Polites mardon

Poanes mardon is a year-round resident in southwest Washington state and northwestern California (Scott 1986), and probably occurs in Oregon. Habitats are humid transition zone grassy lowlands west of the Cascades, and Hudsonian to alpine zone grassland. Hostplants are grasses. Individuals overwinter as pupae. There is one flight each year with the approximate flight time June 15-July 15 (Scott 1986).

Global Range: (1000-200,000 square km (about 400-80,000 square miles)) The Xerces Society (Sheperd et al., 2005) summarized the range as follows. Historically, mardon skippers were collected from three counties in Washington (Thurston, Klickitat, and Yakima), two counties in Oregon (Klamath and Jackson), and one (Del Norte) in California. The mardon skipper is now known from 37 sites located in four geographic areas: (1) southern Puget Sound, (2) the Mt. Adams area (eastern side of the Cascade Range) in southern Washington, (3) the Cascade Range in southern Oregon, and (4) Del Norte (north-coastal) California. A few additional counties have been added since.

See also "number of EOS comments".

endemic to a single nation

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

See literature. No sight records acceptable for new EOs.

Comments: According to Pyle (1981) gravel outwash prairies in Puget Sound basin and mountain meadows in Washington. Scott (1986) adds serpentine outcrops for California. Generally grassy openings in subalpine coniferous forests in mountain regions. See also USFWS (1998). According to John Fleckenstein general site character ranges from open prairie on south Puget Sound sites to small native grasslands and planted grasslands and tree plantings where grasses dominate the groundcover in the southern Washington Cascades to a powerline clearing in the southern Oregon Cascades and serpentine grasslands in coastal California.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Presumably some movement between habitat patches but if so it seems to be rare. However occurrences do not seem to move from year to year, and new occurrences have not been found in previously surveyed locations. This suggests that individuals do not move far, and the species may be a poor colonist.

Comments: Adults oviposit on FESTUCA IDAHOENSIS in southern Oregon and nectar on clovers (Mattoon et al., 1998). In Del Norte County, California, the larval food plant is FESTUCA RUBRA, and FESTUCA OVINA is suspected as the larval host for this species in Washington (Mattoon et al., 1998). This grass genus seems implicated in California also. It could feed on several grasses, however. Adults nectar at dandelion (TARAXACUM OFFICINALE) and western wallflower (ERYSIMUM CAPITATUM) in western Washington (Newcomer, 1966). According to John Fleckenstein Mardon skipper is usually associated with Festuca spp. grasses. Potter (pers. comm.) and Mattoon (1998) have recorded ovipositioning on Festuca spp. Newcomer (1966) raised larvae on lawn grasses but thought Festuca spp. might be the native foodplants. Festuca idahoensis or Festuca rubra have been found on all Washington sites hosting mardon skipper (Potter, pers. comm., Fleckenstein, per. obs). Numerous nectar sources have been noted, including dandelion, wallflower (Erysimum capitatum) (Newcomer 1966), violet (Viola adunca), vinca (Vinca), penstemon (Penstemon), and Calochortus (Potter, per. comm.).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: USFWS (2010) provides a recent summary. They conclude the 139 recent sites represent about 59 populations. There are slightly more than 70 sites in the southern Washington Cascades, for example in Gifford Pinchot National Forest, the Gotchen Creek and Okanogan-Wenatchee National Forest, Yakima Indian Reservation; 21 sites in the southern Cascade-Siskiyou Mountain in southern Oregon; and a few in serpentine grasslands in a a small area of the northern California (Del Norte) and southern oregon coast. The species also occurs in the Puget Sound prairies but it is now down to only two occurrences, one of which is a metapopulation on military land.

All stages apparently above ground. R. Pyle says prescribed burns have recently eradicated some Washington populations.

Males probably perch for females (Scott, 1986).

Comments: Adults are active on warm sunny days in May and June in lowland Washington, and about a month later in the mountains according to Pyle (1981). Newcomer (1966) reared the skipper indoors on lawn grass. Newcomer (1966) found that eggs hatch in 6-7 days; he also described the larval stages and reported that the pupae hibernate.

Current Listing Status Summary

Status: Resolved Taxon
Date Listed:
Lead Region:   Pacific Region (Region 1) 
Where Listed:

For most current information and documents related to the conservation status and management of Polites mardon, see its USFWS Species Profile

Rounded Global Status Rank: G2 - Imperiled

Reasons: There are still dozens of populations, USFWS (2010) concludes about 59, of varying quality but some are substantial metapopulations, with threats in most or all of its range and evidence of decline in many areas. Some occurrences are at least hundreds of adults in many years, possibly a few are more than that. On the other hand the species has only a handful of occurrences in one of the four parts of its range, and is nearly extirpated in the other coastal part of the range. It is thus now nearly confined to two small limited areas: in the Cascades of southern Washington and much farther south in the Cascades and Siskiyous of southern Oregon. It has been looked for and not found in between. The species is at least rare with four widely separated limited ranges, and has declined in at least two of these. Polites mardon is critically imperiled in the Puget Prairies, probably imperiled farther south on the coast, but not as imperiled farther east in the mountains. There still are some substantial potentially viable populations, and others that could be restored. This information points to either G2 or G3 as the correct rank. NatureServe's Rank Calculator rank also returns this rank.

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Other Considerations: Status of this species varies in different parts of the range. It appears extremely imperiled in the Puget Prairie region where it has probably already declined by more than 95%. However this is not a large part of the current range.

United States

Rounded National Status Rank: N2 - Imperiled

Global Short Term Trend: Decline of 10-30%

Comments: This species has declined drastically in the Puget Sound area (probabl by >95%) and has continued to do so. USFWS (2010) found some evidence of recent decline in the southern Cascades. Not in obvious current decline otherwise.

Global Long Term Trend: Decline of 50-90%

Comments: Clearly more than 95% decline in Puget Prairie part of range and substantial decline in some other parts of the range. It is not clear to what extent this species has really declined in the Southern Cascades especially.

Degree of Threat: High - medium

Comments: Threats include invasive herbs, grasses, and shrubs at many sites, inappropriate fires at some. Other threats applicable at some sites include human disturbance associated with roads, recreation and development, grazing, herbicides and pesticides. Se USFWS (1998, 2010).

The 1998 USFWS review suggests exotic plants as probably the greatest overall threat. Threat from prescribed fires seems to be mainly in the Puget prairies and might not be applicable to current practices. Threats from exotic plants are probably a concern at most or all occurrences but are especially severe in the Puget Prairie portion of the range where this threat must be considered operational now. Grazing is a threat in the Southern Cascades and elsewhere, but the potential severity of this impact is uncertain and some level of grazing is probably compatible.

Use of BTK against forest pests has been suggested as a threat (USFWS, 1998 and 2003) and between Asian Gypsy Moth and the Spruce Budworm and other native conifer pests this is a potentially widespread but not universal concern. However there does not appear to be any actual evidence whether or not BTK poses any risk to Mardon Skipper. None of the major scientific studies on BTK impacts are referenced by USFWS (2003) or in the Center for Biological Diversity listing petition, and no relevant evidence is given. It is simply not true that BTK is lethal or even toxic to all caterpillars. There are extremely few data on BTK sensitivity of skippers and sensitivity can vary greatly among species in the same genus in several other families. So it is quite possible but undocumented and very far from certain that Mardon Skipper larvae would have high mortality from BTK spraying. According to USFWS (2003) this skipper hibernates as a pupa. Only actively feeding caterpillars can be harmed by BTK. If this species hibernates as a pupae or as a fully fed larva, then the risk from BTK could be substantial or nonexistent depending on when applications occur relative to when eggs hatch. Among Lepidoptera in general mortality ranges from zero to 100% depending on species and instar in the lab and slightly less in the field; with virtually the full range of sensitivity found even within genera and sometimes even within instars of the same species (e.g. Peacock et al., 1998). However almost all species tested are sensitive as first or second instars and about half are highly so. With few exceptions the lethal period of BTK residue to Lepidoptera is about 10 days or less although for a few species it can remain lethal for a month. Both sunlight and rain usually rapidly affect BTK residue. Therefore if BTK is applied before the adult flight season, the risk should be minimal. Few or no larvae would likely be exposed. If it is applied during or within a week after the flight season most or all first instars could be exposed--depending on where exactly they feed. If it is applied substantially after the adult flight season then risk is unknown (possible range: zero to nearly 100% mortality) but should be assumed to be very high until actual data are available for the instars that would be exposed. Data for other skippers, including congenerics, might not be a reliable indicator of sensitivity.

Even ignoring the uncertainty related to BTK it appears that between exotics, livestock grazing, herbicides, and direct human use and in some places fire most populations are under some degree of threat. Some may be too reduced now to have much chance of persistence. Threats appear very widespread but variable, less in the southern Cascades than elsewhere.

Biological Research Needs: It is unclear whether actual populations sizes are important to managing this species, but if this information is needed, mark-release-recapture studies should be used. It should be noted that the usual objections to m-r-r are in most cases without merit. For example the Gall 1984) study sometimes cited as showing harmful impacts in fact showed only brief behavioral impacts on the same day as marking only (also Gall, pers. com., November 2010). There is no actual evidence presented that m-r-r actually contributed to the demise of the famous Jasper Ridge checkerspots, although these wer unusually intensively studied and once they began their final decline m-r-r perhaps played a minor role. That said skippers are very difficult to handle safely (D. Schweitzer, based mostly on Hesperia attalus). Transects are other types of census might be sufficient for most monitoring and other assessments, but should be used with caution. Unlike m-r-r, at least when done over much of the flight season, single day counts can be misleading if the population ecloses early or late, or is more staggered in some years than others.

Global Protection: Several to many (4-40) occurrences appropriately protected and managed

Comments: See USFWS (2010). Many sites are on public lands with some level of habitat protection.