Substantive posts will be thin on the ground until the end of October, as I’m off to NYC on Thursday and to Bulgaria two days after I return to Chicago (next Monday).  What with the final version of the Albatross due Thursday, it’s lucky I can post anything.

So go read Natalie Angier’s nice piece on giraffes in today’s New York Times. Setting aside one gaffe (one researcher calls the beast a “gentle giant and the world’s most graceful animal,” though we know that any species of felid can beat them by a neck in gracefulness), the piece packed with interesting information, including new data on the giraffe’s complex social life. It turns out that, until recently, we knew nothing about the world’s tallest animal. Here’s one bit about their physiology:

Also of interest is the giraffe’s exceptional cardiovascular system. A large giraffe can stand 20 feet tall — the height of a second-story window — with its neck accounting for roughly a third its span and its long legs the same. The multitiered challenge, then, is how to both pump blood very high and retrieve it from far below while avoiding burst capillaries in the brain or blood pooling around the hooves.

As part of the Danish Cardiovascular Giraffe Research Program, scores of scientists have traveled to South Africa to study giraffe physiology. They have measured blood pressure at different sites and found readings that range from high to ridiculous — up to five times human blood pressure — yet with none of the organ damage commonly seen in hypertensive patients.

Instead, the giraffe has extremely thick blood vessel walls to prevent blood from leaking into surrounding tissue, while rugged, inflexible collagen fibers in its neck and legs help keep the blood traffic moving, rather as the tight antigravity suits worn by astronauts and fighter pilots will maintain blood flow under the most extreme gravitational shifts. A complex mesh of capillaries and valves store and release blood in the neck, allowing the giraffe to bend over for a drink of water and then raise its head again quickly without fainting; when the giraffe is standing still, sphincters at the top of the legs limit circulation to the lower extremities, to minimize the risk of fluid buildup around the hooves.

Researchers were also surprised to find that contrary to old textbook wisdom, giraffes do not have unusually large hearts for animals their size. “It’s half a percent of body mass, and that’s the same as we see in a cow, dog or mouse,” said Christian Aalkjaer of the department of biomedicine at Aarhus University in Denmark.

Moreover, Dr. Aalkjaer and his colleagues have determined that the giraffe’s cardiac output — the amount of blood pumped into circulation each minute — is modest, proportionally lower than it is in humans. That finding could help explain why giraffes rarely run for very long: Their hearts can’t deliver oxygen to their muscles fast enough to power extended aerobic exertion.

There’s also some information about their nerves two (I’ve discussed the giraffe’s recurrent laryngeal nerve in WEIT as evidence for evolution; see GrrlScientist’s post on it).

Or maybe the giraffes are worried about tripping over their own feet. Heather More and Shawn O’Connor of Simon Fraser University in British Columbia and their colleagues measured so-called sensorimotor responsiveness in the giraffe: how long it takes a nerve signal to travel from a muscle in the ankle up to the brain and back again. Reporting in The Journal of Experimental Biology, the researchers found that the nerve conduction rate in the giraffe is pretty much the same as it is in a shrew, rat or any other mammal.

Given the comparatively greater distance a nerve signal has to travel in the giraffe, Dr. More said, it’s possible the giraffe faces real challenges in reacting quickly to events down under — a rock beneath its hoof, or a bite to its ankle.

Perhaps. I went and looked briefly at the JEB paper reported above, which estimates the delay between nerve stimulation and the arrival of the information in the spinal cord. I quote from the paper:

We estimate a total conduction distance of 2.3 m for these sensory fibers based on our leg length measurements (1.8 m; Table 1) and our estimated nerve length between the femoral head and spinal cord (0.5 m). Using our measured motor conduction velocity as an approximation of sensory conduction velocity, we estimate that the conduction delay between the foot and the spinal cord would be 46 ms.

That’s 0.046 seconds, not an appreciable delay to my mind. The problem with the recurrent laryngeal nerve, which goes from the larynx down the neck, loops around the heart, and comes back up to the brain (a length of 15 feet in giraffes but also several superfluous feet in humans), is not the delay in getting nerve impulses to the brain, but the danger of injury to a nerve that can be damaged by a blow to the chest.

What Angier doesn’t note is that getting that information involved killing four giraffes. Was it worth it?  Well, the workers apparently did this as part of a larger study. To be fair, I note that their paper says this:

Electrophysiology procedures and tissue collection were carried out simultaneously with many other research projects during the 2010 Danish Cardiovascular Giraffe Research Programme expedition to Hammanskraal, South Africa. Due to the nature of these multi-experiment protocols, we performed each procedure on only four of the eight animals. Experiments and procedures were approved by the Danish Animal Ethics Committee, the Animal Ethics Screening Committee at The University of Witwatersrand (Johannesburg), the Animal Use and Care Committee of the University of Pretoria (South Africa) and the Simon Fraser University Office of Research Ethics. Permission to euthanize the animals was granted by Gauteng Province, South Africa.

 One has, then, to balance the lives of these four giraffes against all the information gathered before they killed them. Will it help the species, and perhaps prevent its drastic reduction in numbers? I hope so. Or will it help humans with hypertension? All too often in the past, researchers killed animals willy-nilly, either to get specimens for museums or to do studies that did nothing to help the species itself. Animals were regularly tortured and mistreated in the lab—until ethical standards for animal care were implemented over the last few decades.

Still, I think that researchers always need to thinl about balancing the need to satisfy their curiosity (and to save endangered species or help our own species), against the fact that animals must to some degree value their own lives, and many certainly feel pain. Even I always anesthetized my fruit flies before I put them in the “morgue” (a coffee can full of motor oil). When I was in college, I didn’t even want to kill my fruit flies and would go up to the roof of the biology department to release them. But my advisor caught me one day and told me I couldn’t do that, for I was polluting the natural gene pool.

I will, however, admit that I eat meat, and I feel bad about being a bit of a hypocrite.