The giant panda has always been an elusive creature. Even the handful of pandas that live in zoos and sanctuaries lead quite mysterious lives … so mysterious, in fact, that panda caretakers have quite a difficult time even coaxing them to mate. What we do know about wild pandas is that they spend most of their days alone slowly munching on bamboo. Because there's so little nutrition in the bamboo plant compared with what's in fruit or meat, they need to eat a lot of it. Males eat as much as seven to nine kilograms of the stuff, chewing and chewing and chewing for up to 14 hours each day.
But here's where it seems we were wrong: it turns out that pandas may not be as solitary as we once thought. (We're pretty sure we're right about the bamboo thing though … it just looks like they might have chewing parties.)
The Chinese government is very protective over their pandas, and rightly so. While recent breeding efforts have been fairly successful, there are only 1,864 pandas in the wild. Climate change as well as habitat fragmentation and degradation still pose serious threats to the survival of the species. That's why, from 1995 to 2006, the government forbid researchers from conducting any sort of telemetry studies on the monochromatic bears. And up to 1995, the technology available to researchers to track panda movements only worked during the daytime and required good weather conditions. Even under the best of conditions, the data suffered from extremely poor spatial accuracy. If wild pandas were hanging out together, we wouldn't have necessarily been able to tell.
But then, Michigan State University researcher Vanessa Hull, together with colleagues from the Chinese Academy of Sciences, China West Normal University and the China Conservation and Research Center for the Giant Panda got rare permission to outfit five giant pandas with GPS collars. Three were adult females, one was an adult male and the last was a subadult female, estimated to be between one-and-a-half and five years old. Their movements were tracked for around two years.
The study centred on pandas within the 2,000 square kilometre Wolong Nature Reserve in Sichuan, China. Around ten percent of the planet's panda population lives there. In addition to the GPS collars, the researchers deployed a set of camera traps and collected panda poop to extract DNA. Using those tools, they estimated that between 16 and 25 pandas were present in their study area within Wolong. They published their findings in the Journal of Mammalogy.
As expected, the GPS data provided the researchers with better, more accurate estimations of the average home range sizes of male and female pandas. Also as expected, the male's range was bigger than the females', perhaps because this allowed him to keep his eye on the females and continually leave his scent marks on trees throughout the area.
The team discovered that while pandas' ranges are small relative to other kinds of bears, each panda's range consisted of multiple 'core areas' that they moved through in sequence. They spend their time in a small area eating up all the bamboo, and when there's not enough food left, they move on to the next core area and begin the process over again. Everything about the panda is highly efficient. "Pandas have small home ranges likely because their low-energy, yet abundantly available, bamboo food source makes it advantageous to limit cost of travel, while maximising intake at a given location," explains Hull.
In an interesting and unexpected twist, she also found evidence that the pandas revisited their previously used core areas, sometimes after absences of up to six months. That suggests that pandas might have a strong spatial memory and the ability to recall where they found good sources of food in the past.
But the most surprising finding, the one that overturned the commonly accepted notion that pandas are usually loners, was that they sometimes hang out together. In total, the researchers recorded 52 instances in which at least two pandas used the same part of the forest at the same time. And three of the five pandas – Chuan Chuan, an adult male, Mei Mei, an adult female, and Long Long, the adolescent female – were found in the same part of the forest at the same time for a period of several weeks. The researchers suspect these three might represent a family group.
This wasn't just a fluke. The pandas stayed together in the same places for an extended period of time during a completely unexpected part of the year, well outside the breeding season. This might mean that pandas are not quite as solitary as most people believe. Hull points out that the sorts of interactions they recorded among their five pandas are common in social mammals like white-tailed deer or brown hyenas, and uncommon in mammals believed to be solitary, like jaguar or lynx.
While giant pandas continue to reluctantly reveal their secrets to scientists, new discoveries such as these underscore the importance of contiguous habitats that allow the pandas to move over broad distances. Indeed, the researchers hope that future GPS research on larger groups of pandas will provide critical information to aid the design and planning of conservation efforts.
Top header image: pwitzel, Flickr