom examined. Even in a defensive trait as extensively studied as vigilance, there are few studies of the purported benefit of the behavior, namely that vigilance enhances survival. We examined whether prey vigilance increased survival and quantified that benefit in a natural system, with white‐tailed deer (Odocoileus virginianus) experiencing unmanipulated levels of predation risk from Florida panther (Puma concolor coryi). Deer that spent more time vigilant (as measured by head position using camera trap data) had a higher probability of survival. Indeed, an individual deer that was vigilant 75% of the time was more than three times as likely to be killed by panthers over the course of a year than a deer that was vigilant 95% of the time. Our results therefore show that within‐population variation in the expression of a defensive trait has profound consequences for the benefit it confers. Our results provide empirical evidence supporting a long‐held but seldom‐tested hypothesis, that vigilance is a behavior that reduces the probability of predation and quantifies the benefit of this defensive trait. Our work furthers an understanding of the net effects of a trait on prey fitness and predator–prey interactions, within‐population variation in traits, and predation risk effects. [ABSTRACT FROM AUTHOR]
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- 2024
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9. A Comparison of Regional Climate Projections With a Range of Climate Sensitivities
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Barnes, Clair R., primary, Chandler, Richard E., additional, and Brierley, Christopher M., additional
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- 2024
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10. Genomics‐informed conservation units reveal spatial variation in climate vulnerability in a migratory bird
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Miller, Caitlin V., primary, Bossu, Christen M., additional, Sarraco, James F., additional, Toews, David P. L., additional, Rushing, Clark S., additional, Roberto‐Charron, Amélie, additional, Tremblay, Junior A., additional, Chandler, Richard B., additional, DeSaix, Matthew G., additional, Fiss, Cameron J., additional, Larkin, Jeff L., additional, Haché, Samuel, additional, Nebel, Silke, additional, and Ruegg, Kristen C., additional
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- 2023
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11. Characterising spatial structure in climate model ensembles
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Chandler, Richard E., primary, Barnes, Clair R., additional, and Brierley, Chris M., additional
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- 2023
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12. Individual-level biotic interactions and species distribution models
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Gaya, Heather, primary and Chandler, Richard, additional
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- 2023
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13. Genomics-informed conservation units reveal spatial variation in climate vulnerability in a migratory bird
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Miller, Caitlin, primary, Bossu, Christen, additional, Sarraco, James, additional, Toews, David, additional, Rushing, Clark, additional, Roberto-Charron, Amélie, additional, Tremblay, Junior A., additional, Chandler, Richard, additional, DeSaix, Matthew, additional, Fiss, Cameron, additional, Larkin, Jeff, additional, Haché, Samuel, additional, Nebel, Silke, additional, and Ruegg, Kristen, additional
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- 2023
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14. Estimating Owl Population Density Using Acoustic Spatial Capture-Recapture.
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Martin, Lily H., Hepinstall-Cymerman, Jeffrey, Chandler, Richard B., Cooper, Robert J., Parrish, Michael C., Hao, Lingyu, and Stevenson, Ben C.
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Acoustic spatial capture-recapture (SCR) methods appear ideally suited for estimating population trends of cryptic species that are difficult to monitor. Despite evidence suggesting acoustic SCR offers greater precision over estimates obtained through distance sampling or mark-recapture approaches, it has seldom been applied to avian taxa. Here we assess the utility of acoustic SCR for estimating population density of owls, a group of birds for which population estimates are generally lacking. We conducted passive acoustic surveys for Barred Owls (Strix varia) and Great Horned Owls (Bubo virginianus) over the spring breeding seasons of 2020–2021 in a protected park in Georgia, USA. We used a combination of acoustic discrimination techniques to identify individuals, including spectrogram cross-correlation, hierarchical clustering, and visual scanning. The resulting estimates of the density of Great Horned Owl individuals (0.28 ± 0.026 [SE] per km
2 ) were consistent with population density estimates from previous studies in other parts of the species' range. However, our methods appeared unsuitable for distinguishing Barred Owl individuals, which prevented estimation of population density for this species. We provide recommendations to improve acoustic sampling and individual discrimination of owls and suggest that acoustic SCR offers important advantages over conventional methods for monitoring some cryptic birds. Los métodos de captura-recaptura espacial (CRE) acústica parecen ser ideales para estimar las tendencias poblacionales de especies crípticas que son de difícil seguimiento. A pesar de la evidencia que sugiere que la CRE acústica ofrece mayor precisión que las estimaciones obtenidas mediante muestreo de distancia o enfoques de marcado-recaptura, ésta rara vez se ha aplicado a taxones aviares. Evaluamos la utilidad de la CRE acústica para estimar la densidad poblacional de búhos, un grupo de aves para el cual generalmente faltan estimaciones poblacionales. Realizamos estudios acústicos pasivos para Strix varia y Bubo virginianus durante las temporadas de cría en las primaveras del 2020 y 2021 en un parque protegido de Georgia, EEUU. Utilizamos una combinación de técnicas de discriminación acústica para identificar individuos, incluyendo correlación cruzada de espectrogramas, agrupacion jerárquica y escaneo visual. Las estimaciones resultantes de la densidad de individuos de B. virginianus (0.28 ± 0.026 [EE] por km2 ) fueron consistentes con las estimaciones de densidad poblacional obtenidas en estudios realizados previamente en otras áreas del rango de distribución de la especie. Sin embargo, nuestros métodos parecieron inadecuados para distinguir individuos de S. varia, lo que impidió la estimación de su densidad poblacional. Ofrecemos recomendaciones para mejorar el muestreo acústico y la discriminación individual de búhos, y sugerimos que la CRE acústica ofrece importantes ventajas sobre los métodos convencionales utilizados para el seguimiento de algunas aves crípticas. [Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]- Published
- 2024
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15. Characterizing Spatial Structure in Climate Model Ensembles.
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Chandler, Richard E., Barnes, Clair R., and Brierley, Chris M.
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ATMOSPHERIC models , *SINGULAR value decomposition , *MULTIVARIATE analysis , *ORTHOGONAL functions - Abstract
This paper presents a methodology that is designed for rapid exploratory analysis of the outputs from ensembles of climate models, especially when these outputs consist of maps. The approach formalizes and extends the technique of "intermodel empirical orthogonal function" analysis, combining multivariate analysis of variance techniques with singular value decompositions (SVDs) of structured components of the ensemble data matrix. The SVDs yield spatial patterns associated with these components, which we call ensemble principal patterns (EPPs). A unique hierarchical partitioning of variation is obtained for balanced ensembles in which all combinations of factors, such as GCM and RCM pairs in a regional ensemble, appear with equal frequency: suggestions are also proposed to handle unbalanced ensembles without imputing missing values or discarding runs. Applications include the selection of ensemble members to propagate uncertainty into subsequent analyses, and the diagnosis of modes of variation associated with specific model variants or parameter perturbations. The approach is illustrated using outputs from the EuroCORDEX regional ensemble over the United Kingdom. [ABSTRACT FROM AUTHOR]
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- 2024
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16. The unmarked R package: Twelve years of advances in occurrence and abundance modelling in ecology
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Kellner, Kenneth F., primary, Smith, Adam D., additional, Royle, J. Andrew, additional, Kéry, Marc, additional, Belant, Jerrold L., additional, and Chandler, Richard B., additional
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- 2023
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17. Genomics‐informed conservation units reveal spatial variation in climate vulnerability in a migratory bird.
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Miller, Caitlin V., Bossu, Christen M., Sarraco, James F., Toews, David P. L., Rushing, Clark S., Roberto‐Charron, Amélie, Tremblay, Junior A., Chandler, Richard B., DeSaix, Matthew G., Fiss, Cameron J., Larkin, Jeff L., Haché, Samuel, Nebel, Silke, and Ruegg, Kristen C.
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CLIMATE change ,MIGRATORY birds ,SPATIAL variation ,WILDLIFE conservation ,ENDANGERED species ,MOBILE genetic elements ,PHYLOGEOGRAPHY - Abstract
Identifying genetic conservation units (CUs) in threatened species is critical for the preservation of adaptive capacity and evolutionary potential in the face of climate change. However, delineating CUs in highly mobile species remains a challenge due to high rates of gene flow and genetic signatures of isolation by distance. Even when CUs are delineated in highly mobile species, the CUs often lack key biological information about what populations have the most conservation need to guide management decisions. Here we implement a framework for CU identification in the Canada Warbler (Cardellina canadensis), a migratory bird species of conservation concern, and then integrate demographic modelling and genomic offset to guide conservation decisions. We find that patterns of whole genome genetic variation in this highly mobile species are primarily driven by putative adaptive variation. Identification of CUs across the breeding range revealed that Canada Warblers fall into two evolutionarily significant units (ESU), and three putative adaptive units (AUs) in the South, East, and Northwest. Quantification of genomic offset, a metric of genetic changes necessary to maintain current gene–environment relationships, revealed significant spatial variation in climate vulnerability, with the Northwestern AU being identified as the most vulnerable to future climate change. Alternatively, quantification of past population trends within each AU revealed the steepest population declines have occurred within the Eastern AU. Overall, we illustrate that genomics‐informed CUs provide a strong foundation for identifying current and future regional threats that can be used to inform management strategies for a highly mobile species in a rapidly changing world. [ABSTRACT FROM AUTHOR]
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- 2024
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18. Habitat associations of Golden-winged Warblers and Blue-winged Warblers during the non-breeding season.
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King, David I., Akresh, Michael E., Murillo, David A., Bennett, Ruth E., and Chandler, Richard B.
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Copyright of Avian Conservation & Ecology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2023
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19. Bayesian Network-Informed Conditional Random Forests for Probabilistic Multisite Downscaling of Precipitation Occurrence
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Legasa, Mikel Néstor, primary, Chandler, Richard E, additional, and Manzanas, Rodrigo, additional
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- 2023
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20. A comparison of regional climate projections with a range of climate sensitivities
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Barnes, Clair, primary, Chandler, Richard E, additional, and Brierley, Christopher Metcalfe, additional
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- 2023
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21. Noninvasive camera data and spatial capture–recapture models reveal strong temporal variation in fawn survival
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Engebretsen, Kristin N., primary, Cherry, Michael J., additional, Conner, L. Mike, additional, Garrison, Elina P., additional, Miller, Karl V., additional, and Chandler, Richard B., additional
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- 2023
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22. Climate‐mediated population dynamics of a migratory songbird differ between the trailing edge and range core
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Lewis, William B., primary, Cooper, Robert J., additional, Chandler, Richard B., additional, Chitwood, Ryan W., additional, Cline, Mason H., additional, Hallworth, Michael T., additional, Hatt, Joanna L., additional, Hepinstall‐Cymerman, Jeff, additional, Kaiser, Sara A., additional, Rodenhouse, Nicholas L., additional, Sillett, T. Scott, additional, Stodola, Kirk W., additional, Webster, Michael S., additional, and Holmes, Richard T., additional
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- 2023
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23. Assessing the implications of sexual segregation when surveying white‐tailed deer Odocoileus virginianus
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Johnson, James T., primary, Chandler, Richard B., additional, Conner, L. Mike, additional, Cherry, Michael J., additional, Killmaster, Charlie H., additional, Johannsen, Kristina L., additional, and Miller, Karl V., additional
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- 2022
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24. Balancing carnivore conservation and sustainable hunting of a key prey species: A case study on the Florida panther and white‐tailed deer
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Bled, Florent, primary, Cherry, Michael J., additional, Garrison, Elina P., additional, Miller, Karl V., additional, Conner, L. Mike, additional, Abernathy, Heather N., additional, Ellsworth, W. Hunter, additional, Margenau, Lydia L. S., additional, Crawford, Daniel A., additional, Engebretsen, Kristin N., additional, Kelly, Brian D., additional, Shindle, David B., additional, and Chandler, Richard B., additional
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- 2022
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25. Abundance and distribution of ruffed grouse Bonasa umbellus at the southern periphery of the range
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Lewis, William B., primary, Chandler, Richard B., additional, Delancey, Clayton D., additional, Rushton, Emily, additional, Wann, Gregory T., additional, McConnell, Mark D., additional, and Martin, James A., additional
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- 2022
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26. Balancing carnivore conservation and sustainable hunting of a key prey species: A case study on the Florida panther and white-tailed deer
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Bled, Florent, Cherry, Michael J., Garrison, Elina P., Miller, Karl, V, Conner, L. Mike, Abernathy, Heather N., Ellsworth, W. Hunter, Margenau, Lydia L. S., Crawford, Daniel A., Engebretsen, Kristin N., Kelly, Brian D., Shindle, David B., Chandler, Richard B., Bled, Florent, Cherry, Michael J., Garrison, Elina P., Miller, Karl, V, Conner, L. Mike, Abernathy, Heather N., Ellsworth, W. Hunter, Margenau, Lydia L. S., Crawford, Daniel A., Engebretsen, Kristin N., Kelly, Brian D., Shindle, David B., and Chandler, Richard B.
- Abstract
Large carnivore restoration programs are often promoted as capable of providing ecosystem services. However, these programs rarely measure effects of successful restoration on other economically and ecologically important species. In South Florida, while the endangered Florida panther Puma concolor coryi population has increased in recent years due to conservation efforts, the population of its main prey, the white-tailed deer Odocoileus virginianus, has declined in some regions. The extent to which panther predation has affected deer populations has been difficult to assess because several other factors have changed during this period, including hydrology and hunting regulations. We collected known-fate survival data on 241 GPS-collared adult deer (156 females and 85 males) from 2015 to 2018 in the Florida Panther National Wildlife Refuge and the Big Cypress National Preserve in Florida, USA, to assess effects of panther predation on the deer population, while also evaluating the impacts of hunting and hydrology. Predation was the primary cause of death (110 of 134 mortalities), and 87% of predation events were attributed to panthers, a much greater rate than reported by studies conducted before the panther genetic restoration effort initiated in 1995. One deer was legally harvested, and two were likely killed by poachers. Increasing water depth decreased female survival but had little impact on male survival, and drowning was never a cause of mortality. Females had greater survival probability than males, except during fawning season. From 2015 to 2018, annual survival rates increased from 0.61 (0.52-0.70) to 0.86 (0.79-0.91) for females, and from 0.45 (95% CI: 0.33-0.58) to 0.79 (0.69-0.86) for males. Synthesis and applications. High predation rates, coupled with previous evidence of low recruitment of deer in South Florida, suggest that it will be challenging to meet society's competing demands for large predator restoration and sustainable deer harvest. Deer hu
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- 2022
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27. Identifying patterns of spatial variability within the EuroCORDEX ensemble
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Barnes, Clair, primary, Chandler, Richard, additional, Brierley, Chris, additional, and Alegre, Raquel, additional
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- 2022
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28. Controls on projected climate extremes in two regional ensembles for the UK
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Brierley, Chris, primary, Barnes, Clair, additional, Keeping, Theodore, additional, and Chandler, Richard, additional
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- 2022
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29. Regridding and interpolation of climate data for impacts modelling – some cautionary notes
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Chandler, Richard, primary, Barnes, Clair, additional, Brierley, Chris, additional, and Alegre, Raquel, additional
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- 2022
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30. Assessing the implications of sexual segregation when surveying white‐tailed deer Odocoileus virginianus.
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Johnson, James T., Chandler, Richard B., Conner, L. Mike, Cherry, Michael J., Killmaster, Charlie H., Johannsen, Kristina L., and Miller, Karl V.
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AUTUMN , *WHITE-tailed deer , *DEER populations , *HUNTING , *CAMERAS - Abstract
Baited camera surveys are often used to study white‐tailed deer Odocoileus virginianus populations and inform harvest decisions. Surveys are commonly conducted in late summer or early fall when deer populations are expected to be segregated sexually, whereas hunting seasons typically occur during the breeding season when sexes are likely to be mixed. However, the effects of socio‐sexual shifts in space use on pre‐season camera surveys has not been evaluated. We conducted a baited survey before the hunting season followed by passive camera surveys during the hunting season on three properties in southwestern Georgia, USA. We collected 51 106 images of deer before and during the hunting season from baited and passive cameras. Based on interpolated maps of camera detections, the populations were highly segregated during the September baited surveys. In contrast, subsequent passive camera surveys indicated high overlap of males and females during the breeding months, with males shifting their distribution towards females. Because most management units on private lands are substantially smaller than our camera arrays (typically < 1000 ha), our results suggest that pre‐season surveys may not accurately reflect the population available for harvest during the hunting season. Establishment of cooperative management programs among adjacent landholdings may improve management effectiveness. In addition, managers should anticipate shifts in male distributions during the breeding months and real‐time analytical approaches could be developed with the use of cellular‐based cameras to rapidly alter harvest objectives. [ABSTRACT FROM AUTHOR]
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- 2023
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31. Informing Amphibian Conservation Efforts with Abundance-based Metapopulation Models
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Howell, Paige E., Hossack, Blake R., Muths, Erin, Sigafus, Brent H., and Chandler, Richard B.
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AbstractScience-based management strategies are needed to halt or reverse the global decline of amphibians. In many cases, sound management requires reliable models built using monitoring data. Historically, monitoring and statistical modeling efforts have focused on estimating occupancy using detection–nondetection data. Spatial occupancy models are useful for studying colonization–extinction dynamics, but richer insights can be gained from estimating abundance and density-dependent demographic rates. We developed an integrated abundance-based metapopulation model of the processes contributing to spatiotemporal variation in patch population density. We fit our model to a combination of detection–nondetection and count data from a 14-yr study of a reintroduced metapopulation of federally threatened Chiricahua Leopard Frogs (Lithobates chiricahuensis). Pond-specific population growth rate was influenced by pond hydroperiod and frog density, such that permanent and semipermanent ponds with low densities of adult frogs experienced the highest annual population growth rates. Immigration rate declined as the distance among ponds increased. After reintroduction in 2003, metapopulation-level abundance increased and appeared to stabilize around 1300 adult frogs (95 CI 1192–1471) by year 2015. Further, changes in metapopulation abundance were driven mostly by changes in abundance at a few ponds. These high-density populations, which would not have been identifiable with traditional occupancy-based metapopulation models, are likely especially important for species recovery in the area. Abundance-based metapopulation models can be widely applied to inform conservation efforts, by providing higher quality information needed to prioritize habitat patches for management and can be used to make more accurate predictions of metapopulation extinction risk.
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- 2024
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32. Abundance and distribution of ruffed grouse Bonasa umbellusat the southern periphery of the range
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Lewis, William B., Chandler, Richard B., Delancey, Clayton D., Rushton, Emily, Wann, Gregory T., McConnell, Mark D., and Martin, James A.
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Peripheral populations of ruffed grouse Bonasa umbellusat the trailing edge of their range are likely to be at risk of population declines and potential extirpation from continued climate and habitat change. Accurate estimates of abundance and distribution are needed for peripheral populations to inform management decisions. We show that ruffed grouse density at the southern periphery of their range is much lower than in areas farther north. We surveyed the abundance of drumming male grouse across northern Georgia during the springs of 2020–2021 by performing roadside point counts at 634 survey points. We used hierarchical distance sampling models to predict grouse abundance across north Georgia and model spatial variation in density. We estimated population size to be 2671 ruffed grouse in Georgia (95% confidence interval 678–11 084). Mean grouse density was 0.003 drumming males/ha (SD = 0.006), with the highest density centered in the high‐elevation mountains. Uncertainty around abundance estimates was high, in part due to low precision when estimating availability. Low detectability and precision are likely to be common issues when surveying low‐abundance populations, as often occurs at range peripheries. We suggest that abundance estimation could be improved by integrating alternate methods, such as automated recording units, into existing monitoring protocols.
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- 2022
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33. The Spatial Ecology of Wild Pigs (Sus scrofa) in Southwest Florida
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Satter, Christopher Blake, Fish and Wildlife Conservation, Kelly, Marcella J., Cherry, Michael J., Ford, W. Mark, and Chandler, Richard B.
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Movement ecology ,space use ,spatial ecology ,wild pigs ,resource selection ,Sus Scrofa - Abstract
Wild pigs (Sus scrofa) are among the world's most destructive mammalian invasive species, and mitigating farther range expansion will require a thorough understanding of movement behavior, diel activity patterns, space use, and resource selection. Currently, limited empirical evidence is available on the ecology of wild pigs in Southwest Florida. Therefore, I examined how wild pigs behaviorally modified their movements and diel activity patterns in response to individual and environmental covariates. I investigated space use dynamics (e.g., home range size and seasonal variation) and evaluated how individual and environmental variation influenced home range size. Next, I determined how fine-scale movement patterns and resource selection of wild pigs are affected by temperature and time of day, and how those resources changed at broad and fine-scales, given their availability. I found that as temperature increased, the probability of foraging increased while the probability of traveling decreased. Foraging behavior occurred predominately between 8:00 and 17:00, and traveling behavior occurred predominately between 18:00 and 7:00, thereby indicating wild pigs were cathemeral. Home range size ranged from 2.6 to 35.8 km2 and averaged 13.0 km2 (n=16). Finally, home range size increased as the proportion of pasture increased and decreased as the proportion of wetlands increased, indicating that resources in agricultural areas were more diffuse than in natural habitats. At the broad (i.e., home range selection) and fine-scale (i.e., within home range) wild pigs selected for wetlands, forests, and pastures. Wild pig movement tended to be tortuous in forested and cropland habitats, but more directed in pasture habitats. Slower movements (i.e., smaller steps) and more directed (i.e., fewer turning) steps were observed during warmer temperatures, particularly avoiding croplands when temperatures were warmer. Wild pigs avoided wetland habitats during dusk and night hours and cropland habitats during dawn hours. Wild pigs selected for forested habitats during night and dawn hours, possibly in response to human activity. In addition, I found that wild pigs were less likely to step into a location with a daily temperature of 35.7°C than 16.1 C°. Wild pigs were less likely to choose warmer locations and more likely to select intermediate temperatures, thus avoiding locations with extremely low or high daily temperatures. Also, I found that wild pigs were more likely to select home ranges nearer to wetlands, forests, and pastures, while avoiding areas near cropland habitats. However, within their home ranges they were more likely to select habitats farther from croplands, forests, and wetlands. My findings reinforce the importance of wetlands, forests and pastures to wild pig selection of home ranges, where they likely utilize these landcover types for thermoregulation (e.g. forests and wetlands) and for foraging resources (e.g. pastures). Within their home ranges wild pigs may avoid forests and wetlands due to perceived predation risk being higher in those habitats, thus causing wild pigs to forgo higher quality resources to reduce risk. These results contribute information useful to wildlife managers to better predict which landcover types provide refuge (e.g., wetlands and forests) or potential movement corridors (e.g., pasture and cropland habitats) for wild pigs. In Southwest Florida, wild pigs have broad inter-individual variation in home range size, are strongly regulated by temperature, and are largely dependent on wetlands and forests to meet their energetic demands. Doctor of Philosophy Wild pigs are one of the world's most destructive invasive species. Although, hunters often oppose efforts to reduce wild pig populations, agricultural and natural resource managers support reduction efforts because they cause major economic and ecological damage. In addition, wild pigs carry a plethora of diseases and pose direct health risks to livestock, wildlife, and humans. Therefore, a better understanding of how environmental and landscape factors influence wild pig movements and space use is of broad interest to multiple stakeholder groups. I found that wild pigs mostly foraged during daytime and traveled at night, indicative of irregular activity patterns. Home range size averaged 13.0 km2 across 16 individuals and tended to increase as the proportion of pasture habitat increased and decreased as herbaceous wetlands increased. This indicated that resources were more abundant in natural habitats. Wild pigs preferred wetlands, forests, and pastures, and avoided croplands. However, they were more likely to forage in forests and croplands, and travel in pastures. Wild pigs avoided wetlands during dusk and night hours and croplands at dawn, while selecting forests during night and dawn hours. Wild pigs tended to move slower with less turning during warmer temperatures, particularly avoiding croplands when temperatures were hot. In general, wild pigs avoided locations with extremely low or high daily temperatures. I found wild pigs were more likely to select home ranges nearer to wetlands, forests, and pastures, while avoiding areas near cropland habitats. Wild pigs likely utilized these landcover types for thermoregulation (e.g. forests and wetlands) and for foraging resources (e.g. pastures), while avoiding open areas (e.g. croplands) due to a lack of shade. However, within their home ranges they were more likely to select habitats farther from croplands, forests, and wetlands, possibly because they perceived these areas to have higher predation risk. I highlight differences in space use among individuals and identify habitat types that are most likely to meet energetic demands. By understanding how environmental factors (e.g., habitat type and temperature) influence home range movement behaviors of wild pigs, land managers can focus on scale-dependent population control efforts. My results will aid land managers in better predicting which landcover types are providing refuge (e.g., wetlands and forests) or serving as potential movement corridors (e.g., pasture and cropland habitats).
- Published
- 2023
34. Population Dynamics and Spatial Ecology of White-tailed Deer in the Central Appalachian Mountains of Virginia
- Author
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Clevinger, Garrett Balee, Fish and Wildlife Conservation, Cherry, Michael J., Ford, William Mark, Lafon, Nelson Wade, Kelly, Marcella J., and Chandler, Richard B.
- Subjects
white-tailed deer ,central Appalachian Mountains ,recruitment ,cause-specific mortality ,predation risk ,spatial ecology ,home range ,Virginia ,population dynamics ,resource selection ,survival ,Odocoileus virginianus - Abstract
White-tailed deer (Odocoileus virginianus) are a highly charismatic game species with considerable ecological and economic impacts across most of their range. In the Central Appalachian Mountains, deer are a keystone species in forested ecosystems. Regionally, populations vary in herd growth or decline. These fluctuations are important in that they often drive many aspects of population management and regulation, which are dependent on herd demographics. Some key population vital rates allowing better understanding of these changes in white-tailed deer herds are survival, cause-specific mortality, home-range variation, both broad and fine-scale resource selection, and ultimately population growth trends in response to changes in both population vital rates and hunter harvest regulations. In this study, I address each of these concepts within a deer population in Bath County, Virginia, that has presumably been in overall decline since the early 1990's. From June-September, 2019-2020, I monitored survival and cause specific mortality of 57 neonate white-tailed deer until 12 weeks of age. Fawn and adult female survival was 0.310 (95% CI = 0.210-0.475) and 0.871 (95%CI=0.790-0.961) respectively. During the study, I observed a total of 37 fawn mortalities and identified the cause of death using field evidence and through analyzing genetics from residual predator salvia recovered on deer carcasses. Mortalities included 28 predation events and 9 deaths from other causes (e.g., abandonment, malnutrition, or disease). Black bears accounted for 48.6% of all mortality and 64.2% of known predations within our study. My top model identified elevation as a significant predictor of fawn survival, with mortality risk increasing 20% for every 100m increase in elevation. My model using observed vital rates predicted an increasing population of λ = 1.10 (interquartile range, IQR 1.06-1.14). The population was predicted to increase by 2% with a 10% increase in doe harvest (λ = 1.02, IQR = 0.97-1.06) but declined by 7% at 20% harvest (λ = 0.93, IQR = 0.89-0.96). I found that fawning home ranges of females that successfully reared fawns to the end of the season had significantly larger home ranges than those that were unsuccessful at higher elevations. Fawning home ranges for females with fawns increased approximately 71ha in size for every 100m increase in mean home range elevation, whereas seasonal home ranges of females without fawns decreased approximately 1.5 ha for every 100m increase in mean home range elevation. Deer selected fawn-rearing areas nearer to forested edges, open habitats, and at higher elevations, while they avoided areas near disturbed and mature forests. Within the fawn rearing area, females selected locations closer to disturbed forest, open habitats, and forested edge, while avoiding mature forest habitats, and higher elevations. Females selected birth sites with higher levels of visual obstruction. Using a step-selection method for real-time resource selection across biological seasons, we found that female deer selected for open areas during the fawning, breeding, early gestational, and late gestational seasons. During the fall breeding season, females avoided forested edge, but selected for areas at higher elevations. During early gestational seasons females selected disturbed habitats and areas at higher elevations while again avoiding forested edge. Overall, my work highlights variations in population dynamics of white-tailed deer in areas of the Central Appalachian Mountains that are primarily characterized by poor habitat quality and provides novel insights into fine-scale spatial ecology of female deer across biological seasons within the region. Ultimately, while the deer population in our study was not predicted to be in decline, this work supports predation risk as being a significant factor associated with habitat quality. Doctor of Philosophy White-tailed deer (Odocoileus virginianus) are a game species with extensive ecological and economic impacts across most of their range. In the central Appalachian Mountains, many populations across the region vary in terms of herd size growth, stability, or decline. These fluctuations are important in that they often drive many aspects of population management and regulation, which are dependent on the status of herd demographics. Some key population vital rates that aid us in better understanding these changes in white-tailed deer herds are survival and cause-specific mortality, home-range variation in association with habitat quality and the ability to successfully reproduce, population trends under hypothetical management scenarios, and resource selection of various habitats that are available across the landscape. In this study, I address each of these concepts within a deer population in Bath County, Virginia, which has presumably been in decline since the early 1990's. As expected, fawn survival was lower than previously reported from other study areas of the Central Appalachians Mountains. Predation was the leading cause of fawn mortality, with black bears being responsible for most predation events. Fawn mortality risk was significantly associated with elevation - where fawns at higher elevations were those at greater risk. Surprisingly, the deer population in Bath County was projected to be increasing under current conditions and was also projected to be stable-to-increasing even under some hypothetical scenarios which would negatively impact population growth (i.e., 10% increase in female harvest or 17% reduction in fawn survival). Fawning home ranges of collared females which successfully reared known fawns to the end of the biological season were significantly influenced by elevation; such that females with fawns had home ranges that increased in size with increasing elevation, whereas females without fawns had home ranges which decreased slightly in size with increasing elevation. At birth sites, females selected locations characterized by higher levels of visual obstruction compared to randomly sampled areas. Of the habitat types analyzed, both selection or avoidance of specific habitats varied across both biological season and spatial scale. Ultimately, while I found that some deer populations associated with poor quality habitats in the Central Appalachians may not be in decline, deer were likely influenced greatly by habitat quality – especially pertaining to predation risk – throughout Bath County.
- Published
- 2022
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