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We are what we eat, plus some per mill: Using stable isotopes to estimate diet composition in Gyps vultures over space and time

Cite 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 [Dataset]. Dryad. https://doi.org/10.5061/dryad.1ns1rn8qf

Abstract

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 (> 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.

README: We are what we eat, plus some per mill: Using stable isotopes to estimate diet composition in Gyps vultures over space and time

https://doi.org/10.5061/dryad.1ns1rn8qf

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

Methods

Data was collected for 10 months as a masters research project. Gyps 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. 

Usage notes

Coordinates have been denatured by +0.5 degrees to preserve the integrity of the overall geographic distribution but ensure confidentiality.

Funding

University of Glasgow, Award: Karimjee Jivanjee Conservation Scholarship