CREEL, Mexico (Reuters) - Six babies with puffed up eyes and swollen bellies lie silently in an intensive care ward, too weak to cry because of hunger and tuberculosis.
They are victims of brutal conditions in northern Mexico's remote and snowy Sierra Tarahumara mountains, where doctors and aid groups say at least 90 indigenous people have died so far this winter from hypothermia, malnutrition and cold-related diseases.
To defend their 1,000-year-old culture from outside influences, the Tarahumara have headed deep into the 7,650 feet (2,300 meter)-high mountains and live in caves in secluded canyons during winter, when temperatures drop as low as 5 degrees Fahrenheit (minus 15 degrees Celsius).
Improved government health care has helped bring a slight drop in mortality rates in recent years but about 70 percent of Tarahumara children under five suffer from malnutrition and many families are reluctant to seek help.
"The children have to be at death's door before the parents or grandparents bring them to hospital. We never know how many die before they reach us," said Sister Marta Rangel at a Roman Catholic clinic, ringed by ice, in Creel, in Chihuahua state.
The babies in the clinic are expected to recover but Rangel said some may return in the same critical condition in a few months time. She said an 8-year-old girl here had brain damage after suffering prolonged hunger and tuberculosis.
Despite such suffering, the Tarahumara are determined to remain Mexico's most isolated indigenous people.
"We're happy this way, we live as well as we can," said Maria Guadalupe Rodriguez, a gaunt-faced mother with two barefoot children and a baby with chapped lips on her back.
Talking through an interpreter as she received government food aid, her breath visible in the bitter cold, she said her family's corn harvest had failed in the hamlet of Rikinapuchi, near Creel. She wore only a brightly colored tribal cotton dress, a thin shawl and open-toed sandals as a dusting of snow covered the ground.
This year's winter is milder than most but visiting doctors can still only stay warm by wearing two pairs of socks, thick sweaters and thermal underwear.
Spanish conquistadors drove the Tarahumara from their nomadic existence on Chihuahua's fertile plains 500 years ago.
Over the past century, lumber companies, miners, tourist development and drug traffickers have pushed them deeper into the steep pine forests of the sierra, where farming land is scarce and corn crops often fail.
In summer, the Tarahumara live in remote pine forests and high plains where they can grow corn. But in winter, they head back to the canyons and have to eat whatever they can find, including mice, roots and reptiles.
Even then, some Western influences do reach them. Alcohol is creeping into their festivities to replace their less-potent traditional fermented corn drink Tesguino, increasing winter deaths from hypothermia as Tarahumara men get drunk and collapse in the snow.
"We've just found one Tarahumara man nearby, frozen to death, still clutching his bottle of firewater," said Oscar Chavez, who runs the state hospital in Creel, the town where tourists start out on a train journey through Mexico's spectacular Copper Canyon.
Mexican doctors have taken on the daunting task of getting medicines to the some 90,000 Tarahumara who live in an area slightly larger than Switzerland with a population density of five inhabitants per square kilometer (0.4 square mile).
The doctors spend weeks forcing jeeps along rutted, muddy roads to reach remote communities who sometimes refuse the medical help on offer.
"There is a great suspicion of outsiders and Western medicines. The Tarahumara have a different concept of illness, as something to be cured with ceremonies and natural remedies," said Victor Martinez, an anthropologist who has worked with the Tarahumara for 20 years.
The Tarahumara often stop the six-month Tuberculosis treatment the government provides as soon as they feel better, allowing harmful bacteria to regenerate and strengthen, becoming more contagious and expensive to treat.
Despite the winter deaths and a population drain as the young are lured away to farm jobs in the neighboring states of Sonora and Sinaloa, the Tarahumara are far from defeated. Their numbers have almost doubled from around 50,000 in the 1970s.
They refer to themselves as Raramuris, which means light-footed people, and think nothing of walking 30 miles (50 km) in a day, up and down canyons, to chop firewood, visit a friend or farm their corn and bean crops.
Runners from rival villages hold 24-hour, 90-mile (145-km)races in flimsy sandals before the harvest, a feat that would test even the world's finest long-distance runners.
"It's not for nothing we believe our women have four souls. We need the spirit that God gives us to face all that life throws at us," said Tarahumara leader Luz Elena Villalobos, or Sopori, as she is called in her native Raramuri tongue.
Editing by Catherine Bremer and Kieran Murray