Understanding species’ habitat use is fundamental for conservation and management. However, quantifying habitat use for small cryptic species is limited by imperfect detection during field surveys and the lack of habitat data at meaningful spatial scales. Topographically-derived habitat variables from digital elevation models (DEMs) have the potential to overcome these limitations. Here we used DEM-derived topographic variables as fine-scale proxies for abiotic conditions to study site-occupancy patterns of the berg adder (Bitis atropos), a small-bodied cryptic viper. We carried out seven repeated field surveys across 219 hectares in a mountainous protected area in north-eastern South Africa to estimate snake detection probability and occupancy using maximum likelihood methods. Although snakes occurred across a third of the surveyed habitat, they were only detected 40% of the time during the springtime when detection was highest. Results showed that these snakes preferred north-west facing, mid and upper slopes, which are exposed to afternoon sun and presumably higher ambient energy. Our results demonstrate the value of using DEM-derived topographic variables for ecological studies where habitat data are either unavailable or inappropriate, thereby providing valuable insights into habitat use of cryptic and difficult to detect species.

中文翻译：

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地形衍生的变量提供了对神秘蛇 Bitis atropos 栖息地占有情况的洞察

了解物种的栖息地利用是保护和管理的基础。然而，量化小型隐匿物种的栖息地使用受到实地调查期间检测不完善以及缺乏有意义的空间尺度的栖息地数据的限制。来自数字高程模型 (DEM) 的地形衍生栖息地变量有可能克服这些限制。在这里，我们使用 DEM 衍生的地形变量作为非生物条件的精细代理来研究 berg adder ( Bitis atropos)，一种体型较小的神秘毒蛇。我们在南非东北部山区保护区的 219 公顷土地上进行了七次重复实地调查，以使用最大似然方法估计蛇发现概率和占用率。尽管蛇出现在被调查的三分之一的栖息地，但在检测率最高的春季只有 40% 的时间被发现。结果表明，这些蛇更喜欢朝西北、中坡和上坡，这些地方暴露在午后的阳光下，并且可能有更高的环境能量。我们的结果证明了在栖息地数据不可用或不合适的生态研究中使用 DEM 派生的地形变量的价值，从而为栖息地使用的神秘和难以检测的物种提供有价值的见解。