Gunnison's Prairie Research Articles

Conservation of prairie dog ecosystem engineering may support arthropod beta and gamma diversity

Ecosystem engineering by animals can create new habitats and increase the heterogeneity of the habitat mosaic that in turn can increase plant and animal diversity. Prairie dogs in North America alter both the above- and below-ground structure of the landscape and create novel habitats in grassland ecosystems. The ground-dwelling arthropod community associated with Gunnison's prairie dog modified habitats is compositionally different from that found in the surrounding grassland. Individual arthropod families and species have different distributions in both active prairie dog towns and inactive towns, compared to unmodified grasslands. These different responses to ecosystem engineering increase beta (between-habitat) and gamma (regional) diversity. This study suggests that simple measures of alpha diversity (species richness) may not adequately quantify overall diversity and that measures of beta diversity may be necessary to assess the role of prairie dogs as keystone engineers. Thus, conservation of prairie dogs and the engineering process may have positive effects for numerous species both locally and regionally.

Vegetation on Gunnison's Prairie Dog Colonies in Southwestern Colorado

Prairie dogs (Cynomys spp.) have been labeled keystone species because of the role they play as disturbance creators and ecosystem engineers in the western grasslands of North America. Most studies have concentrated on the black-tailed species (C. ludovicianus); however, other species of prairie dogs may have different effects on their ecosystems. We measured plant cover and biomass, canopy height, and plant nitrogen concentration on and off 6 Gunnison's prairie dog (C. gunnisoni) towns and 6 paired areas off prairie dog towns in southern Colorado. Multivariate analysis of variance and analysis of variance showed no significant differences (P > 0.05) in vegetation cover or biomass on and off of Gunnison's prairie dog towns, contrary to what has been found for black-tailed prairie dog towns. No significant differences were found in canopy height (P > 0.05); however, this may be due to already short vegetation (5–7 cm). Only 1 of 4 focal plants showed a significant difference in nitrogen concentration. No significant differences were found in species diversity on and off prairie dog towns; however, because of drought, these results are inconclusive. This study found few vegetation differences on and off Gunnison's prairie dog towns. Furthermore, those differences were more subtle than those reported on black-tailed prairie dog towns. While the mechanisms for differences in vegetation on and off Gunnison's prairie dog towns may be similar to those on black-tailed prairie dog towns, the magnitude of these differences may be different.

PREY OF NESTING FERRUGINOUS HAWKS IN NEW MEXICO

During June and July 2000, we collected regurgitated pellets and uneaten prey remains at 26 nests occupied by ferruginous hawks (Buteo regalis) in northwestern, western, and central New Mexico. Analysis of remains from all nests yielded a minimum of 260 individual prey from at least 18 vertebrate (13 mammals, 3 birds, and 2 reptiles) and 2 arthropod species. The taxa most frequently represented were Botta's pocket gopher (Thomomys bottae), ground squirrels (Spermophilus), Gunnison's prairie dog (Cynomys gunnisoni), and desert cottontail (Sylvilagus audubonii). Western diamondback rattlesnake (Crotalus atrox) and barn owl (Tyto alba) were recorded for the first time as prey of ferruginous hawks.

A method for identifying sounds used in the classification of alarm calls

In this study, we present a methodology that identifies acoustic units in Gunnison's prairie dog alarm calls and then uses those units to classify the alarm calls and bouts according to the species of predator that was present when the calls were vocalized. While traditional methods measure specific acoustic parameters in order to describe a vocalization, our method uses the variation in the internal structure of a vocalization to define possible information structures. Using a simple representation similar to that used in human speech to identify vowel sounds, a software system was developed that uses this representation to recognize acoustic units in prairie dog alarm calls. These acoustic units are then used to classify alarm calls and their associated bouts according to the species of predator that was present when the alarm calls were vocalized. Identification of bouts with up to 100% accuracy was obtained. This work represents a first step toward revealing the details of how information is encoded in a complex nonhuman communication system. Furthermore, the techniques discussed in this paper are not restricted to a database of prairie dog alarm calls. They could be applied to any animal whose vocalizations include multiple simultaneous frequencies.

ABIOTIC HABITAT CORRELATES OF GUNNISON'S PRAIRIE DOG IN ARIZONA

Abstract Prairie dog (Cynomys spp.) populations have been reduced by 98% compared to historical levels because of widespread poisoning, habitat loss, recreational shooting, and outbreaks of sylvatic plague (Yersinia pestis). Our objectives were to identify habitat correlates of Gunnison's prairie dog (C. gunnisoni) colonies and to develop a predictive logistic regression model to identify potential reintroduction sites for this species. During 2000 and 2001, we examined habitat features at 50 Gunnison's prairie dog colonies and 50 paired random sites in northern Arizona, USA. When compared to random sites, Gunnison's prairie dog colonies had deeper soils, less variability in slope, and less rock ground cover. Our results suggest the importance of deep soils for allowing Gunnison's prairie dogs to establish hibernacula below the frost line. Our model allows prediction of the probability of Gunnison's prairie dog presence at a site based on soil depth, standard deviation of slope, and surface rock cover, an...

PARENTAGE, MULTIPLE PATERNITY, AND BREEDING SUCCESS IN GUNNISON'S AND UTAH PRAIRIE DOGS

Feasibility of assigning parentage using variable microsatellite loci was assessed for 2 species of prairie dogs. Parentage was determined from 7 microsatellite loci for 46% of juveniles born during 1994 in a colony of Gunnison's prairie dogs (Cynomys gunnisoni), and for 53% and for 45% of juveniles born during 1996 and 1997, respectively, in a colony of Utah prairie dogs (C. parvidens). Frequency of multiple paternity estimated for Gunnison's (77%) and Utah (71% and 90%) prairie dogs was greater than that detected previously for black-tailed prairie dogs (5%–10%) but within the range reported for other ground-dwelling squirrels. Of the 84 adult females and 33 adult males present during 1994 in the colony of Gunnison's prairie dogs, 75 (89%) and 22 (67%), respectively, produced weaned offspring. Breeding success for Utah prairie dogs was relatively low in 1996 (45% for females and 32% for males) but increased in 1997 (80% for females and 81% for males).

SEXUAL DIMORPHISM OF PRAIRIE DOGS

Abstract Body mass is sexually dimorphic and varies seasonally for all 5 species of prairie dogs (Sciuridae: Cynomys), as shown by data from live individuals over a period of 28 years (1974–2001; n = 16,447 body masses). Sexual dimorphism (i.e., body mass of males as percentage of body mass of females) during the breeding season is 105% for black-tailed prairie dogs, 127% for Utah prairie dogs, 131% for Gunnison's prairie dogs, and 136% for white-tailed prairie dogs. Sexual dimorphism is minimal at the end of the breeding season, when exhausted males are thin and early-breeding females are heavy with pregnancy. Sexual dimorphism is maximal at weaning, when rested, well-fed males are heavy and females are emaciated from lactation. The most likely ultimate causation for sexual dimorphism among prairie dogs is sexual selection.

Increased Lesser Earless Lizard (Holbrookia maculata) Abundance on Gunnison's Prairie Dog Colonies and Short Term Responses to Artificial Prairie Dog Burrows

Our studies of the association between the lesser earless lizard (Holbrookia maculata) and Gunnison's prairie dogs (Cynomys gunnisoni) revealed: (1) the lesser earless lizard was more abundant on prairie dog colonies than off; (2) lesser earless lizard abundance was positively correlated with prairie dog burrow abundance; (3) lesser earless lizards responded positively to artificial burrows created on noncolonized areas; and (4) lesser earless lizards used prairie dog burrows as refuges from predators; however, the relative use of burrows was greatest at high and low temperature extremes. Although prairie dogs alter habitat in many ways, our study suggests that burrows are an important mechanism involved in the association between the lesser earless lizard and Gunnison's prairie dogs.

Prairie dog engineering indirectly affects beetle movement behavior

Previous studies have shown that landscape structure influences animal movement and population structure. In this study, we show an indirect interaction between beetles and prairie dogs due to prairie dog ecosystem engineering. Gunnison's prairie dog (Cynomys gunnisoni Hollister) towns have more bare ground and are structurally less complex than adjacent unmodified grasslands. This results in bare ground facilitating beetle movement. Differences in landscape structure between prairie dog towns and unmodified grasslands had a significant effect on the movement of the darkling beetle, Eleodes hispilabris Say. Beetle movement tended to be more linear (pathway fractal dimension approached 1) on prairie dog habitats and more sinuous on adjacent grasslands. Beetle velocity was 44% greater and net displacement 63% farther on the prairie dog habitat. These differences were also evident at fine scales when beetles moved between grass and bare ground patches regardless of habitat. Beetles moved 2.3 times faster and displaced 3.0 times farther after making this microhabitat transition. Beetles avoided grass and selected bare ground for movement 12–22% more than the percent of bare ground on the landscape. Since beetles exhibited directed movements and grasslands inhibit movement, it might be expected that beetles would accumulate in this habitat upon encounter. However, beetles were approximately twice as abundant on prairie dog towns as on adjacent grasslands. A difference in beetle movement behavior, between prairie dog towns and grasslands, suggests that prairie dog towns are an important component of this desert grassland landscape for these beetles.

Habitat structure and alarm call dialects in Gunnison's prairie dog (Cynomys gunnisoni)

We examined the relationship between habitat structure and alarm call characteristics in six colonies of Gunnison's prairie dogs (Cynomys gunnisoni) near Flagstaff, Arizona, before and after a mid-summer vegetation change. We found significant differences in alarm call characteristics between colonies, confirming the existence of alarm call dialects. Differences in frequency components but not temporal components of calls were associated with differences in habitat structure. Playback experiments revealed that differences in alarm call structure affected acoustic transmission of calls through the local habitat. Thus, we identify habitat structure as one factor that may contribute to alarm call differences between colonies of Gunnison's prairie dogs. Relationships between call characteristics and habitat structure changed over seasons. Playback experiments suggested that this changing relationship could reflect a change in the purpose of the alarm call between early and late summer. Some components of alarm calls seem tailored for attenuation over short distances in the early summer but for long-distance transmission at summer's end. These differences might arise because pups stay close to their natal burrows in the early summer and disperse throughout a colony in late summer. Alternatively, these differences in alarm call transmission between seasons could be caused by the increase in vegetation in the mid-summer. At the end of the summer prairie dogs could be more dependent on long-distance antipredator calls to offset the loss of visibility caused by the increase in vegetation in the late summer. Copyright 2002.

Vigilance and predation risk in Gunnison's prairie dogs (Cynomys gunnisoni)

Group living in animals is believed to confer advantages related to a decrease in predation risk and an energetic trade-off between vigilance and foraging efficiency. Eight Gunnison's prairie dog, Cynomys gunnisoni, colonies in Flagstaff, Arizona (elevation 2300 m), were studied from April to August 2000 to examine the adaptive significance of colonial living in the context of predation risk and antipredator behavioral strategies. Each colony was sampled once every 10 days for a period of 3 h. Upright and quadrepedal vigilance was recorded using scan samples. All predation events were recorded. Results suggest that vigilant behavior in Gunnison's prairie dogs is an antipredator strategy because the animals oriented more frequently towards the periphery of the colony while vigilant. Gunnison's prairie dogs engaged in posting, an upright bipedal posture, more frequently than scanning, a quadrepedal posture. Furthermore, there was no relationship between either form of vigilance and population size. The proportion of animals vigilant decreased significantly only on the two smallest colonies as colony size increased. On larger colonies there was no relationship between the proportion of animals vigilant and colony size. The lack of change in the proportion of animals vigilant in larger populations may be a function of perceived risk rather than actual individual risk.

Sampling for sand flies (Diptera: Psychodidae) among prairie dog colonies on ranches with histories of vesicular stomatitis in new Mexico and Colorado.

The possible presence of sand flies (Diptera: Psychodidae) among colonies of Gunnison's prairie dogs, Cynomys gunnisoni Baird, was investigated on or near ranches with histories of vesicular stomatitis (VS) in domestic livestock in the mid-Rio Grande River Valley, NM, and west-slope region of Colorado. Sampling was conducted at six locations, three in each region, using three methods: standard down-draft suction/light traps, up-draft suction/light traps (both supplemented with CO2), and burrow-emergence traps. Two male and four female sand flies, Lutzomyia apache, Young and Perkins were recovered from prairie dog colony and sand-sagebrush association habitats on a cattle ranch in Socorro County, NM. Sand flies were captured only in up-draft suction/light traps. This record is of interest for the following reasons: (1) sand flies have not been reported from the Rio Grande River Valley of New Mexico, (2) sand flies are biological vectors of VS viruses in other areas, (3) the mid-Rio Grande River Valley has been a focus of VS virus activity in domestic livestock during recent outbreaks, and (4) the source of vesicular stomatitis viruses that infect livestock in the western United States is unknown, but may involve introductions of virus from Mexico or an endemic cycle maintained by vector insects.

Prevalence of Eimeria (Apicomplexa: Eimeriidae) in Reintroduced Gunnison's Prairie Dogs (Cynomys gunnisoni)

Fecal samples from 54 Gunnison's prairie dogs (Cynomys gunnisoni) from Albuquerque, NM were analyzed for the presence of coccidia and all were positive. They were then relocated to an abandoned prairiedog town on the Sevilleta Long Term Ecological Research (LTER) site. Six Eimeria species, E. callospermophili, E. cynomysis, E. pseudospermophili (new host record), E. spermophili, E. ludoviciani and E. vilasi (new host record) were found in Albuquerque animals, but only 2 species, E. callospermophili and E. vilasi were present in relocated hosts. A significant (P < 0.05) reduction was seen in the prevalence of E. vilasi (72% vs. 13%) and in the prevalence of infections (P < 0.05) with 2 or more Eimeria species (39% vs. 4%) in pre- and postrelocation animals. To assess the impact of the introduction of C. gunnisoni on the resident rodent population, feces were collected from 6 species of rodents. Five Eimeria species, E. arizonensis (Reithrodontomys), E. chobotari (Dipodomys, Perognathus), E. liomysis (Dipodomys), E. mohavensis (Dipodomys) and E. reedi (Perognathus) were found. We found no evidence of coccidia transfer among introduced and resident rodent species.

Habitats for humanity: Effects of visual affordance on the evolution of hominid antipredator communication

Habitats for humanity: Effects of visual affordance on the evolution of hominid antipredator communication

The Gunnison's prairie dog structures a high desert grassland landscape as a keystone engineer

The influence of landscape spatial structure on ecological processes has recently received much attention. Comparisons are made here between the spatial structure of grasslands, and active and extirpated Gunnison's prairie dog (Cynomys gunnisoni Hollister) towns at the Petrified Forest National Park, Arizona, U.S.A. The spatial structure of bare ground was quatified using a box-counting technique to extract landscape fractal dimensions, D, and bare-ground patch size. These landscapes are fractal, and active prairie dog towns had higher fractal dimensions, i.e. a more homogeneous spatial structure as D approaches 2, than inactive towns, which had higher fractal dimensions than unmodified grasslands. Morisita's index suggested that shrubs were more randomly distributed on prairie dog towns and more aggregated on grassland habitats. The different spatial distributions of bare ground and shrubs have the potential to influence resource distributions between these habitats for both prairie dogs and other fauna. Consequently, the presence of prairie dogs in these grasslands increases grassland landscape heterogeneity at large spatial scales, potentially enhancing beta diversity.

A fuzzy-neural system for identification of species-specific alarm calls of Gunnison's prairie dogs

In this study we describe the design and application of an automated classification system that utilizes artificial intelligence to corroborate the finding that Gunnison's prairie dogs have different alarm calls for different species of predators. This corroboration is strong because it utilizes an entirely different analysis technique than that used in the original research by Slobodchikoff et al. [Slobodchikoff, C.N., Fischer, C., Shapiro, J., 1986. Predator-specific alarm calls of prairie dogs. Am. Zool. 26, 557] or in subsequent study done by Slobodchikoff et al. [Slobodchikoff, C.N., Kiriazis, J., Fischer, C., Creef, E., 1991. Semantic information distinguishing individual predators in the alarm calls of Gunnison's prairie dogs. Anim. Behav. 42, 713–719]. The study described here also is more completely automated than earlier study in this area. This automation allowed a large volume of field data to be processed where all measurements of relevant parameters were performed through software control. Previous study processed a smaller data set and utilized manual measurement techniques. The new classification system, which combines fuzzy logic and an artificial neural network, classified alarm calls correctly according to the eliciting predator species, achieving accuracy levels ranging from 78.6 to 96.3% on raw field data digitized with low quality audio equipment.

Responses of Small Mammals and Vegetation to a Reintroduction of Gunnison's Prairie Dogs

This study addressed the initial effects of a reintroduction of Gunnison's prairie dogs ( Cynomys gunnisoni ) on resident small mammal and plant communities on the Sevilleta National Wildlife Refuge (SNWR), New Mexico. In spring 1997, 60 prairie dogs (36.8 kg live mass) were introduced onto a former prairie dog colony in a desert grassland site. Small mammals and vegetation were sampled on both a treatment (reintroduction site) and a control site (without prairie dogs) before and after the prairie dogs were reintroduced. We tested for differences in small mammal and plant community change during the 1st year of the colony's existence using repeated measures analysis of variance. Although prairie dog biomass was ca. 32 times greater than that of the resident rodent community (1.2 kg), reintroduction of prairie dogs had no significant effect on the resident small mammal and plant communities. Total biomass and abundance of rodents, and percent cover and species richness of plants did not change during the 1st year following reintroduction of prairie dogs. However, two rodent species showed significant differences in abundance between the prairie dog colony and the control site. The banner-tailed kangaroo rat ( Dipodomys spectabilis ) was significantly more abundant on the treatment site before and after reintroduction of prairie dogs. In contrast, the white-footed mouse ( Peromyscus leucopus ) was significantly more abundant on the control site following reintroduction of prairie dogs. Habitat modifications made by the former prairie dog colony may be responsible for the habitat preferences observed by D. spectabilis and P. leucopus . Although reintroduction of prairie dogs had no observable influence on the resident small mammal and plant communities in the short-term, their influences may be more evident on a long-term time scale.

Philopatry, Dispersal, and Social Organization of Gunnison's Prairie Dogs

I examined dispersal and social organization of Gunnison's prairie dogs (Cynomys gunni­ soni) for 7 years at Petrified Forest National Park, Arizona. Within colonies, individuals lived in harem-polygynous family groups called clans. The number of clans at the study site each year ranged from 21 to 23, with a mean of 22.3. Clan size (the number of adults living in the same territory) ranged from 1 to 19, with a mean of 5.30. Clans contained 1.06 ± 0.39 (SD) breeding males, 3.01 ± 2.08 breeding females, and 1.23 ± 1.65 non­ breeding yearling males. Some clans contained two breeding males, and others contained no resident breeding male. The area of clan territories ranged from 0.16 ha to 1.82 ha, with a mean of 0.67 ha. Females were more likely than males to copulate as yearlings (100% versus 24%). Ninety-five percent of females (340/358) remained in the natal clan territory for life, but only 5% of males (3/66) remained in the natal clan territory for> 1 year after weaning. Dispersal of both sexes was most commonly to an adjacent clan territory. Infan­ ticide at the study colony was rare or absent.

Geographic Variation in Alarm Calls of Gunnison's Prairie Dogs

Geographic variation in alarm calls of Gunnison's prairie dogs ( Cynomys gunnisoni ) was analyzed at regional and local scales. Alarm calls in response to a common stimulus (the same human) were recorded at four colonies near Flagstaff, Arizona, and at six sites throughout the southwestern United States. The acoustic structure of calls was analyzed for seven call variables. Regional differences fit the prediction of greater differences with increased geographical separation. Differences between colonies at a local scale were not related to geographical distance, suggesting that local dialects exist within a region. Differences in the level of predation by humans between colonies or habitat effects on sound propagation may explain variation in calls at the local level.

Estrus and Copulation of Gunnison's Prairie Dogs

Because most animals copulate surreptitiously, estimates of male and female copulatory success are elusive. Here I describe six distinctive behaviors that coincide with underground copulations of Gunnison's prairie dogs ( Cynomys gunnisoni ): the underground consortship itself, inordinate male attention toward the estrous female, self-licking of genitals, dustbathing, the mating call, and late final submergence of the estrous female. These diagnostic behaviors allowed me to identify sexual partners for 308 females that came into estrus during a 7-year study.