|Scientific Name:||Cynomys ludovicianus|
|Species Authority:||(Ord, 1815)|
Cynomys ludovicianus subspecies arizonensis Mearns, 1892
Cynomys ludovicianus Mearns, 1892 subspecies arizonensis
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Linzey, A.V. & NatureServe (Reichel, J.D., Hammerson, G., Cannings, S. & Wallace, R.)|
|Reviewer/s:||Amori, G., Koprowski, J. & Roth, L. (Small Nonvolant Mammal Red List Authority)|
Listed as Least Concern because it is very widespread, there are estimated to be millions of individuals, and its populations are not declining fast enough to qualify for listing in a more threatened category. Although it has declined in many parts of its range, there are parts of its range where they are not affected by any threats at present.
|Range Description:||This is primarily a Great Plains species, originally occurring from extreme southern Saskatchewan in Canada (Frenchman River Valley), and Montana south through the western and central Great Plains to the desert grasslands of western Texas, New Mexico, southeastern Arizona (formerly) in the United States, and northeastern Sonora, and northern Chihuahua in Mexico (Koford 1958). The species is now extirpated from southeastern Arizona, southwestern New Mexico, and locally in many other areas throughout its range.|
Native:Canada; Mexico; United States
|Range Map:||Click here to open the map viewer and explore range.|
The total population size in the early 2000s was estimated at between 3,684,000 and 33,156,000; using average density figures, the estimated population was 18,420,000 (USFWS 2004).
This species is represented by a very large number of occurrences or subpopulations. Most occurrences are represented by relatively small populations, and it is unknown how many are viable in the long term, but certainly there are at least several dozen occurrences with good viability.
Currently, the species is declining in some areas, increasing in others; overall trend at present is probably stable or slightly decreasing, with a long-term outlook of slow decline (USFWS 2002). A small stable population exists in Canada (USFWS 2004). Range and abundance appear to be relatively stable in Mexico in recent decades (USFWS 2004).
Area of occupancy has been reduced from about 40 million hectares historically to about 766,400 hectares (USFWS 2004), a decline of about 98 per cent. Range contractions have occurred in the southwestern portion of the range in Arizona, western New Mexico, and western Texas through conversion of grasslands to desert shrublands; in the eastern portion of the range, range contractions are largely due to habitat destruction through cropland development in Kansas, Nebraska, Oklahoma, South Dakota, and Texas (USFWS 2004). Approximately 37 per cent of the historical habitat has been converted to cropland, now generally unavailable due to continuous disturbance.
Prairie dog towns formerly were much larger than at present. For example, one town in central Oklahoma stretched 35 km (Tyler 1968). In 1998, maximum town size in Oklahoma was 427 ha; length 2.1 km) (Lomolino and Smith 2001).
Density of prairie dogs fluctuates within and between years according to colony demographics, environmental conditions, forage availability, and soil and/or vegetation sites within towns (Koford 1958). Typical adult densities are about 12 per hectare (Koford 1958).
|Habitat and Ecology:||
Habitat consists of dry, flat or gently sloping, open grasslands with low, relatively sparse vegetation, including areas overgrazed by cattle. The species occurs in open vacant lots at town edges in some areas. Young are born in underground burrows.
Habitat includes all major grassland types - short, mixed and tall; most abundant and an important community member in the Mixed Grass Prairie and Short Grass Plains associations (Carpenter 1940, in Osborn 1942). Tallgrass prairie habitat is mainly areas where wild or domestic ungulates or other disturbance has reduced the stature of the tallgrass; prairie dogs maintain the vegetation in a low stature.
Fine to medium textured soils are preferred (Koford 1958), presumably because burrows and other structures tend to retain their shape and strength better than in coarse, loose soils. However, sandy soils often support larger, coarser graminoids with lower forage quality; prairie dogs may avoid these forages and thus associated sandy areas. Colonies commonly are found on silty clay loams, sandy clay loams, and loams (Agnew et al. 1986). Encroachment into sands (e.g., loamy fine sand) occurs if the habitat is needed for colony expansion (Osborn 1942).
By colonizing areas with low vegetative stature, prairie dogs often select areas with past human (as well as animal) disturbance. In North Dakota and Montana, colonies tended to be associated with areas heavily used by cattle, such as water tanks and long-term supplemental feeding sites (Licht and Sanchez 1993).
Breeding system is harem-polygamous, with most females copulating with one male and males with several females (Hoogland and Folts 1982). Litter size typically averages about four. Individual females produce one litter per year.
Threats fall into four main categories. 1) Exotic disease, particularly sylvatic plague (Yersinia pestis) to which prairie dogs are highly susceptible. 2) Loss of habitat to agriculture and urbanization. 3) Habitat fragmentation and its many effects. 4) Control activities by government, private organizations, and individuals via poisoning and shooting.
EXOTIC SPECIES/DISEASE: Sylvatic plague was introduced to North America around 1899 (Cully 1989) and first reported in black-tailed prairie dogs from Texas in the mid-1940s (Reading et al. 1989). It is a serious threat given its pervasiveness and efficacy, as it can kill more than 99% of prairie dogs in a colony (Cully 1989), and numbers do not appear to fully recover (USFWS 2002). Though prairie dogs have persisted in the presence of plague since about 1900 and prairie dog numbers are high given habitat loss and control efforts, plague is still of concern to local populations and for long-term persistence. Plague is not well documented in black-tailed prairie dogs across their range though there is no reason to believe that plague is not as significant in black-tailed as it is in white-tailed prairie dogs (Cully 1992). On large areas originally selected as possible ferret reintroduction sites, declines of up to 90 per cent from about 1985-2000 are "generally attributed to sylvatic plague" (USFWS 2000). Only about 10 percent of the historical range is both plague-free and available (not cropland) (USFWS 2000). Widespread outbreaks in 2001 may indicate the beginning of an 'up' cycle in plague occurrence (USFWS 2002). The significance of plague in range-wide prairie dog mortality is unclear, though experts agree that where plague occurs it is extremely important in population dynamics (Cully 1992). Plague may be introduced into a colony by other species or by dispersing prairie dogs, which bring plague-ridden fleas into a colony.
USFWS (2004) noted that: (1) High exposure doses of plague bacilli may be necessary for disease contraction in some individuals; (2) limited immune response has been observed in some individuals; (3) a population dynamic may have developed in low-density, isolated populations that contributes to the persistence of these populations; (4) the apparent ability of some sites to recover to pre-plague levels after a plague epizootic; and (5) approximately one-third of the species' historic range has not been affected by plague. Based on this and on recent estimates of occupied habitat, USFWS (2004) concluded that plague no longer appears to be as significant a threat as previously thought and that plague in combination with other factors is not likely to cause the black-tailed prairie dog to become an endangered species within the foreseeable future.
HABITAT LOSS AND DEGRADATION: Habitat loss has been an important factor in prairie dog declines in the past. Cheatheam (1977) estimated that about 36% of the land area in regions used by prairie dogs was covered by water developments, urban expansion, cropland, and improved pasture. Similarly, Bishop and Culbertson (1976) detected extensive colony loss on river terraces as a result of farming activities. Conversion of native prairie to farmland does not necessarily represent habitat loss to prairie dogs, but farmers will not tolerate prairie dogs in their fields (Merriam 1902). Similarly, prairie dogs prosper in empty urban lots and fields, yet this is not often tolerated given the plague risk. However, in New Mexico, urban (Gunnison's) prairie dogs are often allowed to remain because colony fleas are killed instead. Still, developments that destroy patches of grassland (e.g., roads, buildings, water impoundments) result in loss of potential prairie dog habitat and restriction of area for colony expansion.
USFWS (2004) concluded that present or threatened habitat destruction is not a threat to the species, although considerable effects due to this factor have occurred in the past. Additionally, USFWS concluded that present or threatened habitat modification as it relates to plague is not a significant threat to the species.
CONTROL: Control by humans, interacting with low forage production, is probably the main cause of loss of the prairie dog from the more arid parts of its range, including southwest New Mexico and southeast Arizona (Cully 1992) and Texas (see map in Cheatheam 1977). For most of the 20th century, Animal Damage Control, its forerunners, and other control agencies worked hard to eliminate prairie dogs over wide areas (Cully 1992). Towns were poisoned primarily with strychnine and zinc-phosphide baits (e.g., oats mixed with rodenticide). Poisoning was immediately followed up with extermination of any remaining living prairie dogs (Cully 1992). Indeed, control efforts, with some help from plague, resulted in a reduction in prairie dog acreage from 700,000,000 to 1,500,000 in 1971 (Cain et al. 1971, in Fagerstone and Biggins 1986; Cully 1989). Today prairie dog poisoning efforts are limited to local, problem populations and entail control, not extermination. Public control agencies, including ADC, do very little prairie dog control work, as most control is practiced by land managers. These agencies do provide technical information and assistance, however.
USFWS (2004) acknowledged extant and potentially significant local population reductions due to chemical control of prairie dogs but concluded that impacts due to this factor are not a threat to the extent that the species could become endangered in the foreseeable future.
USFWS (2004) acknowledged that recreational shooting can reduce population densities at specific sites and that extirpation possibly may have occurred in isolated circumstances due to this factor. However, USFWS noted that populations can recover from very low numbers following intensive recreational shooting and therefore concluded that effects due to recreational shooting do not constitute a significant threat.
Distribution, abundance, and trend data indicate that inadequate regulatory mechanisms are not limiting black-tailed prairie dog populations at present, nor are they likely to within the foreseeable future (USFWS 2004).
Many colonies are in national parks, state parks, and other protected lands, most of which prohibit prairie dog control/eradication. However, few colonies are provided protection, even in parks. Large, core occurrences need protection from population control.
Inventories are needed range-wide, and they should determine locations and sizes of colonies, ownership, and the presence of plague.
Of primary concern is the long-term viability of colonies in relation to size and distance to nearby colonies. Additionally, research into prairie dog genetics is needed to determine if currently reduced populations and habitat fragmentation are causing damaging levels of inbreeding.
|Citation:||Linzey, A.V. & NatureServe (Reichel, J.D., Hammerson, G., Cannings, S. & Wallace, R.) 2008. Cynomys ludovicianus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 20 May 2013.|
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