My wife and I traveled to Iquitos by river from Yurimaguas, where the last Andean slopes give way to the endless Amazon lowlands--and, consequently, where the new highway finally peters out. The boat trip lasts three days, assuming all goes according to plan. At every stop between Yurimaguas and Iquitos--tiny jungle settlements for which the river is the only link to the outside world--people pile on board, until the hammock deck is absolutely jam-packed with families, luggage, produce, and--right next to us--two tiny dogs and their doting owner.
The dogs must have been veteran river travelers, as they adjusted to hammock-bound life better than some of the tourists on board. Though they did get every bit as excited as the gringos when the occasional blue river dolphin would pirouette alongside us.