Invasion success of the red-bellied squirrel in Argentina

BENITEZ VV; C GOZZI; S ALMADA CHÁVEZ ; ML GUICHÓN

Congreso; 2ndWorld Conference on Biological Invasions and Ecosystem Functioning; 2011

Establishment and population increase of introduced species depends on niche opportunities mainly defined by resources, natural enemies and environmental conditions found in the recipient community.  We evaluated which population parameters could explain the invasive success of the Red-Bellied Squirrel Callosciurus erythraeus in Argentina, in comparison to their reported invasion in Japan. Squirrels spread over 1336 km2 in 36 years in the main invasion focus in Luján, Argentina, while 304 km2 where invaded in 52 years in Kanagawa Prefecture, Japan. Higher densities in Luján (12-20 ind/ha) than in Kanagawa (6-7 ind/ha) could be explained by high availability of fruits and seeds, their main food item, throughout the year. Adult survival rate was 0.5 in Luján and decreased from 0.6 to <0.1 from 2 to 3 years old individuals in Kanagawa. Different combinations of ectoparasites yielded a prevalence of 3% in Luján and 34% in Kanagawa. Climate matching between native and introduced areas are similar in both cases (0.7-0.8 likelihood of establishment as a function of latitude). Squirrels seem to suffer low predation pressure in both areas, where highly fragmented urban forests are invaded. The availability of larger, continuous natural forests and plantations in Kanagawa may contain the spread of squirrels that seem to expand further in the highly fragmented rural-urban Pampean Region. In this context, repeated translocations by people keen on this charismatic species, which is now present in a region lacking native squirrels, play a key role both in the invasion front and in the creation of new invasion foci.