Invasion status of Asiatic red-bellied squirrels in Argentina

Abstract

The only known introduction of a squirrel species into South America is the case of the Asiatic red-bellied tree squirrel Callosciurus erythraeus that was introduced in the Pampas Region of Argentina in 1970. To inform management programmes, we analysed the current distribution, expansion rate, and abundance of the red-bellied squirrel in Argentina, and identified invasion pathways. Apart from the first and main focus of invasion, three other invasion foci have originated as a consequence of intentional releases between 1995 and 2000. The main invasion focus already extends over >1300 km 2 , where estimated density averaged 15 ind ha −1 and numbers of squirrels may reach 100,000 individuals. The area invaded in the other three invasion foci varied between <1 and 34 km 2 and mean densities were around 3-5 ind ha −1 . Squirrel abundance and residents' attitude towards this introduced species in the main invasion focus make eradication unfeasible, though management actions such as control, containment and mitigation of damages should be undertaken. Eradication of the relatively small invasion foci must be immediately evaluated, with priority given to valuable conservation areas under high invasion risk.

From a lag in vector activity to a constant increase of translocations: invasion of Callosciurus squirrels in Argentina

“…At present we cannot distinguish the invaded area that initiated at Arrecifes release site from the invaded area initiated at Capitán Sarmiento, therefore, we treat them as a single invasion focus resultant from two independent releases Date of release Cumulative number of releases Fig. 2 Cumulative number of successful (black dots) and failed (grey dots) release events of red-bellied squirrels recorded in Argentina per year, taking into account the four invasion foci previously described Lag in vector activity: Callosciurus translocations The spread rate described in these new invasion foci is comparable to the expansion rate observed throughout the first 30 years in the main invasion focus in Luján (0.53 km/year) that increased to 1.66 km/year between 20041.66 km/year between and 20091.66 km/year between (Guichón et al 2005Benitez et al 2013). The total invaded area in Argentina now exceeds 2100 km 2 though densities are quite variable.…”

“…3), but opposition to control actions is stronger in tourist and urban areas such as La Cumbrecita and Escobar (Fig. 3), even if the latter site has high conservation priority (Guichón and Doncaster 2008;Benitez et al 2013;Borgnia et al 2013). Prevention of new releases, which are illegal, should be a first national action that must prioritise areas of high conservation value and where native squirrels Sciurus aestuans and S. ignitus are present (Cassini and Guichón 2009;Borgnia et al 2013).…”

“…In each site, we conducted field surveys and interviews with residents to confirm the presence of red-bellied squirrels, describe their history of introduction, and estimate their abundance and range expansion, as previously done in similar sites (Guichón et al 2005;Benitez et al 2013). Red-bellied squirrels are diurnal and no native squirrels inhabit the study region.…”

“…We estimated relative abundance of squirrels using time-area counts based on previous squirrel studies (Bayne and Hobson 2000;Parker and Nilon 2008;Benitez et al 2013). Our aim was not to estimate absolute population size but to compare relative abundances reached since squirrel release in each site.…”

Genetic characterization ofCallosciurus(Rodentia: Sciuridae) Asiatic squirrels introduced in Argentina

“…Other populations of C. erythraeus have been introduced in three Argentinian provinces due to its charismatic appearance . Interviews with local residents indicated that squirrels were subsequently translocated from the invasion focus in Luján to other locations within Argentina, where they were established as a consequence of intentional releases (Guichón et al 2005;Benitez et al 2013).…”