DOI: 10.5061/dryad.ksn02v7ft
title: Details and raw isotope data for samples related to a semi-controlled feeding study involving rats fed to a red-tailed hawk (Buteo jamaicensis) and Eurasian eagle owl (Bubo bubo).

description: Rationale: We investigated isotopic diet-excreta offset (Ddiet-excreta)
 for predatory birds, and the isotopic influence of bird digestion on
 consumed prey tissues. The foraging ecology of predatory birds can be
 non-invasively monitored using excreta or regurgitated prey. However, one
 must account for Ddiet-excreta and any influence of digestion on
 prey tissues. Neither of these has been previously evaluated for predatory
 birds. Methods: We worked with a captive Eurasian eagle owl (Bubo bubo)
 and red-tailed hawk (Buteo jamaicensis) fed frozen rats. We collected rat
 feet, as well as regurgitated pellets and excreta from each bird’s
 enclosure. We analyzed carbon (d13C) and nitrogen (d15N) isotopes in
 undigested rat muscle, undigested and digested fur and bone collagen
 (extracted from pellets); d13C, oxygen (d18O), and strontium (87Sr/86Sr)
 isotopes in rat bone bioapatite; and d13C, d15N and 87Sr/86Sr in bird
 excreta. Results: Diet-excreta offset differed slightly between
 individuals, and depended on how we estimated diet (muscle or muscle +
 collagen), and if excreta were acidified. We tentatively suggest using
 +1-1.5‰ for Δ13Cdiet-excreta and +0.5-1‰ for Δ15Ndiet-excreta when working
 with proteinaceous tissues and unacidified or acidified excreta,
 respectively. For bioapatite, we suggest 9-10‰ for Δ13Cdiet-excreta and
 0.001 for 87Sr/86Srdiet-excreta. Fur isotopes, collagen d15N, and
 bioapatite d18O were unaffected by digestion, but 87Sr/86Sr decreased by
 0.0005-0.001, and collagen and bioapatite d13C shifted 0.5-1‰ (decreasing
 collagen-apatite spacing by 1.5-2‰). Conclusions: For both birds,
 Ddiet-excreta for carbon and strontium were similar to previous studies,
 but nitrogen was notably different, possibly because excreta contained
 some urine or urates, or because raptors have distinct digestive
 physiologies. The influence of digestion on bone d13C and 87Sr/86Sr is
 large enough to affect interpretations of diet and bioavailable strontium.
 Researchers should use caution when using potentially digested bone to
 evaluate the diet of consumed prey, establish strontium baselines, or
 infer past climate or environmental conditions.
description: This dataset summarizes raw isotope data for rat tissues before
 and after digestion by Rhett, the red-tailed hawk, or Caspian, the eagle
 owl, who were individually housed at the Cincinnati zoo. We have also
 included isotope data for excreta produced by the birds. The study was
 conducted for a total of 11 days. A foot from each consumed rat was
 collected before feeding the birds, and then a regurgitated casting and
 excreta sample were collected from each bird's enclosure the
 following day.  Rat collagen was isolated by soaking
 samples in 0.5 N HCl at 4°C ultil they were demineralized, rinsing in
 ultrapure water five times. Lipids were removed from rat muscle, hair and
 bone by sonicating samples in trace metal grade petroleum ether 2 to 5
 times, then sonicating in ultra pure water 2 to 5 times, and
 drying. Rat bioapatite was processed by soaking
 powdered sample in 30% H2O2 for 72 hours, rinsing with ultrapure water
 five times, soaking in 1 M Acetic Acid buffered with calcium acetate, and
 then rinsing again with ultra pure water five times, and
 drying.  Excreta were dried and homogenized. We also
 acidified a subset of samples to remove potential minerals. 
 Stable isotope values were obtained at the Stable Isotope
 Biogeochemistry Lab at the University of Cincinnati and strontium isotope
 data were obtained at the Multicollector ICPMS Laboratory in the
 Department of Geology at the University of Illinois,
 Urbana-Champaign. 
description: # Details and raw isotope data for samples related to a semi-controlled
 feeding study involving rats fed to a red-tailed hawk (Buteo jamaicensis)
 and Eurasian eagle owl (Bubo bubo).
 [https://doi.org/10.5061/dryad.ksn02v7ft](https://doi.org/10.5061/dryad.ksn02v7ft) ## Description of the data and file structure ### Files and variables #### File: Dryad\_dataset.xlsx **Description:**  This dataset summarizes raw isotope data for rat tissues before and after digestion by Rhett, the red-tailed hawk, or Caspian, the eagle owl, who were individually housed at the Cincinnati zoo. We have also included isotope data for excreta produced by the birds. The study was conducted for a total of 11 days. A foot from each consumed rat was collected before feeding the birds, and then a regurgitated casting and excreta sample were collected from each bird's enclosure the following day.  Within the dataset, blank cells indicate analyses that were not performed for specific samples. No data were excluded from the dataset.   ##### Variables The dataset includes one spreadsheet with the following variables:  * Rat bone collagen carbon (d13C), nitrogen (d15N) and oxygen (d18O) values both before and after digestion by the birds of prey.  * Rat bone apatite d13C and d18O values, as well as strontium isotope ratios (87Sr/86Sr) both before and after digestion by the birds of prey.  * Rat fur d13C and d15N values both before and after digestion by the birds of prey.  * Rat muscle d13C and d15N values, only available for undigested rats.  * d13C, d15N, and 87Sr/86Sr for excreta produced by both birds. Data are provided for dried homogenized excreta, as well as excreta that were acidified with 0.5 N HCl for 5 hours.  * Weight %C, %N, and both weight% and atomic C:N, as well as Sr concentration data.  ## Code/software Data were analyzed using JMP Pro 16.0. There are no codes or software to report. ## Access information Other publicly accessible locations of the data: * Data are also included as a supplementary table in the associated scientific article.