Having high levels of cortisol in your blood for long periods of time can lead to chronic stress which has many negative health effects. Surprisingly, having high levels of cortisol is not always bad, especially if you are a North American red squirrel. Scientists are studying the impact of population density on survival found that pregnant red squirrels in a more crowded forest had higher cortisol levels and produced babies that grew faster.
Snails respond to stress like mammals do. Similar stress responses in both humans and snails make the snail a perfect animal model for researchers studying this constant factor in our lives. Researchers found that when snails must cope with strenuous and varied stressors, their memory stops working. In the study, snails became stressed when they experienced low levels of calcium, needed for proper shell growth, and when the presence of other snails caused overcrowding.