Hibernation in the Columbian Ground Squirrel
The Columbian ground squirrel can hibernate seven to eight months a year, although it may start early as July. Its burrow has a special hibernation chamber, which it uses to store fat, seeds, and bulbs that it eats during the summer months. When springtime rolls around, it eats these same sources of food. During the summer months, it can be seen foraging for food in the forest and storing these for later consumption in the spring.
Age
The timing of hibernation in the Columbian ground squirrel is influenced by a number of factors, including age and reproductive activity. Females undergoing reproductive activity are typically older than males, so hibernation is delayed in females. Age at death and longevity were both significant factors but were not as powerful as age or reproductive activity. The females’ body mass before hibernation was also a factor, as was the animal’s age at death. The reproductive activities of the females were also associated with delayed hibernation and fattening.
We calculated the annual fitness of female Columbian ground squirrels using a regression analysis. The results indicated that females with higher fitness during the spring and summer months had earlier onsets of hibernation. The results also suggested that the early emergence of females from hibernation is negatively associated with the severity of summer conditions. The findings have implications for determining the optimal timing of hibernation in columbian ground squirrels.
Parity
In the early days of the Columbian ground squirrel’s history, it was difficult to discern its genetic ties. Lewis and Clark wrote about it, but modern molecular genetics has revealed its close relationship with other ground squirrel species. These researchers have identified several factors that might trigger hibernation. Here, we explore these factors. A female must mate at least twice before hibernation occurs in order to have a successful litter.
To study this question, we studied the reproductive behavior of Columbian ground squirrels. We observed the appearance of the vulva in female ground squirrels and regularly trapped females. We found that females mated early and entered hibernation earlier than did later-matting females. Furthermore, successful females tended to immigrate earlier than did unsuccessful females. The researchers concluded that the appearance of reproductive hormones is a key factor in determining the timing of hibernation in female ground squirrels.
Body condition
Female ground squirrels with good body condition allocate more resources to reproduction, producing larger and heavier litters than those with poor body condition. These females also exhibit better survival and subsequent breeding. Moreover, they also exhibit increased somatic effort. This suggests that these changes in resource allocation may be associated with costs that the parents must bear and pass on to their offspring. Therefore, better body condition may be a crucial factor in triggering hibernation in the Columbian ground squirrel.
Physiological and biochemical changes in the heart are also implicated in triggering hibernation. The efficiency of excitation-contraction coupling is affected by junctophilin-2 and caveolin-3, which are both upregulated by a hormone known as serum response factor (SRF). These changes are likely to affect heart failure, and the study may provide a new strategy for correcting deficient Ca2+ signaling in heart diseases.
Genetics
The genes responsible for hibernation in the columbian ground squirrel are often closely related to genes that regulate body temperature and sexual maturity. In addition, the genes regulating bone growth and differentiation are not altered during hibernation. Interestingly, ground squirrels are able to urinate during IBA events. Thus, a shift in the composition of the myosin isoforms may increase the contractility of the hibernating heart.
In addition, the ground squirrel’s bone marrow transcriptome reveals that genes that control the immune system are enhanced during torpor. Interestingly, this is the opposite of what is observed in golden-mantled ground squirrels, which undergo torpor. Moreover, compared to the golden-mantled ground squirrel, the expression levels of the genes responsible for the immune response were elevated.
Climate
One study suggests climate triggers hibernation in Columbian ground squirrels. This small, free-living mammal emerges from its hibernacula three to five days earlier than its female counterparts. However, the study’s findings are not universal. It’s important to keep in mind that many species of ground squirrels exhibit some degree of plasticity when it comes to emergence from hibernation.
Observations of Columbian ground squirrels have revealed that climate change affects both the male and female reproductive phenology. In 2012, for example, only three out of eight males exhibited a pink scrotum. This suggests that unusually high temperatures in this year may have induced earlier emergence of females, resulting in a phenological mismatch. Males did not develop their reproductive organs in time to breed, as they would typically need a long period to mature.
What is the primary trigger for hibernation in Columbian ground squirrels?
The amount of daylight is the primary trigger for hibernation in Columbian ground squirrels.
How does the amount of daylight trigger hibernation?
The amount of daylight triggers hibernation by causing the squirrels’ pineal gland to produce less melatonin.
How does the production of less melatonin by the pineal gland trigger hibernation?
The production of less melatonin by the pineal gland disrupts the squirrels’ circadian rhythms and makes them sleepy.
How does the disruption of the squirrels’ circadian rhythms trigger hibernation?
The disruption of the squirrels’ circadian rhythms makes them want to sleep for longer periods of time which leads to hibernation.
How long do Columbian ground squirrels typically hibernate for?
Columbian ground squirrels typically hibernate for seven to eight months out of the year.
How does the length of hibernation compare between Columbian ground squirrels and other types of squirrels?
The length of hibernation for Columbian ground squirrels is much longer than that of other types of squirrels.
What are some of the reasons why Columbian ground squirrels hibernate for such a long period of time?
Some of the reasons why Columbian ground squirrels hibernate for such a long period of time include the lack of food availability and the cold weather.
How does the lack of food availability trigger hibernation?
The lack of food availability trigger hibernation by causing the squirrels to store up fat reserves to use for energy during hibernation.
How does the cold weather trigger hibernation?
The cold weather trigger hibernation by causing the squirrels to lower their body temperature to conserve energy.
Do Columbian ground squirrels hibernate alone or in groups?
Columbian ground squirrels hibernate alone.
How does hibernation help Columbian ground squirrels to survive the winter?
Hibernation helps Columbian ground squirrels to survive the winter by allowing them to avoid the cold weather and lack of food.
What happens to Columbian ground squirrels if they do not hibernate?
If Columbian ground squirrels do not hibernate they will not be able to survive the winter.
What are some of the signs that a Columbian ground squirrel is preparing to hibernate?
Some of the signs that a Columbian ground squirrel is preparing to hibernate include gaining weight building a nest and spending less time outside.
How does gaining weight help Columbian ground squirrels to prepare for hibernation?
Gaining weight helps Columbian ground squirrels to prepare for hibernation by providing them with extra fat reserves to use for energy during hibernation.
How does building a nest help Columbian ground squirrels to prepare for hibernation?
Building a nest helps Columbian ground squirrels to prepare for hibernation by giving them a safe and comfortable place to sleep.
Jessica Watson is a PHD holder from the University of Washington. She studied behavior and interaction between squirrels and has presented her research in several wildlife conferences including TWS Annual Conference in Winnipeg.
