So I spent some time and went through my Mammal lifelist and came up with the following 252 species that few zoochatters have likely seen. I appologize for the formatting ahead of time. Most of these I've only seen once before and usually somewhere outside North America or Europe (where most zoochatters call home.) If you'd like me to specify where I saw any of these just let me know!
I'm guessing there's a chance I'm the only zoochatter to have seen Zeledon's mouse opossum, Honduran white Bat, Palawan stink badger, Peale's dolphin, Merida Brocket Deer
I issue a challenge to see if anyone has seen over 100 of these (I can think of a few who may have a good shot!)
1. (Zaglossus bruijni) western long-beaked echidna
2. (Caluromys philander) bare-tailed woolly opossum
3. (Chironectes minimus) Yapok
4. (Didelphis aurita) big-eared opossum
5. (Marmosa zeledoni) Zeledon’s mouse opossum (wild)
6. (Antechinus agilis) Agile Antechinus
7. (Sminthopsis douglasi) Julia Creek Dunnart
8. (Parantechinus apicalis) Dibbler
9. (Dasyurus geoffroii) Chuditch or Western Quoll
10. (Myrmecobius fasciatus) Numbat
11. (Isoodon auratus) Golden Bandicoot
12. (Isoodon macrourus) Northern Brown Bandicoot
13. (Isoodon fusciventer) western brown bandicoot
14. (Parameles gunnii) Eastern Barred Bandicoot
15. (Trichosurus arnhemensis) Northern brushtail possum
16. (Trichosurus caninus) short-eared Possum
17. (Trichosurus cunninghami) Mountain Brushtail possum
18. (Phalanger ornatus) ornate cuscus
19. (Strigocuscus celebensis) Sulawesi dwarf cuscus
20. (Spilocuscus maculates) Common Spotted cuscus
21. (Hypsiprymnodon moschatus) Musky Rat-kangaroo (wild)
22. (Bettongia gaimardi) Tasmanian Bettong
23. (Bettongia lesueur) burrowing bettong
24. (Bettongia tropica) Northern Bettong
25. (Dendrolagus inustus) grizzled tree-kangaroo
26. (Dendrolagus lumholtzi) Lumholtz’s Tree-kangaroo
27. (Lagorchestes conspicillatus) Spectacled Hare-wallaby
28. (Petrogale lateralis) Black-footed Rock-wallaby
29. (Petrogale concinna) Nabarlek
30. (Petrogale persephone) Proserpine Rock-wallaby
31. (Petrogale wilkinsi) Wilkin's Rock-wallaby
32. (Onychogalea fraenata) Brindled nail-tailed Wallaby
33. (Onychogalea unguifera) northern nail-tail wallaby
34. (Macropus antilopinus) Antilopine Wallaroo
35. (Macropus bernardus) Black Wallaroo
36. (Macropus dorsalis) Black-striped Wallaby
37. (Macropus Irma) Western Brush Wallaby
38. (Macropus parryi) Pretty-faced, Whiptail Wallaby
39. (Burramys parvus) Mountain Pygmy-possum
40. (Cercartetus nanus) Eastern Pygmy-possum
41. (Pseudocheirus occidentalis) Western Ringtail
42. (Petaurus australis) Yellow-bellied Glider
43. (Petaurus gracilis) Mahogany Glider
44. (Diplomesodon pulchellum) Piebald shrew
45. (Sorex araneus) Common shrew
46. (Sorex minutissimus) Eurasian least shrew
47. Sorex unguiculatus) Long-clawed shrew
48. (Mogera wogura) Japanese Mole
49. (Mogera imaizumii) Small Japanese Mole
50. (Atelerix frontalis) Southern African Hedgehog
51. (Hemiechinus auritus) long-eared Hedgehog
52. (Anoura geoffroyi) Geoffroy’s tailless bat
53. (Artibeus lituratus) Great fruit-eating bat
54. (Carollia castanea) Chestnut short-tailed bat
55. (Carollia sowelli) Sowell’s short-tailed bat
56. (Dermanura toltecus) Toltec fruit-eating bat
57. (Dermanura watsoni) Thomas’s fruit-eating bat (wild)
58. (Diaemus youngi) White-winged vampire bat
59. (Ectophylla alba) Honduran white bat (wild)
60. (Erophylla sezekorni) buffy flower bat (wild)
61. (Glossophaga commissarisi) Commissaris’s long-tongued bat
62. (Lasionycteris noctivagans) silver-haired bat
63. (Lonchophylla robusta) Orange nectar bat (wild)
64. (Macroderma gigas) Ghost bat
65. (Mesophylla macconnelli) MacConnell’s bat (wild)
66. (Myotis albescens) Silver-tipped myotis (wild)
67. (Myotis nigricans) Black myotis (wild)
68. (Nycticeius humeralis) evening bat
69. (Peropteryx kappleri) Greater dog-like bat (wild)
70. (Pipistrellus abramus) Japanese pipistrelle
71. (Platyrrhinus vittatus) Greater broad-nosed bat
72. (Plecotus auritus) Brown long-eared bat
73. (Pteropus alecto) Black Flying Fox
74. (Pteropus dasymallus) Ryukyu fruit bat
75. (Rhinolophus luctus) woolly horseshoe bat (wild)
76. (Rhynchonycteris naso) proboscis bat (wild)
77. (Rousettus leschenaultia) Leschenault’s Rousette
78. (Saccopteryx leptura) Lesser sac-winged bat (wild)
79. (Uroderma bilobatum) Tent-making bat (wild)
80. (Vespertilio murinus) Parti-colored bat
81. (Tupaia minor) pygmy tree shrew
82. (Tupaia tana) large tree shrew
83. (Tupaia palawanensis) Palawan tree shrew
84. (Galeopterus variegatus) Malayan colugo (wild in the zoo)
85. (Cephalopachus bancanus) Western Tarsier
86. (Tarsius spectrum) spectral tarsier
87. (Microcebus lehilahytsara) Goodman's mouse lemur
88. (Mirza zaza) Northern giant mouse lemur
89. (Eulemur sanfordi) Sanford’s brown lemur
90. (Cebus kaapori) Kaapori capuchin
91. (Sapajus flavius) blonde capuchin
92. (Chiropotes albinasus) white-nosed saki
93. (Pithecia inusta) Burnished saki
94. (Pithecia irrorata) Rio Tapajos saki
95. (Pithecia mittermeieri) Mittermeier’s Tapajos saki
96. (Aotus miconax) Peruvian night monkey
97. (Ateles marginatus) White-cheeked spider monkey
98. (Brachyteles arachnoids) Southern muriqui
99. (Mico humeralifer) tassel-eared marmoset
100. (Callicebus bernhardi) Prince Bernhard's titi
101. (Callicebus brunneus) brown titi monkey
102. (Callicebus nigrifons) black-fronted titi monkey
103. (Callicebus oenanthe) San Martin titi monkey
104. (Callicebus vieirai) Vieira’s titi monkey
105. (Macaca assamensis) Assam macaque
106. (Macaca cyclopis) Formosan rock macaque
107. (Macaca leonine) northern pig-tailed macaque
108. (Macaca ochreata) booted macaque
109. (Macaca pagensis) Pagai Island macaque
110. (Macaca siberu) Siberut macaque
111. (Pygathrix cinerea) grey-shanked douc langur
112. (Pygathrix nigripes) black-shanked douc langur
113. (Rhinopithecus bieti) black snub-nosed monkey
114. (Rhinopithecus brelichi) gray snub-nosed monkey
115. (Rhinopithecus roxellana) golden monkey
116. (Trachypithecus barbei) Tenasserim lutung
117. (Trachypithecus crepusculus) Gray Langur
118. (Trachypithecus delacouri) Delacour's langur
119. (Trachypithecus germaini) Indochinese lutung
120. (Trachypithecus hatinhensis) Hatinh langur
121. (Trachypithecus laotum) Laotian Langur
122. (Trachypithecus margarita) Annamese silvered langur
123. (Trachypithecus poliocephalus) white-headed or cat ba langur
124. (Hylobates klossii) Kloss's gibbon
125. (Hoolock hoolock) western hoolock gibbon
126. (Cyclopes didactylus) silky anteater
127. (Cabassous unicinctus) Southern naked-tailed armadillo
128. (Chaetophractus nationi) Bolivian hairy armadillo
129. (Priodontes maximus) Giant Armadillo
130. (Ochotona princeps) American pika (wild)
131. (Lepus brachyurus) Japanese hare
132. (Lepus capensis arabicus) Arabian hare
133. (Romerolagus diazi) volcano rabbit
134. (Allactaga major) Great jerboa
135. (Apodemus argenteus) small Japanese field mouse
136. (Apodemus speciosus) large Japanese field mouse
137. (Brachytarsomys albicauda) white-tailed antsangy
138. (Cuniculus taczanowskii) Mountain Paca
139. (Dasyprocta mexicana) Mexican agouti
140. (Eliurus grandidieri) Grandidier’s Tufted-tailed Rat
141. (Euchoreutes naso) Long-eared jerboa
142. (Funisciurus pyrropus talboti) Cameroon fire-footed rope squirrel
143. (Glirulus japonicas) Japanese dormouse
144. (Heliophobius argenteocinereus) Silvery mole rat
145. (Hylopetes alboniger) Particoloured flying squirrel
146. (Hystrix javanica) Sunda porcupine
147. (Hystrix sumatrae) Sumatran porcupine
148. (Melomys burtoni) Grassland Melomys
149. (Meriones vinogradovi) Vinogradov's jird
150. (Microsciuris alfari) Alfaro’s Pygmy Squirrel (wild)
151. (Microtus montebelli) Japanese grass vole
152. (Petaurista elegans) spotted giant flying squirrel
153. (Petaurista leucogenys) Japanese Giant Flying Squirrel
154. (Poliocitellus franklinii) Franklin’s ground squirrel
155. (Pseudomys australis) Plains, Eastern mouse
156. (Pteromys momonga) Japanese flying squirrel
157. (Rattus tanezumi) Tanezumi rat (wild, but in zoo)
158. (Salpingotus crassicauda) thick-tailed pygmy jerboa
159. (Salpingotus kozlovi) Kozlov's pygmy jerboa
160. (Sicista betulina) Northern birch mouse
161. (Tachyoryctes daemon) Demon mole rat
162. (Typhlomys cinereus) Chinese pygmy dormouse
163. (Uromys caudimaculatus) giant white-tailed rat (wild, no photo)
164. (Vulpes cana) Blanford’s fox
165. (Vulpes rueppellii) Rueppell’s fox
166. (Cerdocyon thous) Crab-eating Fox
167. (Lycalopex culpaeus) Colpeo Fox
168. (Lycalopex griseus) Argentine grey fox
169. (Lycalopex gymnocercus) pampas fox
170. (Lycalopex sechurae) Sechura Fox
171. (Lycalopex vetulus) hoary fox
172. (Bassaricyon gabbii) Bushy-tailed Olingo
173. (Mustela eversmanii) Steppe polecat
174. (Mustela itatsi) Japanese weasel
175. (Ictonyx libycus) Saharan striped polecat
176. (Meles anakuma) Japanese Badger
177. (Martes melampus) Japanese Marten
178. (Martes zibellina) Sable
179. (Melogale orientalis) Javan ferret-badger
180. (Melogale personata) Burmese ferret-badger
181. (Lontra feline) Marine Otter
182. (Mydaus marchei) Palawan stink badger
183. (Conepatus chinga) Molina’s hog-nosed skunk
184. (Conepatus humboldtii) Humboldt’s hog-nosed skunk
185. (Conepatus semistriatus) striped hog-nosed skunk
186. (Spilogale angustifrons) Southern spotted skunk (wild, no photos)
187. (Fossa fossana) Malagasy civet or fanaloka
188. (Galidictis grandidieri) Grandidier’s mongoose
189. (Prionodon linsang) Banded Linsang
190. (Paradoxurus aureus) golden wet-zone palm civet (possibly mislabeled)
191. (Viverra zibetha) large Indian civet
192. (Herpestes brachyurus palawanus) Palawan short-tailed mongoose
193. (Herpestes urva) crab-eating mongoose
194. (Leopardus braccatus) Pantanal Cat
195. (Leopardus colocolo) Colocolo
196. (Pardofelis marmorata) marbled cat
197. Prionailurus planiceps) flat-headed cat
198. (Lynx pardinus) Iberian lynx
199. (Zalophus wollebaeki) Galapagos sea lion (wild)
200. (Arctocephalus galapagoensis) Galapagos Fur Seal (wild)
201. (Arctocephalus forsteri) New Zealand fur seal (wild)
202. (Arctocephalus townsendi) Guadalupe fur seal
203. (Arctocephalus tropicalis) subantarctic fur seal
204. (Hydrurga leptonyx) leopard seal
205. (Monachus schauinslandi) Hawaiian monk seal
206. (Mirounga leonine) Southern elephant seal
207. (Balaenoptera acutorostrata) northern
minke whale (wild)
208. (Balaenoptera musculus) blue whale (wild)
209. (Balaenoptera physalus) fin whale (wild)
210. (Eschrichtius robustus) gray whale (in captivity!)
211. (Physeter macrocephalus) sperm whale (wild)
212. (Neophocaena phocaenoides) finless porpoise
213. (Orcaella brevirostris) Irrawaddy dolphin
214. (Grampus griseus) Risso’s Dolphin
215. (Cephalorhynchus hectori) Hector's dolphin (wild)
216. (Lagenorhynchus australis) Peale’s dolphin (wild)
217. (Lagenorhynchus obscurus) dusky dolphin (wild)
218. (Stenella frontalis) Atlantic Spotted Dolphin
219. (Steno bredanensis) Rough-toothed Dolphin
220. (Trichechus inunguis) Amazonian manatee
221. (Trichechus senegalensis) African manatee
222. (Ceratotherium simum cottoni) Northern White Rhinoceros
223. (Dicerorhinus sumatrensis) Sumatran Rhinoceros
224. (Potamochoerus larvatus) bushpig
225. (Sus philippinensis) Philippine Warty Pig
226. (Moschiola kathygre) yellow-striped chevrotain
227. (Muntiacus crinifrons) black muntjac
228. (Muntiacus feae) Fea's muntjac
229. (Cervus macneilli) MacNeill’s Deer
230. (Rusa marianna) Philippine brown deer
231. (Capreolus pygargus) Siberian roe deer
232. (Mazama bricenii) Merida Brocket Deer
233. (Mazama pandora) Yucatan brown brocket deer
234. (Blastocerus dichotomus) Marsh deer
235. (Ozotoceros bezoarticus) Pampas deer
236. (Tetracerus quadricornis) Four-horned Antelope
237. (Cephalophus jentinki) Jentink's Duiker
238. (Cephalophus zebra) Zebra Duiker
239. (Kobus leche smithemani) Black lechwe
240. (Pelea capreolus) Grey Rhebok
241. (Alcelaphus buselaphus) Jackson's hartebeest
242. (Madoqua saltiana) Salt’s dik-dik
243. (Ourebia ourebi) Oribi
244. Gazella bennettii) Chinkara
245. (Gazella marica) Arabian sand gazelle
246. (Saiga tatarica) saiga
247. (Capricornis swinhoei) Formosan serow
248. (Capricornis maritimus) Indochinese serow
249. (Arabitragus jayakari) Arabian tahr
250. (Nilgiritragus hylocrius) Nilgiri tahr (no photos)
251. (Naemorhedus goral) Himalayan Goral
252. (Ovis nivicola) snow sheep