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

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.

野生动物管理者通常会设立空间庇护地（spatial sanctuaries），为野生动物提供躲避致死性（如狩猎）与非致死性（如非消耗性休闲活动）人类干扰的场所。然而随着社会对户外休闲的兴趣持续攀升，诸多区域面临着放宽休闲活动准入的额外压力，但现有研究日益表明，户外休闲会对野生动物造成负面影响。因此，厘清野生动物对人类活动的响应机制，对于制定可持续的户外休闲指南、兼顾人类多重福祉与野生动物种群及适合度保护至关重要。本研究于2019—2022年的11月1日至2月28日期间，针对模拟水禽庇护地可能出现的三类实验性干扰，考察了GPS标记绿头鸭（GPS-marked mallard）的响应情况。研究评估了干扰对其移动、空间利用与位点保真度（site fidelity）的影响，并假设重复干扰会促使动物产生习惯化。此外，本研究还验证了风险干扰假说（risk-disturbance hypothesis）的相关预测，即预测狩猎期内以及面对更强刺激时，野生动物会表现出更强烈的行为响应。研究在10处庇护地共开展了140次带篷车辆（如卡车）、40次步行以及43次敞篷车辆（如全地形车（ATV））干扰，共使195只绿头鸭暴露于至少1次干扰中（中位数为2次，范围1—12次）。无论处于哪个时段，绿头鸭的日间庇护地使用时长占总活动时长的比例均超过83%；但仅当绿头鸭在狩猎前时段遭遇敞篷车辆干扰时，其庇护地使用量才会出现下降。除了遭遇步行与敞篷车辆干扰的当日清晨，绿头鸭的小时移动距离出现即时上升外，受干扰个体的小时移动距离未出现显著变化。在昼夜尺度（diel-scale）上，步行干扰引发的响应最为强烈：狩猎前与狩猎早期，受干扰个体的空间利用范围翻倍。与之相对，车辆干扰仅会在非狩猎期降低绿头鸭的移动能力。重复干扰会导致空间利用范围逐渐缩减：狩猎期内，每多经历一次干扰，绿头鸭的空间利用范围便会减少12%。狩猎季遭遇干扰后，绿头鸭的行为响应受限且庇护地位点保真度未发生改变，这表明可替代的安全区域匮乏限制了绿头鸭对干扰的响应能力。