Greater short-horned lizard COSEWIC assessment and status report: chapter 2

Executive Summary

Greater Short-horned Lizard
Phrynosoma Hernandesi

Species information

The Greater Short-horned Lizard (Phrynosoma hernandesi) is the only species of lizard found in Alberta and Saskatchewan. It is the most widespread and generalist of all horned lizard species. Horned lizards (Genus Phrynosoma) are small (generally <100 mm) lizards most readily recognized by the protective row of spiked “horns” protruding along the posterior rim of the head. Their blotched dorsal coloration and ability to remain motionless provide excellent camouflage to protect them from predators and to ambush their prey.

Distribution

All horned lizards are endemic to western North America. Greater Short-horned Lizards are the most widespread of horned lizard species, ranging from Mexico to southern Alberta and Saskatchewan. In Saskatchewan they are apparently limited to two small areas within Grasslands National Park. In Alberta, the species is more widespread, with known locations along four main watercourses within the southeastern corner of the province. These populations are isolated and scattered, from along the South Saskatchewan River at their northernmost, south to the US border.

Habitat

In Canada, Greater Short-horned Lizards prefer sparsely vegetated, south facing slopes with friable soils. They prefer loose soils in which to bury themselves for overnight and over-winter protection. In Canada, the habitats they are associated with are often secluded, with generally low levels of human presence, and their populations have been relatively undisturbed, with some exceptions.

Biology

Most species of horned lizards feed primarily on ants, but Greater Short-horned Lizards are more generalized in their preferences and will consume crickets, beetles, spiders, and other arthropods. In Canadian populations, mature females give birth to live young annually in late July or early August. Litter sizes vary widely, but exceed 10 offspring. The survival rate of neonates is low. Adult males are smaller than females. Females tend to establish a series of small territories within a larger home range over the summer active period, and move relatively short distances in total. Males may roam more widely. Activity has been recorded between April and November in Alberta populations.

Population sizes and trends

Population sizes in Alberta as of 2003 appeared to be declining. There are four main population sites in Alberta and two in Saskatchewan. An extremely tentative and imprecise population estimate of between 2677 and 16379 mature individuals was put forward for Alberta. The populations in Saskatchewan are apparently less dense than those in Alberta, and are confined to a much smaller area. Population level information from Saskatchewan is unavailable.

Limiting factors and threats

The distribution of Short-horned Lizards in Canada is primarily dictated by climate. Threats to the persistence of current populations include industrial development, irrigation and intensive agriculture, oil and gas exploration, and associated linear features (pipelines, roads, seismic lines), proposed surface mining for humate and ammonite, and urbanization. Many of these threats are most intense in the Manyberries Sensitive Area, which may hold one-third of the Alberta population. Anthropogenic threats likely affect Alberta populations more than Saskatchewan populations.

Special significance of the species

The Greater Short-horned Lizard is the only lizard species that inhabits Alberta and Saskatchewan. These populations are the most northerly of the entire horned lizard genus, which is endemic to North America, and are adapted to the extreme climate of the Canadian prairies.

Existing protection

The Greater Short-horned Lizard has recently been designated as “Endangered” in Alberta. The provincial rank of S2 in Alberta is defined as “6-20 or fewer occurrences or with many individuals in fewer locations”. In Saskatchewan, they are listed as “Vulnerable (proposed)”. A rank of S2S3 has been assigned in Saskatchewan, where the species straddles the criteria defining two separate ranks (S2; S3). S2 is defined in Saskatchewan as “6-20 occurrences or few remaining individuals” whereas S3 is defined as a species that has “21-100 occurrences; …may occur in a restricted provincial range”. In Montana the Greater Short-horned Lizard is listed as a “Species of Concern” by state agencies with a state rank of S3 defined as “potentially at risk because of limited and potentially declining numbers, extent and/or habitat, even though it may be abundant in some areas”.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

Definitions

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)
A wildlife species that no longer exists.

Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A wildlife species facing imminent extirpation or extinction.

Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)Footnoteb
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)Footnotec
A category that applies when the available information is insufficient (a) to resolve a species' eligibility for assessment or (b) to permit an assessment of the species' risk of extinction.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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