Turn alternation is a locomotory behaviour wherein an animal makes consecutive turns in opposite directions (left-then-right or right-then-left). It has been suggested that its adaptive function is to maintain locomotion in a relatively constant general direction while negotiating obstacles. Previous work has focussed on the use of turn alternation in prey species in artificial horizontal mazes. In the first study presented here, we tested whether predatory seven-spot ladybirds (Coccinella septempunctata) exhibit turn alternation when repeatedly presented with consecutive choice turning decisions on vertically oriented twigs. Our findings suggest that turn alternation occurs vertically as well as horizontally, on plant structures as well as terrestrially, and in a type of animal (predatory insect) in which turn alternation has received little attention. In the second study presented here, we tested whether characteristics of branched structures explored by two-spot ladybirds (Adalia bipunctata) influence turning decisions. Our findings suggest that ladybirds exhibit preferences for thicker over thinner, straighter over more deviating headings, and higher over lower turning choice options at bifurcations. These exploratory studies indicate that while turn alternation is an observable phenomenon in ladybirds, it is not the only predictor of searching behaviour on branched structures.

中文翻译：

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瓢虫（七星瓢虫和双点瓢虫）通过分支结构的转向交替和环境因素对搜索路线的影响

轮流交替是一种运动行为，其中动物在相反的方向（先左后右或先右后左）连续转弯。有人提出，它的适应功能是在克服障碍时保持相对恒定的总体方向的运动。以前的工作集中在人工水平迷宫中的猎物物种中轮流交替的使用。在此处介绍的第一项研究中，我们测试了掠食性七点瓢虫（七星瓢虫）在垂直方向的树枝上反复连续选择转向决策时是否表现出转向交替。我们的研究结果表明，轮流交替发生在垂直和水平上，在植物结构上和陆地上，并且在一种很少关注轮流交替的动物（捕食性昆虫）中。在此处介绍的第二项研究中，我们测试了双点瓢虫 (Adalia bipunctata) 探索的分支结构的特征是否影响转向决策。我们的研究结果表明，瓢虫表现出偏好更厚而不是更薄，更直而不是更多偏离的航向，以及更高而不是分岔处的低转弯选择。这些探索性研究表明，虽然轮流交替是瓢虫中可观察到的现象，但它并不是分支结构搜索行为的唯一预测因素。我们的研究结果表明，瓢虫表现出偏好更厚而不是更薄，更直而不是更多偏离的航向，以及更高而不是分岔处的低转弯选择。这些探索性研究表明，虽然轮流交替是瓢虫中可观察到的现象，但它并不是分支结构搜索行为的唯一预测因素。我们的研究结果表明，瓢虫表现出偏好更厚而不是更薄，更直而不是更多偏离的航向，以及更高而不是分岔处的低转弯选择。这些探索性研究表明，虽然轮流交替是瓢虫中可观察到的现象，但它并不是分支结构搜索行为的唯一预测因素。