Recovery Strategy for the Dakota Skipper (Hesperia dacotae) in Canada
- 2.1 Recovery Feasibility
- 2.2 Recovery Goal
- 2.3 Population and Distribution Objective (2007–2012)
- 2.4 Recovery Objectives (2007–2012)
- 2.5 Approaches Recommended to Meet Recovery Objectives
- 2.6 Critical Habitat
- 2.7 Effects on Other Species
- 2.8 Recommended Approach for Recovery Implementation
- 2.9 Performance Measures
- 2.10 Statement on action plans
2.1 Recovery Feasibility
Recovery of the Dakota skipper is considered biologically and technically feasible based on four criteria (Environment Canada 2005).
First, there are currently three populations (22 sites) of the Dakota skipper in Canada, which contain an estimated 28 500–40 500 individuals. The Dakota skipper has demonstrated the ability to persist at these locations, showing that they are capable of reproduction, although it is unknown if these populations are at or below carrying capacity.
Second, there appears to be sufficient habitat to maintain the Dakota skipper at its current population level, at least in the short-term. Additional suitable habitat will, however, be necessary to recover the Dakota skipper in Canada. Although the Dakota skipper has specific habitat requirements for intact native prairie, it may be possible to attain and enhance suitable habitat, either adjacent to known populations or at extirpated sites, such as the Tall Grass Prairie Preserve.
Third, the main threats to the Dakota skipper, including habitat loss and degradation, can be mitigated through recovery actions. Because almost all current populations are located on private land, it will require the cooperation of landowners to ensure that these populations persist. The Dakota skipper is typically found on lands with late-season haying, thus, maintaining this land use is the first step to conserving the habitat for the Dakota skipper.
Fourth, the main recovery technique will be the use of stewardship agreements to conserve Dakota skipper habitat. Stewardship agreements have been used for a number of other conservation projects and have been successful in securing habitat for species at risk. Some habitat modification may be required at certain sites.
2.2 Recovery Goal
The overall recovery goal is to achieve a self-sustaining metapopulation of Dakota skippers in secure habitat distributed throughout their historical range in Manitoba and Saskatchewan.
Suitable information to quantify long-term population and habitat targets is not available. Addressing knowledge gaps identified in the recovery strategy will help refine the recovery goal for this species.
2.3 Population and Distribution Objective (2007–2012)
The short-term population and distribution objective is:
2.4 Recovery Objectives (2007–2012)
- Establish reliable population estimates for all Dakota skipper populations and assess viability under current conditions.
- Identify, secure, and enhance significant habitat for the Dakota skipper.
- Increase knowledge of the Dakota skipper in Canada, including distribution, abundance, biology, and management practices.
2.5 Approaches Recommended to Meet Recovery Objectives
2.5.1 Recovery planning
|Priority||Threats addressed||Broad strategy to address threats||Recommended approaches to meet recovery objectives|
|Objective 1. Establish reliable population estimates for all Dakota skipper populations and assess viability under current conditions.|
|High||All||Inventory and monitoring|
|Objective 2. Identify, secure, and enhance significant habitat for the Dakota skipper.|
|High||Habitat loss, habitat degradation||Habitat inventory, habitat modelling|
|High||Habitat loss, habitat degradation||Stewardship, habitat management|
|Medium||Habitat degradation||Habitat restoration, stewardship|
|Objective 3. Increase knowledge of the Dakota skipper in Canada, including distribution, abundance, biology, and management practices.|
2.5.2 Broad strategies to implement recovery and address threats
Almost all extant populations of Dakota skippers in Canada are found on private land; thus, habitat protection for this species will require a stewardship approach that engages the voluntary cooperation of landowners and managers. This may include implementing stewardship agreements, conservation easements, or land covenants and following best management practices. Once habitats are identified and prioritized, best management guidelines will be developed to address all potential threats to the habitat. These may include guidelines on timing of haying, use of burning, domestic grazing, and pesticide use (see habitat management section below). In many instances, landowners are already using good management practices compatible with the Dakota skipper; otherwise, the species would not be present on their land.
A metapopulation approach to habitat conservation, where occupied habitat as well as unoccupied habitat that could be used by dispersing skippers is conserved, should be used. For example, some studies have suggested that managing roadsides for native vegetation can benefit butterfly communities by allowing them to disperse between suitable habitats (e.g., Ries et al. 2001). Priority habitats for securement will be those currently occupied by the Dakota skipper and those adjacent to existing populations. Areas that historically supported the Dakota skipper could also be conserved for potential reintroductions, once the reason for their extirpation has been determined and addressed.
Inventory and monitoring
Additional survey effort is required to estimate population sizes and trends and area of occupancy of the Dakota skipper in Canada. There is an incomplete inventory of potential habitat, especially in southeastern Saskatchewan, southwestern Manitoba, and the Interlake region of Manitoba. In the Interlake region, most areas surveyed were adjacent to major roads and highways; additional populations likely exist away from these roads (COSEWIC 2003). Suitable Dakota skipper habitat was also found near Baldur in southwestern Manitoba, although no Dakota skippers were present; the presence of this prairie habitat suggests that additional sites may exist (COSEWIC 2003).
Reliable population estimates need to be determined for the Dakota skipper at all known sites. In addition, there is a need to collect complete demographic data, including information on survival, fecundity, immigration/emigration, residence time in patch, dispersal distances, and density dependence. A monitoring scheme should be developed with the help of a population biologist to ensure complete data collection. Collaboration with researchers in the United States would be beneficial.
Population viability analysis could be used to assess persistence under current conditions, and the addition of complete demographic as well as landscape and dispersal data could be used in a spatially explicit population viability analysis to assess the number, size, and location of habitat patches that are required to support a self-sustaining population of Dakota skipper well into the future. These analyses will allow further refinement of the recovery goal.
Habitat management / habitat restoration
Best management practices will need to be developed for each Dakota skipper site. Some conservation guidelines have been developed for the Dakota skipper and are summarized in Cochrane and Delphey (2002) and USFWS (2005). These guidelines are briefly discussed below and should generally be followed until new information suggests otherwise. Management practices should be monitored and evaluated as to their effects on the Dakota skipper.
Habitat loss: To reduce the threat of habitat loss, stewardship agreements, including the possible use of easements, should be put in place where possible to prevent conversion of prairie for agriculture. Stewardship agreements adjacent to or near occupied Dakota skipper habitat are also beneficial for providing dispersal corridors or potentially buffering occupied sites from external threats such as pesticide drift.
Haying: Haying may be the best method for maintaining Dakota skipper populations. Haying in late fall (September–October) should be encouraged. Late-season haying occurs after the skipper's flight season is finished, the eggs have hatched, and the larvae have moved to shelters close to the ground. This timing also ensures that plants have senesced and set seed. If possible, deferred haying in alternate years or rotational haying to leave some portions unmowed each year is advisable. To provide habitat for overwintering larvae, at least 20 cm of stubble should be left. In mesic tall-grass prairies, midsummer haying may benefit the Dakota skipper, because it removes the bulk and height of warm-season grasses that can suppress forb flowering (Dana 1991; Swengel 1998b).
Grazing: The intensity and duration of grazing should be limited on sites with the Dakota skipper. In general, dry-mesic prairies should not be grazed, whereas wet-mesic prairies could be lightly grazed in spring, to avoid removing floral nectar sources and to maintain vegetation for egg deposition and larval food.
Prescribed fire: Burning is not recommended on sites with the Dakota skipper. Alternative methods such as haying, grazing, and brush cutting should be considered. If burning is deemed necessary, then it should be done sparingly (Moffat and McPhillips 1993). The habitat should be divided into as many burn units as feasible; within each unit, fires should be burned in a patchy pattern. Prescribed fires should not be used if the smallest feasible burn unit would burn most of the habitat or the entire habitat in 1 year. The maximum length of fire return interval should be used, allowing at least 3–4 years before reburning, and adjacent units should not be burned in consecutive years. Spring burns should be conducted as early as possible to limit larval mortality (before they emerge from their buried shelters). Late-spring and fall burns should be avoided. Late-spring burns may delay flowering and emergence of nectar sources, whereas fall burns typically have higher soil temperatures, which result in greater larval mortality (Dana 1983). As well, fall burns may result in greater fluctuations in winter temperature, affecting larval overwinter survival (Cochrane and Delphey 2002). Prior to a spring burn, fuel levels could be reduced by haying in the fall. Fires should be directed away from the previous season's main oviposition sites if they are known (McCabe 1981).
Habitat fragmentation: Habitat should be managed to maximize genetically effective population sizes by conserving large patches and maintaining potential connections between sites/locations. Roadsides managed for native vegetation may benefit butterfly communities by allowing individuals to disperse (Ries et al. 2001). When it is not possible or feasible to connect isolated populations, management plans will need to be developed to ensure the persistence of these populations in the absence of immigration of new individuals.
Control of weeds and invasive species: Broadcast applications of pesticides or herbicides should be avoided, and sites should be managed to minimize the likelihood of invasion by exotic species. Biological control, spot herbicide application, and spot brushing could be used to control weeds or invasive species.
There are a number of gaps in knowledge on the life history of the Dakota skipper. Some key areas for future research include estimating survival rates (adults and larvae), fecundity rates, dispersal distances, and the average time that adults spend in patch, assessing the isolation of populations, estimating the exchange of individuals among locations, important habitat characteristics (see section 2.6.2 below), determining which environmental factors influence survival, and potential effects of various land uses. Whenever possible, Canadian researchers should collaborate with researchers in the United States.
Population reintroductions may be considered in historical locations with suitable habitat; however, reintroductions should be considered only secondarily after maintaining existing habitat and maintaining or restoring connectivity between habitat patches (Thomas 1995).
A communication plan should be developed to increase landowner and public awareness of this species. Such an outreach program could be developed with other lepidopterans in mind as well, to use resources more effectively.
2.6 Critical Habitat
2.6.1 Identification of the species' critical habitat
Critical habitat has not been identified for the Dakota skipper in this recovery strategy, but will be identified in an Action Plan by the end of December 2010.
Although there is some knowledge regarding Dakota skipper habitat needs, more work is necessary before critical habitat can be reasonably identified. Most of the information regarding the Dakota skipper biology and habitat use has been taken from work done in the United States. Critical habitat cannot be identified at this time due to incomplete inventory of potential habitat for the Dakota skipper, and a lack of knowledge on the specific habitat requirements of the Dakota skipper. In addition, more research is required on the effects of different management practices in maintaining the Dakota skipper and its habitat.
It is expected that critical habitat will be identified within the recovery action plan following: 1) quantification of specific habitat and area requirements, 2) surveys of potential habitat, and 3) consultation and development of effective stewardship options with potentially affected landowners.
2.6.2 Schedule of studies to identify critical habitat
|Description of activity||Outcome/rationale||Timeline|
|Inventory and monitor occupied habitat.||Identification of species distribution, population size, and persistence. Identification of site-specific habitat threats, movement barriers, and land ownership.||2007–2010|
|Conduct research to quantify habitat requirements and use.||Identification of habitat requirements for adults, larvae, and host plants. Identification of optimal patch size, and clarification of dispersal capabilities.||2007–2010|
|Survey similar unoccupied habitat and assess the feasibility of re-establishing populations.||Identification of potential suitable habitat and requirements for reintroduction.||2007–2011|
|Develop a population viability model.||Identification of options for establishing a network of managed sites to support a viable population over the long term.||2007–2012|
2.7 Effects on Other Species
The Dakota skipper is an obligate resident of the tall- and mixed-grass native prairie; as such, the conservation of this species will in turn maintain some remaining remnants of this endangered ecosystem. A number of other lepidopteran species are found in association with the Dakota skipper. A few of these lepidopterans are of conservation concern, including the Ottoe skipper and the Poweshiek skipperling. The Ottoe skipper and the Poweshiek skipperling are listed as Endangered and Threatened, respectively, in Canada under the Species at Risk Act.
Plant species that could benefit from Dakota skipper conservation include the western prairie fringed-orchid (Platanthera praeclara) and the small white lady's-slipper (Cypripedium candidum), both endangered plant species found in tall-grass prairie habitat. These plant species occur in the Tall Grass Prairie Preserve, an area formerly inhabited by the Dakota skipper.
The preferred habitat management strategy for the Dakota skipper is late-season mowing, which will maintain the plant community. This provides the best cover for ground-nesting birds and is beneficial for prairie orchids (McCabe 1981), such as the small white lady's-slipper.
2.8 Recommended Approach for Recovery Implementation
The recovery of the Dakota skipper will likely be a combination of single-species and multispecies approaches to consider the needs of other species, especially small white lady's-slipper and western prairie fringed-orchid where they occur together.
2.9 Performance Measures
The recovery strategy will be evaluated in 5 years, based on new information obtained during the intervening period. Table 3 provides performance measures for each recovery objective.
|Recovery Objective||Performance Measures|
|1. Establish reliable population estimates for all Dakota skipper populations and assess viability under current conditions.|
|2. Identify, secure, and enhance significant habitat for the Dakota skipper.|
|3. Increase knowledge of the Dakota skipper in Canada, including distribution, abundance, biology, and management practices.|
2.10 Statement on action plans
An Action Plan for the Dakota skipper will be completed by the end of December 2010.
4 Estimated to be approximately 12 000–35 000 adults in the Interlake area, 1700–5000 in Griswold, and >250 in southeastern Saskatchewan.
5 The three current population centres are the Interlake area, Manitoba, Griswold, Manitoba, and southeastern Saskatchewan.
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