Cynomys gunnisoni

Genetic data support recognition of two subspecies, gunnisoni and zuniensis (Sacket et al. 2014).

Historically, this species has declined by over 90% within its range due to poisoning, introduced sylvatic plague, habitat loss, persecution, and climate change in the southern portion of their range. It still occupies most of its historical range, although at much reduced densities. Rangewide surveys have revealed that by the mid-2000s, the population appears to have stabilized at a much lower level than historically. Colonies remain susceptible to rapid declines and extirpations due to outbreaks of sylvatic plague.

In montane Colorado and New Mexico, drastic declines in area of occupancy, number of subpopulations, and population size have occurred over the past several decades, and populations remain small, fragmented, and threatened by plague. In central and south-central Colorado and north-central New Mexico, the subspecies zuniensis is considered common with no substantial immediate threats, although plague episodes and poisoning can cause localized extirpations.

This species occurs from central Colorado to central Arizona, including a small portion of southeastern Utah and much of northwestern New Mexico, US.

There are two subspecies recognized: Cynomys gunnisoni gunnisoni, occurring in the higher-elevation, “montane” northeastern portion of the range, and C. g. zuniensis, occurring in the lower-elevation, “prairie” southwestern portion of the range (USFWS 2013, Sacket et al. 2014).

Cassola (2016) estimates the current range extent at 406,222 sq. km. This estimate aligns with one derived from iNaturalist records, which calculate to 403,769 sq. km. using GeoCat (accessed August 2021).

As of 2021, state natural heritage programs have records of at least 300 occurrences.

Sylvatic plague, caused by the non-native bacterium Yersinia pestis, is the greatest single threat as of 2021. Prairie dogs are highly susceptible to plague, with outbreaks often causing >90% mortality in affected colonies (Cully and Williams 2001, Sacket et al. 2013, Russell et al. 2019). C. gunnisoni has the distinction of being the most susceptible of the 5 living species of Cynomys, apparently sometimes experiencing greater than 99% mortality from plague (Cully et al. 1997) or loss of entire colonies (Lechleitner et al. 1962, Raynor 1985). Based on observations of prairie dog die-offs, the general consensus is that plague outbreaks occur rapidly, such that only a few survivors are observed after 6-8 weeks (Salkeld et al. 2010, citing Pauli et al. 2006 and Webb et al. 2006). In a study on sylvatic plague and fragmentation of black-tailed prairie dogs (Cynomys ludovicianus), Keuler et al. (2020) found that colonies became smaller and more fragmented after the arrival of plague; the total area of each colony and the mean area per patch within a colony decreased, the number of patches per colony increased, and mean contiguity of each patch decreased, leading to population fragmentation. However, there is increasing evidence from natural populations and experimental studies that resistance to plague may be evolving (see citations in Tsuchiya et al. 2020), and recent developments in vaccines and vaccine delivery have raised the possibility of plague control in prairie dog populations.

Climate in the southern portion of this species range is projected to experience continued warmer temperatures, rapid drying, and inhibited recovery from drought conditions (Seager et al. 2007, Gutzler and Robbins 2011) (Davidson et al. 2014). Long-term research in the southern portion of their range in New Mexico and Mexico shows that both established and restored prairie dog colonies in more xeric environments are highly vulnerable to drought, and climate change increases this vulnerability (Davidson et al. 2014).

Intentional eradication and population control efforts through indiscriminate poisoning and recreational shooting is also a potential threat. Poisoning has caused considerable range contraction of the species in parts of Colorado and New Mexico (Armstrong et al. 2011). In Arizona, recreational shooters shot 91,000 animals in 2001 (B. Van Pelt pers. comm.) (Cassola 2016). Since then, Arizona Game and Fish Department have implemented a hunting closure for Gunnison's prairie dogs, and hunters are not allowed to shoot them during the breeding season (April 1- June 30th). Overall, the effects of recreational shooting may be localized and do not result in rangewide population declines (USFWS 2013).

Additional habitat associated risk factors such as conversion of habitat to agriculture, grazing, invasive plant species, urbanization, alteration of fire regimes, and oil and gas exploration and development are not considered major, rangewide threats (USFWS 2013, USFS 2015). This opinion is not universal as others claim that habitat loss and fragmentation from agricultural development is the foremost cause of population declines (Farid 2019).