Spruce-Fir Moss Spider (Microhexura Montivaga) Monitoring Plan Christopher Sacco, 5 June 2020 I. Introduction On June 20, 2019, the U.S. Fish and Wildlife Service (USFWS) announced it would conduct a 5-year status review of the Spruce-Fir Moss Spider as part of the process mandated by the Endangered Species Act.1 Although the Spruce-Fir Moss Spider has been listed as endangered since 1994, minimal research has been done on its basic ecology, and there is presently no long-term monitoring plan in place. This inhibits proper management of the species (USFWS 2019). It is also worth noting that few field surveys have been done on the Spruce-Fir Moss Spider because there are only a handful of people with sufficient experience and skill to find and identify this cryptic species2, and because frequent surveys would disturb the spider’s limited and fragile habitat. Furthermore, given the Spruce-Fir Moss Spider’s endangered status, observers must employ non-lethal survey methods. Traditional methods that kill the target species would undermine conservation efforts (Lecq et al. 2015). This further complicates research on the species. In light of these challenges, as well as limited availability of human and material resources, this plan focuses on occupancy rather than abundance. Compared to abundance studies, occupancy studies tend to be more cost effective and also more appropriate for cryptic species (Dibner et al. 2017). I hope that the information presented here will contribute in some small way to the development of a long-term monitoring plan for this difficult to monitor, endangered species. II. Natural History & Conservation Status Overview The Spruce-Fir Moss Spider’s known range is limited to 23 peaks in the Southern Appalachian Mountains of western North Carolina, eastern Tennessee, and southwest Virginia (Coyle 2009; Seaborn 2014; Seaborn & Catley 2016; USFWS 2019). There are 6 known montane populations. The spider lives in fir and spruce-fir forests only on the highest mountains (typically over 6,000 feet in elevation) and on slopes with northern aspects. It lives in damp, but well-drained moss mats growing on rocks and boulders in well-shaded areas within these forests (Coyle 2009; USFWS 2019). 1 USFWS listed the Spruce-Fir Moss Spider as endangered on February 6, 1995, produced a recovery plan in 1998, and designated critical habitat on July 6, 2001. 2 Dr. Frederick A. Coyle is recognized as the preeminent expert on the Spruce Fir Moss Spider. Unfortunately, Dr. Coyle recently retired. Spruce-Fir Moss Spider Monitoring Plan 1 The Spruce-Fir Moss Spider’s limited range and very specific habitat requirements make it vulnerable to habitat loss, human disturbance, air pollution and other threats. Climate change represents a potentially existential threat to the species because it is exacerbating most of these threats and creating new ones. Specifically, climate change’s negative impacts on the spruce-fir forests – increasing pest pressures, extreme weather events (e.g., drought and severe rain events), and changing weather variables (including maximum temperature, minimum relative humidity and annual rain-free days) – are serious threats to the spider (USFWS 2019). As the spruce-fir forest decreases in health and size, the thinning and death of the tree canopy can result in dramatic changes to the microclimate (USFWS 2019). The increased temperatures and decreased moisture dry out the moss mats that the spider depends on for its survival; it is very sensitive to desiccation and therefore requires high and constant humidity. As the mats dry out, so does the spider. Thus, the dwindling forest patches and loss of the mossy habitats they harbor could result in the extinction of this species (USFWS 1998; Seaborn & Catley 2016). In this context, effectively monitoring the Spruce-Fir Moss Spider and its fragile habitat are critical to conservation efforts. III. Survey Protocol Overview This standardized monitoring program is designed to systematically and consistently monitor the status and track trends in occupancy of the federally endangered Spruce-Fir Moss Spider, evaluate the health of its habitat, and guide future conservation and management decisions. Monitoring Goals: 1. Establish a standardized and robust survey protocol to assess status and trends in habitat occupancy of the Spruce-Fir Moss Spider and to monitor the health of the spruce/fir forest and bryophyte mats essential to the species survival. 2. Use the monitoring information to evaluate progress towards recovery criteria. 3. Use monitoring information to evaluate current and potential stressors and inform conservation and management decisions. Monitoring Objectives: 1. Monitor naïve occupancy at previously surveyed sites every 5 years in order to assess population status with the power to detect a 30% decline (with 80% confidence) in the number of sites occupied by the Spruce-Fir Moss Spider. 2. Observe and document population demographics at all survey locations, including stage of development (spiderlings, small, medium or large juvenile, and adults); Spruce-Fir Moss Spider Monitoring Plan 2 sex of adult spiders; and, signs of reproduction (egg sacs and spiderlings) and recruitment. 3. Observe and document habitat health at all survey locations, including percent canopy cover, bryophyte mat thickness, evidence of trampling, canopy cover decline, or other noticeable environmental or anthropogenic stresses. The Spruce-Fir Moss Spider survey, when conducted according to the guidelines provided here, will help determine presence or probable absence and trends in occupancy at 74 sites with suitable spider habitat and which have been previously surveyed. It will not provide sufficient data to determine population size or structure. This monitoring plan is designed around the concept of naïve occupancy, which is defined as the ratio of number of sites where a species is detected compared to the total number of sites surveyed, without correcting for imperfect detection (Ewing & Gangloff 2016). This methodology does not directly test for changes in abundance, yet because occupancy and abundance are usually strongly correlated, naïve occupancy is the best approach with the resources available (Ewing & Gangloff 2016). IV. Sampling Design • Survey area: Observers will survey 74 of the 81 sites surveyed by Dr. Coyle between 2007 and 2009 (Annex B). Seven of the previously surveyed sites will be excluded from the monitoring effort because they lack suitable habitat. • Sampling units: Moss “pulls” on rock outcrops with suitable moss mat habitat (at the right elevation and aspect and sufficiently thick and moist) will serve as the sampling units. • Sample size: USFWS will hire a statistician to determine the number of sampling units (moss pulls) required to detect a 30% decline, with 80% confidence, in Spruce-Fir Moss Spider occupancy at all 74 previously surveyed sites. • Sample selection method: Observers will engage in opportunistic sampling. Though this method limits our inference ability, random selection is unrealistic given the extremely limited number of rock outcrops that are accessible and the number of moss mats that are likely to serve as spider habitat. • Survey timing and frequency: Site visits will be conducted during the most biologically productive, warmest and wettest time of year to increase detection potential (Wynne et al. 2018). Monitoring will be conducted every 5 years. • Search time and effort: Observers will dedicate between 1- and 5-days surveying sites at each of the 6 mountain ranges where the 74 sites are located. Mountain ranges with more sites and which are more difficult to access will require the most number of search days. Spruce-Fir Moss Spider Monitoring Plan 3 • Sources of error: Unaccounted false absences are the main potential source of error because they result in an underestimation of the true level of occupancy. Repeat surveys on a regular interval, every 5 years, will reduce the impact of this source of error while also minimizing habitat disturbance. Additionally, to avoid the statistical bias that could arise if observers only survey sites where the Spruce-Fir Moss Spider was previously detected, all previously surveyed sites (whether the spider was present historically or not) will be re-surveyed every 5 years (Ewing & Gangloff 2016). This will allow observers to determine if the spider now occurs in some sites where it was previously not detected, indicating that status may therefore be stable or increasing (Strayer & Smith 2003). V. Field Methods • Pre-survey logistics and preparation: o Equipment/supplies: To ensure the safety and effectiveness of observers during field surveys, each person on the survey team should carry the following equipment and supplies: § Safety: Map of the search area; appropriate clothing and footwear; headlamp; backpack; any required medications; sufficient food and water; and signaling equipment, including a whistle and cell phone (or radio where there is no cell coverage). § Data collection and recording: Survey forms; pen and pencil; ruler (with millimeters and centimeters); GPS unit (to measure latitude, longitude, and elevation); hand lens, forceps, headlamp, compass, densiometer; camera (or cell phone with a camera); aspirator; jars; and, funnel. • Selection of sites and sampling units: § Locating survey sites: Observers will survey 74 sites over a 5-year period. Approximately one fifth of the survey sites (15) will be surveyed in any given year to allow observers to invest more search effort on those sites, thus increasing detection probability (MacKenzie & Royle 2005). Observers will locate the general survey site on each mountain peak using the GPS coordinates contained in the fourth column of the table in Annex B. § Selecting sampling units: At each of the 74 sites in the survey area, observers will identify rock outcrops at the right elevation (above 6,000 feet) and with the right aspect (north facing). Then observers will select moss mats on each outcrop that appear to be suitable habitat for the spider based on their thickness and moistness. Please see Annex F: Photos of Representative Spruce-Fir Moss Spider Microhabitats (Coyle 2009).