Animals in Looking-Glass World: Fables of Überhumanism and Posthumanism in Heidegger and Nietzsche, by Richard Iveson
http://www.depauw.edu/humanimalia/issue02/iveson.html

Some points of note:

• "The nonhuman animal remains, however, and remains a problem. Given the essential withholding of apprehension from the animal, it is clear that the “poverty” [Armut] attributed to it by Heidegger can only ever be a “deprivation” [Entbehrung] when viewed from the perspective of the human, and thus, in truth, is neither poverty nor privation. This then, and as Heidegger himself points out, appears to disallow the positing of the tripartite thesis from the first, in that such an essential characterization is in fact conceived only in comparison with man and “not drawn from animality itself and maintained within the limits of animality”. Curiously, Heidegger does not object to this charge: to imagine otherwise, he says, is perhaps the privilege only of poets."