Translating the color code

From snail shells to bird feathers to the changing skin of a chameleon, nature uses colors in ways that range from the electric blue of a poison dart frog’s warning to the invisible ultraviolet patterns of flowers that call bees to pollinate.

The development, use, and perception of color is the subject of a new exhibit at the Harvard Museum of Natural History called “Language of Color,” which opened Sept. 26 and runs until September 2009.

“It’s important to keep in mind that colors are used in different ways by different organisms,” said Loeb Associate Professor of the Natural Sciences Hopi Hoekstra, who together with Lehner Professor for the Study of Latin America Jonathan Losos was a scientific adviser for the exhibit. “[Humans] have great vision for what we need it for, but other organisms have vision for what they need it for.”

Museum Executive Director Elisabeth Werby said the exhibit illustrates the museum’s unique ability to draw on the research of its associated faculty members and on the University’s vast collections to create exhibits that are both visually compelling and intellectually stimulating.

“We really have an extraordinary opportunity at Harvard to develop exhibits like this,” Werby said, adding that the exhibit is aimed at the general public and the Harvard community alike.

“Language of Color” examines not just the uses of color for camouflage, mating, and warning, it also examines the structure of color, highlighting how the color blue, for example, is not made from pigments, as yellow and red are, but rather through physical structures that absorb longer wavelengths of light. Similarly, green is most often created by creatures that have yellow pigment augmented by these blue physical structures.

Colors are also viewed differently by different creatures. Some, such as whales, do not have the color vision that humans do; their world is black and white. Other animals, like bees, see colors in the ultraviolet spectrum that humans don’t, perceiving patterns on flowers invisible to the human eye.

Color patterns are critically important to the creatures that employ them, whether the potentially life-preserving stripes of a prey animal like the zebra or the concealing camouflage of a predator. Males of some species put on elaborately colorful displays to attract females. The displays, Hoekstra said, reflect a trade-off between a male’s increased odds of mating and his increased visibility to predators. Some animals that are toxic use bright colors to warn off predators, while others that are nontoxic mimic those colors in an attempt to fool predators about their identity.