Data from: How to find home backwards? Navigation during rearward homing of Cataglyphis fortis desert ants

Cataglyphis ants are renowned for their impressive navigation skills, which have been studied in numerous experiments during forward locomotion. However, the ants' navigational performance during backward homing when dragging large food loads has not been investigated until now. During backward locomotion, the odometer has to deal with unsteady motion and irregularities in inter-leg coordination. The legs' sensory feedback during backward walking is not just a simple reversal of the forward stepping movements: compared with forward homing, ants are facing towards the opposite direction during backward dragging. Hence, the compass system has to cope with a flipped celestial view (in terms of the polarization pattern and the position of the sun) and an inverted retinotopic image of the visual panorama and landmark environment. The same is true for wind and olfactory cues. In this study we analyze for the first time backward-homing ants and evaluate their navigational performance in channel and open field experiments. Backward-homing Cataglyphis fortis desert ants show remarkable similarities in the performance of homing compared with forward-walking ants. Despite the numerous challenges emerging for the navigational system during backward walking, we show that ants perform quite well in our experiments. Direction and distance gauging was comparable to that of the forward-walking control groups. Interestingly, we found that backward-homing ants often put down the food item and performed foodless search loops around the left food item. These search loops were mainly centred around the drop-off position (and not around the nest position), and increased in length the closer the ants came to their fictive nest site.

箭蚁属（Cataglyphis）蚂蚁以其卓越的导航能力著称，此前已有诸多实验针对其正向移动时的导航行为展开研究。然而，该类蚂蚁在拖拽大型食物载荷进行反向归巢时的导航表现，迄今尚未得到探究。在反向移动过程中，其里程计（odometer）需应对不稳定的运动状态以及步足间协调的异常波动。反向行走时，步足的感官反馈并非正向迈步的简单反转：与正向归巢相比，蚂蚁在反向拖拽食物时朝向完全相反的方向。因此，其罗盘系统（compass system）需适配翻转的天体视野（涵盖偏振光模式与太阳位置）以及视觉全景与地标环境的倒置视网膜拓扑图像（retinotopic image）。风力与嗅觉线索的处理亦面临同样的适配需求。本研究首次对反向归巢的蚂蚁进行分析，并在通道与开放场地实验中评估其导航表现。研究结果显示，福氏箭蚁（Cataglyphis fortis）在反向归巢时的导航表现与正向行走的对照组存在显著相似性。尽管反向行走过程中导航系统面临诸多挑战，但实验表明蚂蚁的整体表现依旧出色。其方向与距离测算能力与正向行走的对照组相当。值得关注的是，研究团队观察到反向归巢的蚂蚁常会放下食物，并围绕原食物放置点开展无食搜索循环。这类搜索循环主要以食物投放位置为中心（而非巢址），且随着蚂蚁愈发接近假想巢址，搜索循环的长度也随之增加。