The tight-knit relationship between snowy owls and lemmings reveals a very interesting set of selective pressures. Due to the large percentage of a snowy owl's diet that is composed of lemmings, lemming population dynamics strongly affect the snowy owl. This plays a large role when it comes to feeding offspring, and thus producing offspring. The timing between the peak of lemming population and breeding peaks of snowy owls is a dynamic and pivotal relationship. As was mentioned in the previous tab, lemming populations are affected greatly by the collapsing of their subterranean tunnel systems. Tunnel system collapse can either directly decrease lemming populations through tunnel cave-ins, or indirectly by trapping food under the surface and away from the lemmings. So, one can infer from this that the lemming population will peak during the coldest part of the winter, as their tunnels will still have structural integrity. Lemming population peaks mean that an ideal time for the snowy owl to rear young would fall around the same time as this indicates an abundant prey population. As climate change comes in to effect, this peak of lemmings will move to be earlier and earlier in the year, forcing the snowy owl populations to adjust.
Image Created by William Harvey (author)
This, like any other shift in population dynamics, will require some adaptive change on the part of the snowy owls. This adaptive change will be spurred on by selective pressures, which will naturally lead to a, hopefully, temporary thinning in population. This is due to the fact that not every snowy owl will respond to this change in the same way, and only the ones that are able to successfully adapt to the change in lemming population peak will survive. This could mean a selection for females that ovulate at earlier times in the year, or offspring that can see better at night to avoid nocturnal predation as they will be presented with more darkness with an earlier breeding time.
However, this selective pressure could spell the downfall of the snowy owl, as their already thin population might not be able to rebound from a decrease in numbers. All of these effects will have to be closely monitored as further action will be taken to help maintain and preserve this unique species.
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