Camouflage is just one of many reasons for greenness in the natural world. Leaf insect photo by R. Straatman, California Academy of Sciences.

"Green" events, companies, buildings and advocates are enjoying a spotlight as Earth Day approaches, but what about green itself—you know, the color from which the sustainability movement gets its nickname? Lest green be shortchanged this month, I've investigated a selection of plants and animals and their green properties.

At a fundamental level, green objects look green because they reflect green wavelengths of light back to our eyes, while absorbing red and yellow. But organisms have evolved to be green for a wide variety of reasons.

Chlorophyll comes to mind first, as the pigment which makes most plants green. I’m going to focus on green algae here because it’s the granddaddy of all the green plants we know today. While red and brown algae are more common in today’s oceans, it’s green algae that colonized terrestrial environments. From pond scum to swimming pools and aquarium tanks, it is still found in land-locked freshwater systems. Like the "higher plants" which evolved from it, green algae gets its color from chlorophyll, turning sunlight into food, and expelling oxygen into the atmosphere. It thrives in water with easy access to sunlight, places like shallow pools and even the fur of slow-moving sloths. In return for providing an algae-friendly habitat, the sloth gains a green tint, helping it blend into its surroundings.

Next up: unripe fruit. Bananas, strawberries, peaches and tomatoes are all tart, mealy and green when unripe. Then there are green grapes and green apples; although ripe, they tend to be more tart than their red counterparts. Is green just a sour-puss? Not of its own accord, but it is tied to the chemical process of fruit ripening. Once a fruit has reached its optimal size, a burst of ethylene causes new enzymes to be produced. In addition to breaking down starch and pectin (making fruit softer and sweeter), ethylene breaks down the chlorophyll which helps it grow and appear green. To propagate, these plants need their fruit to be eaten by animals who will go on to drop the seeds across the landscape. Since animals enjoy their fruit soft and sweet — rather than hard and tart (sound familiar?) — as chlorophyll breaks down many fruits, the production of brighter yellow and red pigments as a form of advertisement to passing animals. Even those with monochromatic vision can tell the difference between green fruit and fruit that’s ready to eat. Scientific American has a great article with more on fruit's ripening process.

In the animal world, coloration can serve a multitude of purposes. Muddy-green American alligators enjoy great camouflage in their swampy homes, allowing them to sneak up on their prey. But camouflage works in both directions. At the opposite end of the food chain, bright green leaf insects use it to evade detection by predators amongst the trees. Then there's Claude, the albino alligator at the California Academy of Sciences, who lacks pigment, but has been known to grow a mean coat of algae on his back. It's a start, but I don't expect him to blend into his surroundings anytime soon.

Contrary to popular belief, chameleons change color not for the purpose of camouflage but in response to changes in their environment and as a means of communication. Color changes occur based on temperature, lighting, time of day, and the individual’s mood. Chameleons get their eye-catching coloration from melanin and chromatophore cells, lying just under a transparent outer layer of skin. Cells near the surface contain red or yellow pigment, and the lower layers contain blue or white. When the pigment shifts within the cells, different colors appear more (or less) intense, showing a range of colors that is unique to each species.

For green and black poison dart frogs in South America, coloration serves as a visual warning sign to predators that they are poisonous, and should be avoided. But it’s not quite that simple. Poison dart frogs' coloration and patterns evolve on a hyper-local scale, giving local frogs a hometown advantage when it comes to scaring off predators. Color can range from pale yellow to electric blue or green. In its home turf, predators will recognize a green striped frog as poisonous, but should that frog wander into territory full of yellow spotted frogs of the same species, his warning coloration would not protect him.

Happy 15th Birthday, Claude! Image courtesy of Ron DeCloux © California Academy of Sciences.

I have a birthday month in common with Claude, the Albino Alligator at the California Academy of Sciences! On Wednesday morning, September 15, 2010 – Claude celebrated his golden birthday and turned 15 years old. He was serenaded by staff and guests alike signing happy birthday and several children, also with September birthdays, fed Claude cupcakes that aquarium biologists had made. They were not chocolate or vanilla but fish flavored especially to suit Claude’s taste buds.

When born, Claude only weighed 2 ounces. At fifteen, he has tilted the scales at 181 pounds and sprouted to over eight feet. At his last physical earlier this month, biologists counted 76 teeth. He can often be found on his favorite rock in the swamp exhibit which is heated between 78 and 95 degrees. I first saw Claude when he arrived with Bonnie back in 2008. He was taken out of his crate given and vet check and then put back into the crate and hoisted over the railing into his new home. Since then, Bonnie has moved to a farm in Florida. "Because he is albino, he has reduced vision. Claude would go into the water and bump into things, and Bonnie would snap at him…Claude has been more active since Bonnie left," biologist Brian Freiermuth said. "He is better by himself, as he was stressed out with her there. He has interactions with his turtles. He is eating well. He knows his name and responds to whistle commands."

One morning, when I was with the biologists, I saw Claude coming to whistle and station calls. They would use the whistle to show audibly where they were throwing food. The biologists and Claude work very well together during feeding time! Claude has become a favorite amongst staff and guests alike and is become one of the icons of the new Academy.

What is wonderful about this is that he also conveys our mission in a truly unique way. Carol Tang, Director of Public Engagement, noted, “There are no white alligators in the wild because they're too show-offy…They get eaten in the wild. So, you can use that to talk about food chains and adaptation. You can talk about how alligators are green because they live in the swamp where there are plants and trees and they can be camouflaged…You can also use Claude to talk about variation, which is the fuel of evolution. It's one mutation in Claude's DNA that causes this kind of albinism. That shows how sensitive our DNA can be.”

Claude can live up to 80 years in captivity which is a far measure longer than he would have survived in the wild. He is still a young alligator on his golden birthday and he will be a beloved and celebrated icon of the Academy for years to come.

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photo by Andrew McCormick, Graphic Designer at the Academy

The swamp tank was an iconic feature of the old academy complete with a seahorse railing. It has been recreated with some additional touches. There is now a viewing window from the aquarium level so guests have the opportunity to either look down at the swamp's inhabitants or get eye level with them in the aquarium. For months, we have seen this tank filled and drained to test water quality. Last week the tank was filled and readied for animals.

Two large coolers were brought in filled with water and specimens. A host of aquarium staff took turns catching catfish and crayfish out of the coolers and transplanting them into the swamp by way of ladder. The swamp tank has no entrance so the only way to get animals transplanted in the tank is either ladder or crane. The crane has been tested numerous times with weight bags for larger animals. Last week the crane transported live cargo for the first time. The alligator snapping turtles were given a physical on the floor, complete with cutting of toenails and then were hoisted into the tank by crane. As exciting as it was seeing the turtles and fish acclimate to their new home, staff came out in bunches before noon today to see the final additions.

Two alligators came in the back entrance of the Academy around 11am this morning. They were individually carted in wooden crates. The female was taken out of her box first with many aquarium staff on hand for safety. The Academy vet and animal health staff gave the alligator a quick physical and herded her back into the wooden box for final transport. Her box was then fitted onto the crane by half of the attending staff while the other half of staff readied the male alligator for his physical. The male came out fighting and it took quite a bit of staff to restrain him. Staff let out a collective yelp when seeing him, as he is an albino alligator and the white of his skin was striking.

After both physicals, the alligators were housed back in their crates & they were hoisted one by one into the swamp. An alligator handler was waiting in the tank to steer the crates and coax the alligator out of it once it was set down. He unhooked two of the ropes securing the crane and lifted up the back of the crate so each alligator could slide easily in to the water. The female went into the water with no hiccups but the male took more coaxing. Even with lifting the back of the crate, he wasn't budging initially. But with a steep incline for the crate, he eventually slipped into the water. Collective cheers and clapping occurred when both alligators were in the tank. The audience of staff had been safely watching the whole episode from the catwalks above the tank. All in all, the whole transport from truck to tank took two hours.

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