Greater Short-horned Lizard - Phrynosoma hernandesi
The body of the Greater Short-horned Lizard is broad and flattened. The back is spiny, with an especially noticeable single row of scales fringing each side of the body. The spines at the back of the head are about as long as they are wide at the base. The coloration of the back usually blends cryptically with the soil and can vary somewhat from region to region and at single localities. The maximum total length is about 15 centimeters. In males, there is a swelling at the base of the tail, and the tail is proportionally longer than in females. Newborn young have the broad and flattened body shape, and are about 2.0 to 2.5 centimeters snout-vent length and up to 3.8 centimeters by the time of first hibernation.
The broad, flattened body separates this lizard from the other three lizard species regularly documented in Montana, and the range overlaps only with the Common Sagebrush Lizard. The Pygmy Short-horned Lizard has been reported from extreme southwestern Montana, in the Centennial Valley, Beaverhead County (Maxell et al. 2003), but adults of this species are much smaller than Greater Short-horned Lizards, the small horns on the back of the head project almost vertically rather than horizontally, and they lack the wide notch between the horns on the back of the head that gives the head of Greater Short-horned Lizards a "heart-shaped" appearance when viewed from above (St. John 2002).
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Records associated with a range of dates are excluded from time charts)
No information currently exists regarding the migration patterns of Greater Short-horned Lizards in Montana.
Habitat use in Montana is poorly described, but appears to be similar to other regions. Reports mention individuals on ridge crests between coulees, and in sparse, short grass and sagebrush with sun-baked soil (Mosimann and Rabb 1952, Dood 1980). On the southern exposures of the Pryor Mountains, Carbon County, individuals occur among limestone outcrops in canyon bottoms of sandy soil with an open canopy of limber pine-Utah juniper, and are also present on flats of relatively pebbly or stony soil with sparse grass and sagebrush cover (Paul Hendricks, personal observation).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at email@example.com
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
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- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Open Water / Wetland and Riparian Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
This species is an invertivore. The diet of Greater Short-horned Lizards includes mostly ants and beetles, as well as other insects, spiders, snails, sowbugs, and other invertebrates. Individuals may sometimes gorge themselves on a single type of prey (Hammerson 1999). The diet in Montana is virtually undescribed; stomach contents of three individuals from coulees near the Marias River in Toole County included mostly ants with a few beetles, grasshoppers, and spiders (Mosimann and Rabb 1952).
Adult Greater Short-horned Lizards are diurnal and active during the warmer daylight hours. Specific information for Montana is limited, but information from other areas within their range indicates they may appear as early as late March (Hammerson 1999), with most surface activity in the northern parts of the range occuring from mid-April to mid-September. Extreme records in Alberta extend from April 1 to November 10 (Powell and Russell 1998), but most have disappeared by the mean date of the first fall frost. Young-of-the-year are generally not active during mid-day hours, and small lizards appear more dependent on air temperatures than on substrate temperatures, while large ones are more dependent on substrate temperature. Predators of this species are mostly unknown, but Striped Whipsnake (Masticophis taeniatus) and Burrowing Owls (Speotyto cunicularia) have been reported (Hammerson 1999), and birds have been identified as the primary predatory group (Russell and Bauer 1993). The annual period of activity in Montana is poorly defined, and no predators have been reported.
No studies of the life history and reproduction of this species have been conducted in the state. In extreme southern Montana, young about 3.0 to 3.5 centimeters snout-vent length have been observed in early August and early September (Hendricks 1999).
Based upon information gathered from other areas within the species' range, adult Greater Short-horned Lizards mate shortly after emerging from hibernation in late March to early June, depending on location, and young are born about two or three months after eggs are fertilized. The Greater Short-horned Lizard is viviparous, giving live birth to 5 to 36 young (3 to 15 in the Pacific Northwest) during July to September (Nussbaum et al. 1983, Stebbins 2003). The size of 8 litters from Alberta, born in late July to early August, ranged from 6 to 13 young (Laird and Leech 1980, Powell and Russell 1998) and 5 litters in Colorado ranged from 14 to 18 young (Hammerson 1999). A litter of 13 young was born in southern Wyoming in early August (2.3 to 2.4 centimeters snout-vent length at birth) and consisted of two color morphs (Ashton and Ashton 1998); 4 young were stillborn. Sexual maturity is reached in at least two years (Nussbaum et al. 1983, Hammerson 1999).
Threats to this species in Montana are speculative, due to lack of study and poor survey coverage. The Greater Short-horned Lizard was considered the most abundant reptile along the Missouri River in Montana in the late 19th Century (Cope 1879), second only to the Western Rattlesnake, but it is no longer thought common anywhere in the state, with the possible exception of southern Carbon County (Maxell et al. 2003). The relatively few records in recent years parallel the pattern for Colorado (Hammerson 1999), but inadequate survey coverage makes conclusions regarding trends in Montana tenuous. Habitat loss due to the conversion of prairie to cropland has undoubtedly contributed to the apparent decline, but livestock grazing is probably not a serious threat to any population, judging from reports in other regions. However, clearing of sagebrush to increase grass production for livestock could have detrimental impacts on local populations of Greater Short-horned Lizards. Off-road recreational vehicle traffic and increased traffic associated with road building to oil and gas developments in eastern Montana could also have negative impacts on some populations. Indiscriminant use of insecticides to control some insect species could also affect the food supply of this lizard. No management activity for this species in Montana is currently underway, nor is any proposed at this time, but the conversion of native prairie to cropland or other use will contribute to the decline of this species in the state. Collecting of animals for export to the pet trade should be prohibited. Within the range of the Greater Short-horned Lizard in Montana where sagebrush control is planned, some sage should be left in a network of patches to insure population persistence of these lizards. Given the small home range size of the species, thinning of sagebrush or removal in small patches is probably a better management guideline than removing sagebrush entirely or in large patches.
- Literature Cited AboveLegend: View WorldCat Record View Online Publication
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- Additional ReferencesLegend: View WorldCat Record View Online Publication
Do you know of a citation we're missing?
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- Additional Sources of Information Related to "Reptiles"