|Sources for Dataset S1
Sources of search effort data for species with high numbers of searches (≥ 12)
Pemberton’s deer mouse (Peromyscus pembertoni)
 reported that there have been 10 years of trapping, and more than 7000 trap nights all over the island (the entire former range) since the first and last collection of this species in 1931 .  and  reported that none were found in their surveys in 1997, and  reports that a colleague also surveyed the island for this species in the early 1980s (10 + 1 + 1 = 12 surveys).
Angel Island deer mouse (Peromyscus guardia)
This species formerly occurred on three islands. It has not been trapped since 1987 , although  reported that a colleague saw two individuals in 1991.  and  reported trapping for this species in 1990, 1991, 1995, 1998, 1999, 2001 (11 trips to these islands).  trapped for this species on two islands in 1997. (= 11 + 2 = 13 surveys since 1987).
Baiji (Lipotes vexillifer)
This species has not been caught since 2001, but  reported that the last sighting of a live wild animal by a reliable witness was in mid 2006.  says that Dongting and Poyang lakes have been surveyed every 3 months since 2000 by researchers surveying cetaceans (these researchers are studying Finless Porpoises, but also monitoring the presence of the sympatric, ecologically and morphologically similar Baiji). The Poyang lakes area is one of the last places where the species was found in the 1990s.  surveyed nearly the entire former range of the species (the main river channel) using visual and acoustic methods and two boats to cover 1669 km twice in 2006 (= four surveys a year, 2 in the second half of 2006, 4 in 2007, 4 in 2008 and 4 in 2009, + a comprehensive survey in 2006 = 15 surveys since 2006).
Wild horse (Equus ferus)
This species was last recorded in the wild in Mongolia in 1969.  reported that there were annual searches for it by the Joint Mongolian-Soviet Expedition between 1970 and 1990, which have failed to find conclusive evidence of survival in the wild, and that Chinese biologists conducted a survey in northeastern Xinjiang from 1980 to 1982 and found none (20 + 2 = 22 surveys since 1969).
Kouprey (Bos sauveli)
The last reliable sightings and a photograph of this species in the wild were in 1969 . However,  reported that extensive questionnaire surveys of villagers suggested that it survived in several areas in 1986.  also stated that surveys in 1986 obtained the last reliable reports.  summarized searches for this species since 1989 including surveys of markets for body parts, searches on foot, and aerial surveys. Searches are reported in [253-264]. Most of these include multiple years and separate expeditions. Additionally,  cites two personal communications reporting extra expeditions to search for evidence of this species in 2008. The number of separate searches reported in these publications is at least 23 since 1986.
Thylacine (Thylacinus cynocephalus)
The last record of this species in the wild was in 1933. Surveys to find living animals began in the 1930s . The major searches are summarized by the Tasmanian Department of Primary Industries Parks, Water and the Environment [http://www.dpiw.tas.gov.au/inter.nsf/WebPages/BHAN-53777B], ,  and .  reported that the ‘Animals and Birds Protection Board’ sponsored several expeditions to western Tasmania in 1939, and a ‘thylacine expeditionary research team’ conducted several major searches from 1968 to the early 1970s. [266, 267] report that there were three major searches earlier than this, between 1937 and 1939, and 16 others between 1939 and 1992. The Tasmanian Department of Primary Industries Parks, Water and the Environment list includes expeditions by well-qualified personnel (wildlife researchers, parks and wildlife officers, zoo workers, wildlife photographers and naturalists), including searches on foot and in the later searches, deployment of camera traps, in 1937, 1945, 1959, 1963, 1968, 1980,1982, 1983, 1984, 1988, 1989, 1990, 1991, 1992, and 1993. There have also been numerous private expeditions by less well-qualified personnel. The number of separate searches by qualified personnel reported in these publications is at least 25 since 1933.