Dissertation Research: Why Animals Form Groups: Predator Avoidance Versus Foraging Success in Fiddler Crabs

9701063我们为什么要把动物作为群体，这是社会生物学领域的中心问题。研究人员提出了五个模型来解释社交聚集形成的原因。其中三项表明，群体之所以形成，是因为它们有助于保护群体成员免受捕食者的伤害。从数学上讲，群体成员身份应该会降低每个个体被捕食的风险，而代价是其邻居的利益。相反，许多实验表明，在捕食者攻击期间迅速驱散一群动物，可以通过迷惑捕食者并允许猎物逃跑来降低被捕食的风险。其他研究表明，成群捕食的风险降低了，因为有更多的眼睛来观察可能的危险。另外两个解释社会聚集的模型表明，群体形成将提高每个成员寻找食物的能力。实验证明，许多动物都有能力观察彼此的行为，并从彼此那里了解到好的食物来源，而且在大群体中这样做的机会比在小群体中更高。此外，较大的动物群体往往比较小的群体走得更直，数学上已经表明，这将导致进入原始的、未觅食的地区的可能性增加。为了验证这五个模型，这项研究将检查洞穴建造甲壳类动物的群体形成情况，这些甲壳类动物经常形成大群，在沿海沼泽中数量极多。使用野外实验、直接观察和对视频记录的计算机分析，将确定哪种模型最能解释动物形成群体的原因。

9701063 Wethey Why animals for groups is central question in the field of sociobiology. Researchers have proposed five models to explain why social aggregations form. Three of these suggest that groups form because they help protect group members from predators. Mathematically, group membership should lower the risk of predation to each individual at the expense of its neighbors. Conversely, many experiments have demonstrated that rapid scattering of a group during a predator's attack can decrease the risk of predation by confusing the predator and allowing the prey to escape. Other work has shown that predation risk is decreased in groups because there are more sets of eyes to watch for possible danger. The other two models that explain social aggregation suggest that group formation would increase each member's ability to find food. Experiments have demonstrated that many animals are capable of watching each other's behavior and learning about good food sources from one another, and the opportunity for this would be higher in large groups than in small ones. Additionally, larger groups of animals tend to move in straighter lines than smaller groups, and it has been shown mathematically that this will lead to an increased likelihood of entering pristine, un-foraged areas. To test these five models, this study will examine group formation in burrow-building crustaceans that regularly form large flocks, and are extremely numerous in coastal marshes. Use of field experiments, direct observations, and computer analysis of video recordings, will determine which model best explains why animals form groups.