Individual and collective decision making and risk evaluation in slavemaking ants

群居昆虫群体是合作决策和集体智慧的主要例子。与人类社会的组织不同，人类社会的决策通常由一个或几个特别指定的个人做出，而蚂蚁社会的决策是基于简单的经验法则，由每只蚂蚁注意。为了让这种分散的过程发挥作用，所有个人都必须能够获得相关信息，以做出适应性决策。酿酒蚂蚁是一种专职的社会寄生虫，它们完全依赖它们的奴隶--异种工蚁--来完成所有例行的蚁群任务。它们的繁殖成功以及社会寄生虫群体的适合性直接取决于在寄生虫群体中发现的奴隶的数量。奴隶是通过定期的奴隶突袭获得的，这对奴隶制造者来说本身就是危险的任务：大约10%参与突袭的寄生虫工人在这个过程中严重受伤或死亡。决定攻击哪个宿主群体是至关重要的，寻找新的宿主群体的侦察蚁在招募巢友进行攻击之前，应该仔细权衡风险和收益。早期的研究表明，寄生虫群体--如果可以选择的话--确实更喜欢攻击防御较差的宿主物种的群体，并调整突袭队中寄生虫工作者的数量，以适应受害者宿主的巢大小。在这里，我们计划调查两个奴隶制蚂蚁物种的风险评估和决策，这两个物种代表着独立的奴隶制起源，平均群体大小不同。我们想把重点放在侦察蚂蚁做出的个人决定和寄生虫群体关于是否对给定宿主巢发起攻击的集体决定上。对这些决定来说，重要的是关于潜在受害者群体和寄生虫群体状况的信息，这些信息必须由寄生虫群体成员获得、分发和评估。

Colonies of social insects are prime examples for cooperative decision making and collective intelligence. In contrast to the organisation of human societies where decisions are often made by one or few specially assigned individuals, decisions in ant societies are based on simple rules of thumb, heeded by each ant. For this kind of decentralized processes to work, all individuals must have access to relevant information to make adaptive decisions. Slavemaking ants are obligate social parasites that completely rely upon their slaves, allospecific workers, for all routine colony tasks. Their reproductive success and thus the fitness of a social parasite colony directly depend on the number of slaves found in a parasite colony. Slaves are obtained via regular slave raids, which are in itself risky tasks for the slavemakers: around 10% of the parasite workers involved in a raid are severely injured or killed during the process. The decision which host colony to attack is so crucial and scout ants searching for new host colonies should weigh risks and benefits carefully before recruiting nest mates for an attack. Earlier studies showed that parasite colonies - when given a choice - indeed prefer to attack colonies of less well defended host species and adjust the number of parasite workers in a raiding party to victim host nest size. Here, we plan to investigate risk evaluation and decision making in two slavemaking ant species, which represent independent origins of slavery and differ in average colony size. We want to focus on individual decisions made by scout ants and on collective ones of parasite colonies on whether or not to initiate an attack on a given host nest. Important for these decisions are information on the potential victim colony and on the condition of the parasite colony, which has to be obtained, distributed and evaluated by parasite colony members.