The U.S. Fish and Wildlife Service announced the arrests Thursday after an undercover operation that included officers from 16 states, three federal agencies and three Asian countries.
Items seized under "Operation Wild Web" include the pelts of endangered big cats such as the Sumatran tiger, leopard and jaguar; live migratory birds such as the California scrub jay; whale teeth; elephant and walrus ivory; and a zebra pelt.
"Our message is clear and simple: The Internet is not an open marketplace for protected species," said Edward Grace, deputy assistant director for law enforcement for the Fish and Wildlife Service.
Working with counterparts in California, Texas, New York, Florida and Alaska and other states, federal officials targeted illegal wildlife sellers who operate through Craigslist, eBay and other Internet marketplaces and classified ads. Wildlife officers in Singapore, Thailand and Indonesia ran similar operations at the same time.
The items were seized last August, although charges are still being brought in many cases.
"As a major platform for the illicit trade in wildlife, the Internet has become a dangerous place for animals," said Jeff Flocken, North American regional director for the International Fund for Animal Welfare, an advocacy group that worked with the federal task force.
"Wildlife crimes are not only harmful to endangered species, they also pose serious threats to national and global security," Flocken said.
Illegal wildlife trade generates an estimated $19 billion a year worldwide and ranks fourth on the list of the most lucrative global illegal activities behind narcotics, counterfeiting and human trafficking, the animal welfare group said in a report last year.
Federal laws regulating the sale of wildlife include the Endangered Species Act, Migratory Bird Treaty Act, Bald and Golden Eagle Protection Act; the Marine Mammal Protection Act and the Lacey Act, which prohibits trade in wildlife, fish and plants that have been illegally taken, transported or sold.