Surveying Wild Animals from Satellites, Manned Aircraft and Unmanned Aerial Systems (UASs): A Review

Dongliang Wang,Huanyin Yue,Quanqin Shao

doi:10.3390/rs11111308

Abstract

This article reviews studies regarding wild animal surveys based on multiple platforms, including satellites, manned aircraft, and unmanned aircraft systems (UASs), and focuses on the data used, animal detection methods, and their accuracies. We also discuss the advantages and limitations of each type of remote sensing data and highlight some new research opportunities and challenges. Submeter very-high-resolution (VHR) spaceborne imagery has potential in modeling the population dynamics of large (>0.6 m) wild animals at large spatial and temporal scales, but has difficulty discerning small (<0.6 m) animals at the species level, although high-resolution commercial satellites, such as WorldView-3 and -4, have been able to collect images with a ground resolution of up to 0.31 m in panchromatic mode. This situation will not change unless the satellite image resolution is greatly improved in the future. Manned aerial surveys have long been employed to capture the centimeter-scale images required for animal censuses over large areas. However, such aerial surveys are costly to implement in small areas and can cause significant disturbances to wild animals because of their noise. In contrast, UAS surveys are seen as a safe, convenient and less expensive alternative to ground-based and conventional manned aerial surveys, but most UASs can cover only small areas. The proposed use of UAS imagery in combination with VHR satellite imagery would produce critical population data for large wild animal species and colonies over large areas. The development of software systems for automatically producing image mosaics and recognizing wild animals will further improve survey efficiency.

Highlights

Poaching activities, climate change, rapid habitat loss and environmental degradation have led to massive population decline and even extinction for many types of wild animals in recent decades [1]
We review recent studies that used remote sensing data collected from satellites, manned aircraft, and unmanned aircraft systems (UASs) to estimate the abundance of wild animals by directly detecting and counting individuals
Medium to low (1–60 m) spatial resolution spaceborne remote sensing data have been used for indirect animal surveys by identifying some form of ‘sign’ that indicates that animals have been in the area, such as fecal counts [24,25,26], food removal, and burrow counts [27,28], since the early 1980s

Summary

Introduction

Climate change, rapid habitat loss and environmental degradation have led to massive population decline and even extinction for many types of wild animals in recent decades [1]. To ensure a sufficient sample number and geographic coverage of field surveys, some field-based surveys, such as the North American Breeding Bird Survey (1966–2011) [9], have been conducted with the help of thousands of volunteers along roadsides. Such data are not representative of either the amount of habitat or the rate of change at a large spatial scale [10]. Collecting data for animals sensitive to humans, such as waterbirds, is difficult [11] For this purpose, researchers have developed various methods to survey wild animals from satellites, manned aircraft, and unmanned aircraft systems (UASs) [12,13,14]

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Conclusion