Oarisma poweshiek - (Parker, 1870)
Poweshiek Skipperling
Other English Common Names: Poweshiek skipperling
Synonym(s): Oarisma powesheik (Parker, 1870)
Taxonomic Status: Accepted
Related ITIS Name(s): Oarisma poweshiek (Parker, 1870) (TSN 706688)
French Common Names: hespérie de Poweshiek
Unique Identifier: ELEMENT_GLOBAL.2.116340
Element Code: IILEP57010
Informal Taxonomy: Animals, Invertebrates - Insects - Butterflies and Moths - Butterflies and Skippers
 
Kingdom Phylum Class Order Family Genus
Animalia Mandibulata Insecta Lepidoptera Hesperiidae Oarisma
Genus Size: B - Very small genus (2-5 species)
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Concept Reference
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Concept Reference: Opler, P. A., and A. D. Warren. 2002. Butterflies of North America. 2. Scientific Names List for Butterfly Species of North America, north of Mexico. C.P. Gillette Museum of Arthropod Diversity, Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado. 79 pp.
Concept Reference Code: B02OPL01EHUS
Name Used in Concept Reference: Oarisma poweshiek
Taxonomic Comments: Commonly misspelled "powesheik". This species was named after Poweshiek County, Iowa and therefore the name has been emended.
Conservation Status
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NatureServe Status

Global Status: G1
Global Status Last Reviewed: 07Feb2013
Global Status Last Changed: 07Feb2013
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G1 - Critically Imperiled
Reasons: With a well-documented (USFWS, 2011a) collapse throughout the core range in less than a decade, likely extirpation of over 95% of populations that were extant in the core range in the 1990s and early 2000s, an annual adult population now possibly only a few hundred mostly in isolated fens away from the core range, no known robust metapopulations remaining, and the causes of this sudden collapse unknown, G1 is assigned. The rank of G2G3 from 2007 is no longer tenable, and even that rank was based in part on known decline which proved to be much more severe than anticipated.
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Nation: United States
National Status: N1 (07Feb2013)
Nation: Canada
National Status: N1 (24Aug2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Illinois (SH), Indiana (SH), Iowa (S1), Michigan (S1), Minnesota (S1), North Dakota (SNR), South Dakota (S2), Wisconsin (S1)
Canada Manitoba (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LE: Listed endangered (24Oct2014)
Canadian Species at Risk Act (SARA) Schedule 1/Annexe 1 Status: T (14Jul2005)
Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Endangered (28Nov2014)
Comments on COSEWIC: Reason for designation: The Canadian population is isolated and disjunct from the populations in United States which are 1000 km to the south.  Widespread declines within the past decade on both sides of the border mean Canada holds a significant portion of the species global range. Within Canada this species is restricted to native tall-grass prairie, a habitat that has also undergone similar declines. Although most of the occupied habitat is protected, even with appropriate management, its range is so small that the butterfly is increasingly vulnerable to stochastic events.

Status History: Designated Threatened in November 2003. Status re-examined and designated Endangered in November 2014.

NatureServe Global Conservation Status Factors

Range Extent: 100-1000 square km (about 40-400 square miles)
Range Extent Comments: The original core range was orders of magnitude larger from extreme southern Manitoba south more or less along the Dakotas-Minnesota border region into northeastern South Dakota, with an isolated (extant) occurrence well to the south in Lincoln County, then expanding southeastward across much of southern Minnesota and northern Iowa and formerly into Illinois, with disjunct fen populations in small areas of northern Indiana and Michigan (several extant). It is unclear whether the three recent (at least one extant) Wisconsin occurrences were part of the core prairie distribution or a disjunction comparable to those in Michigan. See Selby (2005). The former core range would fit with room to spare in a 60,000 square mile polygon if the small range fragments in Wisconsin and Michigan and extirpated populations in Illinois were excluded. As of 2010 there appears to be no meaningful remaining range except for a few counties in southern Michigan. The other three known extant populations are hundreds of kilometers apart in Manitoba, South Dakota, and Wisconsin.

Area of Occupancy: 6-25 4-km2 grid cells
Area of Occupancy Comments: Best guess for Michigan colonies plus about four others. Individual sites probably all under 50 hectares, some under one.

Number of Occurrences: 21 - 300
Number of Occurrences Comments: As of 2010 according to USFWS (2011a) over 99% of core populations had negative most recent efforts. Apparently the nine isolated fen population in Michigan, one (possibly two) in Wisconsin, one each in South Dakota, Manitoba, and maybe Iowa constitute all occurrences that probably are or are known to be still extant. Ironically it was mainly the small disjunct isolated populations that survived the first decade of the 21st century. Many sites have multiple consecutive negative searches. Extirpation is quite likely at most of them and fairly likely at nearly all of them.

As of the late 1990s or early 2000s: about 260 sites, probably not representing that many separate occurrences, are known since 1965 and "not confirmed extirpated" (Selby, 2005). Undoubtedly some of them were extirpated. For example at least 31 had negative results in the most recent survey, and 19 of these were last checked in or after 2003 which corresponds with a massive crash of this species. Many occurrences, including most isolated ones, might be of low viability either due to small size or (e.g. likely at least one in Wisconsin) sometimes due to incompatible fire practices. It is unclear in some cases how many "sites" are demes rather than separate occurrences. Best guess would be on the order of 50-100 potentially viable populations remain and numerous low C to D quality isolated colonies. Only Minnesota (which included much of the core range) ranked this species S3, all other ranks were SH to S2 before the massive decline of this species.

Population Size: 250 - 2500 individuals
Population Size Comments: Fluctuated drastically on occasion even without fires. With most (very possibly 121 of 123) recent populations from Manitoba to Iowa and South Dakota apparently extirpated, the best guess for the surviving Michigan and Wisconsin populations would be under 1000 adults total most years. There is even less basis for any guess as to sizes of any others that are not zero. However the relationship of number observed to population size is unknown, census counts are not population estimates

Number of Occurrences with Good Viability/Integrity: Few (4-12)
Viability/Integrity Comments: One of the best populations declined by about 99% from 2002 to 2003 for no obvious reason and none were seen after that. Similar crashes occurred widely In Minnesota, the Dakotas, and Iowa at that time and none of the populations appear to have recovered as of the 2011 field season. USFWS (2011a) considers the nine extant isolated Michigan populations the best chance for survival of the species. Some of these are considered to be viable populations, but these ranks may be unjustified, if as is likely, populations are small (hundreds or less most years) and their habitats too isolated for gene flow or for recolonization. However all nine seem viable for the short term and most are protected.

Overall Threat Impact: High
Overall Threat Impact Comments: The nature of the "unknown stressor" (USFWS, 2011) that apparently eliminated virtually all populations in the core of the range in much less than a decade remains a mystery. In some places other skippers, including the formerly rarer Dakota Skipper, seem less affected and regal fritillary is still being found in many affected habitats. Thus the stressor may be fairly species-specific, or at least rather skipper-specific, as well as pervasive. Among collapses of widespread insects in North America, that of Bombus affinis and B. occidentalis are among the very few that seem to have been so pervasive and rapid. An obvious similarity is that sudden pervasive habitat changes cannot explain the collapses, although habitat degradation certainly had occurred with O. Poweshiek over the previous 150 years. The Bombus declines appear to have been due primarily to non-native pathogens (references in Schweitzer et al., 2011), and a similar explanation may apply here. However there is no evidence of any kind actually supporting this hypothesis, except for the inadequacy of many other explanations and the extreme rapidity and pervasiveness of the decline. Whatever happened, it started in the core of the range or possibly just to the north and within perhaps five years. After the first decade or so, some peripheral populations, including most at the southeast corner of the range, remained unaffected.

Short-term Trend: Decline of >90%
Short-term Trend Comments: USFWS (2011a) summarizes rather exhaustive survey efforts by Selby, Skadsen and others (see USFWS, 2011a and references therein for details) after Selby (2005) initially reported a sharp decline by 2003. In the core prairie range, as of 2010 out of 120 resurveyed previously known occurrences, most with 1990s or 2000s records, the most recent survey was negative for 119, as it was by then for one of two newly discovered populations. Decline has so far probably not been as severe at the edges of the range with populations extant as of 2010 at the extreme northern limit in Manitoba, near the southwestern limit in Lincoln County South Dakota, and at the eastern edge of the prairie distribution in Wisconsin. In fact the Manitoba population was robust enough to survive a large wild fire. There is no indication of unexplained recent decline of the isolated Michigan fen populations, with nine of 16 extant from 2008 to 2010, six verified in 2010 and USFWS and other consider these to offer the best chance for the survival of the species..

Long-term Trend: Decline of >90%
Long-term Trend Comments: Overall tall grass prairie loss given by Selby (2005) as 98.65% for states and provinces where this species occurs. USFWS (2011a) gives the same figure. Actually decline of this species was probably higher even by the 1990s because even then most prairies remnants lacked the species and metapopulation dynamics probably already broken down in much of range.

Intrinsic Vulnerability: Highly vulnerable
Intrinsic Vulnerability Comments: There is so far no explanation for what happened to this skipper in the 2000s, but it was exceeding vulnerable to something except (so far) around the extreme edges of its range.

Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.
Environmental Specificity Comments: Prior to the 2000s, this was primarily a skipper of the northern tall-grass prairies. As of about the mid 2000s nearly all populations there seem to have disappeared and as far as known remaining occurrences are primarily calcareous fens.

Other NatureServe Conservation Status Information

Inventory Needs: Not much can be done other than periodically monitor some recent occurrences in case the species was not quite extirpated in a few of them.

Protection Needs: Unclear other than maintain the Michigan and Wisconsin habitats.

Distribution
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Global Range: (100-1000 square km (about 40-400 square miles)) The original core range was orders of magnitude larger from extreme southern Manitoba south more or less along the Dakotas-Minnesota border region into northeastern South Dakota, with an isolated (extant) occurrence well to the south in Lincoln County, then expanding southeastward across much of southern Minnesota and northern Iowa and formerly into Illinois, with disjunct fen populations in small areas of northern Indiana and Michigan (several extant). It is unclear whether the three recent (at least one extant) Wisconsin occurrences were part of the core prairie distribution or a disjunction comparable to those in Michigan. See Selby (2005). The former core range would fit with room to spare in a 60,000 square mile polygon if the small range fragments in Wisconsin and Michigan and extirpated populations in Illinois were excluded. As of 2010 there appears to be no meaningful remaining range except for a few counties in southern Michigan. The other three known extant populations are hundreds of kilometers apart in Manitoba, South Dakota, and Wisconsin.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States IA, IL, IN, MI, MN, ND, SD, WI
Canada MB

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
IA Calhoun (19025), Cerro Gordo (19033), Dickinson (19059), Emmet (19063), Hancock (19081), Howard (19089), Jasper (19099)*, Kossuth (19109), Osceola (19143), Plymouth (19149)*, Poweshiek (19157)*, Woodbury (19193)*
MI Jackson (26075), Kent (26081)*, Lenawee (26091)*, Livingston (26093), Oakland (26125), Washtenaw (26161)
MN Becker (27005), Beltrami (27007)*, Big Stone (27011), Chippewa (27023), Clay (27027), Clearwater (27029)*, Cottonwood (27033), Dodge (27039), Douglas (27041), Grant (27051), Hubbard (27057)*, Jackson (27063), Kandiyohi (27067), Kittson (27069), Lac Qui Parle (27073), Lincoln (27081), Lyon (27083), Mahnomen (27087), Marshall (27089)*, Mcleod (27085), Murray (27101), Nobles (27105), Norman (27107), Pennington (27113)*, Pipestone (27117), Polk (27119), Pope (27121), Rock (27133)*, Roseau (27135), Sibley (27143)*, Stearns (27145), Stevens (27149)*, Swift (27151), Traverse (27155), Wilkin (27167), Yellow Medicine (27173)
ND Richland (38077)
SD Brookings (46011), Codington (46029), Day (46037), Deuel (46039), Grant (46051), Hamlin (46057), Marshall (46091), Moody (46101), Roberts (46109)
WI Green Lake (55047), Waukesha (55133)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
04 Upper Fox (04030201)+, Upper Grand (04050004)+, Lower Grand (04050006)+*, Shiawassee (04080203)+, Flint (04080204)+, Huron (04090005)+, Raisin (04100002)+*
07 Mississippi Headwaters (07010101)+*, Crow Wing (07010106)+*, Long Prairie (07010108)+, Sauk (07010202)+, Crow (07010204)+, South Fork Crow (07010205)+, Upper Minnesota (07020001)+, Pomme De Terre (07020002)+, Lac Qui Parle (07020003)+, Hawk-Yellow Medicine (07020004)+, Chippewa (07020005)+, Redwood (07020006)+, Cottonwood (07020008)+, Watonwan (07020010)+*, Lower Minnesota (07020012)+*, Upper Iowa (07060002)+, Turkey (07060004)+, Upper Wapsipinicon (07080102)+, North Skunk (07080106)+*, Upper Cedar (07080201)+, Winnebago (07080203)+, Upper Iowa (07080207)+, Middle Iowa (07080208)+*, Lower Iowa (07080209)+*, Crawfish (07090002)+, Des Moines Headwaters (07100001)+, Upper Des Moines (07100002)+, East Fork Des Moines (07100003)+, North Raccoon (07100006)+
09 Bois De Sioux (09020101)+, Mustinka (09020102)+, Otter Tail (09020103)+, Western Wild Rice (09020105)+, Buffalo (09020106)+, Elm-Marsh (09020107)+, Eastern Wild Rice (09020108)+, Maple (09020205)+, Sandhill-Wilson (09020301)+, Red Lakes (09020302)+*, Red Lake (09020303)+, Clearwater (09020305)+*, Grand Marais-Red (09020306)+*, Snake (09020309)+*, Lower Red (09020311)+, Two Rivers (09020312)+, Roseau (09020314)+*
10 Upper James (10160003)+, Lewis and Clark Lake (10170101)+*, Middle Big Sioux Coteau (10170201)+, Upper Big Sioux (10170202)+, Lower Big Sioux (10170203)+, Rock (10170204)+, Blackbird-Soldier (10230001)+*, Floyd (10230002)+*, Little Sioux (10230003)+, Monona-Harrison Ditch (10230004)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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General Description: See any butterfly guide covering eastern North America.
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Palustrine Habitat(s): Bog/fen, HERBACEOUS WETLAND
Terrestrial Habitat(s): Grassland/herbaceous
Habitat Comments: Habitats are usually more or less virgin prairie but it also occurs in fens and grassy lakeshores especially eastward (Michigan, Indiana). Sometimes noted as preferring wetter parts of prairies but this may be an artifact of frequent prescribed fires excluding them from most suitable habitat (Borkin, 1995). This issue is still unresolved as of Selby (2005). Habitat would be in part a function of larval foodplant and information on this topic is confusing.
Adult Food Habits: Nectarivore
Immature Food Habits: Herbivore
Food Comments: Larvae apparently use several grasses and occasionally sedges. At least in Wisconsin, SPOROBOLUS HETEROLEPIS and SCHIZACHYRIUM SCOPARIUS appear to be major foodplants. However, in Michigan fens spike rushes (Rynchospora) appear to be the usual foodplants. Adults take nectar from flowers such as black-eyed susan and many other others. See Selby (2005) for details.
Adult Phenology: Diurnal
Immature Phenology: Hibernates/aestivates
Phenology Comments: Larvae hibernate. Adults fly in late June and July in most places. Always univoltine.
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Prior to the nearly total collapse in its core range, management needs appear to have been much the same as other prairie skippers in most of its range, that is leaving unburned refugia and several years between fires in prescribed burning cycles, avoiding June-July haying, and not applying broadcast herbicides that can wipe out nectar sources for the season. Some level of grazing was compatible. Compared to other skippers, Poweshiek might have been somewhat more sensitive to fires. For further details see references including many cited by USFWS (2011a). If any persisting prairie populations are found in its core range, the focus needs to be on not inadvertently wiping the population out by management activities. Protection from pesticide drift may also be critical. For now focus needs to be on preventing extirpation of the small remnant fen populations in Michigan that are not collapsing which USFWS and others suggest may be the only real hope for survival of the species anywhere, perhaps also the remaining one or two in Wisconsin. Among major long-term threats to most of these are invasive plants, especially Frangula alnus, isolation sufficient to preclude recolonization, and in some, perhaps all, populations small annual generations of adults. Invasion by F. alnus has probably eliminated one fen population already. Captive breeding from a few prairie populations, if any suitable sources remain, should be considered in case the cause of the decline is ever learned and proves to be reversible. Establishing connectivity between some of the Michigan populations seems desirable, but probably not practical.

Restoration Potential: Unknown, especially long-term. The cause of the massive collapse of this skipper in the 2000s is unknown, but was something pervasive. Untill this threat can be assessed, restoration potential is probably low, except perhaps in case of historic fen sites eastward if any are still suitable habitats.
Management Requirements: If any prairie populations do survive, management needs are probably similar to other skippers. Use fire conservatively, if at all.
Monitoring Requirements: See USFWS (2011a) and various inventory reports cited in that document. It should be kept in mind that the relationship between number observed and actual population size is unknown, but likely that typical observation methods would pick up large changes in abundance.
Biological Research Needs: The major research need is getting an idea of what caused the widespread crash in about 2002-2003. If any prairie populations do persist, it would be extremely useful to be able to predict likely crash scenarios and avoid the added stress of fires. Also information is needed on real foodplant preferences in various parts of the range.
Population/Occurrence Delineation
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Group Name: Hesperiinae

Use Class: Not applicable
Minimum Criteria for an Occurrence: A location where the species occurs, or has occurred, where there is potential for persistence or regular recurrence. Minimally a suitable habitat with the larval foodplant where at least one adult has been verified by a photograph or preferably a specimen. Photographs must be diagnostic and will probably need to show both wing surfaces, and there will be circumstances where only a specimen will suffice. Specimens are usually much easier to obtain. Sight records are not an acceptable basis for a new occurrence. Note that these Specs should not be applied to temporary seasonal colonies of common migratory species.
Mapping Guidance: Note the suitable habitat distance will not apply often since most habitats today are no more than a few hundred hectares. However, many were once major landscape features. Suitable habitat distances may be used for barrens, savanna, and prairie species across degraded portions of these habitats that still contain some of the foodplant grasses or nectar flowers. Usually habitat boundaries are fairly obvious based on vegetation (e.g. suitable grassland). With metapopulations map the main breeding sites separately within the overall occurrence. Consult the habitat and food comments fields for species-specific information on what constitutes suitable habitat when mapping occurrences for individual species. Note many, if not most, habitat specialists feed one more than one grass genus at many or all occurrences. Note some species readily and some almost never entere wooded areas, so check habitat fields for the species before mapping.
Separation Distance for Unsuitable Habitat: 4 km
Separation Distance for Suitable Habitat: 10 km
Alternate Separation Procedure: When multiple occupied habitats occur within a large community complex or remnants of one such as patchily within a barren, savanna, or prairie remnant use the suitable habitat distance. When occurrences in a region are all small (under 10 hectares) and are widely scattered and there is some actual evidence of persistent patch vacancy, a separation distance of one kilometer may be used instead of two.
Separation Justification: These are mostly potentially strong fliers and the weaker ones like least skipper are often still very good colonizers probably because they fly persistently. Few species fly slower than 20 km per hour but they do not often seem to sustain flight for very long. A few are migratory and move hundreds of kilometers. Even some of the rarest taxa such as ATRYTONE AROGOS AROGOS and HESPERIA ATTALUS SLOSSONAE (both of which have individual Specs) are documented as moving several kilometers and implied to move much farther. HESPERIA LEONARDUS still shows up as singles in gardens and on roadsides ten kilometers or more from at least one of its three remaining large occurrences in New Jersey. Skippers do find and occupy small habitat patches up to a few kilometers from major ones, but are very often absent from small or recently created habitats five kilometers or more from good habitats or even over shorter distances separated by highly unsuitable habitats. Schweitzer notes adults of several species readily fly over forests which obviously would allow them to move between habitats. Most of them will move at least a few hundred meters to find nectar. While exceptions do occur, in general hesperiine skipper colonies occupy nearly all or none of a given suitable habitat or habitat complex. However very often mere presence of the larval foodplant does not mean suitable habitat.


Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 1 km
Inferred Minimum Extent Justification: In most cases the inferred extent is simply all contiguous or nearly contiguous habitat and usually this will be a few to a few hundred hectares which for almost all species is likely to be fully occupied even if at uneven densities. Use this distance only where the habitat is that extensive, but generally if the taxon is present any habitat patches within a kilometer will be occupied unless the species is excluded for example by extremely high fire frequencies or complete burns or lack of nectar. This figure is based in part on observations for ATRYTONE AROGOS AROGOS in New Jersey where it occurs in clusters of patches up to about a kilometer apart with within cluster patch occupancy nearly 100%, except approaching zero where fire intervals are about two years or less. This is one of the most imperiled skippers in North America and it is highly likely most other taxa are at least as effective colonizers. Another consideration in inferring any extent is that often the exact habitat is not clear and since it cannot be defined on the basis of any particular grass species there may be some doubt. One should not infer across any large distance based on one observation but if the habitat extends that far, a kilometer seems safe and most species can cover that distance in a few tens of seconds.
Date: 14Sep2001
Author: Schweitzer, Dale F.
Notes: Thes Specs are applied with reservation to AMBLYSCIRTES species.
Population/Occurrence Viability
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Excellent Viability: EOs that seem likely to contain over 2000 adults most years and at least 500 in very bad years in at least five demes in different burn units each occupying 100 acres with at least 1000 acres of total prairie and with at least three demes producing 500 adults most years; or if the adults are widespread more or less throughout a prairie system the total habitat is at least 1500 acres with at least five burn units such that at least 1000 acres remains unburned in all years and the interval between fires is no less than five years for each unit. Generally one should be able to see at least 100 adults per hour. If the habitat is managed without fire there could be as few as three demes meeting the above criteria and/or 500 acres of habitat but still should be at least 2000 adults most years.
Good Viability: Habitats where at least 1000 adults are apparently present most years and rarely less than 200 per year on at least 500 acres. There are either at least three demes each producing over 300 adults most years and each occupying 100 acres or the population is spread out over not less than three burn units such that there will always be 500 acres unburned in any year. The interval between fires must be no less than four years. For managed EOs not maintained by fire there could be as little as 300 acres but still must be 1000 adults most years. Generally one should be able to observe 100 adults per hour but a BRANK should not be based on this observation alone.
Fair Viability: Seemingly viable sites not meeting the BSPECS. In general a CRANK EO should produce at least 100 adults most years and not less than 20 in very bad years and will usually contain at least 20 acres of available habitat all years. If fire is used there should be two or more burn units. All sites of less than 300 acres total available habitat or that usually produce under 1000 adults per year or occasionally drop below 100 adults should rank no higher than C. All sites where fire return interval is three years or less per unit are C or D rank unless it can be shown that population on each unit FULLY recovers between fires--this may be possible if fires are light or habitat is moist. In general sites where the species has persisted without obvious decline for at least 20 years can be presumed to be at least CRANK. Eastern fen populations apparently are small, persistent and isolated so probably mostly should be ranked C. It is anticipated that the CRANK will cover a substantial spread of more or less average EOs.
Poor Viability: EOs that are not likely to persist, e.g. due to factors such as excessive burning, small population size coupled with normal fluctuations or other factors. Generally factors such as normal population size of less than 100 adults per year or less than 20 in very bad years or less that 20 acres of available habitat some years are suggestive of DRANK. Beware though that census counts underestimate true brood size. Larger EOs might merit DRANK if too frequently burned and/or most of the population is in one burn unit (e.g. perhaps Scuppernong prairie, WI) such that prescribed burning puts the population at risk of estirpation either from one catastrophic burn or through gradual reduction.
Justification: The A and B SPECs should separate really outstanding EOs and the D criteria attempt to separate out non-viable EOs. It is possible populations at the low end of the C criteria may prove non-viable also. Also implicit in the A and B criteria is the possibility of recovery were a wild fire or other catastrophic event to wipe out 90% of the population. The A criterion might even allow recovery without a genetic bottleneck effect if the even happened in an otherwise good year. One could make a good case that A should not be applied at all since this really would not approach an all time best occurrence.
Key for Ranking Species Element Occurrences Using the Generic Approach (2008).
Date: 15Feb2007
Author: Schweitzer, D.F., Opler, P.A.
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 07Feb2013
NatureServe Conservation Status Factors Author: Schweitzer, D.F.
Management Information Edition Date: 07Feb2013
Management Information Edition Author: Schweitzwer, D.F.
Element Ecology & Life History Edition Date: 14Jun2007
Element Ecology & Life History Author(s): SCHWEITZER, D.F.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Borkin, S. S. 1995. 1994 Ecological studies of the Poweshiek Skipper (Oarisma poweshiek) in Wisconsin. Report to Bureau of Endangered Resources, Wisconsin Department of Natural Resources, Madison, Wisconsin. 13 pp. + ii.

  • Borkin, S. S. 1996. Ecological studies of the Poweshiek Skipper (Oarisma poweshiek) in Wisconsin-1995 season summary. Report to Bureau of Endangered Resources, Wisconsin Department of Natural Resources, Madison, Wisconsin. 5 pp. + Appendix and Table.

  • Borkin, Susan S. 1994 Ecological studies of the poweshiek skipper (Oarisma poweshiek) in Wisconsin. Report to WI Bureau of Endangered Resources, Madison, WI. 13pp.

  • Bouseman, J. K., J. G. Sternburg, and J. R. Wiker.  2006.  Field guide to the skipper butterflies of Illinois.  Illinois Natural History Survey Manual 11.  Champaign.  viii = 200 pp.

  • Committee on the Status of Endangered Wildlife in Canada (COSEWIC) 2014. COSEWIC assessment results. November 2014. Online: http://www.cosewic.gc.ca

  • Dana, R. P. 1991. Conservation management of the prairie skippers Hesperia dacotae and Hesperia ottoe: basic biology and threat of mortality during prescribed burning in spring. Station Bulletin 594-1991. Minnesota Agricultural Experimant Station, University of Minnesota, St. Paul, Minnesota. 63 pp.

  • Ferris, C. D., editor. 1989. Supplement to: a catalogue/checklist of the butterflies of America north of Mexico. The Lepidopterists' Society Memoir No. 3. 103 pp.

  • Gall, L. F. 1985. Measuring the Size of Lepidopteran Populations. Journal of Research on the Lepidoptera. 24(2):97-116.

  • General Status, Environment Canada. 2015. Manitoba butterfly species list and subnational ranks proposed by Environment Canada contractor.

  • Huber, R. L. 1981. An updated checklist of Minnesota butterflies. Minnesota Entomological Association Newsletter 14(3):15-25.

  • Klassen,P.,Westwood, A.R., Preston. W.B. and W.B. McKillop. 1989. The butterflies of Manitoba. Manitoba Museum of Man and Nature. Winnipeg. 290 pp.

  • Layberry, R. A., P. W. Hall, and J. D. LaFontaine. 1998. The butterflies of Canada. University of Toronto Press, Toronto, Ontario. 280 pp. + color plates.

  • Marrone, G. M. 2002. Field guide to butterflies of South Dakota. South Dakota Department of Game, Fish, and Parks, Pierre, South Dakota. 478 pp.

  • McCabe, T. L. and R.L.Post, 1977. Skippers (HSEPEROIDEA) of North Dakota. Dept. of Entomology, Agric. Expt. Station, North Dakota State University, publ. 714

  • Nielsen, M. C. 1999. Michigan butterflies and skippers: a field guide and reference. Michigan State University Extension, East Lansing, Michigan. 248 pp.

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