Expansion of the Asiatic red - bellied tree squirrel in the Pampas

ALMADA CHAVEZ, S; BENITEZ, V; MESSETTA, ML; GUICHÓN, ML

Mendoza, Argentina

Congreso; International Mammalogical Congress; 2009

Biodiversity Research Group (GIB), Institute for Aridlands Research (IADIZA), Center for Science & Technology Mendoza (CCT), National Council of Science and Technology (CONICET), International Federation of Mammalogists(IFM) and SAREM

Habitat features influencing the spread of exotic species provide relevant information to predict and control invasion. We aim to analyse the spread rate and landscape correlates of the main population of the red-bellied squirrel Callosciurus erythraeus that was introduced in Luján (Buenos Aires, Argentina) in 1970. Between June 2008 and February 2009 we interviewed residents in the range periphery, and expanding outwards, of squirrel?s known distribution by 2004 to evaluate: (1) area of distribution, (2) spread rate, (3) correlation with forested patches and (4) opinion regarding the presence of this arboreal squirrel. Presence/absence of squirrels was entered to a GIS database and the invaded area was calculated using the minimum convex polygon method. Squirrels have almost doubled the occupied area in 5 years, now invading 1336 km2. The rate of spread since liberation is 0.62 km/year, which exceeds the spread rate estimated until 2004 of 0.53 km/year. Distribution area is asymmetric, mainly elongated along the Luján river; therefore, we calculated spread rate in NE-SW (along the river, 0.67±0.01 km/year) and NW-SE (0.52±0.04 km/year) directions. Low density of forested, fragmented patches correlated with spread rate along the river (NE-SW: 0.07±0.00 forested patches/km2, NW-SE: 0.04±0.00 forested patches/km2, r=0.96, p