风险对两种南非蜥蜴逃跑启始距离和逃避策略的影响

逃避理论预测,不逃跑若增大适合度代价则导致逃跑启始距离加长,逃跑若增大代价则导致逃跑启始距离缩短。逃跑路径和去向等受生境结构影响。作者通过模拟捕食者逼近研究喀拉哈里树石龙子(Trachylepis sparsa)和黑环蜥(Cordylus niger)逃避策略和风险因子对逃跑启始距离的影响。与迂回逼近相比较,直接逼近不仅提高蜥蜴逃跑几率还能缩短其逃跑启始距离。喀拉哈里树石龙子在两种逼近方式下的逃跑启始距离有显著差异,这种差异对黑环蜥而言是边缘性的。喀拉哈里树石龙子以树为避所,树上个体可逼近的距离短于地面个体;快速逼近地面个体的逃跑启始距离比慢速逼近更长。习惯于有人环境的黑环蜥逃跑启始距离比人迹罕至环境中的个体更短。地面喀拉哈里树石龙子多遁至树上而很少逃入倒木或倒伏编巢中。树上喀拉哈里树石龙子通常奔逃至远侧和高处,有时遁入树洞或编巢中;黑环蜥则逃入石缝中。所有发现都证实逃避理论中有关逃跑启始距离的预测。逃跑策略的种间差异表明每一种蜥蜴都利用其生境中逃跑路径和避所的有利条件。在风险不同的生境中,生境结构可影响逃跑启始距离,似乎对逃跑策略亦有重要影响。

Effects of risk on flight initiation distance and escape tactics in two southern African lizard species

Escape theory predicts that flight initiation distance increases with fitness costs of not fleeing and decreases with cost of escaping. Habitat structure may affect aspects of escape such as routes and destinations. We studied escape tactics and effects of risk factors on flight initiation distance in Kalahari tree skinks Trachylepis sparsa and black girdled lizards Cordylus niger by simulating approaching predators. Probability of fleeing and flight initiation distance were greater when lizards were approached directly versus on paths bypassing them. The difference in flight initiation distance was significant in T.sparsa and marginal in C.niger. Trachylepis sparsa on trees used as refuges permitted closer approach than those on the ground. Those on ground had longer flight initiation distances when approached rapidly than slowly. Flight initiation distance in C.niger was shorter where they were habituated to human presence than where people were present infrequently. When on ground, T.sparsa escaped to trees and less frequently to logs or fallen weaver nests. When on trees, they usually escaped by running to the far side and up, and sometimes entered tree holes or weaver nests.C.niger escaped by entering rock crevices. All findings verify predictions of escape theory about flight initiation distance. Differences in escape tactics suggest that each species took advantage of routes and refuges available in its habitat. Habitat structure may affect flight initiation distance when habitats differ in risk, and seems to strongly affect escape tactics.