On the relationship between herbaceous cover and vigilance activity of degus (Octodon degus)
On the relationship between herbaceous cover and vigilance activity of degus (Octodon degus)
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DOI：
10.1111/j.1439-0310.2005.01084.x
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发表时间：
2005-06-01
期刊：
影响因子：
1.7
通讯作者：
Hurtado, MJ
中科院分区：
文献类型：
--
作者：
Ebensperger, LA;Hurtado, MJ
许多研究表明，植被为被捕食动物提供了避难所，以减少对捕食者的脆弱性。然而，其他人建议植物覆盖物在视觉上阻碍捕食者或同种的检测。我们认为，这些看似矛盾的结果可以在一定程度上得到解决，如果开销与横向覆盖区分。我们记录的自然种群的degus（degus），一个昼夜，半地下和社会啮齿动物从智利中部的警惕活动的季节性变化。我们用这些数据来确定草本植被提供的覆盖是否主要是阻碍。草质植被的高度随季节而变化，草质植被高时，草质植被对潜在捕食者的探测能力（由人类观察者估计）下降。这种效应对于使用四足动物姿势和处理陆地模拟捕食者的迪格斯来说更为重要。相应地，迪格斯调整了它们警戒活动的质量而不是数量：当草本植物的高度较高时，雄性和雌性迪格斯分配了同样多的时间用于双足警戒。这种两足动物警觉性的增加似乎是以牺牲四足动物的警觉性而不是觅食时间为代价的。总的来说，这些结果支持了这一假设，即草本植被覆盖主要是阻碍了迪格斯活跃在地面上时，一个发现，与以前的证据支持灌木覆盖提供避难所对捕食者。灌木和草本植物对德古警戒的不同影响可能与每种覆盖类型的成本和收益差异有关。对于迪格斯，灌木可以提供更多的头顶（保护）比侧面（阻碍）覆盖。
A number of studies demonstrate that plant cover provides prey animals with refuges to decrease vulnerability to predators. However, others suggest plant cover to visually obstruct detection of predators or conspecifics. We suggest these seemingly conflicting results can, to some extent, be resolved if overhead vs. lateral cover are distinguished. We recorded seasonal variation in vigilance activity of a natural population of degus (Octodon degus), a diurnal, semi-subterranean and social rodent from central Chile. We used these data to determine whether cover provided by herbaceous vegetation is mostly obstructive. The height of herbaceous vegetation in the habitat of degus varied seasonally, and the ability of degus (estimated from human observers) to detect potential predators decreased when herbaceous vegetation was high. This effect was more important for degus using quadruped postures and when dealing with terrestrial simulated predators. Accordingly, degus adjusted the quality rather than the quantity of their vigilance activity: male and female degus allocated similarly more time to bipedal vigilance when the height of herbs was high. Such increase in bipedal vigilance seemed to occur at the expense of quadruped vigilance instead of foraging time. Collectively, these results support the hypothesis that cover of herbaceous vegetation is mostly obstructive to degus when active above ground, a finding that contrasts with previous evidence supporting that shrub cover provides refuges against predators. The differential effects of shrubs and herbs on degu vigilance are likely linked to differences in the costs and benefits associated with each cover type. For degus, shrubs may provide more overhead (protective) than lateral (obstructive) cover.