Thursday, March 21, 2013

Sausages edible only to elephants

Species name: Kigelia africana

Common name: sausage tree

Location: Dominican Republic

This was by far one of my favourite trees (but not my absolute favourite; that one is coming soon) that I saw on my trip, possibly the coolest tree I've ever seen period. And that's saying a lot; I've seen a lot of cool trees! The sausage tree is native to Africa (and hence the Latin name), but grows commonly in desert and tropical regions around the world. It was introduced to South America as a potential medicinal and edible plant hundreds of years ago, only for South Americans to find that it's actually not edible at all. Now it's used purely as an ornamental plant, but some native tribes in Africa still use it for its medicinal potential. Oh, and elephants still use it as a prime food source whenever they come across the fruit growing from the tree.

One unique aspect of this tree is that it is either deciduous or evergreen, depending on environmental conditions. If the area its growing in has a prolonged dry season, the tree will lose its leaves to decrease the amount of water it needs to keep itself alive (leaves take a lot of resources to maintain!). When the monsoon or rainy season starts up again, the tree will regrow its leaves. In areas with no pronounced dry season, the tree will retain its leaves all year. The leaves on the tree aren't the only remarkable feature of the tree; the flowers are incredibly unique. When we first "moved in" to our hotel room, we walked right past this tree and I thought the hanging cords off it were strange, but just figured they were some sort of mangrove-like root emerging from the canopy and figured I would look more at them later. Imagine my surprise when I saw that some of these cords actually had flowers at the bottom! They aren't aerial roots at all, they're inflorescence stalks. The flowers form at the bottom of these cords, which can be up to six meters long depending on the height of the tree. I saw that some of the flowers has not yet opened, and I was determined to go back every day to catch one of the flowers in full bloom. Imagine my surprise when, the next day, all of the flowers that seemed like they were about to open were all over the ground. Seriously?! I missed it?! No big deal, I'll just come back tomorrow morning. And guess what? Same thing. Flowers on the ground, none open on the tree. Now, once I might believe I was just unobservant and there really were some. But twice? No way. I'm not that blind. And then it hit me--the flowers are maroon. Why does it matter if the flowers are maroon? Maroon flowers would absorb release heat at night, just like black pavement does. The petals are transparent enough that the light would pass from the back to the front and the heat would be absorbed, then released into the cooler air at night...

So what? Well, what animal might be looking for warm areas at night? Bats! I don't know why I didn't think of it before, but these flowers are bat-pollinated. The heat of the flowers acts like a beacon for the bats to approach, and the reportedly intoxicating scent that these flowers release as it starts to get dark would further entice them to drink the sweet nectar. The stamens would rub all over the bat's head and back while it is consuming the nectar, and the pollen on the bat would be deposited on the next flower it visits. Cross-pollination: successful! Since that's the only purpose of the flower, it falls off by morning like nothing ever happened, and if pollination was successful then the enormous fruit would start to develop. The "sausages" are up to four feet long (this one is about a foot to a foot and a half) and can weigh up to TEN KILOGRAMS. That's one flexible, strong cord it's growing off of! Each one of the flowers can make a sausage, so there could be up to fifteen sausages on a single cord (more often between three and six end up developing). The fruit are popular food sources for some large animals in the African Savannah (Elephants, Greater Kudu, Hippos and Giraffes, amongst others), and are used medicinally in Africa as a treatment for rheumatism, a cure for snake venom, a cure for syphilis, a way to purge evil spirits from a home, and to prevent tornadoes from occurring. Whether it has any actual medical value I don't know (I highly doubt it could prevent a tornado...), but sausage tree extract is popular as a face cream additive since it is believed to slow the aging process (another claim I find hard to believe). The fruit to humans is highly toxic and should not be consumed raw or cooked under any circumstances. In Botswana specifically, this tree is a very important lumber source as the wood is produced quickly but is very strong and can be carved into different shapes (it is used mostly to make oars for boats and yokes to transport buckets of water long distances).

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