Dolphin and Whale Sleep
July 31, 2011 4:30 PM   Subscribe

Are dolphins and whales considered cathemeral? [as opposed to diurnal, nocturnal or crepuscular].

Are dolphins and whales considered cathemeral? [as opposed to diurnal, nocturnal or crepuscular]. Is there a word to describe how they sleep, half a brain at a time?
posted by ChloeMills to Science & Nature (1 answer total) 6 users marked this as a favorite
 
Sleeping one half of the brain at a time is called unihemispheric sleep. But it's not the only way whales sleep - at least some appear to have short periods of full sleep.

I'm no expert, but the research on sleep patterns seems to be all over the place. It appears that different species sleep/rest for different periods, different total amounts of time per day, and at different times of day or night. Sometimes members of the same species in different locations (.pdf) show different sleep behavior. In the study just linked, humpbacks in one area appear to be cathemeral, and in another diurnal. That suggests it may be that sleep is determined by what and how much is available to eat in a particular environment, and when it needs to be caught.

Killer whales might provide another example of that. In places such as the Prince Edward Islands (.pdf) where prey (seals and penguins) is crepuscular or nocturnal, so are the whales. In places such as Vancouver Island (.pdf) where prey (seals, seabirds, fish) is available during the day, the whales do at least some hunting during the day. And in places (eg Patagonia, Crozet Island) where the whales hunt juvenile elephant seals or southern sea lions through intentionally stranding themselves, feeding seems to be primarily a daytime activity. Whether this last one is because that's when the seal/sealion pups feel safe playing in the shallows, or because that's when the whales feel safe throwing themselves onto a beach is a bit hard to tell.

So I'd guess there's no single simple answer to whether whales and dolphins in general are cathemeral/diurnal/nocturnal/crepuscular. I'd hit google scholar for the finer details on sleep and feeding patterns of particular species, then try to define that one for yourself.
posted by Ahab at 11:14 PM on July 31, 2011 [1 favorite]


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