The first year of excavations in 85-foot-deep Natural Trap Cave, Wyoming, is now a wrap, but challenges remain, such as going through customs with masses of dirty bones from dead creatures.

Alan Cooper, co-leader of the excavation, caught up with Discovery News this week after emerging from the cave, where many hundreds of mammals fell to their deaths over the past 100,000 years. Thanks to sturdy caving ropes, he wasn’t one of them.

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Cooper, who is director of the Australian Center for Ancient DNA, is now visiting various museums, so he left the bone samples extracted from the cave with colleague and fellow researcher Laura Weyrich. She just met one of the biggest challenges: getting the samples through Australian Quarantine and Inspection Service.

“Australian Quarantine folks are very energetic people,” Cooper said, explaining that they are usually not very familiar with the permit process that allows scientists like him to bring such materials into the country.

Weyrich had to take the bone samples — packed surrounded by ice to keep them refrigerator cold — directly into the Ancient DNA Lab. She could not go anywhere else with them. That’s because the lab, Cooper explained, is specially rated to be able to handle such materials.

As for all countries, Australia is concerned about bringing in items like seeds, bacteria and viruses. (Seeds could contain bacteria and might belong to invasive plants, for example.)

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With the samples back at the lab, the next steps are to analyze them for DNA and stable isotopes. They are also being dated using radiocarbon methods. The goal is to construct a picture of how animal populations adapted and responded to past climate change and major extinction events.

The researchers have quite a cast of characters to work with, considering all of the animals that fell into the cave.

"The range of species we recovered, especially carnivores such as the American lion and cheetah-like cat, are remarkable,” Julie Meachen of Des Moines University, who is the other co-leader of the excavation, said in a press release. "The condition of the bones varies a lot, as you'd expect -- but some of it is definitely DNA-containing, which is great after 30–50,000 years."

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Both she and Cooper said that, in addition to the lion and cheetah-like cat, the other bone samples come from Pleistocene-age mammal species that are now extinct in North America. These include the giant camel, several horse species, wolf, bison, mountain sheep, as well as many small mammals and birds.

This year's excavation was just the first of a three-year program. Meachen and the other scientists previously expressed fear about rappelling down the incredibly deep shaft of the cave.

Now that they've literally worked out the kinks, they're looking forward to the DNA analysis and the additional excavations.

Photo: A scientist rappelling into Natural Trap Cave, Wyoming. Credit: Alan Cooper, Australian Centre for Ancient DNA