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Long Necked Giraffes And Their Hearts
Some implications for long necked dinosaurs...
However, exactly how they maintain this neck, and get blood to a head that
is two metres from their heart, has remained unknown.
Now research reveals that giraffes have a small, powerful, supercharged
heart that is different to that possessed by other similar mammals.
Scientists have published the discovery in the journal Comparative
Biochemistry and Physiology, Part A.
"There are not many animals that have evolved to have a very long neck,"
says giraffe expert Professor Graham Mitchell from the Centre of Wildlife
Studies in Onderstepoort, South Africa.
Prof Mitchell undertook the study along with Prof John Skinner at the
University of Wyoming, Laramie, US.
Previous studies have found the giraffe has an extremely high blood
pressure that is twice that found in other animals.
"We established that the heart is actually quite small. It's smaller than
you'd expect in similar-sized animals, but the walls are incredibly
thick," Prof Mitchell says.
"You have a small but a very powerful heart delivering the blood
The giraffe also has other specialist mechanisms to help deal with the
high blood pressure, Prof Mitchell says.
"Blood pressure depends on the capacity of the cardiovascular system as
well as the efficiency of the pump."
"Giraffes have got a way of adjusting the capacity of the cardiovascular
system and are able to shrink and expand their blood vessels to change the
volume of the cardiovascular system very efficiently."