Richardson's Ground Research Articles

REMOVAL OF PSEUDO-ODONTOMAS VIA LATERAL MAXILLOTOMY IN THREE RICHARDSON'S GROUND SQUIRRELS (UROCITELLUS RICHARDSONII).

Pseudo-odontoma can occur in some species with elodont teeth. Pseudo-odontomas affecting maxillary dentition may result in obstruction of the nasal cavities and lead to dyspnea. Effective treatments for the disease in Richardson's ground squirrels (Urocitellus richardsonii) have not yet been established. Three Richardson's ground squirrels exhibiting dyspnea and with maxillary pseudo-odontomas, based on diagnostic imaging, were surgically treated. The animals were placed under general anesthesia, and following excision of skin and subcutaneous tissue at the midpoint of the line connecting the medial canthus and ipsilateral nasal opening, maxillotomy of the incisive bone was performed. The reserve crown of the maxillary incisor tooth was exposed via the maxillotomy site and was sectioned into labial and palatal fragments, and the diseased tooth was completely extracted. In all three cases, dyspnea improved immediately after surgery. In one case, no recurrence was observed 600 d following surgery. These results suggest that the procedure used provides a practical approach for treating maxillary pseudo-odontomas in Richardson's ground squirrels.

Seasonal differences in the morphology and spine density of hippocampal neurons in wild ground squirrels.

Seasonally reproducing small mammals often undergo changes in brain anatomy throughout the year. Much of the research on this seasonal neuroplasticity has focused on changes in hippocampus volume and neurogenesis, with relatively little attention paid to neuronal morphology. Here, we test for sex, season and sex-season interaction effects on hippocampal neuron morphology and dendritic spine density in a seasonally reproducing rodent: Richardson's ground squirrel (Urocitellus richardsonii). We quantified the morphology and spine densities of Golgi-stained pyramidal neurons and granule cells in the hippocampus and tested for differences between sexes and seasons with generalized linear models. Although we found no significant sex differences or sex-season interaction effects on any of our morphological measurements, there were significant differences in neuron morphology and spine density between breeding and non-breeding seasons. In the non-breeding season, ground squirrels had CA1 neurons with longer basal dendrites with more branches than in the breeding season. Non-breeding season animals also had higher apical and basal dendrite spine density in CA1 and CA3 neurons than breeding-season animals. Conversely, the spine densities of CA1 somata and granule cells were higher in breeding than in non-breeding season. These differences in neuron morphology and spine density between breeding and non-breeding seasons likely arise from a combination of activity levels, stress hormones, and photoperiod. Although the functional implications of seasonal changes in hippocampal neuron morphology and spine density are uncertain, our data suggest that ground squirrels may be a good model for understanding seasonal neuroplasticity in mammals.

Purification and characterization of NADP-isocitrate dehydrogenase from skeletal muscle of Urocitellus richardsonii.

NADP-dependent isocitrate dehydrogenase (NADP-IDH, EC 1.1.1.42) catalyzes the oxidative decarboxylation of isocitrate to α-ketoglutarate with the concomitant production of NADPH. NADPH plays important roles in many biosynthesis pathways, maintenance of proper oxidation-reduction balance, and protection against oxidative damage. This present study investigated the dynamic nature of NADP-IDH during hibernation by purifying it from the skeletal muscle of Richardson's ground squirrel (Urocitellus richardsonii) and analyzing its structural and functional changes in response to hibernation. Kinetic parameters of purified NADP-IDH from euthermic and hibernating ground squirrel skeletal muscle were characterized at 22°C and 5°C. Relative to euthermic muscle, -NADP-IDH in hibernating muscle had a higher affinity for its substrate, isocitrate at 22°C, whereas at 5°C, there was a significant decrease in isocitrate affinity. Western blot analysis revealed greater serine and threonine phosphorylation in hibernator NADP-IDH as compared to euthermic NADP-IDH. In addition, Bioinformatic analysis predicted the presence of 18 threonine and 21 serine phosphorylation sites on squirrel NADP-IDH. The structural and functional changes in NADP-IDH indicate the ability of the organism to reduce energy consumption during hibernation, while emphasizing increased NADPH production, and thus antioxidant activity, during torpor arousal cycles.

Prairie dogs, cattle subsidies and alternative prey: seasonal and spatial variation in coyote diet in a temperate grassland

As the dominant predator on North America's grasslands, coyotes Canis latrans have a large influence on biodiversity, both on working ranches and in protected parks. Ground squirrel (sciurid) species and livestock carrion are often abundant on grasslands worldwide and have the potential to influence a predator's consumption of alternative prey. We collected 1321 scats in four seasons over two years in and adjacent to Grasslands National Park, Saskatchewan, to test the hypothesis that seasonal and spatial variation in consumption of sciurid prey and cattle Bos taurus carrion influenced coyote consumption of alternative prey. Sciurid (black‐tailed prairie dog Cynomys ludovicianus and Richardson's ground squirrel Urocitellus richardsonii) remains were common from spring to fall and had a strong inverse relationship with deer (mule deer Odocoileus hemionus and white‐tailed deer O. virginianus), which were most common in winter scats. Cattle remains were most common during spring, fall and winter, and occurred in 10.6% of scats annually. Biomass estimates suggest that cattle was the highest ranked food on cattle grazing land year‐round, and the 2nd ranked food, after deer, during winter on the portion of the park from which cattle were excluded. Closer proximity of scats to a prairie dog colony increased the likelihood of prairie dog remains throughout the year and reduced the likelihood of cattle remains in scats from spring to fall, but not during winter. Individual differences in foraging and ranging behavior may explain the spatial distribution of prairie dog versus cattle in scats. Further work is needed to determine whether sciurid prey, deer, or livestock carrion support large predator populations on grassland habitats to a level that may negatively affect coexisting prey species, including species at risk.

Skeletal muscle of torpid Richardson's ground squirrels (Urocitellus richardsonii) exhibits a less active form of citrate synthase associated with lowered lysine succinylation

Hibernation is a metabolic/physiological strategy employed by many mammals to cope with periods when energy usage is greater than its input. Animals undergoing hibernation need to greatly reduce their metabolic rate and reshape their catabolic processes to survive on stored triglycerides. Citrate synthase (CS) is one of only two irreversible steps in the citric acid cycle (CAC) and forms an important regulatory checkpoint that gates the entry of acetyl-CoA formed in glycolysis or fatty acid catabolism into this critical central metabolic hub. This study investigated the regulation of citrate synthase in the muscle tissue of a small mammalian hibernator through comparison of functional and structural properties. The results demonstrated a significant decrease in the Vmax of purified torpid CS compared to the control euthermic enzyme (1.2–1.7 fold greater in the control) that was evident over a wide range of temperatures (8, 22 and 37 °C) that are encountered by the enzyme in hibernation. This was also reflected in the specific activity of the enzyme in crude muscle protein extracts. Analyzing the purified CS through immunoblotting demonstrated that the enzyme contained noticeably less lysine succinylation in the torpid state (about 50% of euthermic levels) and this was correlated with an increase in total levels of SIRT5, the enzyme responsible for mediating desuccinylation in the mitochondria (2.2 fold increase). Taken together, the results of this study support the idea that CS is inhibited during hibernation in the ground squirrel skeletal muscle and that this alteration could be mediated by decreases in succinylation.

Functional and post-translational characterization of pyruvate dehydrogenase demonstrates repression of activity in the liver but not skeletal muscle of the Richardson's ground squirrel (Urocitellus richardsonii) during hibernation.

Hibernation consists of a series of physiological and biochemical alterations in an animal that allows for reduced body temperatures down to near ambient levels and substantial fuel conservation allowing it to survive on stored fat supplies accumulated during the summer. The Richardson's ground squirrel is one such hibernator that undergoes such changes for as long as 9 months of the year. This study examines the role of regulation of the pyruvate dehydrogenase complex (PDC) during hibernation in the skeletal muscle and liver of the Richardson's ground squirrel. The current study demonstrates a great reduction in the activity of PDC in the hibernating liver, but not in the skeletal muscle. This was matched by a significant increase in the phosphorylation on a regulatory serine residue (S300) of the pyruvate dehydrogenase (PDH) E1α subunit. Examining the expression patterns of the relevant kinases for PDH and the associated phosphatase demonstrated some unexpected results. Specifically, an increase in PDKs 1 and 2 and a decrease in PDK4 was noted in the skeletal muscle tissue in response to hibernation and no alterations in the expression patterns of any of these enzymes were noted in the liver. This suggests that alternative modes of regulation of the kinases may be at play in hibernation to bring about the observed effects. Taken together this study demonstrates that PDH regulatory responses differ markedly between tissues and emphasize the importance of inhibition of the complex in the liver during hibernation.

5'-Adenosine monophosphate deaminase regulation in ground squirrels during hibernation.

Hibernation is an important winter survival strategy for many small mammals. By sinking into a deep torpor where metabolic rate can be as low as 1-5% of the resting rate in euthermia, animals accrue huge energy savings that allow survival, typically without eating, for many months. Hibernating ground squirrels show a net reduction in the total adenylate pool of skeletal muscle during torpor, but the ATP/ADP ratio and adenylate energy charge remain stable. A key enzyme involved in managing adenylate pool size is 5'-adenosine monophosphate deaminase (AMPD). Assessing skeletal muscle AMPD from both Richardson's ground squirrels (Urocitellus richardsonii) (RGS) and 13-lined ground squirrels (Ictidomys tridecemlineatus) (TLGS), the present study shows that muscle AMPD of euthermic versus hibernating animals displays markedly different kinetic properties, differential responses to temperature and to effectors, and is regulated by reversible protein phosphorylation. AMPD activity decreased during hibernation in both TLGS and RGS skeletal muscle, by 70 and 84%, respectively. Stimulation of total protein phosphatases, total serine/threonine protein phosphatases, PP1, PP2B or PP2C, all reduced AMPD activity between 54 and 92% in extracts of euthermic RGS muscle. The same incubation did not change the activity of AMPD from muscle of hibernating animals. Oppositely, both euthermic and hibernating AMPD showed a strong increase in activity when incubated under conditions that promoted the enzyme phosphorylation by PKA, PKC or PKG. Overall, the data indicate that both low activity of AMPD and low affinity of the enzyme for AMP during torpor reduce the rate of adenylate degradation, the primary driver of these changes being covalent phosphorylation of AMPD.

Richardson's ground squirrel litter size-sex ratio trade-off reveals conditional adaptive sex allocation.

Trivers and Willard proposed that female mammals should adjust their investment in male versus female offspring relative to their ability to produce high-quality offspring. We tested whether litter size-sex ratio trade-offs predicted by Adaptive Sex Allocation (ASA) theory occur among Richardson's ground squirrel (Urocitellus richardsonii) dams over 10 distinct breeding years in a population where individuals experienced variability in food availability and habitat disruption. Litters of primiparous dams became increasingly female-biased with increasing litter size, but that trend waned among second litters born to dams, and reversed among third litters, with larger litters becoming more male-biased, suggesting that ASA is a product of interacting selection pressures. Trade-offs were not associated with habitat disruption, the availability of supplementary food, or dam age. An association between habitat disruption and male-biased sex ratios, the prevalence of litter size-sex ratio trade-offs and placental scar counts exceeding the number of juveniles at weaning in our population, but not in a geographically distinct population of conspecifics exposed to different environmental conditions reveal that the expression of ASA varies among populations and among years within populations, illustrating the conditional nature of ASA.

Pathology of Ground Squirrels in a Research Colony.

This paper presents a retrospective review of the postmortem findings in a colony of wild-caught ground squirrels used in medical research. The species included in this study were Richardson's ground squirrel Urocitellus richardsonii, Columbian ground squirrel Urocitellus columbianus and golden-mantled ground squirrel Callospermophilus lateralis. The pathologic findings in 160 ground squirrels from this colony demonstrated a wide variety of conditions, with chronic nephritis and hepatic adenomas being the most frequent overall. All animals with gross lesions of chronic interstitial nephritis had both glomerular and tubulointerstitial disease upon microscopic examination. As the first review of pathology in a research colony of ground squirrels. this study provides data for use in comparative studies about rodent diseases and important information for those who maintain such animals for research.

Richardson's ground squirrel (Urocitellus richardsonii) alarm call receivers experience an auditory continuity illusion.

Auditory continuity illusions are perceptual illusions in which receivers perceive an auditory signal as continuous when part of the signal has been removed or obfuscated by a louder noise. Richardson's ground squirrels (Urocitellus richardsonii) communicate alarm acoustically in noisy natural settings. Thus, we tested whether they experience an auditory continuity illusion by presenting free-living squirrels with repeated whistle alarm calls within which every second syllable remained unmanipulated, was partially obfuscated by relatively brief (25 ms) bursts of white noise, or partially obfuscated by longer duration (100 ms) white noise bursts. Field playbacks of alarm calls with brief white noise bursts failed to elicit increased vigilance from receivers relative to unmanipulated calls, whereas calls with longer white noise bursts elicited increased vigilance relative to the other 2 call types. As with previous empirical demonstrations of the auditory continuity illusion in vertebrates, relatively short obfuscating noise resulted in receivers perceiving each syllable as a whole, while longer obfuscating noise caused receivers to perceive the beginning and end of each manipulated syllable as 2 distinct syllables, increasing the perceived syllable repetition rate. These results reveal that Richardson's ground squirrels experience an auditory continuity illusion allowing the extraction of the rate of syllable repetition from conspecific repeated alarm calls in the face of short duration environmental noise. Selection has acted upon receivers to refine the cognitive mechanisms underlying signal perception, facilitating the extraction of information masked by environmental noise. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Characterizing the regulation of pyruvate kinase in response to hibernation in ground squirrel liver (Urocitellus richardsonii).

The Richardson's ground squirrel (Urocitellus richardsonii) undergoes numerous changes to its core physiological and metabolic processes over the months it spends hibernating during the winter. Winter torpor is characterized by an overall reduction in metabolic rate, a lowering of core body temperature, and a switch to preferential consumption of lipids instead of carbohydrates. The alterations in central metabolic pathways are often accomplished by the regulation of key enzymes within the glycolytic pathway. The regulation of one such enzyme, pyruvate kinase (PK), was characterized in the present study in the liver of torpid ground squirrels. PK was purified from liver tissue of euthermic and hibernating U. richardsonii and subsequently assayed to determine the kinetic parameters of the enzyme at 22° and 5°C. Additional studies assessed the relative degree of post-translational modifications in PK from control and hibernating ground squirrels. The results from this study demonstrated significantly lowered maximal activity in the hibernating form of the enzyme and decreased sensitivity to the activator FBP when compared to the control. Immunoblotting demonstrated increased relative serine and threonine phosphorylation (~3 fold) in the hibernating PK. Taken together these results suggest that phosphorylation of liver PK is an important step in inhibiting glycolytic activity in the liver of the Richardson's ground squirrel during torpor.

Regulation of the α-ketoglutarate dehydrogenasecomplex during hibernation in a small mammal, the Richardson's ground squirrel (Urocitellus richardsonii)

The citric acid cycle (CAC) is a central metabolic pathway that links carbohydrate, lipid, and amino acid metabolism in the mitochondria and, hence, is a crucial target for metabolic regulation. The α-ketoglutarate dehydrogenase complex (KGDC) is the rate-limiting step of the CAC, the three enzymes of the complex catalyzing the transformation of α-ketoglutarate to succinyl-CoA with the release of CO2 and reduction of NAD to NADH. During hibernation, the metabolic rate of small mammals is suppressed, in part due to reduced body temperature but also active controls that suppress aerobic metabolism. The present study examined KGDC regulation during hibernation in skeletal muscle of the Richardson's ground squirrel (Urocitellus richardsonii). The KGDC was partially purified from skeletal muscle of euthermic and hibernating ground squirrels and kinetic properties were evaluated at 5°, 22°, and 37 °C. KGDC from hibernator muscle at all temperatures compared with euthermic controls exhibited a decreased affinity for CoA as well as reduced activation by Ca2+ ions at 5 °C from both euthermic and hibernating conditions. Co-immunoprecipitation was employed to isolate the E1, E2 and E3 enzymes of the complex (OGDH, DLST, DLD) to allow immunoblot analysis of post-translational modifications (PTMs) of each enzyme. The results showed elevated phospho-tyrosine content on all three enzymes during hibernation as well as increased ADP-ribosylation and succinylation of hibernator OGDH. Taken together these results show that the KGDC is regulated by posttranslational modifications and temperature effects to reorganize enzyme activity and mitochondrial function to aid suppression of mitochondrial activity during hibernation.

Effects of scent lure on camera trap detections vary across mammalian predator and prey species.

Camera traps are a unique survey tool used to monitor a wide variety of mammal species. Camera trap (CT) data can be used to estimate animal distribution, density, and behaviour. Attractants, such as scent lures, are often used in an effort to increase CT detections; however, the degree which the effects of attractants vary across species is not well understood. We investigated the effects of scent lure on mammal detections by comparing detection rates between 404 lured and 440 unlured CT stations sampled in Alberta, Canada over 120 day survey periods between February and August in 2015 and 2016. We used zero-inflated negative binomial generalized linear mixed models to test the effect of lure on detection rates for a) all mammals, b) six functional groups (all predator species, all prey, large carnivores, small carnivores, small mammals, ungulates), and c) four varied species of management interest (fisher, Pekania pennanti; gray wolf, Canis lupus; moose, Alces alces; and Richardson's ground squirrel; Urocitellus richardsonii). Mammals were detected at 800 of the 844 CTs, with nearly equal numbers of total detections at CTs with (7110) and without (7530) lure, and variable effects of lure on groups and individual species. Scent lure significantly increased detections of predators as a group, including large and small carnivore sub-groups and fisher specifically, but not of gray wolf. There was no effect of scent lure on detections of prey species, including the small mammal and ungulate sub-groups and moose and Richardson's ground squirrel specifically. We recommend that researchers explicitly consider the variable effects of scent lure on CT detections across species when designing, interpreting, or comparing multi-species surveys. Additional research is needed to further quantify variation in species responses to scent lures and other attractants, and to elucidate the effect of attractants on community-level inferences from camera trap surveys.

Enzootic maintenance of sylvatic plague in Canada's threatened black‐tailed prairie dog ecosystem

AbstractData paucity can seem to hinder science‐based approaches to the conservation of imperiled species. Yet, even individually limited datasets can improve understanding and management of complex ecological systems when carefully integrated. We demonstrate this approach to gain first insights on the transmission ecology of Yersinia pestis in Grasslands National Park (GNP), Canada, where both the bacterium and its rodent host, the nationally threatened black‐tailed prairie dog (BTPD, Cynomys ludovicianus), reach the northern limit of their distribution in North America. Primarily flea‐borne, Y. pestis causes sylvatic plague, a disease of exceptional relevance to both human health and wildlife conservation. We integrated data collected independently by multiple organizations in 2010–2017 across 17 BTPD colonies, where the species co‐occur with Richardson's ground squirrels (RGS, Urocitellus richardsonii). Available data included estimates of BTPD density and occupancy from visual counts and colony mapping; information on flea distribution, abundance, and prevalence of infection with Y. pestis from burrow swabbing, animal combing, and PCR assays; and the response of these variables to deltamethrin application on BTPD colony sections. Our analyses suggest that sylvatic plague in GNP is maintained at an enzootic level (i.e., chronic presence affecting a low proportion of individuals) with no evidence of widespread mortality, at least partially due to reduced flea activity after spring (percentage of prevalence in burrows: April–May = 11.69–33.89%; June–September: 1.75–3.19%), low prevalence of Y. pestis in flea samples (95% CI = 0.42–2.27%), and relatively low BTPD densities. Nonetheless, reducing flea prevalence through insecticide application had a positive effect on BTPD abundance, suggesting that enzootic plague is causing chronic mortality. Because flea prevalence on hosts was higher following drier years and higher on RGS than on BTPD (26.69% vs. 3.27%), insecticide application may be particularly important during dry periods and may need to take RGS and their movements into consideration. Differences between flea communities sampled by burrow swabbing and host combing suggest that plague surveillance should integrate both methods. Effects of projected climate change on vector life cycles, flea community composition, and host–parasite interactions warrant continued monitoring and an adaptive approach to species recovery actions and plague mitigation measures.

Call-specific patterns of neural activation in auditory processing of Richardson's ground squirrel alarm calls.

IntroductionRichardson's ground squirrels use alarm calls to warn conspecifics about potential predatory threats. Chirp calls typically indicate high levels of threat from airborne predators, while whistle calls are associated with lower levels of threat from terrestrial predators. These types of calls primarily elicit escape behaviors and increased vigilance in receivers, respectively. While much is known about the neural mechanisms involved in the production of vocalizations, less is known about the mechanisms important for the perception of alarm calls by receivers, and whether changes in perceived risk are associated with unique patterns of neuronal activation. Thus, to determine whether alarm calls associated with different levels of predation risk result in differential neuronal activation, we used immunohistochemistry to identify and quantify c‐Fos immunopositive cells in brain regions important in stress, fear, danger, and reward, following alarm call reception.MethodsWe exposed 29 female Richardson's ground squirrels (10 control, 10 whistle receivers, and 9 chirp receivers) to playbacks of whistles, chirps, or a no‐vocalization control. We then assessed neuronal activation via c‐Fos immunohistochemistry in 12 brain regions.ResultsGround squirrels receiving high‐threat “chirp” vocalizations had reduced neuronal activation in the medial amygdala and superior colliculus compared with controls. It is likely that changes in activity in these brain regions serve to alter the balance between approach and avoidance in turn promoting escape behaviors.ConclusionsThus, we conclude that in Richardson's ground squirrels, these brain regions are important for the perception of risk resulting from receiving alarm calls and allow for appropriate behavioral responses by receivers.

Identification of bacteria in the Rocky Mountain wood tick, Dermacentor andersoni, using single-strand conformation polymorphism (SSCP) and DNA sequencing.

PCR-based single-strand conformation polymorphism (SSCP) analyses combined with DNA sequencing of the prokaryotic 16S ribosomal (r) RNA gene encompassing the hypervariable V4 region was used to determine the bacterial composition of Rocky Mountain wood ticks (Dermacentor andersoni) attached to Richardson's ground squirrels (Urocitellus richardsonii) and questing on vegetation in southern Saskatchewan, Canada. The bacteria present in questing adult ticks from Saskatchewan Landing Provincial Park included Rickettsia peacockii, a Francisella-like endosymbiont (FLE) and an Arsenophonus-like endosymbiont. Bacteria in the adult and nymphal ticks attached to U. richardsonii collected from Beechy included R. peacockii, a FLE, and several other genera (e.g., Ralstonia, Sphingobium, Comamonas and Pseudomonas). The bacteria detected in D. andersoni in the present study are consistent with the findings of other studies that have characterized the microbiome of this tick species in the USA using next generation sequencing. This result demonstrates that the SSCP-based approach used in this study is cost- and time-effective for examining bacterial composition in ticks.

Burrowing Richardson's ground squirrels affect plant seedling assemblages via environmental but not seed bank changes.

In grassland ecosystems, burrowing mammals create disturbances, providing habitat for animal species and increasing plant community diversity. We investigated whether seedling assemblages on Richardson’s ground squirrel Urocitellus richardsonii mounds result from seed rearrangement or environmental changes that favor germination of certain species over others. To test whether ground squirrels rearrange the seed bank by burrowing, we compared seed compositions among mounds, burrows, and undisturbed soil. To test whether ground squirrels change environmental conditions, we compared soil nitrate and bare ground cover on and off mounds. We also compared seedlings that germinated on mounds with seedlings that germinated on artificial disturbances from which we removed aboveground vegetation. Soil nitrate and bare ground cover were significantly higher on mounds than artificial disturbances. While seed richness and abundance did not differ among mounds, burrows, and undisturbed soil, seedling richness was reduced on mounds relative to artificial disturbances. Burrowing disturbance favors seedlings that can capitalize on bare ground availability but are less able to immobilize nitrate, as opposed to perennial species that immobilize more nitrate but take longer to establish. Our results suggest that Richardson’s ground squirrels act as ecosystem engineers, although future research following succession on ground squirrel mounds is necessary to understand how they influence plant communities past the seedling stage.

Gone girl: Richardson's ground squirrel offspring and neighbours are resilient to female removal.

Within matrilineal societies, the presence of mothers and female kin can greatly enhance survival and reproductive success owing to kin-biased alarm calling, cooperation in territory defence, protection from infanticidal conspecifics, joint care of young and enhanced access to resources. The removal of mothers by predators or disease is expected to increase the stress experienced by offspring via activation of their hypothalamic-pituitary-adrenal axis, increasing circulating glucocorticoids and reducing offspring survival and reproductive success. Yet, few studies have removed mothers in the post-weaning period to examine the assumed physiological and fitness consequences associated with these mortality events. We examined how the loss of a mother affects juvenile Richardson's ground squirrels' (Urocitellus richardsonii) faecal glucocorticoid metabolites and their survival. Given that neighbours are often close kin, we further hypothesized that conspecific removal would similarly diminish the fitness of neighbouring individuals. Upon removing the mother, we detected no impact on offspring or neighbouring conspecific faecal glucocorticoid metabolites in the removal year, or on overwinter survival in the following year. Furthermore, no impact on neighbour reproductive success was detected. Given the high predation rates of ground squirrels in wild populations, resilience to a changing social environment would prove adaptive for both surviving kin and non-kin.

Predation by Long-Tailed Weasels Mustela frenata during a Richardson's Ground Squirrel Urocitellus richardsonii Population Outbreak in Southwestern Saskatchewan

Long-tailed weasels (Mustela frenata) are known to feed on mice and voles. However, in the Canadian Prairies, where Richardson's ground squirrels (Urocitellus richardsonii) are abundant (particularly during drought periods), long-tailed weasel predation on these medium-size rodents is poorly documented. In this study, predation by long-tailed weasels on Richardson's ground squirrels was documented from April 2008 to September 2008 in southwestern Saskatchewan during a drought period. I found that Richardson's ground squirrel remains were the dominant food item in percentage of occurrence, volume, and biomass from April to July. In August–September, however, deer mice (Peromyscus maniculatus) and insects became more important. During years of Richardson's ground squirrel abundance, weasels may temporarily switch predation onto these rodents.

Central distribution of oxytocin and vasopressin 1a receptors in juvenile Richardson's ground squirrels.

Oxytocin and vasopressin are well-conserved peptides important to the regulation of numerous aspects of social behavior, including sociality. Research exploring the distribution of the receptors for oxytocin (Oxtr) and for vasopressin (Avpr1a) in mammals has revealed associations between receptor distribution, sociality, and species' mating systems. Given that sociality and gregariousness can be tightly linked to reproduction, these nonapeptides unsurprisingly support affiliative behaviors that are important for mating and offspring care. We localized these receptors in juvenile Richardson's ground squirrel brains to determine whether distribution patterns of Oxtr and Avpr1a that are associated with promiscuous mating systems differ in rodents that also exhibit non-reproductive affiliation. These squirrels are social, colonial, and engage in nepotistic alarm calling behavior and affiliation outside of a reproductive context. Juveniles are the most affiliative age-class and are non-reproductive; making them ideal for examining these associations. We found that juveniles had dense Oxtr binding in the dentate gyrus of the hippocampus, amygdala, lateral septum, bed nucleus of the stria terminalis and medial geniculate nucleus. Juveniles had low to modest levels of Avpr1a binding in the medial preoptic area, olfactory bulbs, nucleus accumbens, superior colliculus, and inferior colliculus. We noted Oxtr and Avpr1a binding in the social behavior neural network (SBNN), further supporting a role of these nonapeptides in modulating social behavior across taxa. Oxtr and Avpr1a binding was also present in brain regions important to auditory processing that have known projections to the SBNN. We speculate that these neural substrates may be where these nonapeptides regulatecommunication.