Tamara Volkmer, Krisztina Kupán, Veronika A. Rohr-Bender, Miguel Guirao-Ortiz, Medardo Cruz-López, Salvador Gómez del Angel, Lourenço Falcão Rodrigues, Luke Eberhart-Hertel, Clemens Küpper
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引用次数: 0
Abstract
Camouflage represents an important component of self-protection when animals cannot easily evade predators and is often altered by behavioural responses to a predation threat. The cryptic plumage of many precocial chicks inspired early theoretical work on camouflage mechanisms, but so far, limited efforts have gone towards empirically testing the crypsis of chick plumage properties in their natural environment. We studied background matching and hiding behaviour in precocial snowy plovers Charadrius nivosus in Bahia de Ceuta, Northwest Mexico. This ground-nesting wader breeds in sparsely vegetated open habitats such as salt flats and sandy beaches. The open habitats provide a challenge for young chicks to evade predator detection. Examining background matching of wild chicks for luminance, pattern and colouration at their hiding spots, we found that chicks matched the luminance of their chosen spot better than at unchosen nearby spots. Pattern and colouration matching were age-related, with the plumage of older chicks matching their hiding spots better than those of recently hatched chicks. This suggests that with increasing mobility, chicks may be better able to find hiding places that optimise camouflage. Finally, we found that chicks were more likely to hide in soil cracks than expected by chance, suggesting that chicks chose these soil features in a barren landscape as preferred hideouts. We conclude that the cryptic plumage is an understudied but essential part of the anti-predator repertoire of precocial chicks. The plumage most likely works hand-in-hand with the anti-predator behaviours of chicks and their parents to increase survival chances of precocial young.
Significance statement
Many chicks rely on effective camouflage to evade predators and survive until fledging. We studied how plumage characteristics and behavioural choices enable snowy plover chicks to hide effectively from approaching predators in an open landscape. These chicks leave their nest scrapes shortly after hatching, relying on their cryptic plumage for several weeks to evade predator detection. We found that chicks chose hiding spots where their plumage had a higher match in luminance and, for older chicks, a higher match in pattern and colouration than at adjacent spots. When available, chicks chose to hide in small cracks that appeared in the soil from the evaporation of moisture. This study represents the first quantitative characterisation of cryptic chick plumage features in a natural population. Our results demonstrate that plumage and behavioural responses jointly contribute to the effective camouflage of small chicks.
摘要 当动物无法轻易躲避捕食者时，伪装是自我保护的重要组成部分，而且往往会因捕食威胁的行为反应而改变。许多初生雏鸟的隐蔽羽色激发了早期伪装机制的理论研究，但迄今为止，对雏鸟羽色特性在自然环境中的隐蔽性进行实证检验的努力还很有限。我们研究了墨西哥西北部Bahia de Ceuta地区早熟雪鸻的背景匹配和躲藏行为。这种在地面筑巢的鸻在植被稀疏的开阔栖息地（如盐滩和沙滩）繁殖。开放的栖息地为幼雏躲避捕食者的发现提供了挑战。通过研究野生雏鸟藏身地点的亮度、图案和颜色的背景匹配情况，我们发现雏鸟对所选地点亮度的匹配程度要高于对附近未选地点的匹配程度。图案和颜色的匹配与年龄有关，年龄较大的雏鸟的羽毛比刚出壳的雏鸟的羽毛更匹配它们的藏身点。这表明，随着活动能力的增强，雏鸟可能更有能力找到最适合伪装的藏身之处。最后，我们发现雏鸟更有可能藏身于土壤裂缝中，这表明雏鸟选择贫瘠地貌中的这些土壤特性作为首选藏身之处。我们的结论是，隐性羽色是社会前雏鸟反捕食者的一个未被充分研究的重要组成部分。这种羽色很可能与雏鸟及其父母的反捕食行为共同作用，以增加社会前幼鸟的存活机会。 意义声明许多雏鸟依靠有效的伪装来躲避捕食者，并存活到羽化。我们研究了羽色特征和行为选择如何使雪鸻雏鸟在开阔地上有效地躲避接近的捕食者。这些雏鸟在孵化后不久就离开了巢穴，在数周内依靠其隐蔽的羽色躲避捕食者的发现。我们发现，雏鸟会选择羽色亮度匹配度较高的地方躲藏，对于年龄较大的雏鸟来说，则会选择羽色图案匹配度较高的地方躲藏。在有条件的情况下，雏鸟会选择躲藏在土壤中因水分蒸发而出现的小裂缝中。这项研究首次对自然种群中的隐性雏鸟羽色特征进行了定量描述。我们的研究结果表明，羽色和行为反应共同促成了小雏鸟的有效伪装。
期刊介绍：
The journal publishes reviews, original contributions and commentaries dealing with quantitative empirical and theoretical studies in the analysis of animal behavior at the level of the individual, group, population, community, and species.
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