| Species (N=919) | GC (%) | AT (%) | G (bases) | C (bases) | A (bases) | T (bases) | Maximum lifespan (yrs) |
|---|---|---|---|---|---|---|---|
| Nyctalus noctula | 41.0 | 59.0 | 360 | 273 | 502 | 410 | 12.0 |
| Nyctereutes procyonoides | 42.5 | 57.5 | 381 | 276 | 464 | 424 | 16.6 |
| Nycticebus coucang | 42.9 | 57.1 | 380 | 282 | 477 | 403 | 25.8 |
| Nycticorax nycticorax | 44.9 | 55.1 | 441 | 255 | 420 | 435 | 21.1 |
| Nymphicus hollandicus | 47.8 | 52.2 | 495 | 245 | 381 | 427 | 35.0 |
| Ochotona princeps | 44.7 | 55.3 | 435 | 254 | 437 | 416 | 7.0 |
| Octodon degus | 38.8 | 61.2 | 347 | 252 | 486 | 460 | 14.0 |
| Odocoileus hemionus | 37.5 | 62.5 | 334 | 245 | 515 | 451 | 22.0 |
| Odocoileus virginianus | 37.2 | 62.7 | 332 | 243 | 517 | 451 | 23.0 |
| Okapia johnstoni | 43.2 | 56.8 | 403 | 265 | 447 | 430 | 33.5 |
| Oncorhynchus clarkii | 45.0 | 55.0 | 417 | 281 | 464 | 389 | 10.0 |
| Oncorhynchus gorbuscha | 45.6 | 54.4 | 422 | 286 | 447 | 396 | 3.0 |
| Oncorhynchus keta | 45.2 | 54.8 | 419 | 282 | 451 | 399 | 7.0 |
| Oncorhynchus kisutch | 45.8 | 54.2 | 417 | 293 | 459 | 382 | 5.0 |
| Oncorhynchus mykiss | 45.2 | 54.8 | 417 | 284 | 456 | 394 | 11.0 |
| Oncorhynchus nerka | 45.9 | 54.1 | 426 | 286 | 448 | 391 | 8.0 |
| Oncorhynchus tshawytscha | 45.6 | 54.4 | 419 | 288 | 455 | 389 | 9.0 |
| Onychodactylus fischeri | 33.7 | 66.3 | 283 | 240 | 562 | 466 | 17.0 |
| Ophiodon elongatus | 47.1 | 52.9 | 446 | 284 | 450 | 371 | 20.0 |
| Ophiophagus hannah | 43.3 | 56.7 | 451 | 243 | 437 | 471 | 22.5 |
| Orcaella brevirostris | 40.2 | 59.8 | 364 | 259 | 488 | 440 | 30.0 |
| Orcinus orca | 39.7 | 60.2 | 366 | 250 | 486 | 448 | 90.0 |
| Oreamnos americanus | 40.7 | 59.3 | 373 | 256 | 473 | 443 | 20.8 |
| Oreochromis esculentus | 45.7 | 54.3 | 447 | 283 | 470 | 396 | 10.0 |
| Oreochromis mossambicus | 46.0 | 54.0 | 452 | 285 | 464 | 401 | 11.0 |
| Oreochromis niloticus | 45.6 | 54.4 | 446 | 282 | 463 | 405 | 9.0 |
| Oreoleuciscus potanini | 44.8 | 55.2 | 395 | 300 | 470 | 386 | 40.0 |
| Oreotragus oreotragus | 40.5 | 59.5 | 368 | 258 | 481 | 438 | 25.9 |
| Ornithorhynchus anatinus | 38.7 | 61.3 | 344 | 252 | 539 | 407 | 22.6 |
| Orycteropus afer | 40.0 | 60.0 | 370 | 249 | 478 | 451 | 29.8 |
| Oryctolagus cuniculus | 42.6 | 57.4 | 389 | 268 | 478 | 407 | 9.0 |
| Oryx dammah | 41.4 | 58.6 | 378 | 261 | 467 | 439 | 27.5 |
| Oryx gazella | 40.9 | 59.1 | 373 | 259 | 474 | 439 | 23.8 |
| Oryx leucoryx | 40.5 | 59.5 | 372 | 254 | 476 | 443 | 20.8 |
| Oryzias latipes | 44.8 | 55.2 | 396 | 301 | 476 | 384 | 5.0 |
| Osmerus mordax | 49.3 | 50.7 | 446 | 319 | 460 | 326 | 7.0 |
| Osteoglossum bicirrhosum | 41.3 | 58.7 | 378 | 269 | 488 | 431 | 6.5 |
| Osteolaemus tetraspis | 41.7 | 58.3 | 397 | 251 | 455 | 452 | 70.0 |
| Otis tarda | 47.5 | 52.5 | 475 | 261 | 400 | 415 | 28.3 |
| Otolemur crassicaudatus | 45.9 | 54.1 | 422 | 286 | 435 | 399 | 22.7 |