KUNMING -- To be a purposeful traveller, one not only needs time, money and good health, luck is also essential.
Without luck, you may miss a sunrise or sunset over the sea, or a glimpse of the snow-capped peaks of towering mountains.
And without a huge amount of good luck, you will definitely not see the wild elephants in Wild Elephant Valley, even if you stay there for a couple of weeks.
When I headed for the valley in Xishuangbanna in the deep south of Yunnan Province recently for a two-day trip, luck was with me in spades.
On the way to the valley, I began to discuss with Lao Liu, my guide, the possibility of meeting wild elephants inside the reserve.
Suddenly the driver put on the brakes, pulled the car over to the side of the winding road, and yelled, "Get out quick, look at the elephants over there!''
Standing on the other side of the road looking down over a brook at the bottom of the valley, I saw a group of five wild elephants breaking out of bamboo clusters in the dense tropical rain forest.
The four adults and a baby walked slowly by the stream ignoring the cars and people just 20 metres away from them.
After two or three minutes in the valley, where the sunlight pierced through the canopy of trees, the elephants finally made their way into the jungle, and disappeared into the trees.
 "Luck is on your side,'' Liu told me when we returned to the car.
 "Believe me, it would be extremely unlikely that the elephants will reappear in this area in the next few weeks.''
According to the plant taxonomy researcher, the wild elephants are voracious eaters and therefore have to keep moving to find food. In the forest reserve of 100,000 hectares, it usually needs one or two months before a group of elephants appear in the same area twice.
 "So don't expect to see elephants again in Wild Elephant Valley for a while,'' he said. "And the other groups might be miles away.''
In fact, they were the only elephants I saw, but the five-minute encounter had satisfied my curiosity.
My exploration of the valley did not actually start until Lao Liu and I headed for the tree houses at 7:00 pm after our dinner in the administrative section of the reserve.
Since the cableway connecting the tree houses -- the main scenic area of the reserve -- with the built-up area (including the administrative section) stopped operations at 6 pm, we had to walk into the jungle.
According to my guide, the walk would take about an hour. And we had to hurry up to arrive before darkness fell.
So we hiked into the valley along a cement path stretching along the stream.
Then I saw the tropical rain forests veiled by the darkening night -- human-size ferns and sturdy vines wrapped around thick tree trunks spread across the path, and dense bamboo clusters and huge banyan trees stood alongside.
I could not tell how many levels the canopies had. But the trees, like rusted, ivy-choked rockets, looked imposingly tall.
From time to time, I saw some dark tunnels along the slope with broken bamboos and tree trunks.
Liu told me that most of them were elephant tunnels. "Occasionally some lonely male elephants will come out of the tunnels to cross the path to drink in the stream,'' he said.
 "They are extremely dangerous,'' he said.
Once or twice, I ran into spiderwebs across the path and had to brush them away from my face. Finally, as darkness fell, I heard the sound of people's voices floating through the dense forests and then saw light from windows. We had arrived at the tree houses.
The following morning, I was woken by Lao Liu at 5:00 am. "Let's go to the nitrate pond,'' he said. "Elephants might come down to drink.''
But they didn't. Except for a shallow pond and heaps of elephant droppings, there was nothing.
According to Liu, elephants have to absorb nitrate from time to time. So park workers put nitrate along the stream at times to attract them.
 "It depends on elephants, though,'' he said.
So in the next two hours, we turned our attention to the jungle itself. We went back to the walkway stretching across the valley above the stream and I got a closer look at the forests.
Then I found the canopies were three levels deep. There were some giant trees hanging with stalactite vines. I looked up, following the trunk of one of them, and found that the height of the tree alone was breathtaking.
I also saw some huge "strangler trees'' with weird roots sprawling along the mountain slope like rolling walls, some trees with 10-foot roots that fanned out from the trunk like stabilizer fins, and various beautiful flowers breaking abruptly out of the trunks.
Birds were shuttling back and forth between the trees, adding a lively touch to the mystical jungle.

(Photos: top: A family of elephants stroll through the tropical jungle; next to top:Tree houses built in the valley provide good viewpoints for watching the wild elephants.  By Chen Liang)