Lingle Susan, Feldman Alex, Boyce Mark S, Wilson W Finbarr
McIntyre Ranch Coyote and Deer Project, Box 914, Magrath, Alberta T0K1J0, Canada.
Am Nat. 2008 Nov;172(5):712-25. doi: 10.1086/591675.
Variation in the temporal pattern of vulnerability can provide important insights into predator-prey relationships and the evolution of antipredator behavior. We illustrate these points with a system that has coyotes (Canis latrans) as a predator and two species of congeneric deer (Odocoileus spp.) as prey. The deer employ different antipredator tactics (aggressive defense vs. flight) that result in contrasting patterns of age-dependent vulnerability in their probability of being captured when encountered by coyotes. We use long-term survival data and a simple mathematical model to show that (1) species differences in age-dependent vulnerability are reflected in seasonal predation rates and (2) seasonal variation in prey vulnerability and predator hunt activity, which can be associated with the availability of alternative prey, interact to shape seasonal and annual predation rates for each prey species. Shifting hunt activity from summer to winter, or vice versa, alleviated annual mortality on one species and focused it on the other. Our results indicate that seasonal variation in prey vulnerability and hunt activity interact to influence the impact that a predator has on any particular type of prey. Furthermore, these results indicate that seasonal variation in predation pressure is an important selection pressure shaping prey defenses.
脆弱性时间模式的变化能够为捕食者与猎物的关系以及反捕食行为的进化提供重要见解。我们以一个系统为例来说明这些观点，在该系统中，郊狼（犬属）作为捕食者，两种同属的鹿（白尾鹿属）作为猎物。鹿采用不同的反捕食策略（攻击性防御与逃跑），这导致它们在遭遇郊狼时被捕获概率呈现出不同的年龄依赖性脆弱模式。我们利用长期生存数据和一个简单的数学模型表明：（1）年龄依赖性脆弱性的物种差异反映在季节性捕食率上；（2）猎物脆弱性和捕食者狩猎活动的季节性变化（这可能与替代猎物的可获得性有关）相互作用，塑造了每个猎物物种的季节性和年度捕食率。将狩猎活动从夏季转移到冬季，反之亦然，会减轻一个物种的年度死亡率，并将其集中在另一个物种上。我们的结果表明，猎物脆弱性和狩猎活动的季节性变化相互作用，影响捕食者对任何特定类型猎物的影响。此外，这些结果表明，捕食压力的季节性变化是塑造猎物防御的重要选择压力。
