Tuesday, February 3, 2009
For ABC Wednesday this week we are on the letter C. So I am going with one of my all time favorite words - C is for Crepuscular. I don't know what it is about this word but I just love the way it rolls off my tongue and the way it sounds!
In case you were wondering "Crepuscular is a term used to describe animals that are primarily active during twilight, that is at dawn and at dusk. The word is derived from the Latin word crepusculum, meaning "twilight." (Wickipedia)
One great example of a crepuscular species is the Short-eared Owl.
In North America this owl has evolved to hunt at dawn and dusk in order to avoid competition with large raptors. But like so many of these things, there is an exception to every rule. On one island in the Galapagos the Short-eared Owl has no competition from any other aerial predators and has adapted to hunt during the day, ambushing Storm Petrels as they return to their roosts and nesting spots in the lava fields.
Another crepuscular species is the Rat. Scabbers (our Museum rat) is actually sitting on my shoulder as I write this post - just to make sure I don't write anything bad about him! The rat does not have good vision either in daylight or darkness so in order to minimise the chances of becoming dinner for a diurnal predator they utilise the narrow window between when the diurnal predator stops hunting and the nocturnal one begins, and visa versa at dawn.
For many species a crepuscular lifestyle is the perfect compromise. If they have not developed the visual acuity to see well in darkness and yet they want to avoid heavy competition for food or alternatively, an increased likelihood of becoming food then this particular niche is an ideal one.
For Many other C posts, check out the ABC Wednesday site.
Photo Credits - Dominick V & CJT
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