Synergistic use of UAV surveys, satellite tracking data, and mark‐recapture to estimate abundance of elusive species

Estimating population abundance is central to many ecological studies and important in conservation planning. Yet the elusive nature of many species makes estimating their abundance challenging. Abundance estimates of sea turtles, marine birds, and seals are usually made when breeding adults are ash...

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Bibliographic Details
Published in:Ecosphere (Washington, D.C) Vol. 14; no. 3
Main Authors: Stokes, Holly J., Mortimer, Jeanne A., Laloë, Jacques‐Olivier, Hays, Graeme C., Esteban, Nicole
Format: Journal Article
Language:English
Published: Hoboken, USA John Wiley & Sons, Inc 01.03.2023
Wiley
Subjects:
Altitude
Aquatic birds
Aquatic reptiles
Archipelagoes
Chelonia mydas
conservation
density
drone
Ecological studies
Endangered & extinct species
endangered species
Eretmochelys imbricata
Estimates
Global positioning systems
GPS
Indian Ocean
Lagoons
marine megafauna
marine protected area (MPA)
mark-recapture studies
mark‐resight
Reptiles & amphibians
satellite tracking
Satellites
Seals
shifting baseline
species abundance
Trends
Wildlife conservation
Chagos Archipelago
Indian Ocean
United States > US
Diego Garcia
ISSN:2150-8925, 2150-8925
Online Access:Get full text
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Summary:Estimating population abundance is central to many ecological studies and important in conservation planning. Yet the elusive nature of many species makes estimating their abundance challenging. Abundance estimates of sea turtles, marine birds, and seals are usually made when breeding adults are ashore, while life stages spent at sea, including as juveniles, are often poorly sampled. We used a combination of high‐resolution satellite tracking (Fastloc‐GPS), uncrewed aerial vehicle (UAV) surveys, and capture‐mark‐recapture approaches to assess the abundance of immature hawksbill (Eretmochelys imbricata) and green turtles (Chelonia mydas) in a tidal lagoon of the Chagos Archipelago (Indian Ocean). We captured, marked, and released 50 turtles (48 hawksbill and 2 green turtles) prior to UAV surveys and used satellite tracking data from 27 immature turtles (25 hawksbill and 2 green turtles) to refine the estimated numbers of marked turtles available for resighting and those likely to have emigrated from the study area. We estimated a total of 339 turtles in the lagoon with a density variation at different tidal heights between 265 turtles km−2 at high water and 499 turtles km−2 at low water. Of these, 91% were hawksbills and 9% were green turtles. These hawksbill densities are the highest reported among 17 foraging sites recorded around the world and likely reflect successful long‐term protection of turtles in the Chagos Archipelago.
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ISSN:2150-8925
2150-8925
DOI:10.1002/ecs2.4444