Madre Selva field station, Depto Loreto, Peru. January 11, 2011.
One of the most common frogs in NE Peru; they can be found in vegetation on the edge of pretty much any body of water. This species usually sports some kind of triangular marking on the dorsum. Specimens with solid backs and / or spotted flanks were long thought to be variations, but these were shown to be a separate species (D. reticulatus) by Caminer, M., B. Milá, M. Jansen, A. Fouquet, P. J. Venegas, G. Chávez, S. C. Lougheed, and S. R. Ron. 2017. D. triangulum does have a reticulated form which is quite distinct (and beautiful; see bottom picture).
My Flickr album for this species is here.