Arctic Ground Squirrel Study

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The Arctic Ground Squirrel (AGS), is the largest of the North American Ground Squirrel species and has many adaptations enabling it to survive its North American tundra habitat. Many mammals can survive the cold with thick, layered fur and by hibernating during the winter months. The AGS is no exception. However, no other hibernating mammal has a physiological adaptation during hibernation that is quite like the AGS (Dave et al., 2012).
While hibernation itself is a biological feat, the AGS has an impressive brain adaptation – synaptogenesis. They have the ability to sever synapses in the brain for hibernation and then reconnect them when they wake and warm up seven months later, completely healthy (von de Ohe et al., 2006). When the AGS is
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They then remain in this state for 12-15 hours before their body temperature cools to below 0C again.
AGS brains have evolved impressive resilience and plasticity (Popov, et al., 1992). Victor Popov and his colleagues did experiments that revealed the AGS brain renewing itself repeatedly and rapidly. They kept wild AGS in temperature controlled enclosures during hibernation. They then sacrificed different animals at 3 stages: hibernation; 2 hours after arousal; 1 day after hibernation. They removed the AGS brains to examine the neurons in the hippocampus. They discovered that, in the brains of the AGS during hibernation, there were shrunken neurons and fewer dendrites (see Figure 3) compared to the aroused and awake squirrels. It was also found that the dendrites had fewer dendritic spines which would result in a decreased number of synapses and neural connections. In stark contrast, when examining the brain of an AGS in the arousal period, there was a dense overlapping of dendrites. The AGS brains had regained all synapses lost during hibernation and had even more neural links than the active squirrels (Dave et al., 2012). However, on returning back into hibernation, these newly gained neural connections wither away. From this research, it is believed that these intermittent arousal phases are vital to the AGS
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During hibernation the AGS metabolism is too slow and their brains too cold and inactive to keep functioning properly. By shutting down the brain, the AGS conserves vital energy to keep itself alive (von der Ohe et al., 2006). Not only that, this adaptation provides protection against cerebral ischemia and brain damage (Drew et al., 2001) throughout the extremes of hibernation (Schwartz, et al., 2013). During hibernation, the blood flow within the AGS decreases by 90% but is maintained to some degree to the brain (Schwartz et al., 2013). Because of this, the brain is kept marginally warmer, thus preventing any stroke, cardiac arrest or trauma that would otherwise occur (Ross et al., 2009). Therefore, the AGS saves as much energy as possible during hibernation yet also manages to conserve the minimal crucial neural connections while avoiding cerebral ischemic damage (Drew et al.,
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