Ultra-compact dwarf galaxies (UCDs) are a relatively new type of compact stellar system, intermediate in luminosity between globular star clusters and dwarf elliptical galaxies. More than a decade since their discovery, it is still unclear whether they are simply large globular clusters, or the remains of tidally disrupted dwarf elliptical galaxies. We are testing if UCDs are formed from tidal stripping of dwarf galaxies by measuring the numbers and radial distributions of UCDs out to 1 Mpc from their host galaxies. To do so we have developed a novel pre-selection method using DECam multi-band photometry, which greatly increases the efficiency of UCD detection. In this talk I will describe our tests in the context of the two major formation scenarios, and demonstrate our pre-selection method, including some preliminary results from our January 2013 pilot DECam run.