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

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Executive Summary

Species information

The Pygmy Short-horned Lizard was recently recognized as a separate species.  It is the smallest of the horned lizards, rarely exceeding 6 cm from its snout to vent. Compared to some other ornately armored horned lizards, the Pygmy Short-horned Lizard has relatively small horns on its head and body. It is often referred to (incorrectly) as a horned toad. All 13 species of horned lizards are confined to the arid and semi-arid portions of North and Central America.

Distribution

The Pygmy Short-horned Lizard inhabits the Great Basin and surrounding areas from northern California and Nevada through eastern Oregon and Washington, most of southern and eastern Idaho and into the extreme south-central part of British Columbia, in the Okanagan and Similkameen Valleys.

Habitat

A broad variety of habitats are used from deep-soiled desert basins to shallow-soiled slopes and ridges.  Consistent features are well-drained sites with exposed ground and access to friable soils for burrowing, thermoregulating and foraging. The Okanagan and Similkameen Valleys still appear to have suitable habitat for this species, and some of this habitat is currently protected. Parts of the Pygmy Short-horned Lizard’s range are over 2000 m above sea level. 

Biology

Pygmy Short-horned Lizards give birth to up to 15 live young, unlike some other horned lizards that lay eggs.  Sexual maturity in females usually occurs in their third year.  Longevity is unknown but is at least five years in the wild.  Like all temperate-zone reptiles, Pygmy Short-horned Lizards must hibernate through the winter, which they do in shallow burrows.

The primary prey of all horned lizards is ants, especially the harvester ant. Other invertebrates, such as beetles, grasshoppers, and snails, are also eaten, most commonly by adults.  Foraging starts after the lizards have warmed in the morning sun and continues until the heat of the afternoon when they seek refuge in shade or a burrow.

Pygmy Short-horned Lizards have many potential predators, including birds, snakes, coyotes and weasels.  The first line of defence is remaining motionless, to take advantage of their cryptic colouration, texture, and posture.  If detected, the lizards can flee from slow moving predators or inflate their bodies and make intimidating gestures.  Their horn-like projections are minor deterrents, but can be effective against predators that must swallow them whole.  Some horned lizards are capable of shooting a stream of foul-tasting blood into the mouths of certain predators, but this behaviour has not been observed in Pygmy Short-horned Lizards. 

Population sizes and trends

The Pygmy Short-horned Lizard is considered to be extirpated (locally extinct) in Canada, as confirmed observations have not been made in the last 100 years.  Four survey attempts have failed to locate this lizard, although the public has reported at least 18 anecdotal observations since the first specimens were collected.  The most recent of these was in 2004.

Limiting factors and threats

Habitat loss has been extensive in the Okanagan Valley and to a lesser extent in the Similkameen Valley.  Although this habitat loss is likely a contributing factor to the species’ extirpation, it appears that Pygmy Short-horned Lizards were already rare by the early 1900s.  This rarity may have been a result of relatively recent colonization, trampling by many large herds of cattle driven through this narrow valley en route to the Cariboo goldrush, or severe population declines when extreme cold or prolonged winters with little snowfall caused mortality during hibernation.  If the species were reintroduced, current potential threats would include extensive habitat loss, road mortality, and predation by native and exotic animals.

Special significance of the species

The Pygmy Short-horned Lizard was one of Canada’s most intriguing creatures that ventured north from the deserts in the south.  It encountered the limits of its ecological tolerance in the southern interior of British Columbia.  It was one of only 7 species of lizards in Canada.

Existing protection

The Pygmy Short-horned Lizard is listed in Schedule 1 under the Species at Risk Act and listed under the BC Wildlife Act.  Both acts protect individuals and their residences from deleterious activities. In the United States, Idaho appears to be the only state where it is illegal to collect, harm, or otherwise remove this species from its natural habitat (Idaho Fish and Game 2006). 

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.

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 comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species. 

Species:

Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X):

A species that no longer exists.

Extirpated (XT):

A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E):

A species facing imminent extirpation or extinction.

Threatened (T):

A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*:

A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)**:

A species that has been evaluated and found to be not at risk.

Data Deficient (DD)***:

A species for which there is insufficient scientific information to support status designation.

*       Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
**     Formerly described as “Not In Any Category”, or “No Designation Required.”
***   Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994.

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.

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