Macadamia Nuts

In Do Penguins Have Knees?, when discussing "Why Can't You Buy Macadamia Nuts in Their Shells?" I wrote:

"Macadamia nuts do have shells. But selling them in their shells would present a serious marketing problem. Only Superman could eat them. According to the Mauna Loa Macadamia Nut Corporation, the largest producer of macadamias in the world, "It takes 300-pounds-per-square-inch of pressure to break the shell."

We heard from reader Katie Barnes, a third-year veterinary school student:

"Your chapter included a question as to why Mother Nature even has such a nut that no human or animal can break open? I contest this statement -- there are several animals out there who are more

than happy to muster up the necessary 300 psi of jaw pressure to break

open macadamia nutshells, such as the spotted hyena (estimates from

1000-4000 psi), crocodile, and several species of sharks.

"One in particular that I know not only has the capability but also the desire to do so -- the very rare but very beautiful Hyacinth Macaw. My godmother raises these birds and I have had the pleasure of watching them (even the young ones) casually split these shells open with their massive beaks and then proceed to gently gnaw on their owner's earlobes or hair (yikes!) So there are animals who can and frequently do shell macadamias and eat them. Just thought you'd like to know."

I emailed Katie and asked her if any other animals might be able to crack open macadamias. She kindly replied:

"I don't know of any other animal other than the hyacinth macaw that would eat macadamias. I know of the South American agouti (a type of lagomorph), which can gnaw through Brazil nuts and their extremely hard husks, but I don't think that even the Brazil nut can match the toughness of a macadamia nut.

"Macadamia nuts are from Australia originally (not from Hawaii as the Mauna Loa Company would have us believe), and hyacinths are from South America, so this is not a natural food of theirs, but they do eat them in captivity. I don't think any native Australian animal can manage them - they don't have any native macaws down there and their other birds are pretty wussy (maybe the palm cockatoo, but I couldn't find any data on it online)."