I'll stick to using Haar feature-based cascade classifier, and I'll be training it with garden wildlife images actually obtained using the device. I think will be more accurate than having to use 1000s of elephant images I obtained from wikimedia commons etc for the elephant project.. but might try HOG + Linear SVM instead, although I'm not sure and have never used this on Raspberry Pi.

UPDATE: I will not be using Haar ! An object detector using HOG + SVM will be used to start with!