Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel.
J R Soc Interface. 2013 Mar 13;10(82):20130079. doi: 10.1098/rsif.2013.0079. Print 2013 May 6.
We study how desert ants, Cataglyphis niger, a species that lacks pheromone-based recruitment mechanisms, inform each other about the presence of food. Our results are based on automated tracking that allows us to collect a large database of ant trajectories and interactions. We find that interactions affect an ant's speed within the nest. Fast ants tend to slow down, whereas slow ones increase their speed when encountering a faster ant. Faster ants tend to exit the nest more frequently than slower ones. So, if an ant gains enough speed through encounters with others, then she tends to leave the nest and look for food. On the other hand, we find that the probability for her to leave the nest depends only on her speed, but not on whether she had recently interacted with a recruiter that has found the food. This suggests a recruitment system in which ants communicate their state by very simple interactions. Based on this assumption, we estimate the information-theoretical channel capacity of the ants' pairwise interactions. We find that the response to the speed of an interacting nest-mate is very noisy. The question is then how random interactions with ants within the nest can be distinguished from those interactions with a recruiter who has found food. Our measurements and model suggest that this distinction does not depend on reliable communication but on behavioural differences between ants that have found the food and those that have not. Recruiters retain high speeds throughout the experiment, regardless of the ants they interact with; non-recruiters communicate with a limited number of nest-mates and adjust their speed following these interactions. These simple rules lead to the formation of a bistable switch on the level of the group that allows the distinction between recruitment and random noise in the nest. A consequence of the mechanism we propose is a negative effect of ant density on exit rates and recruitment success. This is, indeed, confirmed by our measurements.
我们研究了沙漠蚂蚁（Cataglyphis niger）是如何在没有基于信息素的招募机制的情况下相互告知食物的存在的。我们的研究结果基于自动化跟踪，这使我们能够收集大量的蚂蚁轨迹和相互作用的数据库。我们发现，相互作用会影响蚂蚁在巢内的速度。快速的蚂蚁往往会减速，而遇到更快的蚂蚁时，速度较慢的蚂蚁会加快速度。较快的蚂蚁往往比较慢的蚂蚁更频繁地离开巢穴。因此，如果一只蚂蚁通过与其他蚂蚁的相遇获得了足够的速度，那么它就会倾向于离开巢穴去寻找食物。另一方面，我们发现蚂蚁离开巢穴的概率仅取决于它的速度，而与它是否最近与找到食物的招募者进行了互动无关。这表明蚂蚁通过非常简单的相互作用来传达它们的状态的招募系统。基于这个假设，我们估计了蚂蚁的两两相互作用的信息论信道容量。我们发现，对相互作用的巢内同伴速度的反应非常嘈杂。那么，如何将与巢内蚂蚁的随机相互作用与找到食物的招募者的相互作用区分开来呢？我们的测量结果和模型表明，这种区分并不依赖于可靠的通讯，而是依赖于找到食物的蚂蚁和没有找到食物的蚂蚁之间的行为差异。招募者在整个实验过程中保持高速度，无论它们与谁互动；非招募者与有限数量的巢内同伴进行交流，并根据这些互动来调整它们的速度。这些简单的规则导致群体水平上形成了一个双稳态开关，从而允许在巢内区分招募和随机噪声。我们提出的机制的一个后果是蚂蚁密度对退出率和招募成功率的负面影响。这确实被我们的测量结果所证实。
