Extreme climate event promotes phenological mismatch between sexes in hibernating ground squirrels

Hibernating ground squirrels rely on a short active period for breeding and mass accrual, and are thus vulnerable to extreme climate events that affect key periods in their annual cycle. Here, we document how a heatwave in March 2012 led to a phenological mismatch between sexes in Richardson’s ground squirrels (Urocitellus richardsonii). Females emerged from hibernation and commenced breeding earlier in 2012 relative to average female emergence. Although males had descended testes and pigmented scrota, it appeared that not all males were physiologically prepared to breed since 58.6% of males had non-motile sperm when breeding commenced. Body condition, relative testes size, and the relative size of accessory glands were significant predictors of sperm motility. Males with non-motile sperm had smaller accessory glands than males with motile sperm. There was no decrease in the number of juveniles that emerged in 2012 or female yearlings recruited in 2013, nor did juveniles emerge later than other years. The impact of this heatwave on male ground squirrels emphasizes the importance of assessing the consequences of climate change on the breeding success of hibernating species in both sexes, since the different sensitivity to external cues for emergence led to a mismatch in timing under this event.

Richardson’s ground squirrels (Urocitellus richardsonii) are associated primarily with intermediate levels of grassland, clay loam soils, and human development in Canadian mixed-grass prairies

Richardson’s ground squirrel (Urocitellus richardsonii, Sabine 1822) is a widespread burrowing mammal on the Northern Great Plains. This species is a prominent prey item for a variety of predators, and its burrows provide important habitat for other wildlife; however, Richardson’s ground squirrel is also considered an economically damaging agricultural pest. Despite the ecological importance of Richardson’s ground squirrels and their status as pests, there are gaps in our knowledge about large-scale habitat associations for this species. In 2011 and 2012, we conducted 1840 road-side surveys in a 130,000-km2 area of southern Saskatchewan, Canada to understand which habitat features are associated with Richardson’s ground squirrel occurrence. Ground squirrels were observed on 8% of the surveys. Probability of ground squirrel occurrence was highest in areas with moderate amounts of grassland (approximately 30%), areas that were developed by humans (>30%), and had a high proportion of clay loam soils, presumably for burrowing. Our study highlights the importance of heterogeneous landscapes and that areas disturbed by humans may provide suitable vegetation structure for ground squirrels. This information can help to identify important habitat for species that rely on Richardson’s ground squirrels and identify areas where Richardson’s ground squirrels could come into conflict with agriculture.

Shooting blanks: extreme climate event promotes phenological mismatch between sexes in hibernating ground squirrels

Hibernating ground squirrels rely on a short active period for breeding and mass accrual, and are thus vulnerable to extreme climate events that affect key periods in their annual cycle. Here, we observed how a heatwave in March 2012 led to a phenological mismatch between sexes in Richardson’s ground squirrels (Urocitellus richardsonii). Females emerged from hibernation and commenced breeding earlier in 2012 relative to average female emergence. Despite external indicators suggesting that males were prepared for breeding, it appeared that not all males were physiologically prepared since 58.6% of males had non-motile sperm when breeding commenced. We found that males with non-motile sperm had smaller accessory glands than males with motile sperm. Body condition, relative testes size, and the relative size of accessory glands were significant predictors of sperm motility. There was no difference in litter size among years, nor a decrease in the number of juveniles emerged in 2012 or female yearlings recruited in 2013. The impact of this heatwave on male ground squirrels emphasizes the importance of assessing the consequences of climate change on breeding success of hibernating species in both sexes, since the different cues for emergence led to a mismatch in timing under this event.

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.