Behavioral Ecology and Sociobiology

, Volume 51, Issue 4, pp 360–367

Interspecific competition in tree squirrels: do introduced grey squirrels (Sciurus carolinensis) deplete tree seeds hoarded by red squirrels (S. vulgaris)?

Authors

  • Luc A. Wauters
    • Department of Structural and Functional Biology, University of Insubria Varese, Via Dunant, 21100 Varese, Italy
  • Guido Tosi
    • Department of Structural and Functional Biology, University of Insubria Varese, Via Dunant, 21100 Varese, Italy
  • John Gurnell
    • Department of Structural and Functional Biology, University of Insubria Varese, Via Dunant, 21100 Varese, Italy
Original Article

DOI: 10.1007/s00265-001-0446-y

Cite this article as:
Wauters, L.A., Tosi, G. & Gurnell, J. Behav Ecol Sociobiol (2002) 51: 360. doi:10.1007/s00265-001-0446-y

Abstract.

Red squirrels (Sciurus vulgaris) and introduced eastern grey squirrels (S. carolinensis) scatterhoard seeds of broadleaf trees. Scatterhoarded seeds are an essential resource in spring and their consumption increases red-squirrel fitness. We examined whether grey squirrels partly deplete the high-energy food resources cached by red squirrels, reducing their consumption, in two ways: (1) at the population level, comparing energy intake of feeding on cached seeds between a study site with red and grey squirrels and one with only red squirrels present; and (2) at the individual level, in the study site where species co-exist, relating hoard recovery of red squirrels to the amount of core-area overlap with grey squirrels. There were no significant site differences in the mean daily energy intake of red squirrels feeding on seeds recovered from caches. However, in the red-grey site, during spring, red squirrels that had a high percentage of their home-range core area overlapped by grey squirrels had a lower daily energy intake than low-overlap red squirrels. Body mass of red squirrels in spring was negatively correlated with the percentage of interspecific core-area overlap, but not with core-area overlap with other red squirrels. Our data suggest that interspecific competition for scatterhoarded seeds, with grey squirrels pilfering red squirrels' food caches, caused a reduced energy intake in red squirrels with a high degree of interspecific core-area overlap, and reduced body mass in spring. Therefore, cache pilfering is likely to reduce reproductive output in red squirrels, and thus play a role in the replacement of red by grey squirrels.

Interspecific competition Squirrels Hoarding behaviour Cache pilfering Food-energy intake

Copyright information

© Springer-Verlag 2002