Range reexpansion after long stasis: Italian otters (Lutra lutra) at their northern edge

Abstract

Species range shifts and expansion are subjects of primary research interest in the context of climate warming and biological invasions. Few studies have focused on reexpansion of species that suffered severe declines. Here, we focused on population recovery of Eurasian otters ( Lutra lutra ) in Italy, first detected in 2003 after a southward range contraction. We modeled the rate of range expansion and occupancy at the northern expanding front (central Italy), to gain insights into the progress of recovery and mechanisms of reexpansion. We performed a field survey in 2021, which redefined the northern limit of distribution further north, in close proximity to the Gran Sasso National Park. Then we analyzed a time series (1985–2021) of distances of northernmost occurrences from the center of the 1985 range. Using segmented regression, we were able to identify a prolonged stasis of the northern range edge and a simultaneous increase in occupancy from 0.151 to 0.4. A breakpoint was estimated in 2006, after which the range expanded northwards at an average rate of 5.48 km/year. From 2006 to 2021, the overall northward shift was about 80 km. Occupancy continued to increase until 2019 and abruptly declined in 2021. These patterns suggest that the reexpansion of the range can be limited by low occupancy at the expanding front. As occupancy increases, long‐distance dispersal increases and then range expands. The low occupancy at the current distribution limit of otters may reflect a higher anthropogenic pressure on northern habitats, which could slow down the reexpansion process.

“Oops…a Beaver Again!” Eurasian Beaver Castor fiber Recorded by Citizen-Science in New Areas of Central and Southern Italy

“…The beaver data in the Abruzzo region (Aterno river, Areas 5 and 6 of Figure 1) were collected using camera traps (© Browning Patriot BTC-PATRIOT-FHD) during an otter Lutra lutra survey along rivers recently occupied by this species [23].…”

“…All signs of presence of the Eurasian beaver were included in a global dataset with the coordinates (latitude and longitude) recorded using GPS devices (Garmin ©) with an XY resolution of 10 m, with the number and the typology of presence signs following [22]. The beaver data in the Abruzzo region were collected using camera traps (© Browning Patriot BTC-PATRIOT-FHD) during an otter Lutra lutra survey along rivers recently occupied by this species [23].…”

Stream size‐dependent effect of urban land use on occupancy of an apex freshwater carnivore recolonizing past ranges

“…A comprehensive survey carried out in 2003 across southern regions detected a high increase in occupancy and a weak range expansion toward the southernmost areas of the peninsula (Marcelli & Fusillo, 2009a). Although range expansion slowly proceeded from both the southern and the northern range edges (Marcelli et al, 2023; Marcelli & Fusillo, 2009b), otter populations in Italy remain essentially confined to southern regions. Accordingly, the Italian IUCN red list of vertebrate species classified the Italian population as vulnerable (Rondinini et al, 2022).…”