In a paper available on academia.edu, Marc Champagne argues for a naturalized ethics via the idea of the "umwelt" or surrounding world which he ascribes to the Estonian biologist Jakob von Uexkull, and which he filters through Ayn Rand's objective egoism. According to Champagne,

In an effort to bring substance to the right-headed suggestion that values are rooted in the biological and conform to species-specific requirements, we present a novel conception that strives to make explicit the elemental structure underlying umwelt normativity. Building and expanding on the seminal work of Ayn Rand in metaethics, we describe values as an intertwined lattice which takes a creature’s own embodied life as its ultimate standard; and endeavour to show how, from this, all subsequent valuations can in principle be determined.

In essence, he argues that the Humean notion of an is/ought dichotomy collapses once one recognizes that every living thing (being a system that's self-sustaining and so inclined to "pursue" its own survival by its very nature) exists in a world with a normative dimension. Everything in such an entity's world is subject to an attraction, repulsion or neutral charge for that entity. It's something to which the entity is either drawn or from which it flees or it is something towards which the entity is indifferent, in the background so to speak. This, he argues, is as true for plants as it is for animals though animals, of course, are differently constituted to interact with their world. For the ant, he writes, the stem of a flower is a highway to its "hunting ground," to us it's what supports a flower while to a cow it's part of its meal. Different organisms have different needs and so different means of responding to the elements of their world. This, he suggests, is Uexkull's "umwelt," the kind of world each organism exists in.

Thus, on this view, value is just the attraction/repulsion charge which any distinguished thing in the surrounding world of the organism has and this charge is always there, always a part of the world of that organism, i.e., it comes with the territory of being a living, self-sustaining system such as we and all the plants and animals of our universe are. . . .