DOI: 10.5061/dryad.f1vhhmh30
title: Predator home range size mediates indirect interactions between prey species in an arctic vertebrate community

description: Indirect interactions are widespread among prey species that share a
 common predator, but the underlying mechanisms driving these interactions
 are often unclear, and our ability to predict their outcome is limited.
 Changes in behavioural traits that impact predator space use could be a
 key proximal mechanism mediating indirect interactions, but there is
 little empirical evidence of the causes and consequences of such
 behavioural-numerical response in multi-species systems.  Here,
 we investigate the complex ecological relationships between seven prey
 species sharing a common predator. We used a path analysis approach on a
 comprehensive 9-year dataset simultaneously tracking predator space use,
 prey densities, and prey mortality rate on key species of a simplified
 Arctic food-web.  We show that high availability of a clumped and
 spatially predictable prey (goose eggs) leads to a two-fold reduction in
 predator (arctic fox) home range size, which increases local predator
 density and strongly decreases nest survival of an incidental prey
 (American golden plover). On the other hand, a scattered cyclic prey with
 potentially lower spatial predictability (lemming) had a weaker effect on
 fox space use and an overall positive impact on the survival of incidental
 prey. These contrasting effects underline the importance of studying
 behavioural responses of predators in multi-prey systems and to explicitly
 integrate behavioural-numerical responses in multi-species predator-prey
 models.
description: The data set contains two sheets
 of data collected from 2008 to 2016 in the southwest plain of Bylot Island
 (72°530N, 79°540W), in Sirmilik National Park, Nunavut, Canada. 
 <strong>Fox home range data.</strong> The first data
 sheet contains home range size of individual foxes estimated from Argos
 relocation data, the sex and breeding status of the fox, and the
 availability of lemmings and goose eggs. Raw Argos relocation data are
 available on Movebank (doi: 10.5441/001/1.3gg33bd4). To
 quantify fox’s annual home range (95% isopleth), we used autocorrelated
 kernel density estimation implemented in the ctmm R package. This approach
 accounts for location accuracy and provides a reliable measure of the
 estimation error associated to each home range contour. We estimated fox
 annual home ranges using locations collected between 01 May and 30
 October, to maximise data between the onset of goose laying and the end of
 the ice-free season. We used filtered Argos locations as available in the
 Movebank data repository (doi: 10.5441/001/1.3gg33bd4), and only kept the
 most precise positions with location classes LC3 and LC2, which correspond
 to positioning errors having a 68% probability of being &lt; 250 m and
 &lt; 500 m. We then made scatter plots of the relocation data and
 calculated empirical variograms to identify and remove obvious
 extraterritorial trips and to ensure that all foxes included in the
 analyses showed range residency. An appropriate home range model was
 selected for each individual using Akaike information criterion
 (AIC<sub>c</sub>) to compare different movement processes
 (independent identically distributed, Ornstein-Uhlenbeck, integrated
 Ornstein-Uhlenbeck, Ornstein-Uhlenbeck Foraging). We estimated the area of
 the 95% home range contour for each individual-year based on the selected
 models and extracted the variance of each home range area to account for
 estimate uncertainty in subsequent analyses. Home
 ranges were then classified based on the availability of goose eggs and
 lemming. Using the goose colony contour traced with a GPS receiver aboard
 a helicopter, we classified each fox home range into one of three classes
 of goose availability: 1) centroid of home range inside the goose colony –
 full access, 2) centroid outside of the colony but home range overlaps the
 colony – partial access, 3) centroid outside of the goose colony and no
 overlap – no access. Based on mark-recapture estimates of annual lemming
 density, we classified each annual fox home range into one of two classes
 of lemming density, that is low (&lt;14.2
 lemming/km<sup>2</sup>) or high (&gt;235.2
 lemmings/km<sup>2</sup>).
 <strong>Incidental prey nest survival data.</strong>
 The second data sheet contains nest survival of fox incidental prey
 species (American golden plovers, sandpipers, and Lapland longspurs)
 monitored within fox home ranges, the id of the fox home range, and the
 number of days nests were monitored. Nest monitoring was conducted as
 follows: Shorebird and passerine nests were monitored
 each year from mid-June to mid-July. Nests were found opportunistically or
 through line transect surveys conducted within fox home ranges across the
 study area, both inside and outside of the goose colony. Lay date and
 expected hatch date were calculated for nests found during laying, or
 estimated using the flotation method for nests found during incubation.
 Nest status was assessed every 2–6 days, increasing monitoring efforts
 when nearing the expected hatch date. A nest was considered successful if
 at least one egg hatched, or if one of the following criteria was met: 1)
 small fragments of residual egg shells were found in the nest material
 close to the expected hatch date, 2) the nest was hatching (starred or
 pipped) on the last visit and was empty on the following visit, 3) the
 nest was empty on the last visit and the banded adult was resighted with
 chicks.
description: # Predator home range size mediates indirect interactions between prey
 species in an arctic vertebrate community The data set contains two sheets
 of data collected from 2008 to 2016 in the southwest plain of Bylot Island
 (72°530N, 79°540W), in Sirmilik National Park, Nunavut, Canada. ##
 Description of the data and file structure **Fox home range data.** The
 file data\_HomeRange.csv contains home range size of individual foxes
 estimated from Argos relocation data, the sex and breeding status of the
 fox, and the availability of lemmings and goose eggs. Raw Argos relocation
 data are available on Movebank (doi: 10.5441/001/1.3gg33bd4). Variable
 list: * **year:** the year of the study * **foxid:** the identity of the
 tracked fox * **id\_merged\_pair:** the identity of the tracked fox, but
 foxes sharing a home range (pair) are given the same identity * **sex:**
 the sex of the fox, either ***M*** (male) or ***F*** (female) *
 **rep\_status:** the reproductive status of the fox, either ***Breeder***
 (pups seen on den) or ***Non-breeder*** (no pups seen on den) *
 **area\_argos:** the area of the fox’s annual home range (95% isopleth)
 estimated from argos relocation - km<sup>2</sup> * **VAR:**
 the variance of the home range estimate * **VAR.log:** the variance of the
 log-transformed home range estimate * **goose\_category:** three-level
 categorical variable that classifies each fox home range in relation to
 goose egg availability. The variable levels are ***inside colony*** (Full
 access, the home range centroid is inside the goose colony contour),
 ***outside with overlap*** (Partial access, the centroid is outside, but
 the home range overlaps with the goose colony contour), ***outside*** (No
 access, the home range does not overlap with the goose colony). *
 **centro\_in\_colony:** two-level categorical variable that indicates
 whether the centroid of a fox home range is inside or outside of the goose
 colony. The variable levels are either **1** (centroid is inside the goose
 colony) or **2** (centroid is outside the goose colony). *
 **lemming\_density:** annual lemming density - lemming/ha * **lem\_cat:**
 two-level categorical variable that classifies each fox home range in
 relation to the annual lemming availability. The variable levels are
 ***Low*** (&lt;0.14 lemming/ha) or ***High*** (&gt;2.35
 lemming/ha) **Incidental prey nest survival data.** The file
 nesting\_success\_data.csv contains nest survival of fox incidental prey
 species (American golden plovers, sandpipers, and Lapland longspurs)
 monitored within fox home ranges, the id of the fox home range, and the
 number of days nests were monitored. Variable list: * **year:** the year
 of the study * **Species:** the nesting species code. The codes are
 ***amgp*** (American golden plover), ***basa*** (Baird's sandpiper),
 ***wrsa*** (White-rumped sandpiper), and ***lalo*** (Lapland longspur). *
 **p\_glob:** the nest fate at the end of the monitoring period, either
 **1** (successful) or **0** (predated). * **monitoring\_time:** the
 duration of the nest monitoring - days * **foxid:** the identity of the
 fox whose home range overlapped the nest ## Sharing/Access information Raw
 Argos relocation data used to estimate home range contours are available
 on Movebank (doi: 10.5441/001/1.3gg33bd4). ## Code/Software R code is in
 the associated file
 *Published\_code\_for\_Predator\_space\_use\_mediates\_indirect\_interactions.R* (doi: 10.5281/zenodo.8356912)