KEY TO THE SMALL TERRESTRIAL OF THE GRAND CANYON RIPARIAN ZONE

JENNIFER K. FREY

ENMU MUSEUM OF NATURAL HISTORY DEPARTMENT OF BIOLOGY, STATION 33 EASTERN NEW MEXICO UNIVERSITY PORTALES, NEW MEXICO 88130

DRAFT 4/23/2001

Note: Keys are for adult specimens. Juvenile are typically a dull gray color; hind feet often measure equivalent to adults in all but the youngest of some species. Use a thin, stiff ruler for measurements; ruler should be cut to start at 0 mm mark. Tail should be measured with ruler placed along the dorsal surface of the tail (0 at the junction between tail and rump) and with the tail perpendicular to the body; measure to the end of the last vertebrae (not the hair). Hind foot should be measured with ruler placed along the bottom of the foot (0 at the heel) with the foot bent perpendicular to the leg; measure to the end of the longest claw (not to the end of the toe). Ear should be measured with the ruler placed into the notch at the base of ear (0 at notch); measure to longest distance to the end of the pinna.

MISCELLANEOUS SMALL TERRESTRIAL MAMMALS 1a. Long pointed flexible nose extends well beyond mouth, small eyes, small external ears…………(Order Insectivora) 2 1b Not as above………………………………………………………..…………………………………………(Order Rodentia) 3

2a Tail < ½ body; external ear extend beyond fur………………………………………….….Notiosorex crawfordi [NOCR] Desert shrew is verified from base Bright Angel Trail; it should be expected anywhere. 2b Tail > ½ body, external ears hidden in fur……………………………………………………………..…………...Sorex spp. Long-tailed shrews occur on both rims but are not expected in canyon. Retain specimen.

3a. External cheek pouches present………………………………………………………….…………………………………...4 3b. External cheek pouches absent………………………………………….………………………………………………….16

4a. External ears reduced, barely visible above fur; tail < 60% body; fusiform body shape; long front claws……………………………………………………………………………………..………….Thomomys bottae [THBO] Botta’s pocket gopher (Family Geomyidae) possible, verified from rim. Gophers are occasionally caught in Sherman traps. 4b. External ears extend beyond fur; tail > 60 body………………….………………………………...(Family ) 5

FAMILY HETEROMYIDAE (KANGAROO RATS)

5a. Hind foot sole densely furred along length…………………………………………………..………………(Kangaroo rats) 6 5b. Hind foot sole partially furred or naked…………………………………………………………………………(Pocket mice) 9

6a. Size large; hind foot > 45; tail tip white…………………………………………….……………Dipodomys deserti [DIDE] Desert kangaroo rat unlikely 6b Size small; hind foot < 45; tail tip dark…………………………………………………………………………………….……7

7a Hind foot with 4 toes……………………………………………………………..……………..Dipodomys merriami [DIME] Merriam’s kangaroo rat possible, verified Toroweap Valley 7b. Hind foot with 5 toes……………………………………………………………………………………………………………....8

8a. Lower incisors rounded; hind foot usually < 42…………..………………………..……………...Dipodomys ordii [DIOR] Ord’s kangaroo rat probable 8b. Lower incisors with flat front face; hind foot usually > 42…………………….……………..Dipodomys micropus [DIMI] Chisel-toothed kangaroo rat possible, verified north rim. This is an Arizona species of concern; only one specimen per location may be collected.

FAMILY HETEROMYIDAE (POCKET MICE)

9a. Long guard hairs often present on rump; tail always tufted………….…………………..……………….…….…………….10 9b. Long guard hairs never present on rump; tail tufted or not…………………..………………………………………………..11

10a. When present, long guard hairs on rump are stiff; hind foot usually < 22…………..Chaetodipus intermedius [CHIN] Rock pocket mouse verified 10b. When present, long guard hairs on rump are wispy; hind foot usually > 22……….. penicillatus [CHPE] Desert pocket mouse unlikely. Retain possible specimens for verification by cranial characters.

11a. Tail bushy; tail very long, usually > 95 and 125-130% of body…………………….….. formosus [PEFO] Long-tailed pocket mouse verified from north side of river throughout length of canyon. Any taken from south side should be saved as specimen 11b. Tail not bushy; tail short to long, < 95 and < 105% of body………………………..…………………………………………12

12a. Hind foot > 22; antitragus with lobe (as in Chaetodipus and P. formosus); size medium; no light patches behind ears……………………………………………………………...………………………………...Perognathus parvus [PEPA] Great Basin pocket mouse possible, verified from North rim 12b. Hind foot < 22; antitragus without lobe; small size; light patches behind ears…………...……………………….….….13

13a Tail < body……………….………………………………………………………………………….…………………………....14 11b Tail > body ………………………….……………………………………………………………………………………….……15

14a Tail > 60; hind foot 18-20, usually 19; light patch behind ear present but not conspicuous……………………………………………………………………….Perognathus flavescens apache [PEAP] Apache pocket mouse is possible, verified from South Rim 14b Tail < 61; hind foot 15-19, usually 17; light patch behind ear conspicuous….……………..Perognathus flavus [PEFL] Silky pocket mouse is probable, verified from South Rim

15a Tail 67-81; hind foot 17-21, usually 19……………………………………………….Perognathus longimembris [PELO] Little pocket mouse is probable. It has been verified from several areas north of river (above Marble Canyon; between Kanab Creek and Toroweap Valley and below Triumphal Arch) and from south of river near Page. Skull critical for identification. 15b Tail 75-88; hind foot 19-22, usually 20 or 21……………………..…………………………Perognathus amplus [PEAM] Arizona pocket mouse is possible. It has been verified from two areas south of river (above Little Colorado River and below peach Springs Canyon). Skull critical for identification.

16a Pelage color pattern with stripes, spots or mottling………………………….……………..(Family Sciruidae, ) 17 16b Pelage color pattern without stripes, spots or mottling……………………………..…………(Family Muridae, murids) 21

FAMILY SCIURIDAE (SQUIRRELS)

17a Black and white stripes on sides of head……………..………………………………………………..…………Tamias spp. Some species of chipmunk from rims are remotely possible in canyon. Retain specimen. 17b No stripes on face……………………………………………………………………………………………………..…………18

18a One white stripe on each side of body……………..…………...…………………………………..….……………………..19 18b No white stripes on body……………………………………………………………………………………….……………….20

19a Underside of tail white; tail 50-77, usually < 70…………………….……………Ammospermophilus leucurus [AMLE] White-tailed antelope ground is verified from the river corridor. Retain any specimens from vicinity Prospect Valley or below. 19b Underside of tail dark; tail 67-92, usually > 70…………………………………….Ammospermophilus harrisii [AMHA] Harris’ antelope ground squirrel is possible; verified from south of river below Peach Springs Canyon.

20a Overall grayish or brownish pelage with mottled appearance; mottling may appear like white spots; tail bushy; adults large (tail >150, hind foot > 48)………………………………………………………….Spermophilus variegates [SPVA] Rock squirrel is verified from river corridor? 20b Overall tannish or reddish pelage with light spots on back; tail well-furred but not bushy; adults medium (hind foot 29-35 tail < 90)……………………………………………………………..…………………..Spermophilus spilosoma [SPSP] Spotted ground squirrel is probable, verified from South Rim.

FAMILY MURIDAE (MICE)

21a Tail < 60% body, soles of feet furred; distinctive odor…..………………………………………………………………….22 21b Tail > 60% body, soles of feet naked or slightly furred….………………………………………………………………….23

22a Tail < ½ body (38-51); hind foot 20-24; many with fur of underparts white to base (some with fur gray to base)……………….………………………………………………………….……………Onychomys leucogaster [ONLE] Northern grasshopper mouse is probable, verified from rim 22b Tail > ½ body (45-49); hind foot 19-20; all with fur of underparts gray to base………...Onychomys torridus [ONTO] Southern grasshopper mouse is possible, verified from N rim

23a Tail long, scaly, with few hairs; belly not obviously lighter than back……………………...….………………………….24 23b Tail at least scantily furred; belly usually light and contrasting with darker back…………………………….………….25

24a. Mouse sized; Pelage uniformly gray...... ……………………………….Mus musculus [MUMU] House mouse is unlikely. 24b Rat sized; Pelage uniformly dark brownish/grayish...... ……………………………….Rattus spp. Murine rats are unlikely. Two species are known from Arizona (R. rattus, R. norvegicus). Specimens required for identification.

25a Mouse-like; hind foot < 26……………..…………………………………………………………...(deer and harvest mice) 26 25b Rat-like; hind foot > 27……………………..……………………………………………………….……………..(wood rats) 31

26a Tail tufted, with at least some terminal hairs longer in length………………………………………………………….…...27 26b Tail not tufted, all hairs of about equal length…………………………………………………………………………………29

27a Tail > 83, sparsely haired appearing almost naked but with more hairs near tip, slightly bicolored (total 169-208; tail 83- 113; hind foot 18-22; ear 17-21)…………..…………………….………………………..Peromyscus eremicus [PEER] The cactus mouse is verified. 27b Tail < 83, haired and slightly to strongly bicolored……………………………………………………………………………28

28a Ear 16-20,; many with white preauricular spot; upper incisor without a longitudinal groove (total 133-165, tail 47-74, hind foot 18-21, ear 16-20)………..………………………………………………….... Peromyscus maniculatus [PEMA] The deer mouse is verified. 28b Ear 11-17; eyes appear set close together and nearer the nose; upper incisor with a longitudinal groove in surface (total 117-156, tail 50-83, hind foot 15-21, ear 11-17)………...…………………..Reithrodontomys megalotis [REME] The western harvest mouse is verified.

29a Ear > 23 (total 173-210, tail 80-110, hind foot 21-26, ear 23-28).………………………..…Peromyscus truei [PETR] Pinyon mouse is verified. 29b Ear < 23……………………………….………………………………………………………………………………………….30

30a Fur long and silky, dorsal pelage usually orangish (total 158-197, tail 80-118, hind foot 17.5-23, ear 16-23)………………………………………………………………………………………..….Peromyscus crinitus [PECR] Canyon mouse is verified. May be confused with P. eremicus. 30b Fur not noticeably long and silky, dorsal pelage usually brownish (total 189-222, tail 95-115, hind foot 21-24, ear 18-22)………………………………..……………………….….………..Peromyscus boylii [PEBO] Brush mouse is verified.

FAMILY MURIDAE (WOOD RATS)

31. Sole of hind foot completely furred; tail very bushy (total 302-398, tail 127-168, hind foot 34-45, ear usually 32-34)………………………………………………………………………………………..Neotoma cinerea [NECI] Bushy-tailed wood rat is probable. It has been verified from Lees Ferry. 31b. Sole of hind foot naked or only partially furred; tail haired to slightly bushy………………………………………….…..32

32a. Tail semi-bushy; throat hairs usually gray at the base (white throated populations occur above the Little Colorado River)……………………………………………………………………………………………….Neotoma stephensi [NEST] Stephen’s wood rat is possible. It is verified from the south rim along the entire length of the canyon. Often confused with N. lepida. 32b. Tail lightly haired; Hairs at base of throat gray at base or all white………………………………………………...……..33

33a. Throat hair all white (total 280-360, tail 115-161, hind foot 30-37, ear 26-33)……………..Neotoma albigula [NEAL] White-throated wood rat is verified. 33b. Throat hair gray at base………………………………………………………….…………………………………………....34

34a. Hind foot < 33; penis very long, thin and often with hook-shaped tip (total 262-330, tail 111-149, hind foot 27-33, ear 25-31)……………………………………………………………………………….Neotoma lepida deva [NELE] Arizona wood rat is verified. 34b. Hind foot > 32; penis short, wide (total 311-382, tail 125-174, hind foot 32-39, ear 25-32)………………………………………………………………………………………….Neotoma mexicana [NEME] Mexican wood rat is unlikely. It has been verified from the higher elevations of the Kaibab Plateau and Prospect Valley area; all localities of record are from south of the river.

Keep eye open for voles, cotton rats and other species not on this list!