Re: what other animals rest/sleep the same as a dolphin 1/2 brain at a time?

Thank you for your most interesting question. I studied biology, did my 
PhD in biology, work since 8 years as biologist … and never came across 
this most interesting fact about dolphins --- and other animals. Thus I 
could learn a lot on my way collecting information to answer your 
question. 

First I wanted to find our whether your information about sleep in 
dolphins is correct or not. As nearly every dolphin internet site answers 
the question “How do dolphins sleep?” exactly as you say, it seems to be 
true. However, looking through a number of sites, the paragraph on sleep 
always looked nearly identical word by word. This pointed that all the 
sites seemed to have one and the same source that they are quoting. Is 
this source reliable?

My best guess is that the original paragraph on sleep in dolphins appeared 
in the “New Scientist” on 26. April 1997. I cite part of it:


SNOOZING WITH HALF A BRAIN 
DOLPHINS spend the night half-asleep. First the right half of 
their brains goes to sleep, then the left. In fact, the two hemispheres of 
a dolphin's brain trade off, like sentries in a military camp, several 
times in the course of a night, according to brainwave recordings by Lev 
Mukhametov of the Academy of Sciences in Moscow. While one hemisphere is 
in deep, slow-wave sleep, the other is always alert. And when 
experimenters keep dolphins awake to prevent the right (or left) brain 
from taking its usual turn, only that side builds up a sleep debt. This 
bizarre sleep pattern has now been seen in several dolphin and whale 
species and some seals. It may ensure that some part of the brain is 
always alert to control breathing in their watery environment. Indeed, 
dolphins stop breathing entirely if given drugs that put both sides of the 
brain to sleep at once. 


Here your question is – at least partly – answered: a number of species of 
dolphins, whales, and seals have this sleep pattern. But there also this 
article is mainly citing one source, research done by Lev Mukhametov. 
Going through scientific articles from this author I found some more 
information about other animals, that seem to sleep in the same way:

Dolphins:
Bottlenose Dolphin (Tursiops truncatus)
Northern Bobwhite (Colinus virginianus)

Seals:
Northern Fur Seal (Callozhinus ursinus)

Birds:
Mallard ducks (Anas platyrhynchos)

Reptiles:
Western fence lizard (Sceloporus occidenetalis)

This is a short but quite diverse list. The diversity suggests that there 
might be many more species sleeping this way. However, I did not find any 
original scientific reference for this type of sleep in whales. It might 
be that I simply missed the references or that this was later added 
without real research done, because they have the most similar lifestyle 
to dolphins.

If you want to dig really deep, try to get some of the following 
references. They are all original scientific work on this type of sleep 
(but very often complicated written – hard work to read). 


Mukhametov L.M. The absence of paradoxical sleep in dolphins. Sleep'86. 
Eds. W.P. Koella, F. Obal, H. Schulz and P. Visser, Gustav Fisher Verlag, 
Stuttgart, New York, 1988, 154-156.

Ball, N. J., et al. 1988. Sleep '86, pp. 127-128.

Lyamin, O. I. 1993. Journal of  Sleep Research, 2:170-174.

Mukhametov, L. M., et al. 1988. Neurophysiology, 20:398-403.
Mukhametov, L. M., et al. 1984. Zh. Vyssh. Nerv. Deyat., 34(3):465-471.

Rattenborg NC, Lima SL, Amlaner CJ. 1999 Facultative control of avian 
unihemispheric sleep under the risk of predation. Behav. Brain Research 105
(2):163-72. 

Rattenborg NC, Amlaner CJ, Lima SL. 1999 Frequency analysis of the avian 
EEG during unihemispheric quiet sleep. Sleep Research Online;2(Supplement 
1):215. 

Rattenborg NC, Amlaner CJ, Lima SL. 1999 Period Amplitude Analysis of 
Avian Unihemispheric Quiet Sleep. Sleep ; 22(1 Suppl): 73. 
Rattenborg NC, Amlaner CJ. 1997 Does one cerebral hemisphere sleep more 
than the other? eye-closure asymmetry in the mallard (Anas platyrhynchos) 
Sleep Research 1997; 26: 176. 
Mathews C, Amlaner C. 1998 Arousal thresholds during asynchronous eye 
closure in the western fence lizard (Sceloporus occidenetalis). Sleep; 21
(3 Suppl): 33
Szymczak JT, Kaiser W, Helb HW, Besszczynska B.1996. A study of sleep in 
the European blackbird. Physiology and Behavior;60(4):1115-20


Thank you again for your question, J. Ziesmann