A harbour seal (Phoca vitulina) can learn geometrical relations between landmarks

Marine mammals travel the world’s oceans. Some species regularly return to specific places to breathe, haul-out or breed. However, the mechanisms they use to return are unknown. Theoretically, landmarks could mediate the localisation of these places. Occasionally, it might be beneficial or even required to localise places using geometrical information provided by landmarks such as to apply a ‘middle rule’. Here, we trained a harbour seal to find its goal in the middle of numerous vertically and horizontally orientated two-landmark arrays. During testing, the seal was confronted with unfamiliar two-landmark arrays. After having successfully learnt to respond to the midpoint of multiple two-landmark arrays, the seal directly and consistently followed a ‘middle rule’ during testing. It chose the midpoint of the two-landmark arrays with high precision. Harbour seals with the ability to localise goals based on geometrical information would be able to home in on places even from unknown positions relative to goal-defining features. Altogether, the results obtained with our harbour seal individual in the current and previous study, examining the basis of landmark orientation, provide evidence that this seal can use landmark information very flexibly. Depending on context, this flexibility is adaptive to an environment in which the information content can vary over time.

海洋哺乳动物穿梭于全球各大洋。某些物种会定期返回特定的地点进行呼吸、晒太阳或繁殖。然而，它们用以返回的机制尚不为人知。从理论上讲，地标可能调节这些地点的定位。偶尔，使用地标提供的几何信息来定位地点可能是有益的，甚至可能是必需的，例如应用‘中点法则’。在本研究中，我们训练海豹在众多垂直和水平排列的双地标阵列中找到其目标。在测试过程中，海豹面临了不熟悉的双地标阵列。在成功学会对多个双地标阵列的中点做出反应后，海豹在测试中直接且一致地遵循了‘中点法则’。它以高精度选择了双地标阵列的中点。能够基于几何信息定位目标的海豹能够从相对于目标特征未知的位置精确地找到地点。总的来说，我们当前和以往研究中使用海豹个体进行的地标定位基础研究的结果表明，该海豹能够非常灵活地运用地标信息。根据环境的变化，这种灵活性是适应性的，能够适应信息含量随时间变化的环境。