豹纹陆龟在半干旱环境中对环境和气候变量的反应行为。
Movement of leopard tortoises in response to environmental and climatic variables in a semi-arid environment.
作者信息
Drabik-Hamshare Martyn, Downs Colleen T
机构信息
School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg, KwaZulu-Natal 3209 South Africa.
出版信息
Mov Ecol. 2017 Mar 20;5:5. doi: 10.1186/s40462-017-0096-y. eCollection 2017.
BACKGROUND
Tortoises (Testudinidae) occur in a wide range of environments, providing important ecosystem functions, such as seed dispersal and refuge in the form of burrows. Tortoise movement has previously been shown to be related to resource availability, reproductive status and local environmental conditions. However, understanding of the variables that drive their movement remains comparatively low. We investigated aspects of movement in leopard tortoises -the largest and most abundant tortoise species in sub-Saharan Africa-in response to environmental, climatic and individual variables in the semi-arid Karoo, South Africa. We used GPS telemetry to calculate bihourly and daily movement and used generalized linear mixed models (GLMMs) to ascertain important predictor variables.
RESULTS
Temperature, distance from water sources, and month were important variables for predicting both bihourly and daily movement. Our results showed that movement increased when individuals were close to known water sources, indicating that individuals close to water resources make regular long distance movements. Movement showed a positive relationship for temperature in both models, whilst rainfall was an important predictor for bihourly movement. Our results displayed aspects of seasonality, with movement highest in spring months, likely related to reproductive activities, although no sex differences were observed.
CONCLUSIONS
We identified temporal and spatial conditions in which leopard tortoise movement increased. Our results further support the relationship between water as a resource and movement in leopard tortoises. Individuals used one of two basic movement behaviours in relation to water in this water scarce environment. Either an individual's home range and movements included permanent water resources allowing internal water storage replenishment, or excluded these with reliance on food resources (such as grasses, forbs, and succulents) for water.
背景
陆龟（陆龟科）生活在广泛的环境中，发挥着重要的生态系统功能，例如种子传播以及以洞穴形式提供避难所。此前已表明陆龟的移动与资源可用性、繁殖状态和当地环境条件有关。然而，对驱动其移动的变量的了解仍然相对较少。我们调查了南非半干旱卡鲁地区豹纹陆龟（撒哈拉以南非洲最大且数量最多的陆龟物种）的移动情况，以回应环境、气候和个体变量。我们使用GPS遥测技术计算每两小时和每日的移动情况，并使用广义线性混合模型（GLMMs）来确定重要的预测变量。
结果
温度、与水源的距离和月份是预测每两小时和每日移动的重要变量。我们的结果表明，当个体靠近已知水源时移动会增加，这表明靠近水资源的个体进行定期的长距离移动。在两个模型中，移动与温度呈正相关，而降雨是每两小时移动的重要预测因素。我们的结果显示出季节性特征，春季移动最高，这可能与繁殖活动有关，尽管未观察到性别差异。
结论
我们确定了豹纹陆龟移动增加的时间和空间条件。我们的结果进一步支持了水资源与豹纹陆龟移动之间的关系。在这个水资源稀缺的环境中，个体在与水相关的方面使用两种基本移动行为之一。要么个体的活动范围和移动包括永久性水资源，以便补充体内水分储存，要么不包括这些，而是依赖食物资源（如草、草本植物和多肉植物）获取水分。
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