Over the past two decades, the area planted in wine grapes increased nearly 4.5 times on the central California coast. Much of this development occurred on oak savanna with scattered oak (Quercus spp.) trees. Remnant trees are retained in some vineyards, but their value to biodiversity retention, and the provision of ecosystem services to grape growers, has not been quantified. During the summers of 2014 and 2015, we recorded foraging activity of bats and insect abundance in 14 central coast vineyards. Within each vineyard, recordings were made at a lone remnant tree and at a location without a tree.
Results/Conclusions
The mean number of insects per night was over two times greater at vineyard trees than in the open vineyard. We recorded over 2.5 times more bat calls at vineyard trees (8,241) compared to the number of bat calls recorded at open vineyard sites (3,162). Vineyard tree attracted significantly more high frequency (91% of high frequency calls) and low frequency (60% of low frequency calls) bat groups than the open vineyard. These findings indicate that large remnant oak trees in vineyards not only support higher levels of bat activity, but also increase the diversity of bats that forage in the vineyard. These remnant trees function as keystone habitat structures, contributing to landscape-level conservation of bat diversity. This study lays the framework for addressing larger, more complex, questions surrounding the benefits of remnant trees for bats and the ecosystem services that the trees provide to grape growers.