Comment on bg-2021-75
2021-06-07

<strong class="journal-contentHeaderColor">Abstract.</strong> Although the burrowing activity of some species (e.g., gophers) is well studied, a comprehensive inventory of burrowing animals in adjacent biomes is not yet known, despite the potential importance of burrowing activity on the physical and chemical evolution of Earth's surface. In this study, we review the available information with a focus on the following: (a) an inventory of burrowing vertebrates and invertebrates along the climate and ecological gradient in Chile; (b) the dimensions and characteristics of burrows; and (c) calculation of excavation rates by local species compositions. Methods used include a literature compilation (<span class="inline-formula"><i>&gt;</i></span> 1000 studies) of Chilean burrowing animal species integrated with global, species-specific excavation rates. A field study augments literature findings with quantification of the zoogeomorphic effects on hillslope mass transport at the animal community level and along the arid to humid–temperate climate gradient within the Chilean Coastal Cordillera (27–38<span class="inline-formula"><sup>∘</sup></span> S latitude). The literature review indicates a minimum of 45 vertebrate and 345 invertebrate burrowing species distributed across Chile in different biomes. Burrowing depths for Chilean mammals range between 3 m (e.g., for skunks, <i>Conepatus</i>) and 0.25 m (for rock rats, <i>Aconaemys</i>). For invertebrates, burrowing depths in Chile range between 1 m for scorpions to 0.3 m for spiders. In comparison, globally documented maximum burrow depths reach up to more than 6 m for vertebrates (gopher tortoises and aardvarks) and 4 m for invertebrates (ants). Minimum excavation rates of local animal communities observed from field sites in Chile are 0.34 m<span class="inline-formula"><sup>3</sup></span> ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> for the arid site, 0.56 m<span class="inline-formula"><sup>3</sup></span> ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> for the semiarid site, 0.93 m<span class="inline-formula"><sup>3</sup></span> ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> for the mediterranean site and 0.09 m<span class="inline-formula"><sup>3</sup></span> ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> for the humid–temperate site, with the latter likely an underestimation. The calculated minimum Chilean excavation rates are within the large range of globally observed single species rates ranging between 0.01 and 56.20 m<span class="inline-formula"><sup>3</sup></span> ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> for vertebrates and from 0.01 to 37.31 m<span class="inline-formula"><sup>3</sup></span> ha<span class="inline-formula"><sup>−1</sup></span> yr<span class="inline-formula"><sup>−1</sup></span> for invertebrates. Taken together, results not only highlight the diverse and latitudinally varying number of burrowing vertebrates and invertebrates present in different biomes, but also foster the understanding of how burrowing activity changes over a gradient and is influenced by mean annual temperature, mean annual precipitation, slope aspect and latitudinal-related incoming solar energy.