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COSEWIC Assessment and Status Report on the Aweme Borer in Canada

Habitat

Habitat Requirements

Until the 2005 specimen was caught, no one alive today had seen a living Aweme Borer and the precise locations and habitats where the specimens were collected were not known. The locality “Aweme” on the label of specimens collected by Norman Criddle included an area to at least 10 km distance from Aweme, which was the name of the Criddle homestead, and includes much of CFB Shilo and adjacent Spruce Woods Provincial Park (Roughley, 2000). The only historic specimen for which reasonably precise information is available is the one collected at Beaver Island, Michigan, which was apparently collected at the lights of a boat anchored offshore (K. Stead, personal communication, November 2004).

The most likely habitat of the Aweme Borer was thought to be associated with sand dunes. The Aweme Borer was almost certainly associated with Great Lakes dunes and former inland lakeshores, or possibly in swales formed between these dunes (Schweitzer 1999). Four of the five collection sites are located along the shoreline of the Great Lakes; the fifth (Aweme) is located within the Brandon sandhills, which were formed by glacio-lacustrine sediments of glacial Lake Agassiz (David 1977).

Several bits of evidence support the hypothesis that Aweme Borers are resident in dune habitats. Norman Criddle collected all three of his specimens over a 3-day period (Table 1). This suggests they were not taken close to his residence at Aweme, where he collected for over 30 years, but during one of his less frequent collecting forays in the region. The pale colour of the Aweme Borer also suggests it comes from a dry sandy habitat. Beach or other sand dunes are present in the vicinity of all but the most recent collection sites. The presence of an undescribed species of Papaipema on Sable Island, Nova Scotia, not much more than a sandbar in the Atlantic Ocean, indicates that Papaipema species can occupy sandy dune habitat (E. Quinter, pers. comm., August, 2004).

Remnant dune habitats, including those at the two localities in Canada where Aweme Borers have been found historically, are known to have a number of otherwise very rarely collected species of moths, including Acronicta albafufa Grote, Pyla areaeola Balogh and Wilterding, Loxocrambus awemensis McD., a number of species of Schinia and others (Lafontaine 1996; D. Schweitzer, pers. comm., 2004).

The most recent specimen of the Aweme Borer was collected from a bur-oak prairie on Manitoulin Island, with no sand deposits in the vicinity of the collection site. Oak prairies are also present in the vicinity of most of the historic collection sites (D. Lafontaine, pers. comm.), but were not thought to be associated with the Aweme Borer. Given the recent record, it is possible that the Aweme Borer inhabits open oak habitats instead of sand prairies, or that it is restricted to dry, open sites and can live in both sand and oak prairies. It will be possible to determine the exact habitat requirements of the Aweme Borer only if and when the larvae can be found and the host plant(s) identified.

Aweme lies within the Prairie Ecological Area, and the other collection sites all lay within the Great Lakes Plains Ecological Area (COSEWIC 2003). The Aweme area is within the Aspen Parkland Ecoregion (Gauthier et al 2001); the Grand Bend and Manitoulin sites are located within the Mixedwood Plains Ecozone (Lafontaine 1996). Although widely separated by non-prairie habitat today, these two areas were linked in the past, during a post-glacial warming trend that reached its peak about 7000 years ago and resulted in the expansion of the prairies into north-eastern North America. The disjunct remnants of this ‘prairie peninsula’ persist today across the northeastern United States and southern Ontario, the areas where Aweme Borers have been collected. Collections of Lepidoptera from relict prairie in southern Ontario (e.g. Windsor Prairie and The Pinery Provincial Park) indicate that prairie species followed this post-glacial expansion eastward, and many persist there to this day in dune habitats (Lafontaine 1996) and other prairie remnants, including oak savannah prairie.


Habitat Trends

Manitoba: Native habitat in the Aweme–CFB Shilo–Spruce Woods Provincial Park area hasbeen affected by both natural and anthropogenic changes over the past century. Most native grasslands in the Aweme region have been converted to agricultural use, in particular to irrigated potato production and forage (Fig. 3). Some small areas of native fescue grassland persist in the immediate area of Aweme (Roughley 2000). Native trees, in particular trembling aspen (Populus tremuloides) and bur oak (Quercus macrocarpa), have replaced much of the original grasslands not converted to agricultural use, in particular in Spruce Woods Provincial Park. However, relatively large areas of native grassland and aspen–oak savannah remain in CFB Shilo and Spruce Woods Provincial Park (Figs. 4-5). Almost all remaining active dunes are now located in the Spirit Dunes within Spruce Woods Provincial Park (Figs. 6-7).


Figure 3: Aweme, Manitoba, type locality for Aweme Borer

Figure 3: Aweme, Manitoba, type locality for Aweme Borer. Native grasslands habitat converted to forage crop (foreground) and woodland (background). July 29, 2004.

Native grasslands habitat converted to forage crop (foreground) and woodland (background). July 29, 2004.


Figure 4: Prairie Openings in Aspen and Oak “Barrens” on Stabilized Sand Hills, Spruce Woods Provincial Park

Figure 4: Prairie openings in aspen and oak “barrens” on stabilized sand hills, Spruce Woods Provincial Park. August 26, 2004.

August 26, 2004.


Figure 5: Moth Trap in Patch of Liatris sp., a Potential Host Plant for the Aweme Borer, Growing in Grassland Opening on Vegetated Sand Hills, Spruce Woods Provincial Park

Figure 5: Moth trap in patch of Liatris sp., a potential host plant for the Aweme Borer, growing in grassland opening on vegetated sand hills, Spruce Woods Provincial Park. August 26, 2004.

August 26, 2004.

Military activity in CFB Shilo has apparently caused numerous fires on CFB Shilo lands, which have in turn maintained much of that area in grassland. At adjacent Spruce Woods Provincial Park much of the original grassland has been, and continues to be, replaced by aspen-oak woodland (Portman 2004). The active dunes of the Spirit Dunes at Spruce Woods Provincial Park have become progressively more stabilized by vegetation since the 1920s (Fig. 6). Aerial photographs taken in 1928 show active dunes covering an area of approximately 45 ha; this declined steadily to 15-25 ha in the 1960s, but has remained relatively stable since that time (Geological Survey of Canada 2001).


Figure 6: Early Stages of Dune Stabilization by Native and Introduced Vegetation, Spirit Dunes, Spruce Woods Provincial Park

Figure 6: Early stages of dune stabilization by native and introduced vegetation, Spirit Dunes, Spruce Woods Provincial Park. August 26, 2004.

August 26, 2004.


Figure 7: Active Dunes, Spirit Dunes, Spruce Woods Provincial Park

Figure 7: Active dunes, Spirit Dunes, Spruce Woods Provincial Park. August 4, 2004.

August 4, 2004.

Ontario: The Grand Bend area, including The Pinery Provincial Park, is located on sandy soils and historically had a significant oak-savannah component. Soon after The Pinery Provincial Park was established in 1957, over 3 000 000 pines were planted (Invista 2004). Since that time, prescribed burns and pine cutting programs have largely restored the habitat to oak savannah. All habitats in the park had previously been “seriously degraded to obliterated by grossly out of control deer” (Schweitzer 1999). However, the deer population is now being managed with periodic culls, and savannah vegetation is being managed through prescribed burns. Habitat on adjacent First Nations land is reported to be in more natural condition than habitat within The Pinery Provincial Park, which has been negatively affected by cottage and recreation developments (Ken Stead, pers. comm., November 2004).

The Manitoulin Island site is a large, low-relief limestone island. The site where the collection was made is a small, remnant piece of oak savannah or prairie. Bur-oak prairies were once fairly extensive on Manitoulin Island, but much of this habitat was converted to agriculture or development. Numerous patches of remnant oak prairies still exist on the island, but many are being gradually lost to succession to forest (D. Lafontaine, pers comm.).


Habitat Protection/Ownership

Aweme is the name of the original Criddle homestead, consisting of two quarter-sections of land. It is now under provincial jurisdiction as Criddle-Vane Provincial Park. Much of the area to the east falls within CFB Shilo and is under federal government jurisdiction. The bulk of the active dunes and a large block of stabilized sand hills, wetlands, oak-aspen woodland and native grassland is under provincial jurisdiction in Spruce Woods Provincial Park. Lands in both areas are largely protected from conversion to most agricultural uses, and large scale alterations of habitat in designated parks are usually subject to more public scrutiny than are lands in private ownership.

In Ontario, the habitat consists of a mix of private, provincial and First Nations (Ipperwash) land. The Pinery Provincial Park is under provincial jurisdiction. Oak savannah on Manitoulin is largely on private property, although the Nature Conservancy also controls a parcel (J. Jones, pers. comm.). The land where the recent specimen was caught is privately owned (J. Morton, via D. Lafontaine, pers. comm.).