This small tree of east-central states is widely distributed in mesic to submesic woods on fertile soils, and it is especially abundant in thin woods and edges with moderate disturbance. It is generally avoided by deer (Atwood 1941, Wakeland & Swihart 2009, Slater & Anderson 2014), but it does not usually survive intensive disturbance by livestock. In FAYE and nearby, Short (1828-9) noted: "This portion of Kentucky was once the paradise of pawpaws, where immense orchards of large trees were every where met with; but cultivation and the ravages of cattle have greatly lessened the number." There is much variation in fruit characteristics, and at Ky. State Univ. Pomper et al. (2008) have been engaged in a national program to make selections for human use. Pawpaw is host for the zebra swallowtail butterfly, which overcomes the unusual toxins in leaves (aporphine & isoquinoline alkaloids, acetogenins). Fruits also contain acetogenins, which have some neurotoxicity as well as anti-cancer potential (Potts et al. 2012). Personal averaions to eating fruits have been reported (e.g. H. Bryan, pers. comm), but no negative human effects from consumption have yet been documented. Fruits can be occasionally dispersed through guts of bears, raccoons, foxes, opossums and deer, but domesticated horses and elephants appear to disike them (Boone et al. 2015). Flowers have unusual foetid or "yeasty" smells, which probably attract flies, small beetles or other pollinators; the complex chemistry includes distinctive butanol and butanone derivatives (Goodrich et al. 2006, Saunders 2012). Flowers are protogynous, and the species appears to be generally self-incompatiblle.