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Dataset and code for "Unexpected effect of geographic origin on post-translocation survival in a long-lived reptile"

Version 2 2024-01-09, 18:12
Version 1 2024-01-09, 17:05
dataset
posted on 2024-01-09, 18:12 authored by Kevin LoopeKevin Loope

Data include release and mortality information for 2,822 gopher tortoises (Gopherus polyphemus) translocated to Nokuse, a private reserve in the panhandle of Florida.

Mitigation translocations move wildlife from specific areas due to conflict with humans over land use at the site. A critical decision when carrying out mitigation translocation is the acceptable distance across which animals can be moved. This decision trades off logistical expediency of unrestricted translocation with the risk of reducing translocation success due to environmental mismatch between origin and translocation site conditions. In this study, we used a large dataset of 502 individually identifiable carcasses to examine the role of geographic origin and translocation distance in the relative survival of 2,822 translocated subadult and adult gopher tortoises (Gopherus polyphemus), a species experiencing large-scale mitigation translocation, at a recipient site in the Florida panhandle, USA. We hypothesized that if climate or habitat differences between the origin and translocation site influenced survival, tortoises translocated from within the Florida panhandle would have the highest survival. To the contrary, we found that survival slightly increased with increasing climatic difference between origin and recipient site, driven by higher survival of tortoises coming from central Florida sites compared to those from the panhandle and north Florida. This suggests that environmental mismatch due to long-distance translocation is not a main driver of mortality. These models also indicated an effect of season, with a survival advantage to tortoises translocated in the spring and late fall, relative to summer translocations, and a negative effect of initial density on survival. Finally, we also estimated the upper bound on annual survival in three well-monitored groups to be quite low (92-95%) for several years following release, suggesting caution when considering large translocated populations to be viable without first assessing adult survival. Our unexpected results highlight the importance of investigating species-specific sensitivities to translocation distances and indicate the limitations of assumed linear effects of translocation distance on outcomes.


History

Publisher

University Libraries, Virginia Tech

Corresponding Author Name

Kevin Loope

Corresponding Author E-mail Address

kjloope@vt.edu

Files/Folders in Dataset and Description

Nokuse_survival_for_publication.R - annotated R script that was used to produce all figures and run all statistical analyses README_code.md - code documentation for R script [Data] - folder containing data files FWC_translocations_by_year.csv - data used to create figure 1. This contains data on the number of translocations within the state of Florida per year. Data taken from Table 6 in the Candidate Conservation Agreement for the Gopher Tortoise October 1, 2021 – September 30, 2022. unknown_dead.csv - This file contains information on unidentified carcasses found in pens used to estimate maximum survival rates (see main text). survival_data.csv - This contains the survival data used in the analysis. MCL.cm is the maximum carapace length in cm. Condition is the body condition index (see main text). Density is the number of individuals with MCL > 18 cm released into the pen, divided by the area of the pen in ha. Season is the release season: either early (first 20%), mid (20-80%), or late (80%) (see main text for details). Dist_km is the distance between source site and the translocation study site in km. Dist_lat is the latitudinal distance between the source site and the translocation study site (in km). Region is whether the origin site in from within the panhandle, north, central or south region. Index.all is a unique index for each tortoise. Area is the pen group. Date.found is the date a carcass was encountered. Mort indicates a carcass was found for that individual. Date_pen_down is the date of pen removal for the individual's pen. Time1 is the day since release that the survival analysis starts (always 0). Time2 is either the days since release that the mortality occurred, or the end of the study. Day_found is the day since release that the carcass was found. Study_end_date is the last day of the study at which point all tortoises without carcasses were censored. Region2-9 encode regional membership under different groupings of the four regions (panhandle, north, central and south). Tmean_diff is the 30 year normal mean temperature difference between the source site and the release site (see main text for details). yday is the day of the year of the realease day, used to calculate release season categories.

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    Fish and Wildlife Conservation

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