Raw Argos data of arctic foxes from Bylot Island

This dataset contains the Argos locations of arctic foxes tracked from July 2007 to May 2013 (66 individuals, 97 fox-years); the file is provided in txt format. More information is provided in the joined ReadMe file

Additional file 2: Figure S1. of Spatio–temporal hotspots of satellite–tracked arctic foxes reveal a large detection range in a mammalian predator

Examples of hotspots not retained by our hotspot selection process. While selected spatio–temporal hotspots (more than one fox present at least two consecutive days) typically showed a high concentration of locations at their center and relatively high temporal synchrony, hotspots that were not selected show a more sequential use of the area or a less clustered pattern of fox locations. Histograms show the chronology of fox presence for each hotspot. Individual foxes are labeled with a letter (M for males and F for females) followed by their identity number. Crosses indicate fox home range centers, with colored crosses identifying foxes detected at hotspots. The study area is depicted in dark grey. (PDF 96 kb

Additional file 3: of Spatio–temporal hotspots of satellite–tracked arctic foxes reveal a large detection range in a mammalian predator

Animation of arctic fox movements. Locations of tracked arctic foxes are shown from 25 October 2010 to 31 May 2011. For each day (indicated at the bottom left of maps), locations of each given fox are connected to locations of the same fox from the previous day, in order to show movement paths. Locations of fox hotspots are depicted by white ellipses and their names correspond to those in Fig. 2. The 40–km travel of individual M327 appears at 0:36. (MP4 20092 kb

Evaluation of Argos Telemetry Accuracy in the High-Arctic and Implications for the Estimation of Home-Range Size

<div><p>Animal tracking through Argos satellite telemetry has enormous potential to test hypotheses in animal behavior, evolutionary ecology, or conservation biology. Yet the applicability of this technique cannot be fully assessed because no clear picture exists as to the conditions influencing the accuracy of Argos locations. Latitude, type of environment, and transmitter movement are among the main candidate factors affecting accuracy. A posteriori data filtering can remove “bad” locations, but again testing is still needed to refine filters. First, we evaluate experimentally the accuracy of Argos locations in a polar terrestrial environment (Nunavut, Canada), with both static and mobile transmitters transported by humans and coupled to GPS transmitters. We report static errors among the lowest published. However, the 68^th error percentiles of mobile transmitters were 1.7 to 3.8 times greater than those of static transmitters. Second, we test how different filtering methods influence the quality of Argos location datasets. Accuracy of location datasets was best improved when filtering in locations of the best classes (LC3 and 2), while the Douglas Argos filter and a homemade speed filter yielded similar performance while retaining more locations. All filters effectively reduced the 68^th error percentiles. Finally, we assess how location error impacted, at six spatial scales, two common estimators of home-range size (a proxy of animal space use behavior synthetizing movements), the minimum convex polygon and the fixed kernel estimator. Location error led to a sometimes dramatic overestimation of home-range size, especially at very local scales. We conclude that Argos telemetry is appropriate to study medium-size terrestrial animals in polar environments, but recommend that location errors are always measured and evaluated against research hypotheses, and that data are always filtered before analysis. How movement speed of transmitters affects location error needs additional research.</p></div

Influence of filtering methods on home-range size estimations.

<p>We present (A) the average home-range size, (B) the size ratio Argos to GPS, and (C) the proportion of Argos locations found in GPS home-range size estimates calculated while estimating home ranges based on Argos and GPS locations from mobile experiments using 95% MCP and 95% kernel (h = 850, cell grid size = 250m). The home ranges were estimated for the following scenarios: raw data (Raw), only LC3 and LC2 locations (LC32), LC3 and LC2 and LC1 locations (LC321), data filtered with the Douglas Argos filter (DAF), data filtered with a homemade speed filter (HSF), simulated Argos locations with errors from the static error distribution (Static), and simulated Argos locations with errors from the mobile error distribution (Mobile). Home-range size (A) using the GPS reference area (Ref) is also shown. Data were obtained from Argos Platform Terminal Transmitters deployed simultaneously with GPS receivers on Bylot Island, Nunavut, Canada in July 2012.</p

Home-range size estimations for simulated Argos errors in circles of varying radii.

<p>We present (A) the average home-range size, (B) the size ratio Argos to GPS, and (C) the proportion of Argos locations found in GPS home-range estimates calculated while estimating Argos and GPS home ranges from mobile experiments using MCP 95% and kernel 95% (h = 850, grid cell size = 250m). Home ranges were estimated for simulated random GPS and Argos locations in circular areas of radius 250 m, 500 m, 750 m, 1,000 m, 2,500 m, and 5,000 m.</p

Comparison between static and mobile errors for all Argos location classes.

<p>Columns show the number and proportion of locations obtained for each location class (LC), the mean error, the mean longitudinal and latitudinal errors, the median error, the 68^th error percentiles as estimated by CLS [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0141999#pone.0141999.ref009" target="_blank">9</a>], and the 68^th and 90^th error percentiles calculated from Argos locations obtained during static (n = 7) and mobile tests (n = 20) from Argos Platform Terminal Transmitters deployed simultaneously with GPS receivers on Bylot Island, Nunavut, Canada in July 2012.</p><p>Comparison between static and mobile errors for all Argos location classes.</p

Comparison of the performance of different filtering methods.

<p>Columns show the number of Argos locations obtained in each location class (LC), as well as the number of Argos locations retained by the Douglas Argos Filter (DAF) and a Homemade Speed Filter (HSF) applied to data obtained during 20 mobile tests from Argos Platform Terminal Transmitters deployed on Bylot Island, Nunavut, Canada in July 2012. The percentage of locations retained by each filter within each LC is shown in parentheses.</p><p>Comparison of the performance of different filtering methods.</p

Number, reproductive status, and sex of arctic foxes sampled annually.

<p>The annual index of lemming relative abundance is also indicated. Some foxes were captured more than once (up to three times), hence the total number of individuals is 60 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042427#s2" target="_blank">methods</a> for details), for a total of 74 samples. Four samples (males of undetermined reproductive status) were not used in the analyses.</p

Proportion of breeding foxes <i>vs.</i> lemming trapping index during the study period.

<p>Proportion of breeding foxes captured annually as a function of the lemming snap-trapping index. The curve represents predictions from a generalized linear mixed-effects model fitted to the data (±1SE, shaded area around the curve). Small vertical bars (gray) represent the original data for breeders (top) or non-breeders (bottom) to which the model was fitted. The bars were jittered (randomly displaced over small distances on the X-axis) in order to better show data concentration. The open circles show the actual proportion of breeders for a given year/lemming index value. Total number of foxes captured each year is also available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042427#pone-0042427-t001" target="_blank">Table 1</a>. Data include only year 2004 to 2008 and lemming abundance data from 2004 to 2006 are drawn from Morrissette et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042427#pone.0042427-Morrissette1" target="_blank">[58]</a>, based on our long term monitoring of lemming abundance on Bylot Island (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042427#s2" target="_blank">methods</a> for details).</p