Predator persistence in fragmented forests: lynx and snowshoe hares

濒危物种面临的主要威胁之一是栖息地的丧失。在森林中，这种损失往往留下原始森林的残余林分，周围是年龄或物种组成不同的其他林分。对于森林哺乳动物，这些不同林分类型的复杂嵌合强烈影响种群动态；对于一些物种，种群数量随着栖息地破碎化的发生而下降。通常，森林中的捕食者和猎物会在不同的空间尺度上对破碎化做出反应，猎物停留在特定的林分中，而捕食者在林分之间移动。随着栖息地的丧失，猎物可以利用的林分变得更小或更远，捕食者可能无法获得足够的猎物来生存，因为带着猎物在林分之间旅行的成本太高了。我对森林哺乳动物对森林破碎化的反应很感兴趣，我的主要研究目标是解释当景观变得越来越破碎时，捕食者-猎物的相互作用是如何改变的。不同林分类型的猎物种群动态将在很大程度上决定它们的捕食者能否在破碎的景观中生存。在一种极端情况下，猎物可能只使用几个相距很远的树桩；在另一个极端，它们可能发生在大多数林分。作为一个模型系统，我关注的是蒙大拿州西部的雪鞋兔（Lepus americanus）和加拿大猞猁（lynx canadensis）。我正在描述不同林分类型野兔的密度、存活率和繁殖情况。然后，我将探索猞猁在狩猎时使用的林分类型，它们每次狩猎的距离，以及在这个地区，它们的饮食中野兔所占的比例。我正在将这些结果统一到空间模型中，这样我就可以模拟改变不同类型栖息地的数量对这些物种的影响。这个研究项目将促进我们对捕食者和猎物如何对森林破碎化做出反应的总体理解，以及预测剩余森林林分的配置，这可能有助于在景观中保留物种。

One of the major threats to imperiled species is the loss of habitat. In forests, this loss often leaves remnant stands of the original forest surrounded by other stands that differ in age or species composition. For forest mammals, these complex mosaics of different stand types strongly affect population dynamics; for some species, populations decline as habitat fragmentation occurs. Often, predators and prey in forests will respond to fragmentation at different spatial scales, with prey staying in particular forest stands and predators moving among stands. As habitat loss occurs and the stands that prey can use become smaller or farther apart, predators may not be able to obtain enough prey to survive because the cost of traveling among the stands with prey becomes too high. I am interested in how forest mammals respond to forest fragmentation, and my main research objective is to explain how predator-prey interactions are changed as a landscape becomes increasingly fragmented. The population dynamics of prey in different stand types will largely determine whether their predators can persist in a fragmented landscape. At one extreme, prey might use only a few, far apart stands; at the other extreme, they might occur in the majority of stands. As a model system, I am focusing on snowshoe hares (Lepus americanus) and Canada lynx (Lynx canadensis) in western Montana. I am characterizing density, survival, and reproduction of hares in different stand types. I am then exploring which stand types lynx use for hunting, how far they travel between kills, and what proportion of their diet consists of hares in this region. I am unifying these results in spatial models so that I can model the effects of changing the amount of different types of habitat on these species. This research program will advance our general understanding of how predators and prey respond to forest fragmentation, as well as predicting configurations of remaining forest stands that might help to retain species in the landscape.