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Eastern Short-horned Lizard

Limiting Factors

Eastern Short-horned LizardLizard populations in Alberta may be impacted by both natural and human-related influences such as Climate, Agricultural Activities, Oil and Gas Exploration, Urbanization and Roadways and Traffic

Climate: The first potentially limiting natural factor for Eastern Short-horned Lizards in Alberta is climate. Phrynosomes in Canada are at the northernmost limit of their range. As such, climatic constraints may play an important role in the distribution of these lizards in the province. Predation may also be a natural factor limiting the size of lizard populations in Alberta. However, losses to predation are presumed to be minimal, because the small size, low density, and cryptic habitats of these lizards would not likely make them the primary prey choice for many predators. 

Agricultural Activities:  Grazing is the most common human-initiated land use over most of the area in which lizards are found in Alberta. Cattle grazing is not likely to have much potential influence on the Short-horned Lizard populations, and is probably comparable to the impact of Bison in the past. 

Cultivation related activities are the second most common human activity over the range of Eastern Short-horned lizards in Alberta. Once again, lizards inhabit areas that are not likely subjected to cultivation, but the extent of use of such "marginal" land is dependent upon individual landowners. Cultivation close to coulee edges could eliminate habitat, but Powell and Russell concluded that, in general, agriculture was not a significant limiting factor for these lizards in Alberta. 

Another aspect of the effects of modern agriculture on lizards in Alberta is the potential impact of insecticides. These lizards consume ants, grasshoppers, crickets and beetles. Agricultural pesticides, although not commonly used on an annual basis over the region, may be used heavily in some years to control insects (primarily grasshoppers) when populations increase to destructive levels, especially in areas near croplands. The possibility exists that these chemicals may be used even in some of the more marginal agricultural areas that are inhabited by phrynosomes. The probability of direct ingestion of poisoned prey would increase greatly under such circumstances.

Oil and Gas Exploration and Development:  The oil and gas industry is active within much of the range of the Eastern Short-horned Lizard in Alberta, particularly in the Manyberries area. While the installation of pipelines may cause some disturbance for Short-horned lizards, there appears to be no great lasting influence. Exploration and development, however, may have more major impacts.

The creation of large cleared areas for the setup of drilling rigs in areas occupied by lizards reduces, or if not properly reclaimed with native grasses, destroys, part of the limited amount of available habitat. Erosion by wind and water may cause further harm to disrupted areas of habitat. The juniper dunes habitat type is particularly vulnerable to such damage, and has been subjected to a notable amount of disturbance from oil and gas exploration in the Manyberries area.

Urbanization:  Urbanization does not directly affect a large amount of Short-horned Lizard habitat in Alberta. The few populations that have been impacted are primarily those near and within the city of Medicine Hat. In this area, urbanization may affect Short-horned Lizard populations directly, through the loss or fragmentation of habitat, predation by domestic predators, and collection by inquisitive children or adults, or indirectly, by the danger of being run over by traffic of various sorts. The extent of the effect of urbanization remains unknown because of the paucity of information regarding exact locations of populations prior to growth of the city.

Roadways and Traffic:  There may be important local ramifications for Short-horned Lizard populations caused by roads or roadways or the use of motorized vehicles such as dirt bikes, all-terrain vehicles, and even truck traffic over the home range areas of the animals. Trucks and other vehicles used by ranchers and the general public within the range of these animals present a danger to the lizards, as their small size and habit of remaining motionless until approached likely reduces their response time to avoid oncoming vehicles.

The use of recreational vehicles in the coulees and river valleys that the lizards occupy is also a potential threat to some. The extensive use of dirt bikes on some hillsides causes extreme damage to vegetation and soil stability over a considerable area, and enhances the possibility of direct mortality to lizards. All-terrain vehicles, as well as truck traffic, are also commonly used in the field areas near or within Short-horned Lizard ranges, and may also present a danger to these lizards. 

Reprinted from Alberta Wildlife Status Report No. 5 (1997), with permission from Alberta Sustainable Resource Development.

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