DOI: 10.5061/dryad.1ns1rn8qf
title: We are what we eat, plus some per mill: Using stable isotopes to estimate diet composition in Gyps vultures over space and time

description: 1. Dietary studies in birds of prey involve direct observation and
 examination of food remains at resting and nesting sites. Although these
 methods accurately identify diet in raptors, they are time consuming,
 resource intensive and associated with biases that stem from the feeding
 ecology of raptors like Gyps vultures (Gyps
 africanus and Gyps rueppelli). Our study set out to
 estimate diet composition in Gyps vultures informed by
 stable isotopes that provide a good representation of assimilated diet
 from carrion resources in local systems.  2. We hypothesized that
 differences in Gyps vulture diet composition is a
 function of sampling location, and that these vultures move between
 Serengeti National Park and Selous Game Reserve to forage. We also,
 theorized that grazing ungulates are the principal items
 in Gyps vulture diet.  3. Through a combination
 of linear and Bayesian models, diet derived from d13C
 in Gyps vultures consisted of grazing herbivores across
 study areas, with those in Serengeti National Park consuming higher
 proportions of grazing herbivores (&gt; 87%). d13C
 differences in vulture feather subsets per site did not indicate vulture
 diet change, and in combination with blood d13C, vultures fed
 largely on grazers for ~159 days before they were sampled in both sites.
 Similarly, d15N values implied
 that Gyps vultures fed largely on herbivores across
 space and time. d34S ratios separated prey source for
 vultures between the two sites. d34S variation in
 vultures across sites resulted from differences in baseline
 (plant) d34S values, though it is not possible to
 match d34S to specific locations.  4. Our findings
 highlight the relevance of repeated sampling that considers tissues with
 varying isotopic turnover and emerging Bayesian techniques for dietary
 studies using stable isotopes. Findings also suggested limited vulture
 movement between the two local systems. However, more sampling coupled
 with telemetry is required to fully comprehend this observation and its
 implications to Gyps vulture ecology and conservation.
description: Data was collected for 10 months as a masters research project.
 <em>Gyps </em>vulture, herbivore muscle tissue samples were
 collected from two protected areas Serengeti National Park and Selous Game
 Reserve in Tanzania. Samples were then processed for stable carbon,
 nitrogen and sulfur isotope analysis. Statistical analyses on stable
 isotope data, were carried out in R to inform Gyps vulture diet over space
 and time. 
description: Coordinates have been denatured by +0.5 degrees to preserve the
 integrity of the overall geographic distribution but ensure
 confidentiality.
description: # We are what we eat, plus some per mill: Using stable isotopes to
 estimate diet composition in Gyps vultures over space and time
 This Gyps_readme.txt file
 was generated on 2021-09-02 by Allan A. Baino ## GENERAL INFORMATION 1\.
 Title of Dataset: Gyps vulture dietary analysis 2\. Author Information A.
 Principal Investigator Contact Information Name: Allan A. Baino
 Institution: Natural Resources Institute, University of Greenwich, UK
 Address: BLAKE Building, ME4 4TB Email: a.a.baino@greenwich.ac.uk B.
 Associate or Co-investigator Contact Information Name: Jason Newton
 Institution: Scottish Universities Environmental Research Council, UK
 Address: Park/Rankine Avenue, G75 0QF Email: Jason.Newton@glasgow.ac.uk C.
 Alternate Contact Information Name: Abdelkader Behdenna Institution:
 Epigene Labs Address: 7 Square GABRIEL FAURE 75017 PARIS 17, France Email:
 abdelkader@epigenelabs.com 3\. Date of data collection (single date,
 range, approximate date) : From 2018-08-18 to 2019-05-31 4\. Geographic
 location of data collection : Serengeti National Park (2.1540S,
 34.6857E), Selous Game Reserve (current Nyerere National Park), 9.0000S,
 37.5000E all in Tanzania. 5\. Information about funding sources that
 supported the collection of the data: University of Glasgow, Karimjee
 Jivanjee Conservation Scholarship. ### SHARING/ACCESS INFORMATION 1.
 Licenses/restrictions placed on the data: n/a 2. Links to publications
 that cite or use the data: n/a 3. Links to other publicly accessible
 locations of the data: n/a 4. Links/relationships to ancillary data sets:
 n/a 5. Was data derived from another source? no A. If yes, list source(s):
 n/a 6. Recommended citation for this dataset: Baino, Allan et al. (2021),
 We are what we eat, plus some per mill: Using stable isotopes to estimate
 diet composition in Gyps vultures over space and time, Dryad, Dataset,
 https://doi.org/10.5061/dryad.1ns1rn8qf ## DATA & FILE OVERVIEW 1\.
 File List: * bf_iso_data.xlsx - Vulture blood and feather stable carbon,
 nitrogen and sulfur raw values. * sources.xlsx - Mean stable carbon,
 nitrogen, sulfur values from herbivores muscle tissue. * Biomass_SER.xlsx
 - categorised biomass estimates for ungulates in Serengeti National Park.
 * Biomass_SGR.xlsx - categorised biomass estimates for ungulates in Selous
 Game Reserve. * AR.feather.xlsx - raw consumer isotope values in vulture
 feathers for use in SIMM. * AR.feather.discr.xlsx - trophic discrimination
 factor values for vulture feathers, for use in SIMM. * AR.blood.xlsx - raw
 consumer isotope values in vulture feathers for use in SIMM. *
 AR.blood.discr.xlsx - trophic discrimination factor values for vulture
 blood, for use in SIMM. * Carcass_tissue.coords.xlsx - carcass tissue
 sampling geographic coordinates Lat, Long for use in QGIS *
 Vulture_trapping.coords.xlsx - vulture capture geographic coordinates Lat,
 Long for use in QGIS * Africa.shp - Africa boundary shapefile * ruaha.shp
 - Ruaha National Park boundary shapefile * Rukwa.shp - Rukwa Game Reserve
 boundary shapefile * serengeti.shp - Serengeti National Park boundary
 shapefile * selous_boundary.shp - Selous Game Reserve boundary shape file
 * TZA_admO.shp - Tanzania boundary shapefile * Thesis_Research_Analysis.R
 - R script * Figure_S1.png - distribution of carbon absolute values in
 vulture feather subsets * Figure_S1.png - distribution of nitrogen
 absolute values in vulture feather subsets * Figure_S3.png - distribution
 of sulfur absolute values in vulture feather subsets * Figure_S4.png -
 regression analysis on carbon values in African white-backed vultures
 (AWB) feather subsets sampled in Serengeti National Park (SER) *
 Figure_S5.png - regression analysis on carbon values in Ruppells griffon
 vultures (RPV) feather subsets sampled in Serengeti National Park (SER) *
 Figure_S6.png - regression analysis on nitrogen values in African
 white-backed vultures (AWB) feather subsets sampled in Serengeti National
 Park (SER) * Figure_S7.png - regression analysis on nitrogen values in
 Ruppells griffon vultures (RPV) feather subsets sampled in Serengeti
 National Park (SER) * Figure_S8.png - regression analysis on sulfur values
 in African white-backed vultures (AWB) feather subsets sampled in
 Serengeti National Park (SER) * Figure_S9.png - regression analysis on
 sulfur values in Ruppells griffon vultures (RPV) feather subsets sampled
 in Serengeti National Park (SER) * Figure_S10.png - regression analysis on
 carbon values in African white-backed vultures (AWB) feather subsets
 sampled in Selous Game Reserve (SGR) * Figure_S11.png - regression
 analysis on nitrogen values in African white-backed vultures (AWB) feather
 subsets sampled in Selous Game Reserve (SGR) * Figure_S12.png - regression
 analysis on sulfur values in African white-backed vultures (AWB) feather
 subsets sampled in Selous Game Reserve (SGR) * Figure_S13.png -
 categorised absolute counts for common ungulates Serengeti National Park *
 Figure_S14.png - categorised absolute counts for common ungulates Selous
 Game Reserve * Figure_S15.png - normality of residuals check for linear
 models with carbon as response * Figure_S16.png - normality of residuals
 check for linear models with nitrogen as response * Figure_S17.png -
 normality of residuals check for linear models with sulfur as response *
 Figure_S18.png - posterior probability of proportion of browser/grazer in
 African white-backed vulture blood * Figure_S19.png - posterior
 probability of proportion of browser/grazer in African white-backed
 vulture feathers * Figure_S20.png - posterior probability of proportion of
 browser/grazer in Ruppells griffon vulture blood * Figure_S21.png -
 posterior probability of proportion of browser/grazer in Ruppells griffon
 vulture feathers * Figure_S22.png - regression analysis on carbon values
 in proximal feather barbs vs. Carbon:Nitrogen ratios in the same *
 Figure_S23.png - regression analysis on carbon values in basal feather
 barbs vs. Carbon:Nitrogen ratios in the same 2\. Relationship between
 files, if important: follow R Script 3\. Additional related data collected
 that was not included in the current data package:n/a 4\. Are there
 multiple versions of the dataset? no A. If yes, name of file(s) that was
 updated: n/a i. Why was the file updated? n/a ii. When was the file
 updated? n/a ## METHODOLOGICAL INFORMATION 1\. Description of methods used
 for collection/generation of data: Noose lines, which are smooth fishing
 line (1.70 mm thick|300lb strength) loosely tied into retractable circles
 along a ~1m parachute rope making a line frame, two-line frames were laid
 loosely around provisioned or natural bait (where available) and pegged to
 the ground by 3-inch x 3mm metal pegs. Traps were set as early as 0730hrs
 before peak vulture food search effort which ranges between 0800hrs and
 1200hrs, we then retreated 50m to 60m from trap sites to observe vulture
 activity (Watson & Watson, 1985). Captured vultures were processed and
 released. Carcass tissue from dead ungulates was opportunistically
 collected within protected areas and stored in ethanol filled 1.5ml
 eppendorf tubes. Established transects under the Serengeti Biodiversity
 Programme in Serengeti National Park and Census data for Selous Game
 Reserve 2018/2019 from TAWIRI were used to estimate ungulate counts. All
 capture and carcass geographic coordinates were recorded with GPS. 2\.
 Methods for processing the data: All samples were prepared and combusted
 in a PyroCube elemental analyzer (Elementar, Hanau, Germany) for d15N,
 d13C and d34S sequentially using an Elementar VisION IRMS at the NERC Life
 Sciences Mass Spectrometry Facility, East Kilbride, UK 3\. Instrument- or
 software-specific information needed to interpret the data: Stable isotope
 carbon, nitrogen and sulfur data were analysed in R Software version
 4.0.4, for packages load R script. 4\. Standards and calibration
 information, if appropriate: n/a 5\. Environmental/experimental
 conditions: n/a 6\. Describe any quality-assurance procedures performed on
 the data: n/a 7\. People involved with sample collection, processing,
 analysis and/or submission: * Joseph Masoy - Serengeti Biodiversity
 Programme * Patrick Mugisha - Serengeti Biodiversity Programme * Jason
 Newton - SUERC * Abdelkader Behdenna - Epigene Labs * Thomas Morrison -
 IBAHCM, University of Glasgow * Grant Hopcraft - IBAHCM, University of
 Glasgow * Linus Munishi - IBAHCM, University of Glasgow * Corinne Kendall
 - North Carolina Zoo, USA ## DATA-SPECIFIC INFORMATION FOR: Main dataset
 [bf_iso_data.xlsx] 1\. Number of variables: 2\. Number of cases/rows: 3\.
 Variable List: * Animal ID - animal ID * Date - date * Location -
 Protected area, Rukwa Game Reserve(RGR), Selous Game Reserve(SGR),
 Serengeti National Park(SER) * Season - climatic condition * Species -
 species of vulture caught * d13C - delta 13 Carbon per mill (‰) * d15N -
 delta 15 Nitrogen per mill (‰) * d34S - delta 34 Sulfur per mill (‰) *
 Tissue type - vulture tissue * T.subset - section of vulture feather or
 type * Weight - weight of vulture caught * Long - Longitude * Lat -
 Latitude 4\. Missing data codes: depicted by symbol n/a 5\. Specialized
 formats or other abbreviations used: n/a