- Evidence reveals what the Donner Party ate during their final days of being snowbound in the Sierra Nevada.

- After eating the family dogs and other animal meat, some members ate bones, hides, twigs and string.

- Human bones were not recovered but researchers believe some Donner Party members resorted to cannibalism.

They had endured months of cold and hunger. The Donner-Reed party had set out for California in 1846 in a journey that normally took four to six months. But after trying a new route, called Hastings Cutoff, rugged terrain left the group snowbound in the Sierra Nevada.

Now a new book analyzing one of the most spectacular tragedies in American history reveals what the 81 pioneers ate before resorting to eating each other in a desperate attempt to survive. On the menu: family pets, bones, twigs, a concoction described as "glue," strings and, eventually, human remains.

The book, "An Archaeology of Desperation: Exploring the Donner Party's Alder Creek Camp," centers on recent archaeological investigations at that campsite near Truckee, Calif., where one quarter of the 81 emigrants spent their nightmarish winter of 1846-47.

No human bone was identified in the fragments analyzed from the extensive bone sample at Alder Creek, but the researchers conclude that "some Donner Party members participated in cannibalism" during the last week of February 1847.

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Co-editor Kelly Dixon, an associate professor in the Department of Anthropology at The University of Montana, told Discovery News that she and her colleagues "are emphasizing the fact that the historical and archaeological sources present a complicated story about humans doing whatever possible, including eating hide and strings as well as consuming their dogs, before making the desperate decision to cannibalize. Thus, the bone remains at the site indicate an avoidance of cannibalism … but not necessarily the absence of it."

Dixon and co-editors Julie Schablitsky and Shannon Novak identified rodent, canine, deer, rabbit, horse and oxen/cattle bones within the over 16,000 bone fragments.

The historical record, consisting of letters and journals kept by members of the Donner Party and rescue groups, as well as the memories of some survivors, supports that the trapped members first ate all of their animals, including captured mice and the family dogs, as well as wild game.

Of the family dog "Cash," emigrant Virginia Reed Murphy wrote, "We ate his head and feet -- hide -- everything about him."

"The Donner Party—A Day in November" is a painting inspired by the recent archaeological work at Alder Creek and painted by James Schablitsky.James Schablitsky

Another member of the group, Patrick Breen, reportedly shot his dog and dressed its flesh. The Donner's dog Uno, itself hungry enough to eat a child's shoe, may have also been consumed.

"When the meat gave out, the emigrants turned to the hides of the slaughtered animals, which, when scraped, cut into strips, and boiled, yielded a thick glue," according to Kristin Johnson, a Salt Lake Community College librarian who has studied the Donner Party for nearly two decades.

"The emigrants also discovered that bones, if boiled long enough or roasted, could be eaten," she added.

Johnson continued that, based on the historical record, some members tried to eat "a decayed buffalo robe, but it was too tough and there was no nourishment in it."

The members even tried eating pine bark and twigs, with Solomon Hook later saying that at one point he "went two weeks without food, chewing only pine pitch."

With nothing else left to eat, the historical record indicates some of the snowbound victims resorted to consuming the bodies of others who perished.

Johnson reports that James Frazier Reed, who left and then returned with men to help at Jacob Donner's camp, "found a gruesome scene."

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Hair, bones, skulls, and the fragments of half-consumed limbs were said to be around the fire. Jacob Donner's body was found with his heart and liver removed and his limbs and arms cut off. Another account describes children having blood on their faces, after trying to consume such flesh.

In human history, several different types of cannibalism exist. Exocannibalism is when a culture, group or tribe consumes members of another group, while mortuary cannibalism is the practice of eating deceased relatives for ritualistic purposes.

There is little doubt that Donner Party members who resorted to eating human flesh exemplified "survival cannibalism."

Dixon and Schablitsky, in a "Concluding Thoughts" chapter of the book, mention that they did not find any intact skeletons at the excavation site. But they add, "If the Donner families consumed only flesh and organs, as would be expected from comparative cases of survival cannibalism, then only soft tissue would have been cooked over a fire or boiled in a pot."

They conclude, "Beyond the cannibal tale, this hero saga reminds us of our own fragility, mortality, and resilience in the face of unfamiliar circumstances and less-than-predictable futures."