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闻名，此前已有大量针对其正向移动时导航行为的实验研究。然而，目前尚无针对该类蚂蚁拖拽大型食物载荷时的反向归巢导航表现的相关研究。
在反向移动过程中，里程计（odometer）需要应对不稳定的运动状态以及腿间协调的异常情况。反向行走时腿部的感觉反馈并非正向行走时的简单逆转：与正向归巢相比，蚂蚁在反向拖拽食物时面朝相反方向。因此，其罗盘系统（compass system）需要适配翻转的天体视野（涉及偏振模式与太阳位置）以及视觉全景与地标环境的倒置视网膜拓扑图像（retinotopic image）。对于风与嗅觉线索（olfactory cues）而言，情况亦是如此。
本研究首次对反向归巢的箭蚁展开分析，并通过通道与开放场实验评估其导航表现。研究发现，反向归巢的撒哈拉箭蚁（Cataglyphis fortis）在归巢表现上与正向行走的蚂蚁存在显著相似性。尽管反向行走时导航系统面临诸多挑战，但实验结果显示蚂蚁仍能出色完成任务。其方向与距离估算能力与正向行走的对照组（control groups）相当。
有趣的是，研究团队观察到反向归巢的蚂蚁常会放下食物，并围绕该食物进行无食物的搜索环路。此类搜索环路主要以食物掉落位置为中心（而非巢址位置），且当蚂蚁接近假想巢址时，搜索环路的长度会随之增加。