There are a few things you should think about when considering the use of external shotgun condenser mics with the DR-100. The first is battery life with phantom power switched on: it's not very long. The second thing covers noise and gain. The noise floor on the DR-100, although reasonable for a hand-held recorder, is not great when it comes to needing high gain for quiet wildlife recordings. Additionally, there is not really enough gain for very low-level sound sources, but this will depend on the microphone sensitivity.
The usual technique for dealing with both of these aspects is an external pre-amp that can supply phantom power of its own, and hence not drain the DR100's battery so quickly. If your wildlife recordings were mono, the standard pre-amp for this sort of use is the Sound Devices MP-1. I don't think SD does a 2-channel version of this unit, but your post does beg the question of what stereo microphone you were thinking of using.