Understanding behavioural responses to disturbances is vital for wildlife conservation. For example, in the Arctic, the decrease in sea ice has opened new shipping routes, increasing the need for impact assessments that quantify the distance at which marine mammals react to vessel presence. This information can then guide targeted mitigation policies, such as vessel slow-down regulations and delineation of avoidance areas. Using telemetry data to determine distances linked to deviations from normal behaviour requires advanced statistical models, such as threshold hidden Markov models (THMMs). While these are powerful tools, they do not assess whether the estimated threshold reflects a meaningful behavioural shift. We introduce a lasso-penalized THMM that builds on computationally efficient methods to impose penalties on HMMs and present a new, efficient penalized quasi-restricted maximum-likelihood estimator. Our framework is capable of estimating thresholds and assessing whether the disturbance effects are meaningful. With simulations, we demonstrate that our lasso method effectively shrinks spurious threshold effects towards zero. When applied to narwhal $\textit{(Monodon monoceros)}$ movement data, our analysis suggests that narwhal react to vessels up to 4 kilometres away by decreasing movement persistence and spending more time in deeper waters (average maximum depth of 356m). Overall, we provide a broadly applicable framework for quantifying behavioural responses to stimuli, with applications ranging from determining reaction thresholds to disturbance to estimating the distances at which terrestrial species, such as elephants, detect water.

翻译：理解野生动物对干扰的行为反应对于物种保护至关重要。例如，在北极地区，海冰减少开辟了新的航运路线，从而增加了对量化海洋哺乳动物对船舶存在产生反应距离的影响评估的需求。此类信息可为针对性缓解政策（如船舶减速规定和规避区域划定）提供指导。利用遥测数据确定与正常行为偏离相关的距离需要先进的统计模型，例如阈值隐马尔可夫模型（THMMs）。尽管这些是强大的工具，但它们并未评估估计的阈值是否反映有意义的行为转变。我们提出了一种套索惩罚THMM，该方法基于计算高效的对HMM施加惩罚的方法，并提出了一种新的高效惩罚准限制最大似然估计器。我们的框架能够估计阈值并评估干扰效应是否具有意义。通过模拟，我们证明我们的套索方法能有效地将虚假阈值效应收缩至零。当应用于独角鲸（Monodon monocros）运动数据时，我们的分析表明，独角鲸对最远4公里外的船舶产生反应，表现为运动持续性降低并更多时间停留在更深水域（平均最大深度356米）。总体而言，我们提供了一个广泛适用的量化对刺激行为反应的框架，其应用范围涵盖从确定对干扰的反应阈值到估计陆地物种（如大象）探测到水源的距离。