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Kojima LV, Kohl MT, Rainwater TR, Parrott BB, Tuberville TD. Association of size, climatic factors, and mercury body burdens with movement behavior in American alligators. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 921:170859. [PMID: 38365032 DOI: 10.1016/j.scitotenv.2024.170859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/18/2024]
Abstract
Animal movement behavior provides insight into organismal and ecological function. These functions are often disturbed by anthropogenic influences, such as urbanization and habitat fragmentation, yet the effects of long-term exposures to environmental contaminants on movement have yet to be examined. The long lifespans and broad diets of crocodilians often lead to bioaccumulation of persistent contaminants and confer a marked vulnerability to consequent physiological effects. In this study, we investigate the relationships between blood concentrations of mercury (Hg), a widespread contaminant with well characterized neurotoxicity, and movement patterns in free living, naturally exposed American alligators (Alligator mississippiensis). We sampled adult male alligators from two former nuclear cooling reservoirs with different Hg contamination histories and placed GPS transmitters on a subset of individuals from each reservoir (13 total). Data collected over the ensuing two years were analyzed using a linear mixed effects framework combined with AICc model selection to resolve the relationships linking seasonal alligator movement (daily activity (s) and daily distance (m)) and home range to climate conditions, individual traits, and blood Hg concentrations (mg/kg; wet weight). We found that climate conditions, alligator size (snout-vent-length), and blood Hg concentrations all influence alligator daily activity but do not contribute to alligator daily movement (distance). Furthermore, we found that blood Hg concentrations were strongly correlated with seasonal home range size where individuals with elevated Hg had larger home ranges in spring, fall, and winter. These findings provide insight into how climate, anthropogenic contaminants, and individual traits relate to alligator movement patterns across seasons.
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Affiliation(s)
- Laura V Kojima
- Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E, Aiken, SC 29802, USA; Odum School of Ecology, University of Georgia, 140 E Green St, Athens, GA 30602, USA.
| | - Michel T Kohl
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green St, Athens, GA 30602, USA.
| | - Thomas R Rainwater
- Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC, USA; Tom Yawkey Wildlife Center, Georgetown, SC, USA
| | - Benjamin B Parrott
- Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E, Aiken, SC 29802, USA; Odum School of Ecology, University of Georgia, 140 E Green St, Athens, GA 30602, USA.
| | - Tracey D Tuberville
- Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E, Aiken, SC 29802, USA.
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Baker LL, Mills Flemming JE, Jonsen ID, Lidgard DC, Iverson SJ, Bowen WD. A novel approach to quantifying the spatiotemporal behavior of instrumented grey seals used to sample the environment. MOVEMENT ECOLOGY 2015; 3:20. [PMID: 26213626 PMCID: PMC4514985 DOI: 10.1186/s40462-015-0047-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 05/11/2015] [Indexed: 03/24/2024]
Abstract
BACKGROUND Paired with satellite location telemetry, animal-borne instruments can collect spatiotemporal data describing the animal's movement and environment at a scale relevant to its behavior. Ecologists have developed methods for identifying the area(s) used by an animal (e.g., home range) and those used most intensely (utilization distribution) based on location data. However, few have extended these models beyond their traditional roles as descriptive 2D summaries of point data. Here we demonstrate how the home range method, T-LoCoH, can be expanded to quantify collective sampling coverage by multiple instrumented animals using grey seals (Halichoerus grypus) equipped with GPS tags and acoustic transceivers on the Scotian Shelf (Atlantic Canada) as a case study. At the individual level, we illustrate how time and space-use metrics quantifying individual sampling coverage may be used to determine the rate of acoustic transmissions received. RESULTS Grey seals collectively sampled an area of 11,308 km (2) and intensely sampled an area of 31 km (2) from June-December. The largest area sampled was in July (2094.56 km (2)) and the smallest area sampled occurred in August (1259.80 km (2)), with changes in sampling coverage observed through time. CONCLUSIONS T-LoCoH provides an effective means to quantify changes in collective sampling effort by multiple instrumented animals and to compare these changes across time. We also illustrate how time and space-use metrics of individual instrumented seal movement calculated using T-LoCoH can be used to account for differences in the amount of time a bioprobe (biological sampling platform) spends in an area.
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Affiliation(s)
- Laurie L Baker
- />Department of Biology, Dalhousie University, Halifax, B3H 4R2 Canada
| | | | - Ian D Jonsen
- />Department of Biological Sciences, Macquarie University, North Ryde, Sydney, NSW 2109 Australia
| | - Damian C Lidgard
- />Department of Biology, Dalhousie University, Halifax, B3H 4R2 Canada
| | - Sara J Iverson
- />Department of Biology, Dalhousie University, Halifax, B3H 4R2 Canada
| | - W Don Bowen
- />Population Ecology Division, Bedford Institute of Oceanography, Department of Fisheries and Oceans, Dartmouth, B2Y 4A2 Canada
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