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Mallard response to experimental human disturbance on sanctuary areas is mediated by hunting

Blake-Bradshaw, Abigail1; Masto, Nicholas2; Highway, Cory3; Keever, Allison3; Feddersen, Jamie4; Hagy, Heath2; Cohen, Bradley3

Published Dec 12, 2024 on Dryad. https://doi.org/10.5061/dryad.zgmsbccm9

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Dec 12, 2024 version files 7.47 MB

Abstract

Wildlife managers often provide spatial sanctuaries for wildlife to escape both lethal (e.g., hunting) and non-lethal (e.g., non-consumptive recreation) human disturbance. However, as societal interest in outdoor recreation continues to climb, many areas face added pressure to allow recreation, yet studies increasingly demonstrate negative effects of outdoor recreation on wildlife. As such, an understanding of how wildlife respond to human activities is essential to develop sustainable outdoor recreation guidelines to preserve multiple benefits for humans, while simultaneously protecting wildlife populations and fitness. We examined GPS-marked mallard responses to three experimental disturbances meant to mimic recreation that could theoretically occur on waterfowl sanctuaries during 1 November–28 February 2019–2022. We evaluated effects on movement, space use, and site fidelity and expected that repeated disturbance would result in habituation. We further evaluated predictions of the risk-disturbance hypothesis, whereby we predicted greater behavioral responses during the hunting period and to more intense stimuli. We conducted 140 covered vehicle (e.g., truck), 40 pedestrian, and 43 uncovered vehicle (e.g., ATV) disturbances across 10 sanctuaries, exposing 195 mallards to ≥1 disturbance (median=2, range=1–12). Diurnal sanctuary use exceeded 83% of proportional use regardless of period; however, mallards only decreased sanctuary use when disturbed before the hunting period with an uncovered vehicle. Besides immediate increases in hourly movements on mornings mallards received pedestrian and uncovered vehicle disturbances, disturbed mallards displayed minimal changes in hourly movements. At the diel-scale, pedestrians elicited the greatest responses; space use doubled for disturbed birds during pre-hunt and early-hunt periods. In contrast, vehicle disturbances decreased movement but only outside the hunting period. Repeated disturbance caused gradual declines in space use: mallards used 12% less space with each additional disturbance during hunting. Constrained behavioral responses and unchanged sanctuary fidelity after disturbance during hunting season suggests the limited availability of alternative safe areas constrained mallard responses to disturbances.