Thwarted by Moonlight - NYTimes.com The full moon rose above our field site in southern central Vietnam, bathing the trees in a pale glow, and foretelling how few lorises we would find that night. The activity of many nocturnal mammals, and especially prey species, is affected by the intensity of the moonlight. In most cases, their activity decreases on nights when the moon is especially bright. This is likely because bright moonlight may increase the vulnerability of these animals to predators. There are a few nocturnal mammals that actually increase their activity on bright nights - like spectral tarsiers and some galagos - presumably because bright nights may increase their success in foraging for insects and ripe fruits. But it seems that lorises are, sadly, in the majority; a slow loris research team working in Cambodia recently found that moonlight and temperature interact to influence pygmy slow loris activity. On very dark nights, the lorises were always active - but on nights with bright moonlight, animals were only active when the temperature was also high. This pattern is related to the cryptic antipredator behaviors of lorises: in order to avoid their predators, including civets, pythons, predatory birds and monitor lizards, lorises may be even more eager to avoid detection on bright nights when they are more likely to be seen by sets of eyes with hungry jaws attached. On cold nights we would also expect less activity because of the increased risk of heat loss. During our surveys in here in southern central Vietnam, the temperature has been quite cool, and the moon has been very bright. Result? No slow loris sightings. It also did not help that we simply did not have much time to survey here, mostly because getting here was so hard. The first part of the journey was easy - we flew from Hanoi to Da Lat, the city of flowers - located at the southern end of the central Annamite (Truong Son) mountain range. The city and the surrounding landscape were exceptionally beautiful. There were flowers everywhere, including an Eiffel Tower made of flower pots in the middle of a traffic circle. But the ornamental flowers and the paved roads ended there. The staff of Bidoup Nui Ba National Park picked us up from our hotel in Da Lat in a large Russian military S.U.V. - a first hint of the rough road ahead. We started on our long and muddy drive into the park. And then there was a hailstorm. Hard, marble-sized white pellets banged on the roof and windows. We pulled over and stared in awe, as they grew larger and larger, pounding harder and harder. It sounded like they would cave in the roof - or at least leave it permanently pockmarked. After 15 minutes of pounding, the storm passed as quickly as it had started. The roof was unaffected. Our blood pressures were not so lucky. We arrived at the Da Long ranger station as it was getting dark, without enough time to hike to our intended survey site. So we laid low that night and started fresh the next morning. After an hour of motorcycling over bamboo bridges, mud and brush, followed by a deep stream crossing by foot, gear hoisted above our heads, we arrived not so fresh at the site. We now only had one night, instead of the two we had planned, to survey for lorises. And that's when we walked straight into a bright moon. We learned the hard way. Now we know to incorporate moonrise times and phases when we are planning our work schedule. We also know to allow for extra days of hard travel and sudden hailstorms. But the perturbing moon wasn't all bad. I came out the experience with some really interesting questions for future studies. For example, would the effect of bright moonlight on the activity of pygmy lorises in Vietnam vary from habitat to habitat? Would moonlight show a stronger effect on loris activity in more open habitats as opposed to more closed forests where moonlight may not penetrate through the dense leaves as easily? I learned a lot from the wonderful national park staff we were able to work with during the trip. The staff is very interested in thinking about how cultural diversity and biological diversity relate in their park. One of our colleagues told me that the K'Ho ethnic group - the people who live in and around Bidoup Nui Ba National Park -believe that slow lorises are cursed. They say if someone goes out into the forest and sees one, they must move to a completely different piece of land to cultivate their crops. This story made me wonder about slow loris populations in the area and how different ethnic groups may value them differently. Understanding local folklore is vital to informing not only our research on slow loris diversity and distribution, but also how to approach their long-term conservation in Vietnam. When it comes to slow loris conservation, human cultural diversity and biological diversity are intertwined. I will continue to think and discuss these issues with my Vietnamese colleagues as we head to the final protected area on our journey, Bu Gia Map National Park in southern Vietnam.