Seth Stapleton

Polar bears from space: Assessing satellite imagery as a tool to track Arctic wildlife

Development of efficient techniques for monitoring wildlife is a priority in the Arctic, where the impacts of climate change are acute and remoteness and logistical constraints hinder access. We evaluated high resolution satellite imagery as a tool to track the distribution and abundance of polar bears. We examined satellite images of a small island in Foxe Basin, Canada, occupied by a high density of bears during the summer ice-free season. Bears were distinguished from other light-colored spots by comparing images collected on different dates. A sample of ground-truthed points demonstrated that we accurately classified bears. Independent observers reviewed images and a population estimate was obtained using mark–recapture models. This estimate (: 94; 95% Confidence Interval: 92–105) was remarkably similar to an abundance estimate derived from a line transect aerial survey conducted a few days earlier (: 102; 95% CI: 69–152). Our findings suggest that satellite imagery is a promising tool for monitoring polar bears on land, with implications for use with other Arctic wildlife. Large scale applications may require development of automated detection processes to expedite review and analysis. Future research should assess the utility of multi-spectral imagery and examine sites with different environmental characteristics.

Factors affecting hatch success of hawksbill sea turtles on Long Island, Antigua, West Indies.

Current understanding of the factors influencing hawksbill sea turtle (Eretmochelys imbricata) hatch success is disparate and based on relatively short-term studies or limited sample sizes. Because global populations of hawksbills are heavily depleted, evaluating the parameters that impact hatch success is important to their conservation and recovery. Here, we use data collected by the Jumby Bay Hawksbill Project (JBHP) to investigate hatch success. The JBHP implements saturation tagging protocols to study a hawksbill rookery in Antigua, West Indies. Habitat data, which reflect the varied nesting beaches, are collected at egg deposition, and nest contents are exhumed and categorized post-emergence. We analyzed hatch success using mixed-model analyses with explanatory and predictive datasets. We incorporated a random effect for turtle identity and evaluated environmental, temporal and individual-based reproductive variables. Hatch success averaged 78.6% (SD: 21.2%) during the study period. Highly supported models included multiple covariates, including distance to vegetation, deposition date, individual intra-seasonal nest number, clutch size, organic content, and sand grain size. Nests located in open sand were predicted to produce 10.4 more viable hatchlings per clutch than nests located >1.5 m into vegetation. For an individual first nesting in early July, the fourth nest of the season yielded 13.2 more viable hatchlings than the initial clutch. Generalized beach section and inter-annual variation were also supported in our explanatory dataset, suggesting that gaps remain in our understanding of hatch success. Our findings illustrate that evaluating hatch success is a complex process, involving multiple environmental and individual variables. Although distance to vegetation and hatch success were inversely related, vegetation is an important component of hawksbill nesting habitat, and a more complete assessment of the impacts of specific vegetation types on hatch success and hatchling sex ratios is needed. Future research should explore the roles of sand structure, nest moisture, and local weather conditions.

Feasibility of using high-resolution satellite imagery to assess vertebrate wildlife populations.

Although remote sensing has been used for >40 years to learn about Earth, use of very high-resolution satellite imagery (VHR) (<1-m resolution) has become more widespread over the past decade for studying wildlife. As image resolution increases, there is a need to understand the capabilities and limitations of this exciting new path in wildlife research. We reviewed studies that used VHR to examine remote populations of wildlife. We then determined characteristics of the landscape and the life history of species that made the studies amenable to use of satellite imagery and developed a list of criteria necessary for appropriate use of VHR in wildlife research. From 14 representative articles, we determined 3 primary criteria that must be met for a system and species to be appropriately studied with VHR: open landscape, target organisms color contrasts with the landscape, and target organism is of detectable size. Habitat association, temporal exclusivity, coloniality, landscape differentiation, and ground truthing increase the utility of VHR for wildlife research. There is an immediate need for VHR imagery in conservation research, particularly in remote areas of developing countries, where research can be difficult. For wildlife researchers interested in but unfamiliar with remote sensing resources and tools, understanding capabilities and current limitations of VHR imagery is critical to its use as a conservation and wildlife research tool.

Occupancy surveys with conditional replicates: An alternative sampling design for rare species

Summary 1.Occupancy models are widely used to describe the distribution of rare and cryptic species— those that occur on only a small portion of the landscape and cannot be detected reliably during a single survey. However, model estimates of occupancy (ψ) and detection probabilities (p) are often least accurate under these circumstances. 2.Available sampling designs for occupancy surveys include standard design, wherein each of S sites is visited K times, and removal design, wherein S sites are visited K times each or until the species of interest is detected. We propose a new conditional design, wherein each of S sites is visited one time, and sites where the species of interest is encountered during the first survey are visited an additional (K−1) times to better estimate detection probability. We used large sample properties of maximum-likelihood estimators and Markov chain Monte Carlo simulations to characterize our proposed conditional design and compare it to standard and removal designs across a wide range of true occupancy and detection probabilities (ψ, p = 0.1 to 0.9 by 0.1 increments), maximum visits (K) and total sampling effort (E, the number of surveys accrued across all sites). 3.The conditional design provided more accurate estimates (lower standard or root mean squared error) of occupancy than standard or removal designs in our calculations and simulations when species were rare (ψ≤0.3) as well as more accurate estimates of detection probability over most combinations of ψ and p. These low-occupancy improvements are achieved by expending a greater proportion of effort at occupied sites, improving estimates of p and thus ψ. When species are common (ψ≥0.5) the removal design generally provided the most accurate occupancy estimates, whereas the standard design performed best when ψ was intermediate and during MCMC simulations when p and K were low. 4.We recommend the conditional design for surveys of rare species and pilot studies. For multi-species surveys that include mixtures of rare and common species, a hybrid standard-conditional design with 2-3 replicates at all sites and additional replicates at sites where rare species are detected improves occupancy estimates of rare species. This article is protected by copyright. All rights reserved.

Moose movement rates are altered by wolf presence in two ecosystems

Abstract Predators directly impact prey populations through lethal encounters, but understanding nonlethal, indirect effects is also critical because foraging animals often face trade‐offs between predator avoidance and energy intake. Quantifying these indirect effects can be difficult even when it is possible to monitor individuals that regularly interact. Our goal was to understand how movement and resource selection of a predator (wolves; Canis lupus) influence the movement behavior of a prey species (moose; Alces alces). We tested whether moose avoided areas with high predicted wolf resource use in two study areas with differing prey compositions, whether avoidance patterns varied seasonally, and whether daily activity budgets of moose and wolves aligned temporally. We deployed GPS collars on both species at two sites in northern Minnesota. We created seasonal resource selection functions (RSF) for wolves and modeled the relationship between moose first‐passage time (FPT), a method that discerns alterations in movement rates, and wolf RSF values. Larger FPT values suggest rest/foraging, whereas shorter FPT values indicate travel/fleeing. We found that the movements of moose and wolves peaked at similar times of day in both study areas. Moose FPTs were 45% lower in areas most selected for by wolves relative to those avoided. The relationship between wolf RSF and moose FPT was nonlinear and varied seasonally. Differences in FPT between low and high RSF values were greatest in winter (−82.1%) and spring (−57.6%) in northeastern Minnesota and similar for all seasons in the Voyageurs National Park ecosystem. In northeastern Minnesota, where moose comprise a larger percentage of wolf diet, the relationship between moose FPT and wolf RSF was more pronounced (ave. across seasons: −60.1%) than the Voyageurs National Park ecosystem (−30.4%). These findings highlight the role wolves can play in determining moose behavior, whereby moose spend less time in areas with higher predicted likelihood of wolf resource selection.

Re-assessing abundance of Southern Hudson Bay polar bears by aerial survey: effects of climate change at the southern edge of the range

The Southern Hudson Bay polar bear (Ursus maritimus Phipps, 1774) subpopulation is considered stable, but conflicting evidence lends uncertainty to that designation. Capture–recapture studies condu...

Full Simulation Data and Worked Examples from Specht et al. Conditional Occupancy Manuscript

To accompany publication of the conditional design for occupancy analysis, we provide the full simulation dataset used to compare the performance of standard, removal and conditional designs in common occupancy analysis programs: R package unmarked, Program MARK and PRESENCE. Specht_etal_AS3_CondOcc_SimulationCode.R is an R script that was used to generate the simulation data in AS4_Specht_etal_SimulationData.csv. AS4_Specht_etal_SimDataSet_metadata.csv contains variable labels for columns in AS4_Specht_etal_SimulationData.csv, including additional calculated variables not generated from the simulations. PRESENCE_files_for_Specht_etal.zip, ProgramMARK_files_for_Specht_etal.zip and Unmarked_example_for_Specht_etal.R provide files to work through examples of conditional, standard and removal occupancy designs for the same case in Program MARK, Program PRESENCE and R package unmarked, respectively. These files allow users to compare estimation by each method in a case where true occupancy probability is 0.2 and true detection probability is 0.5, and provide examples of formatted data input files. See Readme_Specht_etal.txt for more details.

Ecological monitoring of polar bears and seals in Nunavut a step toward the future.

We deployed satellite transmitters on live ringed seals captured in Hudson Bay in the summer of 2009. Polar bear transmitters have been deployed in Hudson Bay in 2007, 2008, and 2009. This project will provide management information and advice for the Hudson Bay and Foxe Basin ringed seal stocks by: (1) delineating movements that may bring juveniles and possibly adults into areas hunted by other communities, (2) assessing sex- and age-specific site fidelity of individual seals during the breeding season, (3) defining critical foraging habitat, movement and diving behaviour, (4) defining spatio-temporal variation in these aspects of ringed seal foraging ecology to complement ongoing diet studies to address a purported shift in prey of top predators associated with climate change in the greater Hudson Bay region. The project also aims to engage northerners in ecosystem science, develop a community-based monitoring and sampling program for seal, and enhance Arctic science. The final outcome of this combined effort is to provide policy information necessary to inform northerners of how they can adapt to marine ecosystem changes associated with polar warming and the resulting changes to marine mammal distribution and abundance. This project is linked to other Canadian IPY projects: ?GWAMM?. ?Marine Birds?, ?Circumpolar Flaw Lead?, ?Greenland Sharks?, ?Pan-Arctic Beluga?, ?Country Food Safety in a Changing Arctic?, ?People of a Feather and Ice? and internationally within the ESSAR and PAN-AME clusters. Collaborations have been developed to extend the community-based monitoring effort across the Canadian Arctic (Makavik, Fisheries Joint Management Commission, Nunatsiavut-Labrador Inuit Association, Ocean Tracking Network), across international governments (Greenland/Denmark, Russia, United States-Alaska, Norway, Finland), and organizations (Circumpolar Biodiversity Monitoring Program, Sustained Arctic Observing Network, Circumpolar Arctic Flora and Fauna).