Sylvilagus palustris hefneri, also known as the Lower Keys marsh rabbit, is an endangered subspecies of marsh rabbit named after Playboy founder Hugh Hefner. General Sylvilagus palustris hefneri was federally recognized as an endangered species on June 21, 1990. The urbanized Florida Keys have left the rabbits with a very small home range, making them more vulnerable to threats such as pollution, vehicular road kill, and predation by stray cats. Forys and Humphrey (1999) predicted a gradual decline in S. p. hefneri abundance and extinction within 50 years (of 1995). The Lower Keys marsh rabbit population is estimated to contain approximately 150 individuals. In 2008, LaFever et al. performed viability assays to determine current extinction rates. They predicted extinction within 10 years if action is not taken immediately. They recommend urgent management of predatory stray cats, and restoration of marshes as possible solutions to reduce the extinction rate of S. p. hefneri. Phylogeny The subspecies was first described in a publication in the Journal of Mammalogy in 1984 by James D. Lazell Jr, after his research was funded in part by a generous contribution from the Playboy Corporation. The Lower Keys marsh rabbit was then named in honor of Hugh M. Hefner in recognition of the financial support received by his corporation. Size Sylvilagus palustris hefneri is small-to-medium-sized, in length and in weight. Their hind feet range from and their ears range from in length. S. p. hefneri is the smallest of the three marsh rabbit subspecies, the others being Sylvilagus palustris paludicola and Sylvilagus palustris palustris. These rabbits do not appear to be sexually dimorphic. Appearance The pelage of S. p. hefneri is short with dark brown fur and a greyish-white belly, and their tails are dark brown. S. p. hefneri is the smaller than the mainland marsh rabbit (S. p. palustris) and Upper Keys marsh rabbits (S. p. paludicola) and is distinguished by its dark fur. S. p. hefneri also differs from S. p. palustris and S. p. paludicola in several cranial characteristics. The Lower Keys marsh rabbit has a shorter molariform tooth row, higher and more convex frontonasal profile, broader cranium, and elongated dentary symphysis. Range Sylvilagus palustris hefneri has been isolated to the Keys by the rise in sea level and human inhabitation to the local area. This isolation may be the cause for the subspeciation from the Upper Keys marsh rabbit, Sylvilagus palustris paludicola. Forys