Natural history and ecology of the slender crayfish (<i>Faxonius compressus</i>): an ecosystem engineer in the Western Highland Rim, USA

Ecosystem engineers influence the physical environment, which changes the distribution and availability of resources to other organisms. Based on their burrowing abilities, freshwater crayfish have been widely recognised as ecosystem engineers. Crayfishes construct burrows that range from simple, rudimentary depressions in aquatic systems, to complex, labyrinth-like terrestrial burrows that may be significant distances from permanent water bodies. Here, we investigate ecosystem engineering and burrowing of the slender crayfish, <i>Faxonius compressus</i>, which lives in lotic environments characterised by an abundance of small cobble- and gravel-sized substrates. Without larger substrates to burrow under, we found <i>F. compressus</i> populations construct extremely high densities of burrows across riffle, run and pool macrohabitats. Based on the average number of burrows, a 5 × 100 m pool is estimated to contain an average of 25,860 burrows. We also conducted behavioural observations of this species to glean information on their natural history. <i>Faxonius compressus</i> regularly inhabits and competes for ownership of burrows which serve as a shelter from predators. Importantly, these burrows are not only used by <i>F. compressus</i>; we documented other crayfishes and fish species utilising these burrows. In total, we documented two other crayfishes and six fish species utilising <i>F. compressus</i> burrows. We discuss the ecosystem engineering abilities of this species in relation to other crayfish and suggest future avenues of research to elucidate this species’ natural and life history.