DOI: 10.5061/dryad.cc2fqz65t
title: Sex-specific foraging of an apex predator puts females at risk of human-wildlife conflict

description: Urbanisation and anthropogenic alteration of ecosystems has led to
 conflict between humans and wildlife. Such conflict is often observed in
 apex predators. Although human-wildlife conflict has been extensively
 studied, male/female differences in behaviour are rarely considered. We
 investigated male/female differences in foraging behaviour of the
 predatory/scavenging brown skua Catharacta antarctica lonnbergi breeding
 on a New Zealand island nature reserve in proximity to farmland. These
 skuas are subject to culling, when perceived as a threat to livestock. As
 part of a long-term ecological study, we used high-resolution Global
 Positioning System (GPS) devices to characterise the space-use of foraging
 brown skuas. We also analysed stable isotopes of carbon (δ13C) and
 nitrogen (δ15N) from modern and archived blood samples to investigate
 possible changes in diet over the past ~30 years. Analysis of 100 GPS
 tracks collected from 2014-16 demonstrated that males and females
 consistently visited different habitats. Males spent most of their time
 close to their breeding territory on the island nature reserve and females
 frequently visited a farmed island approximately two kilometres away.
 Consistent with this finding, we show that male and female skuas also
 differed markedly in their diets: males specialised on burrow-nesting
 white-faced storm petrels Pelagodroma marina (80%) with only a small
 proportion of sheep remains Ovis aries (&lt;6%) contributing to their
 diet. In contrast, female diet comprised 27% white-faced storm petrels,
 other seabirds (18%), and a relatively large proportion of sheep remains
 (47%). Further, our data (186 blood samples from 122 individuals) show
 that this male / female difference in diet has persisted at least since
 1987. Because females fed disproportionally on sheep remains, they may be
 more vulnerable to being culled by farmers. Importantly, our case study
 suggests that intersexual differences in diet and foraging patterns can
 have major implications for the reproduction and survival of apex
 predators that interact with farming. We strongly suggest that intersexual
 differences in behaviour should be considered when investigating
 human-wildlife conflicts. 
description: See published article.
description: <b>Readme files</b> – there are three archived
 datasets associated with this publication. <b>01.
 Skua blood stable isotope data</b> The first file
 contains stable isotope data (d13C and d15N) from whole blood of brown
 skuas (<i>Catharacta antarctica lonnbergi</i>) breeding on the
 Chatham Islands (filename '01. Skua blood isotopes Schultz et al | J
 Anim Ecol.xlsx'). The file contains the following information /
 columns: 
 
 SampleID Unique
 identifier for each blood sample 
 
 Species Species identifier (here brown
 skua) 
 Tissue Type of tissue analysed (here blood
 only) 
 BirdID Unique identifier for each
 bird 
 Sex Gender information
 Year
 Sampling year 
 Origin
 Indicates whether samples are modern
 (2014-16) or archived (1987-1993) 
 d15N
 Stable nitrogen isotope
 values 
 d13C Stable carbon isotope values
 
 d13CadjSuess Stable carbon isotope values adjusted
 for the Suess effect 
   <b>02. Prey muscle
 isotope data</b> A second dataset includes stable
 isotope values (d13C and d15N) from muscle tissue of respective prey
 species (filename '02. Prey isotopes Schultz et al | J Anim
 Ecol.xlsx'). The file contains the following information /
 columns: 
 
 SampleID Unique
 identifier for each blood sample 
 
 Species Species identifier
 
 Atomic.wt.C.N.ratio Atomic C:N ratio 
 
 Mass.C.N.ratio Mass C:N ratio 
 d13C
 Stable carbon isotope values
 
 lipid.corrected.d13C Stable carbon isotope values,
 mathematically corrected for lipid content 
 d15N
 Stable nitrogen isotope
 values 
 Concdepd13C Concentration dependence for stable
 carbon 
 Concdepd15N Concentration dependence for stable
 nitrogen 
   <b>03. Skua GPS tracking
 data</b> A third file includes GPS tracking data
 of brown skua collected during the study period (2014-16) (filename
 '03. Skua GPS Schultz et al | J Anim Ecol.xlsx'). The file
 contains the following information / columns: 
 BirdID
 Unique
 identifier for each bird 
 Sex
 Gender information
 NestID
 Unique identifier for each nest
 site 
 NestDistanceHarv Great Circle Distance from each
 respective location to the nest site 
 Year
 Sampling year 
 
 Latitude Latitude in World Geodetic System
 (WGS84) format 
 Longitude Longitude in WGS 1984 format in World
 Geodetic System (WGS84) format 
 
 POINTX_CITM Longitude in Chatham Islands Transverse
 Mercator projection 
 POINTY_CITM Latitude in Chatham Islands Transverse
 Mercator projection 
 TripID Unique identifier for each trip (i.e.
 series of consecutive locations outside a radius of 100m around the nest
 site)