Q: I noticed that my tamarins seem to like toys and foods that are brightly colored. My female tamarin actually loves the color orange and has a favorite blanket and little cat toy that she plays with all the time--both are a bright, neon orange. When her mouse finally fell apart, I got her another in a different color, everything was the same except it was blue. I noticed that she didn't care to play with it as much. I was told that they don't really see color like we do. Do you know if monkeys do see in color?
A: There have been a few studies done on monkeys and color perception, but because monkeys can't really talk and say "the button is blue" scientists are limited to studying the physical characteristics that give us color vision. Yes, monkeys do have rods and cones to see light and color, but a 2005 study by National Geographic primatologists revealed some interesting findings:
Monkeys and their human cousins don't necessarily see the world in the same way. Some monkeys, even with the same species see things very differently from one another. The research suggests that various forms of sight may confer a range of survival advantages. For almost a decade, Dr Smith, a primatologist at the University of Stirling in Scotland, ventured into the Peruvian Amazon to study how different types of sight affected the foraging behaviors of New World monkeys. The vast majority of his work was on tamarins and the findings were quite interesting. Here are some of his notes verbatim:
"As humans we tend to think that all creatures perceive the world they way we do, but that clearly is not the case. Humans have so-called trichromatic, or three-color vision. So do Old World species such as chimpanzees, gorillas, and orangutans. Trichromats have three types of light sensitive cells in the retina, fine tuned to wavelengths that appear blue, green and red giving them the full color spectrum.
However, New World monkeys have a broad range of vision types. Every Howler monkey, for example, is trichromatic. The owl monkey is monochromatic, seeing only in black and white....sacrificing color for ultra light sensitivity giving them night vision ability. Among tamarins and spider monkeys, all males are dichromats---they can't perceive reds or greens. But females split 60/40 between three and two-color vision. You can therefore have six individuals from same species, even the same family, who see the world in six different ways."
Just like one in 12 human males who are colorblind, many New World monkeys have trouble discriminating between red and green, which can hamper the animal's ability to ripe fruit from raw. Smith and his team of scientists trekked through the forests following troops of tamarins as they jumped from tree to tree high in the canopy. Using a spectrometer, Smith measured the color of the fruit and the leaves on which the tamarins feed.
Tamarins eat the fruit of more than 833 plants from 167 different species. A favorite seemed to be the Abuta fluminum plant...which happens to be a bright orange. Without red-green perception, orange cannot be detected.
A second experiment was devised to give the tamarins an eye test. At the Belfast Zoological Garden in Ireland, Dr. Smith devised a scaffolding decked with large orange paper leaves that roughly simulated the color of the Abuta. Among the leaves he scattered small cardboard boxes with lids whose color matched the shades of Abuta fruit from the raw green to a vibrant ripe orange. The "ripe" boxes concealed chunks of fudge; the less ripe, smaller chunks, "un-ripe" were empty.
Then the researchers guided male and female Saddleback and Red-handed tamarins into the enclosure, one by one, to forage for the "ripe" fruit. As expected the trichromatic tamarins were more than 50% more adept at selecting the preferred treat.
The advantages of trichromatic vision were that the riper fruit was more digestible and nutritious than the green fruit. So, the question remains that if trichromacy is so advantageous why has it not replaced dichromacy altogether in the evolution of the New World primates?
There may actually be some unidentified advantages to being a dichromat. Findings suggest that dichromats may be far better at "breaking camouflage" of predators and prey. New World monkeys, in addition to fruit and foliage, also consume large quantities of prey--katydids, frogs and lizards. Perhaps dichromats are not as distracted by colors and better at seeing shape and form to distinguish prey. Nature endows each way of seeing with a specific advantage. Trichromats may be better at finding fruit, but dichromats may be far better at catching prey.
So, as you can see the answer was a sort of complicated yes... but no. However as it turns out, the color orange is scientifically proven to be one of their favorites, be it a favorite toy rubber mouse or dinner!