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MONITORING AND HABITAT SURVEYS OF mE ENDANGERED KANAB AMlIERSNAIL IN GRAND CANYON AND NOlllBERN AIuzoNA Jeff A. Sorensen and Dennis M. Kubly i: ?~ INTRODUCTION In 1992, the Kanab ambersnail (KAS; Succineidae: Oxy1011lD haydeni kanabensis Pilsbry, 1948) was federally listed as endangered by the U.S. Fish and Wildlife Service (USFWS 1992). Arizona Game and Fish Department (AGFD) also recognizes KAS in its draft Wildlife of Special Concern in Ari2D1IIl (AGFD in prep.). Specific threats to KAS involve the loss and/or adverse modification to wetland habitat and incidental take by dam releases (USFWS 1995). ~:. " ., " Only two populations of the KAS are known to exist currently in the American Southwest. An extant population is found in soutbeastem Utah, on a private1y-owned wet meadow dominated by ca""i1~ (TyphiJ domingensis) and sedges (Carer aqUlJlilus). This population (Three Lakes; 3L) is threatened by habitat loss and possible extirpation by planned commercial development (USFWS 1995). The other population of this rare landsnail was discovered in 1991, at Vaseys Paradise (VP) in Grand Canyon National Park (Blinn et aI. 1992; Spamer and Bogan 1993). Located 75.3 Ian downstream of Glen Canyon Dam, this site has a large, perennial spring with abyndant poison ivy (Toxicodendron rydbergii), crimson monkeyflower (Mimulus cardinaJis), and watercress (Nasturrium officinale). The VP population is threatened by habitat loss and incidental take from controlled and uncontrolled high water reI........ from the dam. This population experienced habitat loss and incidental take during an experimental 45,000 cfs (1275 m3/s) stage flow in March 1996 (Stevens et aI. 1991a). Both populations are geographically isolated (92.9 Ian distant), and are believed to be relics from the Late Pleistocene glaciation, when wetland habitat was more abundant (Spamer 1993; Spamer and Bogan 1993; Stevens et aI. 1997b). ~,: i/-. ., '. )J ~ ~ ~ h .'~ ~. ~l ~ ), .- ~. ;t. ::: ,,:,. ~'l ,-- " KASs are restricted to perennially wet soil surfaces and decaying plant litter of springs and seep- fed marshes near sandstone or limestone cliffs (USFWS 1995). A limiting factor in their distribution may be the presence of cattails, monkeyflower, and watercress, which are identified as the primary vegetation for KAS habitat. They are most abundant under fallen cattail stalks, decadent monkeyflower litter, and young watercress (USFWS 1995; Stevens et aI. 1991b). KASs have an approximately annuallifecycle, and reportedly live 12-15 months (Clarke 1991). They emerge from winter hibernation in spring with the onset of wann weather, and begin reproducing throughout the late spring and summer months. Peak reproduction typically occurs in late summer, when densities of mature KASs are highest. A seasonal decline of KASs occurs in autumn with mass die-offs of mature individuals, while young and immature KASs go into winter donnancy (Blinn et aI. 1992; Stevens et aI. 1997b). KASs are hermaphroditic, possessing both male and female reproductive tracts (Pilsbry 1948). Young snails develop from gelatinous egg masses attached to wet plant litter. Fully mature KASs can have shell lengths up to 20 mm. ". ~, 'J ~~ ,,1. ~ ~ '" ~ -, .... '.~ ~ " ,.> > 0, >~ j .~. ~