Degree of Threat: Very high - high
Comments: Threats are discussed by both USFWS (2004), The Washington Department of Fish and Wildlife (2005), (Black and Vaughn, 2008), among others. Except for three colonies lost to Btk spraying against gypsy moth and probably one to burning, the decline of this once widespread and common subspecies was almost entirely due to loss of habitat, sometimes by conversion to agriculture or development, but also due to succession caused by lack of fires, and to invasive plants. The current threats include most of the causes of decline, although probably not prescribed burning now, as well as small population sizes (most populations may be under 50 adults most years), and also isolation of many colonies. Where population sizes are small even collecting could be a threat. Small populations at most sites, perhaps all sites in some years, suggest the potential for genetic depletion through inbreeding. Climate change may be or become a threat, especially if the region becomes drier. The inability to explain some or most extirpations suggests there could be other pervasive problems. Some populations of this genus are inherently unstable, occur as metapopulations, and naturally undergo frequent extirpation and recolonization. This includes better known subspecies of this species studied by Ehrlich's lab and also the common eastern E. phaeton. Parasites, drought, depletion of foodplant are among possible factors behind any natural instability, but basically E. editha taylor is now so reduced that effective metapopulation dynamics may be unrestorable. If metapopulations consist of generally only two demes, it is also quite possible both could fail in the same season eliminating the occurrence permanently. All remaining occurrences are at serious risk of extirpation due to almost any natural or unnatural negative impact or to lack of management. Washington Department of Fish and Wildlife, finds that this species is management dependent there, and that state contains over 70% of occurrences. Information from Canada and Oregon suggests similar dependence in those places. The most pervasive overall immediate threats are metapopulation disruption and alteration of remaining habitat scraps by alien weeds (see USFWS 2004) but these are far from the only threats.
Robert M. Pyle mentioned extinction of a well known colony following a prescribed burn in the 1990s in at least two oral presentations attended by D. Schweitzer in the 1990s. Larvae in the litter would not be expected to survive any but the "coolest" prescribed burns unless the fire were quite patchy. It is possible that other populations were lost to prescribed burning. Poorly planned or wild fires at any season are a threat due to direct mortality and must be carefully managed. However, in the larger picture lack of fires has contributed to loss of habitat to succession. BTK spraying aimed at Asian Gypsy Moth probably caused or contributed to loss of three populations in the 1990s (USFWS 2004). Butterflies in general seem to be highly sensitive to BTK despite extreme variability among Lepidoptera in general (Peacock et al. 1998 and other references) which ranges from no impact to almost complete mortality even within the same genus in several families. Euphydryas populations would be fully exposed as mid or late instar larvae and must be assumed highly sensitive unless documented otherwise. This is a widespread threat especially to already small populations.
Euphydryas editha bayensis was remarkably little affected by the now classic deliberate removal (which simulated extreme overcollecting) studies by Ehrlich's workers in the 1970s. There is no plausible mechanism by which a mark-release-recapture study at Ft. Lewis could have caused the the crash of the population from 7000 in 1997 to extirpation by 2001, but it is not known what did, and it is not known in what year the decline actually started. Ehrlich's work strongly implies even outright removal of most adults would probably not have had close to that impact. Most workers are prudently reluctant to conduct such studies with severely stressed populations and it is possible, although not really likely and not actually demonstrated, that such studies when numbers were already very low and declining in the last year or two contributed somewhat to the final demise of the famous Jasper Ridge populations of E. editha bayensis (see McGarrahan 1997). Research activities per se pose little or no threat to E. editha taylori or any viable butterfly population (see also USFWS, 2007), but could add additional threats to already severely declining occurrences. Perhaps more important than handling, which does not cause much mortality, would be persistent disturbance disrupting normal behavior if several persons are present in a small habitat for extended periods (D. schweitzer, personal experience with other species).
