Global trade in illegal wildlife is a potentially vast illicit economy, estimated to be worth billions of dollars each year. Some of the most lucrative illicit wildlife commodities include elephant ivory, rhino horn, sturgeon caviar, and so-called "bushmeat." Wildlife smuggling may pose a transnational security threat as well as an environmental one. Numerous sources indicate that some organized criminal syndicates, insurgent groups, and foreign military units may be involved in various aspects of international wildlife trafficking. Limited anecdotal evidence also indicates that some terrorist groups may be engaged in wildlife crimes, particularly poaching, for monetary gain. Some observers claim that the participation of such actors in wildlife trafficking can therefore threaten the stability of countries, foster corruption, and encourage violence to protect the trade.