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Mitchell's satyr butterfly Listed: 6/25/1991 Status since listing: Stable The Mitchell’s satyr butterfly (Neonympha mitchelli mitchelli), a small chocolate brown butterfly, is one of the rarest butterflies in North America [1]. Historically, the Mitchell’s satyr was known from approximately 30 sites in four states including southern Michigan, northern Indiana, northern Ohio, and northern New Jersey [1]. Most historical satyr sites were known from Michigan, which could indicate this was the core of their range [2]. The Mitchell’s satyr was first listed as endangered in 1991 after intensive searches of over 100 sites between 1985 and 1990 found that the satyr had disappeared from approximately half of its historical locations [3]. Loss and modification of habitat, loss of habitat to succession, habitat fragmentation,and collection by butterfly enthusiasts are all thought to have contributed to population declines and local extirpations [1]. Currently there are 17 known extant colonies in Michigan and two in northern Indiana [2]. The butterfly is considered extirpated in Ohio and New Jersey [2] Monitoring conducted from 1981 to 1986 suggested that remaining populations in Michigan and Indiana were stable but at relatively low densities [1]. Surveys conducted in 1993 and 1994 suggested that populations were a bit higher at some locations [1]. The Mitchell’s satyr butterfly is found in peatlands ranging from prairie/bog fen to sedge meadow/swamp [1]. Prairie fens, typically thought to be the butterfly’s characteristic habitat, are shrub and herb peatlands where calcium-rich groundwater seeps through the surface maintaining wet and calcareous conditions [4]. Much remains unknown about this species biology, but it is thought that sedges, in particular Carex stricta, are the primary hostplants [2]. Adult butterflies fly in late June through mid July [1]. During the flight period, which generally lasts 2-3 weeks [5], the butterflies mate, lay eggs, and then die [1]. In Michigan, the Mitchell’s satyr occurs primarily in southern part of the state [2]. It has been documented in at least 22 sites in 11 counties [2]. Surveys conducted from 1995 to 2000, however, confirmed extant populations at only 16 sites [2]. Five were believed extirpated possibly due to wetland alteration [5]. Of the 16 confirmed sites, at least 6 were considered to be of high quality [1]. These sites consistently supported medium to high densities of adult butterflies, and seemed to represent fen complexes that have adequate habitat to support viable populations of Mitchell’s satyr [1]. The Michigan Natural Features Inventory has conducted annual sighting surveys for the satyr at known and potential sites since 1996 [5]. Although the numbers obtained by these surveys can not be used to deduce population estimates (the only way to do this accurately is by using mark-recapture techniques that could be detrimental to the butterflies if conducted over long periods), it appears the populations are remaining relatively stable [5]. Since 1996 five new populations were found and one population (last seen in 2000) appears to have been lost [5]. Surveys conducted in 2005 confirmed satyrs at 17 sites Bone of which was a new population discovered in Cass County [5]. A short-term mark-recapture study conducted in 2003 at a Jackson County site produced a population estimate of 1,106 adult butterflies B the largest population documented thus far [6]. In Indiana, 4 -5 sites are known to have supported Mitchell’s satyr [1]. Two sites in northern Indiana still support Mitchell’s satyr populations [1]. The status of two other sites is unknown [1]. In 1995, the Nature Conservancy translocated eight pairs of Mitchell’s satyr adults from one portion of a fen in LaPorte County to another TNC owned portion in an effort to re-colonize the protected area [1]. The primary threat to the Mitchell’s satyr is the loss and disruption of suitable fen habitats [1]. Alterations in natural drainage from disturbances such as roads, paths, residential development, and agricultural drains can have drastic effects and prairie fens and their Mitchell's satyr populations are very sensitive to changes in groundwater and surface water flow [4]. Alteration of wetlands can also lead to invasions by nuisance plants [1]. Wetland alteration is responsible for extirpating the single known satyr population in Ohio and several populations in Michigan [1], and some wetland complexes currently occupied by Mitchell’s satyrs have been altered or drained for agriculture or development [2]. In addition, landscape-scale processes such as fire and flooding that may be important for maintaining habitat and/or creating new habitat have been virtually eliminated or altered throughout the species range [2]. This suppression of natural processes has resulted in the succession of upland species into wetland habitats which can lead to the shading out of fen plants by shrubs and trees [5]. Without management many wetlands will convert from fens into shrub swamps or shrub carr [5]. Currently The Nature Conservancy, Southwest Michigan Land Conservancy, Michigan Nature Organization, and the State of Michigan are working to manage and acquire satyr habitat on both public and private lands and a landowner incentive program has been put into place to encourage appropriate stewardship of fen habitat [5]. [1] U.S. Fish and Wildlife Service. 1998. Recovery Plan for Mitchell’s Satyr Butterfly (Neonympha mitchellii mitcheliji French). U.S. Fish and Wildlife Service Ft. Snelling, MN. viii+71 pp. |
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