Area-Wide Prediction of Vertebrate and Invertebrate Hole Density and Depth across a Climate Gradient in Chile Based on UAV and Machine Learning

Burrowing animals are important ecosystem engineers affecting soil properties, as their burrowing activity leads to the redistribution of nutrients and soil carbon sequestration. The magnitude of these effects depends on the spatial density and depth of such burrows, but a method to derive this type of spatially explicit data is still lacking. In this study, we test the potential of using consumer-oriented UAV RGB imagery to determine the density and depth of holes created by burrowing animals at four study sites along a climate gradient in Chile, by combining UAV data with empirical field plot observations and machine learning techniques. To enhance the limited spectral information in RGB imagery, we derived spatial layers representing vegetation type and height and used landscape textures and diversity to predict hole parameters. Across-site models for hole density generally performed better than those for depth, where the best-performing model was for the invertebrate hole density (R2 = 0.62). The best models at individual study sites were obtained for hole density in the arid climate zone (R2 = 0.75 and 0.68 for invertebrates and vertebrates, respectively). Hole depth models only showed good to fair performance. Regarding predictor importance, the models heavily relied on vegetation height, texture metrics, and diversity indices.

Burrowing and Anti-Predator Requirements Determine the Microhabitat Selection of Himalayan Marmot in Zoige Wetland

To satisfy their requirements for food and safety, animals need certain habitats to live. Marmots generally select habitats with certain elevation, land surface temperature, soil and vegetation type, and certain mountain slope and aspect; however, what habitats are needed at relatively smaller scales are poorly known. The Himalayan marmot (Marmota himalayana) is distributed mainly on the Qinghai-Tibet Plateau, a region exhibiting diversified topographic features, and the Zoige wetland in the northeast part of the plateau is also the home of the Himalayan marmot. The region is famous for its plateau peat bog, and the suitable habitats for Himalayan marmots are patchily distributed in the wetland. To investigate what kinds of patches are preferred by the marmot in this wetland ecosystem, we measured and compared the soil and vegetation characteristics of used and unused patches. We found that unlike factors governing the habitat selection at macroscales, patches characterized by flat ground and low soil moisture content, with medium vegetation standing height and low vegetation density, are selected in the Zoige wetland. Patches of this kind are selected to meet the marmots' requirements for burrow construction and predator avoidance in such a wetland ecosystem. Together with previous studies on habitat selection of the marmot species at macroscales, we showed that to explore how the animals survive in an environment, it is important to conduct the analysis at multiple scales.

Spatiotemporal habitat use by a multitrophic Alaska alpine mammal community

Evaluating sympatric habitat use of a mammal community can help determine intra- and inter-guild interactions and identify important habitats, potentially improving the management of these communities with a changing climate. Increasingly variable climatic patterns in Alaska, USA, are raising concerns of mismatched phenologies and altered ecosystem structures. We studied the occupancy of 10 mammal species over 15 months, via camera traps, occupying alpine areas of the Alaska Range in interior Alaska, from 2013 to 2014. We tested hypotheses about how habitat use of these species within and between groups varied by spatial and temporal covariates. Furthermore, we modeled two-species occupancy of brown bears (Ursus arctos Linnaeus, 1758) and gray wolves (Canis lupus Linnaeus, 1758) against different potential prey species. Our results suggest that medium-sized and large herbivore use was positively correlated with fine-scale covariates including rock, forb, and graminoid coverage. Large herbivore habitat use was also correlated with abiotic landscape covariates. Detection probabilities of predators and Dall’s sheep (Ovis dalli dalli Nelson, 1884) was improved by camera traps on wildlife trails. Two-species models suggested co-occurrence of habitat use between brown bear – caribou (Rangifer tarandus (Linnaeus, 1758)) and gray wolf – caribou. Results demonstrate the sympatric habitat use by multiple groups of mammals within Alaskan alpine ecosystems and the importance of incorporating multiple groups and spatial scales when making management decisions.