Land use drivers of species re‐expansion: inferring colonization dynamics in Eurasian otters

Abstract

Aim Land use intensity has been recognized as one of the major determinants of native species declines. The re‐expansion of species previously constrained by habitat degradation has been rarely investigated. Here, we use site occupancy models incorporating imperfect detection to identify the land use drivers of the re‐expansion of the Eurasian otter (Lutra lutra). Location Czech Republic. Methods We applied multi‐season occupancy models to otter presence–non‐detection data collected in three national surveys (1992, 2000, 2006) at 552 sites (11.2 × 12 km grid cells). Model parameters included site occupancy, colonization and extinction probabilities, and detection probability at a sub‐site level. We modelled changes in occupancy over time as a function of agricultural, urban and industrial land use and change in the extent of agricultural land use. Results Under the best fitting model, occupancy was estimated to be 34.6% in 1992, 51.3% in 2000 and 83.7% in 2006. Detection probability was neither perfect nor constant. Occupancy probability in 1992 was negatively related to land use gradients. Colonization was more likely to occur where a reduction in agricultural land was larger. Variation in extinction and colonization rates along land use gradients resulted in increased occupancy in industrial and especially urban landscapes. Conversely, occupancy remained almost unchanged along agricultural gradients. Main conclusions Dynamics of otter expansion were strongly associated with the two main patterns of the rapid environmental transition that has taken place in the Czech Republic since the early 1990s. Results show that a reduction in intensive agricultural land use led to an increase in otter distribution, providing evidence of the impact of agricultural land use on stream ecosystems. Moreover, otters recolonized urban and industrial landscapes, probably as a result of extensive reduction in water pollution from point sources. Our results suggest that active conservation of otter populations should focus on restoration of freshwater habitat at large scales, especially in agricultural landscapes.

Home Ranges and Habitat Selection by Black Bears in a Newly Colonized Population in Florida

“…15,No. 2 Therefore, understanding how species use space and habitat as they naturally expand their range can help prioritize land-management practices and aid in corridor design for species of conservation concern (Beier et al 2008, Bocedi et al 2014, Marcelli et al 2012, help identify suitable habitat for future population expansions (Mladenoff et al 1999), and possibly help reduce human-wildlife conflicts (Wilton et al 2014). Few studies have examined space-and resource-use patterns of recently established populations of native carnivores.…”

Mapping and explaining wolf recolonization in France using dynamic occupancy models and opportunistic data

“…To deal with this second issue, occupancy models have been extended (Mackenzie et al , Royle and Kéry ) to account for the influence of dynamic processes such as colonization and extinction on the species range dynamics (Mackenzie et al ). So‐called multi‐season or dynamic site‐occupancy models are increasingly used to assess the range dynamics of expanding or invasive species (Bled et al , Broms et al ), but remain rarely applied to carnivores (Marcelli and Fusillo , Miller et al ).…”

There and back again? Combining habitat suitability modelling and connectivity analyses to assess a potential return of the otter to Switzerland

“…Investigating the possibility of a natural recolonization from neighbouring populations is crucial to prioritize conservation strategies and to establish where to act. In contrast, the species seems to have high dispersal capabilities, as suggested by its fast recovery in many European countries, including Germany, Austria, Italy, France, UK and Spain (Clavero et al, 2010;Marcelli & Fusillo, 2009;Loy et al, 2010;Marcelli et al, 2012), following its overall decline in the 1990s. This is particularly true for the Eurasian otter.…”

“…In fact, otter reintroduction projects did face such a series of problems and extra costs (Weber, 1990;Ralls, 2002). In contrast, the species seems to have high dispersal capabilities, as suggested by its fast recovery in many European countries, including Germany, Austria, Italy, France, UK and Spain (Clavero et al, 2010;Marcelli & Fusillo, 2009;Loy et al, 2010;Marcelli et al, 2012), following its overall decline in the 1990s. In our example, considering that the species is at present close to the Swiss border on the French side and is moving closer on the Austrian side, the investigation of the otter re-expansion dynamics in Austria and France would be a crucial step.…”