Best possible night light: Researchers study how light cycles impact zoo animals

A pygmy slow loris, a big-eyed nocturnal primate, climbs down a branch and begins licking and chewing the swab.

"These primates can navigate through a complicated jungle and avoid predators in the dark," said Fuller standing in the loris exhibit at Cleveland Metroparks Zoo. But in captivity, something as seemingly innocuous as incorrect lighting may negatively impact the health and reproduction of lorises, pottos and their kin.

This is crucial in zoos where their days and nights are switched so that the animals are up and moving when patrons come to see them, not after dark when the zoo is closed. Fuller is interested in whether the swap of light cycle negatively impacts these primates.

That kind of switch is rough on other primates: humans.

"Shift workers have higher rates of cancer, heart problems and reproductive problems than the rest of the population," Fuller said.

To examine the question in another light, Fuller is pulling another switch.

"Animals have long been used as models for human research," said Chris Kuhar, curator of Primates and Small Mammals at Cleveland Metroparks Zoo and chair of Nocturnal Prosimian Species Survival Plan®. "Grace is flipping that, using human research to help animals."

Studies have shown night-shift nurses produce dramatically lower levels of the hormone melatonin, leaving them more susceptible to certain cancers, among other health issues.

Melatonin is an antioxidant and involved in the reproductive cycle and immune system of animals. Called the "hormone of darkness," the chemical is secreted by the pineal gland at night but secretion is suppressed in sunlight.

Human health researchers have used the tiny amount of melatonin in spit as a gauge to determine levels of the hormone present in the body, measuring levels nurses produce while working .

For the lorises and pottos, their daily shift at the zoo is not as dark as nights in the wild, but is gently lighted to enable patrons to see them.

To determine the effect, Fuller's team has developed the first assay to gauge the melatonin level in the spit of zoo primates.

She's also begun trying to gauge the effects of light of different wavelengths and intensities on the animals. Fuller is observing how active the animals are under red, blue and white light and measuring their melatonin levels in each. The least impactful wavelength can be used to illuminate animals for future zoo visitors.

"This is cutting edge research," said Kristen Lukas, an adjunct assistant professor of biology at Case Western Reserve and the curator of Conservation and Science at Cleveland Metropaks Zoo. "No other program is doing this kind of work, linking animal behavior and health to improve animals' lives in zoos."

Video of the research can be seen at: http://www.youtube.com/case#p/a/u/0/7yPiHEmFud0.

Back in its exhibit, the loris finished licking the sweetness away from the swab, leaving its spit behind.

Fuller carries the swab back to the zoo's lab where she uses a centrifuge to separate melatonin from spit and begins her analysis.