This project investigates how merchants, migrants, and mariners involved in incursions of trade and aggression between 1450 and 1600 created an Iberian Atlantic island circuit that enabled and sustained the Portuguese and Spanish empires. Often understood as imperial expansion, these processes gain more analytic clarity if considered under the rubric of "incursionism": episodic, opportunistic initiatives that gradually coalesced into bases for further expeditions. On the Madeiran, Canarian, Cape Verdean, and Azorean archipelagos, as in southwestern Iberia, incursionists participated in resource arrangements and markets in which animals figured prominently as sources of labor, consumption, and concern. Conceptualizing the ways in which incursionism and subsistence drew from the presence and uses of animals, and how these dynamics figured prominently in political and legal arrangements, amplifies the scope for analyzing how incursionists came to build the footholds of Iberian empires on islands that were neither centers nor peripheries. Further, in settlements and their surroundings, municipal charters enumerating rights of access to communal resources created a legal framework with which those invested in benefiting from animals contended. I construct a socio-ecological history of hunting and fishing, pastoralism, and the commerce in animal products, inquiring into what extent these activities held local and regional import at the crossroads of Atlantic thoroughfares. I also investigate the degree to which incursionism and its reliance on animals and islands held political implications for Iberian imperial objectives and the juridical-theological architecture of empire. Materially, I argue, the presence of wild and domesticated animals, and the commerce in animal products, undergirded and contributed to incursionist ventures and regional trade networks; discursively, they served as a living template for conceiving of empire and mobilizing incursionist enterprises.