to complete and during this time the anaconda behaves very sluggishly. Difficulties in determining maximum size The remote location of the snake's habitat has historically made locating, capturing, and returning specimens difficult. Transporting very large specimens to museums, especially before substantial decay, is difficult (though this has not prevented the return of much larger and more cumbersome crocodilian specimens). Skins can stretch substantially, increasing the snake's size by more than 50% if stretched during the tanning process. Reports without physical proof are considered dubious if from non-scientists, as such individuals may at worst be more interested in promoting themselves or telling a good tale, or at the least may not be sufficiently trained in proper measurement methods. Observational reports of animals which were not captured are even more dubious, as even trained scientists often substantially overestimate the size of anacondas prior to capture. According to the Guinness Book of World Records, this species has been perhaps subject to the most extreme size exaggerations of any living animal. Historical records Numerous historical accounts of green anacondas are reported, often of improbable sizes. Several zoologists (notably Henry Walter Bates and Alfred Russel Wallace, among others) note rumors of snakes beyond long, but in each case, their direct observations were limited to snakes around in length. Numerous estimates and second-hand accounts abound, but are generally considered unreliable. To prove the point of overestimating, in Guyana in 1937, zoologist Alpheus Hyatt Verrill asked the expedition team he was with to estimate the length of a large, curled-up anaconda on a rock. The team's guesses ran from ; when measured, this specimen was found to be . Almost all specimens in excess of , including a much-publicized specimen allegedly long, have no voucher specimens including skins or bones. The skin of one specimen, stretched to , has been preserved in the Instituto Butantan in São Paulo and is reported to have come from an anaconda of in length. While in Colombia in 1978, herpetologist William W. Lamar had an encounter with a large female specimen long, estimated to weigh between . In 1962, W.L. Schurz claimed to have measured a snake in Brazil of with a maximum girth of . One female, reportedly measuring in length, shot in 1963 in Nariva Swamp, Trinidad, contained a caiman. A specimen of , reportedly with a weight of , was caught at the mouth of the Kassikaityu River