Data from: Speed kills: ineffective avian escape responses to oncoming vehicles

Animal-vehicle collisions cause high levels of vertebrate mortality worldwide, and what goes wrong when animals fail to escape and ultimately collide with vehicles is not well-understood. We investigated alert and escape responses of captive brown-headed cowbirds (Molothrus ater) in response to virtual vehicle approaches of different sizes and at speeds ranging from 60-360 km/h. Alert and flight initiation distances remained similar across vehicle speeds, but alert and flight initiation times decreased at higher vehicle speeds. Thus, avoidance behaviours in cowbirds appeared to be based on distance rather than time available for escape, particularly at 60-150 km/h; however, at higher speeds (≥ 180 km/h) this behavioral rule seemed to break down. Accordingly, the time needed to assess the approaching vehicle became compromised as vehicle speed increased, and cowbirds generally did not initiate flight with enough time to avoid collision when vehicle speed exceeded 120 km/h. Although potentially an effective strategy for evading predators, the decision-making process used by cowbirds in our study appears maladaptive in the context of avoiding fast-moving vehicles. Our methodological approach and findings provide a framework to assess how novel management strategies could affect escape rules, and the sensory and cognitive abilities animals use to avoid vehicle collisions.

全球范围内，动物-车辆碰撞事件（animal-vehicle collisions）会造成极高的脊椎动物死亡率（vertebrate mortality），但目前学界对动物无法成功逃逸并最终与车辆发生碰撞的内在机制仍未充分明晰。本研究针对圈养棕头牛鹂（Molothrus ater），探究其在面对不同尺寸、以60-360 km/h时速趋近的虚拟车辆时的警戒与逃逸反应（alert and escape responses）。研究结果显示，不同车辆时速下的逃逸启动距离（flight initiation distance）无显著差异，但更高的车辆时速会对应更短的警戒时长与逃逸启动时间（flight initiation time）。由此可见，棕头牛鹂的规避行为似乎基于逃逸可用距离而非剩余时间，这一规律在60-150 km/h时速区间内尤为显著；然而当车速≥180 km/h时，该行为准则（behavioral rule）似乎不再适用。相应地，随着车辆时速提升，棕头牛鹂用于评估趋近车辆的时间被不断压缩，当车速超过120 km/h时，它们通常无法留出足够时间启动逃逸以避免碰撞。尽管该决策机制在躲避天敌时或许是高效策略，但本研究中棕头牛鹂所采用的决策过程，在规避快速移动车辆的场景下却显得适应不良（maladaptive）。本研究的方法路径与研究结果，可为评估新型管理策略如何影响动物逃逸行为准则，以及动物用于规避车辆碰撞的感知与认知能力（sensory and cognitive abilities）提供参考框架。