Mechanisms and Functions of Sexual Segregation in Habitat Use

在许多动物中，雄性和雌性可能分开生活一段时间或大部分时间，称为性隔离。当两性使用其环境的不同部分时，可能会发生性别隔离。古希腊神话讲述了一个由女战士组成的国家，她们被称为亚马逊人，住在一个岛上。亚马逊人只与男人见面进行贸易和繁殖，并将所有的女儿留在岛上。虽然这个古老神话的真实程度有待商榷，但在动物中，栖息地利用的性别差异是常见的，如果我们要保护物种和栖息地，了解这种行为为什么以及如何发生是至关重要的。例如，如果发生性别隔离，可能有必要保护雄性和雌性的不同生境。然而，我们必须了解为什么以及如何发生这种行为才能做到这一点。一段时间以来，科学家们一直试图了解为什么在栖息地使用中性别隔离。在1900年，查尔斯达尔文思考了为什么红鹿一年中的大部分时间都是分开生活的。近年来提出了许多解释，其中三个可能是重要的。第一种观点基于这样一个事实：在许多物种中，雄性和雌性受到捕食者攻击的频率不同。雄性可能更大，并配备了武器，如鹿角，这可能使他们能够使用增加捕食风险的栖息地。第二种观点认为，男性和女性的营养需求可能不同，例如由于怀孕，这可能导致性别选择不同的栖息地来满足这些营养需求。最后，雄性对雌性的骚扰在动物王国中很常见，经常会对雌性或它们的后代造成伤害。最后一个想法是，雌性占据没有雄性的栖息地，以减少这种骚扰。以前关于性别隔离的研究一般集中在鹿和羊等有蹄类动物上，但由于它们体型庞大，需要漫游的空间很大，科学家们通常只能描述隔离的模式。相比之下，拟议的研究将实验测试这些假设使用一个小品种的淡水鱼'孔雀鱼'在特立尼达岛在加勒比海作为一个模型系统。孔雀鱼在不同的溪流中形成相对较小的种群，它们面临的捕食者数量各不相同。此外，孔雀鱼可以很容易地保存在实验室中，使它们特别适合这项研究。我们知道，生活在高捕食风险下的孔雀鱼按性别隔离，雄性孔雀鱼（更容易受到捕食）占据浅水区，被认为是更安全的捕食者，这表明捕食风险在推动性别隔离方面很重要。然而，他们从隔离中获得的好处仍然未知。例如，为什么雌性会接受更大的捕食风险？是为了减少性骚扰还是因为食物竞争减少了？或者是两者的结合？我们也不知道性别隔离的模式是如何产生的，或者为什么一些男性和女性生活在河流的同一部分。是否依赖于环境条件？男性和女性的数量以及人口密度的差异如何影响它？我将比较特立尼达河流中10个野生孔雀鱼种群在不同捕食风险下的性别隔离程度。在每条河流中，我将评估性别隔离的水平，并将其与捕食风险、种群结构和栖息地类型（例如水深）进行比较，以测试驱动性别隔离的主要思想的预测。除了在野外观察行为模式外，这项研究还将在实验室中观察孔雀鱼的行为，在实验室中可以测量标准环境中的性别隔离水平，并测试被认为是孤立地推动性别隔离的因素。

In many animals males and females may live apart for some or most of their lives termed sexual segregation. Sex segregation may occur when the sexes use different parts of their environment. Ancient Greek mythology tells of a nation of female warriors known as the Amazons who lived on an island. The Amazons only met with men to trade and reproduce and kept all daughters on the island. Whilst the degree of truth in this ancient myth is open to debate, in animals sex differences in habitat use are common and understanding why and how this behaviour occurs is essential if we are going to conserve and protect species and habitats. For example, if sex segregation occurs it may be necessary to protect different habitats for males and females. However, we have to understand why and how this behaviour occurs to be able to do this. For some time scientists have tried to understand why the sexes segregate in habitat use. In the 1900's Charles Darwin pondered over why red deer live apart for much of the year. In recent years many explanations have been proposed, of which three are probably important. The first idea hinges on the fact that in many species males and females are attacked at different rates by predators. Males may be larger and be equipped with weapons such as the antlers, which may allow them to use habitats with increased predation risk. The second idea suggests that males and females may differ in their nutritional requirements, for example due to pregnancy, which may lead to the sexes selecting different habitats to meet these nutritional needs. Finally, harassment of females by males is common in the animal kingdom and frequently causes injury to females or their offspring. The final idea suggests that females occupy habitats with no males to reduce this harassment. Previous work on sex segregation has generally focused on hoofed animals such as deer and sheep, but because of their large size and the amount of space they need to roam, scientists have generally been able to do little more than describe patterns of segregation. In contrast the proposed study will experimentally test these hypotheses using a small species of freshwater fish 'guppies' on the island of Trinidad in the Carribean as a model system. Guppies form relatively small populations in different streams that vary in the number of predators they face. Furthermore, guppies can easily be kept in the laboratory, making them particularly suitable for this investigation. We know that guppies living under high predation risk segregate by sex, with male guppies (which are more vulnerable to predation) occupying areas of shallow water, which are thought to be safer from predators, suggesting that predation risk is important in driving sexual segregation. However, the benefits that they gain from segregation remain unknown. For example, why do females accept a greater risk of predation? Is it to reduce sexual harassment or because there is less competition for food? Or is it a combination of the two? We also do not know how patterns of sex segregation arise, or why some males and females live in the same parts of the river. Does it dependent on environmental conditions? How is it affected by differences in the number of males and females and the density of the population? I will compare the degree of sex segregation between 10 populations of wild guppies living under different risks of predation in the rivers of Trinidad. In each river I will assess the levels of sex segregation and compare it to the risk of predation, population structure and habitat type (e.g. water depth) testing predictions from the main ideas thought to drive sex segregation. In addition to observing patterns of behaviour in the wild this study will observe the behaviour of guppies in the laboratory where it is possible to measure the level of sex segregation in a standard environment and test the factors thought to drive sex segregation in isolation.