Spatial and temporal avoidance of risk within a large carnivore guild

Within a large carnivore guild, subordinate competitors (African wild dog, Lycaon pictus, and cheetah, Acinonyx jubatus) might reduce the limiting effects of dominant competitors (lion, Panthera leo, and spotted hyena, Crocuta crocuta) by avoiding them in space, in time, or through patterns of prey selection. Understanding how these competitors cope with one other can inform strategies for their conservation. We tested how mechanisms of niche partitioning promote coexistence by quantifying patterns of prey selection and the use of space and time by all members of the large carnivore guild within Liuwa Plain National Park in western Zambia. Lions and hyenas specialized on wildebeest, whereas wild dogs and cheetahs selected broader diets including smaller and less abundant prey. Spatially, cheetahs showed no detectable avoidance of areas heavily used by dominant competitors, but wild dogs avoided areas heavily used by lions. Temporally, the proportion of kills by lions and hyenas did not detectably differ across four time periods (day, crepuscular, early night, and late night), but wild dogs and especially cheetahs concentrated on time windows that avoided nighttime hunting by lions and hyenas. Our results provide new insight into the conditions under which partitioning may not allow for coexistence for one subordinate species, the African wild dog, while it does for cheetah. Because of differences in responses to dominant competitors, African wild dogs may be more prone to competitive exclusion (local extirpation), particularly in open, uniform ecosystems with simple (often wildebeest dominated) prey communities, where spatial avoidance is difficult.     

Rabies Virus and Canine Distemper Virus in Wild and Domestic Carnivores in Northern Kenya: Are Domestic Dogs the Reservoir?

Rabies virus (RV) and canine distemper virus (CDV) can cause significant mortality in wild carnivore populations, and RV threatens human lives. We investigated serological patterns of exposure to CDV and RV in domestic dogs (Canis familiaris), African wild dogs (Lycaon pictus), black-backed jackals (Canis mesomelas), spotted hyenas (Crocuta crocuta), striped hyenas (Hyaena hyaena) and African lions (Panthera leo), over a 10-year period, in a Kenyan rangeland to assess the role domestic dogs may play in the transmission dynamics of these two important canid pathogens. Observed patterns of RV exposure suggested that repeated introduction, rather than maintenance, occurred in the wild carnivore species studied. However, RV appeared to have been maintained in domestic dogs: exposure was more likely in domestic dogs than in the wild carnivores; was detected consistently over time without variation among years; and was detected in juveniles (≤1-year-old) as well as adults (>1-year-old). We conclude that this domestic dog population could be a RV reservoir. By contrast, the absence of evidence of CDV exposure for each carnivore species examined in the study area, for specific years, suggested repeated introduction, rather than maintenance, and that CDV may require a larger reservoir population than RV. This reservoir could be a larger domestic dog population; another wildlife species; or a “metareservoir” consisting of multiple interconnected carnivore populations. Our findings suggest that RV risks to people and wild carnivores might be controlled by domestic dog vaccination, but that CDV control, if required, would need to target the species of concern.     

Niche relations among three sympatric Mediterranean carnivores

Previous studies carried out in the Doñana National Park reported that red foxes (Vulpes vulpes) were killed by Iberian lynxes (Lynx pardinus), whereas similar-sized Eurasian badgers (Meles meles) were not. Therefore, we predicted that fox would avoid lynx predation risk by niche segregation whereas we did not expect such a segregation between badger and lynx. As an approach for evaluating our predictions, we compared their diet, activity patterns, and habitat use in an area of Doñana where the three carnivores are sympatric. Lynxes preyed almost uniquely on European rabbits (Oryctolagus cuniculus), and though badgers and foxes were omnivorous, rabbits also were a major prey, resulting in high overlaps throughout the year. However, badgers preyed largely on small rabbits, whereas lynxes and foxes preyed mainly on medium-sized rabbits. There were also interspecific differences in activity patterns. Maximum levels of activity among lynxes were during sunrise and dusk (49–67%). Foxes were most active during dusk and night (34–67%), and badgers were mainly nocturnal (53–87%). Though there were seasonal differences in the amount of activity of each species, specific activity patterns changed little throughout the year. There was a strong difference in annual habitat use by the three species (P?MAX) and the resting (P_MIN) periods. During P_MIN, foxes used the Mediterranean scrubland intensively (40% of locations on average), but during P_MAX, they used the pastureland much more intensively despite this habitat being poorer in their main prey (rabbits). As a consequence, foxes and lynxes exhibited segregation in their habitat use during the active period. Badgers also used the Mediterranean scrubland intensively, especially during P_MIN. There were no seasonal differences in habitat use for lynx and fox, but there was for badgers (P?相似文献   

Some relationships Between Prairie Dogs,Black-Footed Ferrets,Paleo-Indians,and Ethnographically Known Tribes

Abstract

Black-footed ferrets (Mustela nigripes) are one of the rarest mammals of North America; ferrets are most often associated with prairie dogs (Cynomys sp.) on which they are thought to be obi igatory predators. Ferret and prairie dog skeletal remains have been found from several sites occupied by Paleo-Indians; these sites are described. The recent history of five Indian groups contain reference to ferrets and prairie dogs: Sioux, Blackfeet, Crow, Cheyenne, and Pawnee. Use of ferrets is described for each tribe. A request is extended to all readers having published or unpublished information about aboriginal associations with prairie dogs (Cynomys sp.) or black-footed ferrets (Mustela nigripes) to please contact the author.     

Domestic Dogs in Rural Communities around Protected Areas: Conservation Problem or Conflict Solution?

Although domestic dogs play many important roles in rural households, they can also be an important threat to the conservation of wild vertebrates due to predation, competition and transmission of infectious diseases. An increasing number of studies have addressed the impact of dogs on wildlife but have tended to ignore the motivations and attitudes of the humans who keep these dogs and how the function of dogs might influence dog-wildlife interactions. To determine whether the function of domestic dogs in rural communities influences their interactions with wildlife, we conducted surveys in rural areas surrounding protected lands in the Valdivian Temperate Forests of Chile. Sixty percent of farm animal owners reported the use of dogs as one of the primary means of protecting livestock from predators. The probability of dog–wild carnivore interactions was significantly associated with the raising of poultry. In contrast, dog–wild prey interactions were not associated with livestock presence but had a significant association with poor quality diet as observed in previous studies. Dog owners reported that they actively encouraged the dogs to chase off predators, accounting for 25–75% of the dog–wild carnivore interactions observed, depending on the predator species. Humans controlled the dog population by killing pups and unwanted individuals resulting in few additions to the dog population through breeding; the importation of predominantly male dogs from urban areas resulted in a sex ratios highly dominated by males. These results indicate that dog interactions with wildlife are related to the role of the dog in the household and are directly influenced by their owners. To avoid conflict with local communities in conservation areas, it is important to develop strategies for managing dogs that balance conservation needs with the roles that dogs play in these rural households.     

Effects of diet on captive black-footed ferret (Mustela nigripes) food preference

Black-footed ferrets (Mustela nigripes) are both habitat and prey specialists that depend on prairie dogs (Cynomys spp.) for food and utilize prairie dog burrows for refuge. In this study we investigated the effects of captive diet during early development on adult black-footed ferret food preferences. To test the hypothesis that early diet affects the food preferences of adult black-footed ferrets, we exposed 22 kits (divided into three experimental groups) to different quantities of prairie dog in the diet: no prairie dog, prairie dog three times per week, and prairie dog daily during the assumed sensitive period for olfactory imprinting, i.e., between 60–90 postnatal days. At age 5 months, kits were individually tested in a food choice cafeteria trial. Results indicated that higher amounts of prairie dog in the ferrets' early diet led to a higher preference for this food item when ferrets reached adulthood. These results have important implications for black-footed ferret recovery and have been considered in the reintroduction protocol. © 1996 Wiley-Liss, Inc.     

Black-Tailed Prairie Dogs,Cattle, and the Conservation of North America’s Arid Grasslands

Prairie dogs (Cynomys spp.) have been eliminated from over 95% of their historic range in large part from direct eradication campaigns to reduce their purported competition with cattle for forage. Despite the longstanding importance of this issue to grassland management and conservation, the ecological interactions between cattle and prairie dogs have not been well examined. We address this issue through two complementary experiments to determine if cattle and prairie dogs form a mutualistic grazing association similar to that between prairie dogs and American bison. Our experimental results show that cattle preferentially graze along prairie dog colony edges and use their colony centers for resting, resembling the mutualistic relationship prairie dogs have with American bison. Our results also show that prairie dog colonies are not only an important component of the grassland mosaic for maintaining biodiversity, but also provide benefits to cattle, thereby challenging the long-standing view of prairie dogs as an undesirable pest species in grasslands.     

Do the antipredator strategies of shared prey mediate intraguild predation and mesopredator suppression?

Understanding the conditions that facilitate top predator effects upon mesopredators and prey is critical for predicting where these effects will be significant. Intraguild predation (IGP) and the ecology of fear are hypotheses used to describe the effects of top predators upon mesopredators and prey species, but make different assumptions about organismal space use. The IGP hypothesis predicts that mesopredator resource acquisition and risk are positively correlated, creating a fitness deficit. But if shared prey also avoid a top predator, then mesopredators may not have to choose between risk and reward. Prey life history may be a critical predictor of how shared prey respond to predation and may mediate mesopredator suppression. We used hierarchical models of species distribution and abundance to test expectations of IGP using two separate triangular relationships between a large carnivore, smaller intraguild carnivore, and shared mammalian prey with different life histories. Following IGP, we expected that a larger carnivore would suppress a smaller carnivore if the shared prey species did not spatially avoid the large carnivore at broad scales. If prey were fearful over broad scales, we expected less evidence of mesopredator suppression. We tested these theoretical hypotheses using remote camera detections across a large spatial extent. Lagomorphs did not appear to avoid coyotes, and fox detection probability was lower as coyote abundance increased. In contrast, white‐tailed deer appeared to avoid areas of increased wolf use, and coyote detection probability was not reduced at sites where wolves occurred. These findings suggest that mesopredator suppression by larger carnivores may depend upon the behavior of shared prey, specifically the spatial scale at which they perceive risk. We further discuss how extrinsic environmental factors may contribute to mesopredator suppression.     

Western Burrowing Owls (Athene cunicularia hypugaea) Eavesdrop on Alarm Calls of Black‐Tailed Prairie Dogs (Cynomys ludovicianus)

Animals sharing a common habitat can indirectly receive information about their environment by observing information exchanges between other animals, a process known as eavesdropping. Animals that use an auditory alarm calling system are an important indirect information source for eavesdropping individuals in their environments. We investigated whether Western burrowing owls (Athene cunicularia hypugaea) nesting on black‐tailed prairie dog (Cynomys ludovicianus) colonies responded to broadcasts of prairie dog alarm calls. Western burrowing owls are closely associated with black‐tailed prairie dogs in Colorado and neighboring states on the Great Plains of the United States. Prairie dog burrows in active colonies can serve as nesting sites for Western burrowing owls, and prairie dogs may act as an alternative prey source for predators, potentially decreasing the burrowing owls' risk of predation through the dilution effect. Burrowing owls nesting on prairie dog colonies may also eavesdrop on prairie dog alarm calls, enhancing their survival and nesting success on prairie dog colonies. We performed broadcast experiments with three different sounds: a prairie dog alarm call, a biological control (cattle mooing), and a non‐biological control (an airplane engine), and characterized burrowing owl responses as either alert or relaxed. For each sound stimulus, we recorded the time to first alert response to broadcast sounds (latency) and also how frequently the target burrowing owl exhibited an alert response within the first ten seconds of the broadcast (intensity). Burrowing owls reacted more quickly to the prairie dog alarm than to the biological control. They significantly increased the intensity of alert behaviors in response to broadcasts of the alarm, but did not show an increased reaction to either the biological or the non‐biological control. Our results suggest that burrowing owls nesting on prairie dog colonies eavesdrop on, and increase their alert behaviors in response to, prairie dog alarm calls.     

Assessing resource and predator effects on habitat use of tropical small carnivores

Habitat use of animals is influenced by a combination of factors including food abundance and interactions with other species. Animals typically must forage while simultaneously avoiding predation from multiple potential predators, but habitat use in tropical forest ecosystems that assesses effects of both predation risk and resources has rarely been conducted. We used camera traps and occupancy analyses to document small mammalian carnivore occurrence in relation to food abundance and interactions with large predators. We hypothesized that habitat use of six small mammalian carnivores (≤15 kg) would be influenced by (1) abundance of resources (fruit, rodents, and streams) and/or (2) large predators. Predictions regarding food and habitat resources were only supported for one species (crab-eating mongoose, Urva urva), which was positively associated with rodents and streams. Three small carnivores (masked palm civet Paguma larvata, common palm civet Paradoxurus hermaphroditus, yellow-throated marten Martes flavigula) were affected negatively by leopard and mesopredators as predicted. Counter to our predictions, two species (masked palm civet and yellow-throated marten) showed spatial avoidance of tiger suggesting that an apex predator might also pose predation risk to small carnivores. The focal small carnivores and large predators of this study appeared to have moderately to highly overlapping temporal activity indicating no temporal avoidance. In conclusion, food resources appeared to have minimal effects for six small carnivores in this ecosystem probably due to continuous resource availability. Predation risk appeared to affect some species in terms of spatial occupancy but not in temporal activity, indicating perhaps complex, but not entirely negative interactions between larger carnivores and this guild of small carnivores. The mechanisms which facilitate co-occurrence between small carnivores and large predators may, however, operate at finer spatiotemporal scales than we investigated here.     

A plague epizootic in the white-tailed prairie dogs (Cynomys leucurus) of Meeteetse, Wyoming

Surveillance for sylvatic plague (Yersinia pestis) was conducted near Meeteetse, Wyoming (USA) from 24 May to 14 June 1985. Ten species of fleas were collected from white-tailed prairie dogs (Cynomys leucurus), and from their burrows and associated rodents. Five of these flea species and two adult prairie dogs were positive for plague. The progression of this plague epizootic appeared to be slower and the intensity was less than in previous epizootics in other prairie dog colonies. The plague epizootic occurred within the only known colony of black-footed ferrets (Mustela nigripes) and was a potential threat to the food source of this endangered species.     

Effects of habitat fragmentation and black-tailed prairie dogs on urban avian diversity

Urbanization and habitat fragmentation have the potential to influence bird communities. In addition, these phenomena, as well as ongoing lethal control measures, have also greatly reduced the range of the black-tailed prairie dog (Cynomys ludovicianus) since the beginning of the 20th century. Although prairie dogs are highly interactive species that can influence avian communities, few studies have investigated whether these interactions persist in urban settings. Our goal was to investigate the relative impacts of habitat fragmentation and prairie dogs on bird communities within an urban matrix. We performed bird surveys on 20 habitat fragments (10 colonized by prairie dogs, 10 uncolonized by prairie dogs) distributed throughout the Denver metropolitan area, and calculated Shannon–Weiner diversity and richness of all birds and native species, as well as total counts of grassland birds and raptors. Diversity, richness, and counts of many species increased with increasing fragment connectivity, and decreased on fragments isolated for longer periods of time. Avian diversity and richness did not differ between fragments with and without prairie dogs, suggesting that this element of the ecological role of prairie dogs is not fully retained in urban habitat. Future studies of the role of prairie dogs as keystone species in urban systems should include other taxa as well as consider the influence of the urban matrix surrounding prairie dog habitat. Our results emphasize that conservation of urban avian diversity should focus on landscape connectivity as well as local habitat features.     

Duration of Plague (Yersinia pestis) Outbreaks in Black-Tailed Prairie Dog (Cynomys ludovicianus) Colonies of Northern Colorado

Plague, caused by the bacterium Yersinia pestis, triggers die-offs in colonies of black-tailed prairie dogs (Cynomys ludovicianus), but the time-frame of plague activity is not well understood. We document plague activity in fleas from prairie dogs and their burrows on three prairie dog colonies that suffered die-offs. We demonstrate that Y. pestis transmission occurs over periods from several months to over a year in prairie dog populations before observed die-offs.     

The influence of environment,sex, and innate timing mechanisms on body temperature patterns of free-ranging black-tailed prairie dogs (Cynomys ludovicianus)

Mechanisms that influence body temperature patterns in black-tailed prairie dogs are not well understood. Previous research on both free-ranging and laboratory populations of black-tailed prairie dogs (Cynomys ludovicianus) has suggested that reductions in ambient temperature and food and water deprivation are the primary factors that stimulate torpor in this species. In other species, however, torpor has been shown to be influenced by a multitude of factors, including innate circadian and circannual timing mechanisms, energy status, and reproductive behaviors. Our objective was to clarify the influence of weather, sex, and intrinsic timing mechanisms on the body temperature patterns of free-ranging black-tailed prairie dogs. We monitored body temperatures of eight adult (>1 yr) prairie dogs from November 1999 to June 2000. Prairie dogs showed distinct daily and seasonal body temperature patterns, which reflected changes in ambient temperatures that occurred during these periods. These patterns of daily and seasonal heterothermy suggest that body temperature patterns of black-tailed prairie dogs may be driven by an innate timing mechanism. All prairie dogs entered torpor intermittently throughout winter and spring. Torpor bouts appeared to be influenced by precipitation and reductions in ambient temperature. Our results also suggest that reproductive behaviors and circadian timing may influence torpor in this species.     

The absence of concordant population genetic structure in the black‐tailed prairie dog and the flea,Oropsylla hirsuta,with implications for the spread of Yersinia pestis

The black‐tailed prairie dog (Cynomys ludovicianus) is a keystone species on the mid‐ and short‐grass prairies of North America. The species has suffered extensive colony extirpations and isolation as a result of human activity including the introduction of an exotic pathogen, Yersinia pestis, the causative agent of sylvatic plague. The prairie dog flea, Oropsylla hirsuta, is the most common flea on our study colonies in north‐central Montana and it has been shown to carry Y. pestis. We used microsatellite markers to estimate the level of population genetic concordance between black‐tailed prairie dogs and O. hirsuta in order to determine the extent to which prairie dogs are responsible for dispersing this potential plague vector among prairie dog colonies. We sampled fleas and prairie dogs from six prairie dog colonies in two regions separated by about 46 km. These colonies were extirpated by a plague epizootic that began months after our sampling was completed in 2005. Prairie dogs showed significant isolation‐by‐distance and a tendency toward genetic structure on the regional scale that the fleas did not. Fleas exhibited higher estimated rates of gene flow among prairie dog colonies than the prairie dogs sampled from the same colonies. While the findings suggested black‐tailed prairie dogs may have contributed to flea dispersal, we attributed the lack of concordance between the population genetic structures of host and ectoparasite to additional flea dispersal that was mediated by mammals other than prairie dogs that were present in the prairie system.     

Does the host matter? Variable influence of host traits on parasitism rates

Parasitism of mammals is ubiquitous, but the processes driving parasite aggregation on hosts are poorly understood, as each system seems to show unique correlations between parasitism and host traits such as sex, age, size and body mass. Genetic diversity is also posited to influence susceptibility to parasitism, and provides a quantifiable measure of an intrinsic unchanging host property, but this link has not been well established. A lack of consistency in host traits predicting parasite heterogeneity may derive from the contribution of environmental factors to parasite aggregation. To evaluate this question, a large dataset was leveraged to explore the relationship between unchanging, intrinsic host traits (heterozygosity and sex), variable host traits (age, length and body mass), and extrinsic factors (sampling date/year and population) and flea presence/absence, abundance and intensity on two species of social burrowing mammal, the black-tailed prairie dog (Cynomys ludovicianus) and the Gunnison’s prairie dog (Cynomys gunnisoni). Prairie dogs experience frequent parasitism by fleas, but the distribution of fleas among individuals is highly skewed. In these systems, intrinsic host traits were nuanced in how they predicted flea aggregation on individual prairie dogs, with sex unimportant to parasitism rates and heterozygosity increasing the probability of infection and influencing the number of fleas in divergent ways. Variable host traits interacted with each other and with environmental or geographic stochasticity to influence flea aggregation. Length and age tended to increase parasitism, whereas the effects of body mass and condition were mediated by date and other host traits to produce both positive and negative effects on parasitism. This finding suggests that the factors affecting ectoparasite infection on individuals are complex, even within species. Importantly, there was no correlation between the number of fleas on an individual in one year and the number of fleas on the same individual the next year, supporting the idea that flea aggregation is not driven by unchanging, intrinsic characteristics of the host. Rather, these findings indicate that host traits influence parasitism in nuanced ways, including interactions with environmental characteristics and stochastic factors.     

Black-tailed prairie dogs and the structure of avian communities on the shortgrass plains

We tested the hypothesis that black-tailed prairie dogs (Cynomys ludovicianus) influence avian community structure on the shortgrass prairie. We surveyed 36 prairie dog towns and 36 paired sites without prairie dogs during summer and fall of 1997, 1998, and 1999 in the Oklahoma Panhandle. Our surveys totaled 9,040 individual observations for 73 avian species. Significantly distinct avian communities were present on prairie dog towns when compared to sites within four different macrohabitats of the surrounding landscape: open rangeland, scrub/sandsage (Artemisia filifolia) habitats, Conservation Reserve Program (CRP) plots, and fallow crop fields. Relative densities of all bird species combined was higher on prairie dog towns versus paired sites in summer and fall. Mean species richness of birds was significantly higher on prairie dog towns than paired sites during summer, but there were no significant differences in fall. Open rangeland had the highest mean species richness in fall. Assemblages of avian communities differed significantly between prairie dog towns and the four macrohabitat types during summer. Burrowing owls (Athene cunicularia), killdeer (Charadrius vociferous), horned larks (Eremophila alpestris), and meadowlarks (Sturnella spp.) were positively and significantly associated with prairie dog towns during summer, while horned larks and ferruginous hawks (Buteo regalis) were significantly associated with prairie dog towns during fall. Even in their current remnant state, black-tailed prairie dogs continue to play a significant role in the assembly of ecological communities across the Great Plains. Conservation of prairie dogs goes well beyond a single species, and is an important strategy for the preservation of the prairie ecosystem as a whole.     

Reintroducing a keystone burrowing rodent to restore an arid North American grassland: challenges and successes

Prairie dogs (Cynomys spp.) are important ecosystem engineers in North America's central grasslands, and are a key prey base for numerous predators. Prairie dogs have declined dramatically across their former range, prompting reintroduction efforts to restore their populations and ecosystem functions, but the success of these reintroductions is rarely monitored rigorously. Here, we reintroduced 2,400 Gunnison's prairie dogs (C. gunnisoni) over a period of 6 years to the Sevilleta National Wildlife Refuge, in central New Mexico, U.S.A., a semi‐arid grassland ecosystem at the southern edge of their range. We evaluated the population dynamics of prairie dogs following their reintroduction, and their consequent effects on grassland vertebrates. We found postrelease survival of prairie dogs stabilized at levels typical for the species (ca. 50%) after approximately 1 month, while average annual recruitment was ca. 0.35 juveniles per female, well below what was required for a self‐sustaining, stable population. Extreme drought conditions during much of the study period may have contributed to low recruitment. However, recruitment increased steadily over time, indicating that the reintroduced colony may simply need more time to establish in this arid system. We also found well‐known associates of prairie dog colonies, such as American badgers (Taxidea taxus) and burrowing owls (Athene cunicularia), were significantly more common on the colonies than off. After 7 years, we have yet to meet our goal of establishing a self‐sustaining population of Gunnison's prairie dogs in this semi‐arid grassland. But despite the uncertainty and challenges, our work shows that reestablishing keystone species can promote ecosystem restoration.     

Bison-prairie dog-plant interactions in a North American mixed-grass prairie

Both bison and prairie dogs have multiple and dramatic effects on grassland landscapes and both are considered by many to be keystone herbivores. Numerous studies have documented their independent or combined impact on grassland ecosystem processes, but there have been few attempts to simultaneously assess the individual and interactive effects of bison and prairie dogs where they co-occur. We began a long-term study in late 1994 in Badlands National Park, South Dakota, USA, to evaluate the ecological consequences of the presence or exclusion of prairie dogs, bison, or both, upon various aspects of plant community dynamics and N cycling. Five different treatments were established at three separate mixed-grass prairie sites in the park: (1) off the prairie dog colony with bison excluded, (2) off colony with continued bison utilization, (3) on colony with bison excluded but continued prairie dog use, (4) on colony with utilization by prairie dogs and bison, and (5) on colony with both excluded. There were few differences in aboveground biomass or plant species composition between the two off-colony treatments or among the three on-colony treatments, even after 3 years of treatment imposition. However, aboveground biomass was >2 times greater in off-colony sites than on-colony sites, primarily due to the near elimination of grasses on prairie dog colonies. Off-colony sites were dominated by a few grass species, resulting in lower plant species diversity, while on-colony sites were dominated by several forb species. Net N mineralization early in the growing season was 4 times greater on prairie dog colonies than at off-colony sites, but all sites exhibited net immobilization by the latter half of the growing season. The results of this study indicate distinct differences in several ecosystem properties between on- and off-colony treatments. Whether these patterns represent relatively stable alternate states or whether distinct changes will emerge in the different herbivore treatments after several additional years is of considerable interest.     

Abundance patterns of two Oropsylla (Ceratophyllidae: Siphonaptera) species on black-tailed prairie dog (Cynomys ludovicianus) hosts.

Behavioral, genetic, and immune variation within a host population may lead to aggregation of parasites whereby a small proportion of hosts harbor a majority of parasites. In situations where two or more parasite species infect the same host population there is the potential for interaction among parasites that could potentially influence patterns of aggregation through either competition or facilitation. We studied the occurrence and abundance patterns of two congeneric flea species on black-tailed prairie dog (Cynomys ludovicianus) hosts to test for interactions among parasite species. We live-trapped prairie dogs on ten sites in Boulder County, CO and collected their fleas. We found a non-random, positive association between the two flea species, Oropsylla hirsuta and O. tuberculata cynomuris; hosts with high loads of one flea species had high loads of the second species. This result suggests that there is no interspecific competition among fleas on prairie dog hosts. Host weight had a weak negative relationship to flea load and host sex did not influence flea load, though there were slight differences in flea prevalence and abundance between male and female C. ludovicianus. While genetic and behavioral variation among hosts may predispose certain individuals to infection, our results indicate apparent facilitation among flea species that may result from immune suppression or other flea-mediated factors.