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Yucca Moth (Tegeticula yuccasella)


Habitat requirements

In Alberta, Yucca Moths are restricted to the Dry Mixed Grass Subregion (ANHIC 2001).  This semi-arid subregion has a continental climate with extremes of weather and large daily and seasonal variations in temperature characterized by low precipitation, hot summers and a high rate of evaporation.  The rate of evaporation is exacerbated by a high average wind speed, often approaching 100 km/hr.

At the northern edge of its range in Alberta and Montana, the Yucca Moth uses only Soapweed for oviposition and for larval feeding.  There is no other Yucca sp. naturally occurring within Canada that could act as a host plant for the Yucca Moth.  This plant grows in sparsely distributed populations on well-drained, mostly south-facing coulee slopes.  Typically, these slopes are eroded, dry and sparsely vegetated with prickly pear cactus (Opuntia polyacantha) and sagebrush (Artemisia cana).  The aspects of slopes supporting Soapweed in Alberta range from 34º (northeast) to 200º (south-southwest), and generally face away from prevailing southwest winds, except in cases where slopes are protected by adjacent slopes.  Soils tend to be alkaline and regosolic without shallow hardpan (Milner 1977, Fairbarns 1984).  In areas further south (northern Wyoming), Soapweed grows on flatter ground and occurs in sand dunes, pine forests and glades in the east and grassland in the southwest, and ranges in altitude from 0 to 1920 m (Pellmyr 1999).


Appropriate habitat for Yucca Moths is naturally limited at the northern edge of  the species' range in Alberta.  Although there are numerous south-facing coulee slopes throughout the southeastern part of Alberta, many of these locations are grass-covered rather than eroded and are not inhabited by either the Soapweed or the Yucca Moth.  Available habitat has not been reduced by agricultural practices (other than the negligible effects of cattle grazing) because Soapweed grows on steep coulee slopes that are unusable for crop production.


Although the Soapweed is designated as Threatened by COSEWIC and the Yucca Moth is recommended to be listed as Endangered by the provincial government in Alberta, neither the Yucca Moth nor the Soapweed has any formal protection.  Preliminary planning for a recovery team and plan for both species is underway.  Fortunately, both populations occur in relatively isolated, undisturbed sites.  The largest population of the Yucca Moth occurs on the Lost River, near Onefour, AB on land owned and managed by Agri-food and Agriculture Canada.  The smaller, declining population, is located on a public grazing reserve managed by the province of Alberta.