Warming spring temperatures have led to advances in breeding dates, parturition and hatch dates, earlier emergence from hibernation, and earlier migration, among others 3, 4, 5, 6, 7. Shifts in phenology are a well-documented effect of climate change on organisms. Increasing temperatures and climate variability as a result of climate change have led to severe consequences for many species around the globe 1, 2.
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. 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. 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.
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.
Females emerged from hibernation and commenced breeding earlier in 2012 relative to average female emergence. Here, we document how a heatwave in March 2012 led to a phenological mismatch between sexes in Richardson’s ground squirrels ( Urocitellus richardsonii). 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.
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