Naturalists Notebook

Field Identification Notes for Rabbits, Rodents and Insectivores of North Central Texas

Gnawed nuts, holes in the ground, runs through the grass and tiny footprints. Who made these? The following is a complete list of rodents, rabbits and insectivores (orders Rodentia, Lagamorpha and insectivora respectively) that have been previously identified as being present in North Central Texas. For our purposes North Central Texas will include the following counties: Collin, Cooke, Dallas, Denton, Ellis, Fannin, Grayson, Hunt, Johnson, Kaufman, Rockwall & Tarrant. I have used the recently published Mammals of Texas (see reference) to determine what small mammals are here. Although these animals are listed as occurring here, many appear to have disappeared in recent years. Current range maps for mammals in our immediate area do not seem to reflect actual conditions today. Several mammals that I remember from a childhood in Collin county 20 years ago are no longer evident. Animals such as thirteen-lined ground squirrels, flying squirrels, and ringtails have largely disappeared. With that in mind, and after consulting several people involved with tracking the status of mammals in our area, I have placed species into two categories within each broad heading -- ‘Common Inhabitants’ those that are most likely to be seen, leave signs of their presence, or are known to be abundant, and those more uncertain, ‘Remote Possibilities’. It is important to learn what animals are weathering the storm of feral cats and dogs, fire ant molestation and rampant habitat loss. If you observe signs of animals in the remote possibilities list, please give us a call and we will put you in touch with members of the scientific community that are active in resolving these questions.

Life histories and common behaviors are also poorly noted for many of these species. By returning to a den or set of runs at different times of the day and sitting quietly, the chances are good you will eventually observe the animal. Any observations you make could be a valuable addition to what we know about that species.

The headings below are not scientific distinctions. They are common-sense categories arranged (hopefully) in such a way as to make this listing easier to use. Beneath the heading, mammals are listed alphabetically by genera. This allows for quick viewing of the affiliations between species. For each animal listed below I have attempted to describe the most distinctive aspects of their presence. The aim of this survey is to help narrow the choices of animals that may have created a particular burrow or left piles of neatly cut vegetation beside a run. Connecting the tracks, scat, and other signs with the species that produced them is a difficult process. These traces are worth learning. They provide an unintentional invitation that leads to further acquaintance. Happy hunting.

Aquatic Rodents

Common Inhabitants

American Beaver (Castor canadensis) - Habitat: Ponds, streams, lakes, rivers. Den: Houses constructed of sticks & mud. In Texas they often dig burrows into cut banks. Burrows are often large enough to admit a person and average 10m or more in length (~30 feet). Runs: 15-25cm wide leading away from the water, well established with muddy appearance & flattened vegetation. Scat: ~2-3cm long, ~2cm dia. May be found at edge of water, uncommon because beavers almost always defecate in the water. Coarse, sawdust appearance. Food: Bark. Favorite trees include willows, cottonwood. Small branches are completely stripped, teeth marks on larger trees are ~5-8mm wide. N/D: Nocturnal. Comments: Tracks are often largely obscured by the tail dragging behind. Look for occasional ‘scent mounds’ which are short piles of mud and vegetation packed into a mound. This is a signpost that the beaver marks with his scent glands. Beavers are making a major comeback in our part of Texas.

Nutria (Myocastor coypus) - Habitat: Ponds, streams, lakes, rivers. Den: Short, shallow burrows above the water line with openings ~20cm in dia. Burrows are often hollowed areas under tree roots exposed by the water. Nests are large assemblages of cut reeds and sedges piled up on land near the water in patches of vegetation. Runs: Trails through water weeds, with cut lengths of vegetation scattered throughout, not left in piles. Food: Aquatic and semi-aquatic vegetation. N/D almost completely nocturnal Comments: Nutrias were imported from South America and widely introduced in Texas for their pelts and as a "cure-all" for ponds choked with vegetation. There is no longer a demand for their fur and nutria populations are increasing rapidly. They compete with our native muskrats and may eliminate any muskrats that have survived into the present. Nutrias reproduce rapidly and devastate shoreline vegetation making large areas unattractive to waterfowl.

Remote Possibilities

Common Muskrat (Ondatra zibethicus) - Habitat: Marshes, Ponds, streams, lakes. Den: In still bodies of water such as ponds & lakes, the muskrat builds dome shaped lodges constructed of marsh vegetation. Access is through underwater openings. The lodge is usually 60cm or more in dia. & 50-60cm tall. Along streams and rivers, muskrats burrow into the banks and live below ground. Entrances to the burrow are underwater. Runs: well traveled runs radiate from around the lodge. Cut lengths of vegetation accumulate at feeding stations along the runs. Scat: Elongated, sausage-like ~16mm long. Found in clusters on logs in the water, on rocks or favorite resting spots on the bank. Food: Tender portions at the base of cattails, rushes & sedges are the principal food. During winter or when the food source is exhausted they will eat most anything, including other muskrats. Tracks: Look for tail marks from the naked, laterally compressed tail. Comments: Muskrats are often found in association with beavers and live together without conflict. Of the Knowledgeable individuals interviewed, none had ever seen or heard of a muskrat being positively identified in our area, even though historical records indicate their presence.

Rabbits

Common Inhabitants

Swamp Rabbit (Sylvilagus aquaticus) - Habitat: Flood plains and river bottoms. Den: In dense thickets of briars or brush, usually a fur lined hollow against a tree or fallen log. Runs: Average width ~ 6-10cm. Scat: Rounded pellets deposited in piles on stumps, on fallen logs or other elevations. Food: Succulent vegetation, grasses and the new shoots of shrubs. N/D?: Secretive by day, probably more active at twilight.

Eastern Cottontail (Sylvilagus floridanus) - Habitat: Brushland & marginal areas, edges of fields. Den: Hollowed out areas in the grass known as ‘forms’, in thickets, sometimes underground burrows. Runs: Average width ~ 6-10cm. Scat: Rounded pellets ~8-10mm in dia. Food: Succulent vegetation, grasses and twigs of shrubs in winter. N/D?: Active at twilight, more at night into the early morning. Comments: Not a sociable rabbit - seldom seen feeding together

Remote Possibilities

Black-tailed Jackrabbit (Lepus californicus) - Habitat: Dry scrubland, sometimes in juniper forests. Den: A bed scratched out at the base of a shrub. Runs: Not apparent. Scat: Rounded pellets ~10-15mm in dia. Food: Cactus, mesquite, grass and forbs. N/D?: Active at twilight, foraging well into the night. Comments: Although range maps show records of captures all over NC TX., these are likely to be old and no longer reflect its current range. It is still found in the extreme western edge of this survey.

Squirrels (including flying squirrels and ground squirrels)

Common Inhabitants

Eastern Fox Squirrel (Sciurus niger) - Habitat: Woodlands, prefers upland forests. Den: Hollow trees when available, otherwise globular leaf & stick nests ~ 30-50 cm in dia. Scat: Elongated, ~10mm, often with a ‘tail’. Food: Mainly acorns, also insects, green shoots, elm seeds. N/D?: Diurnal. Comments: Nuts are buried one at a time, here & there for later use.

Remote Possibilities

Thirteen-lined Ground Squirrel (Spermophilus tridecemlineatus) - Habitat: Short and tall grass prairies. Den: Burrow diameter ~5cm with 2-3 openings. Very shallow. Runs: numerous well marked paths to feeding areas. Average width ~ 5cm. Scat: Pellets ~8-10mm. Food: Grasses and forbs in spring; seeds, flower heads, and insects (sometimes mice) as the season progresses. N/D?: Strictly diurnal. Comments: Formerly common throughout North Central Texas, now seems to have disappeared. Long hibernation ~240 days. Jim Dunlap mentioned a call her received recently from a woman in Collin county that matched the description of a thirteen-lined ground squirrel but the suspected rodent has yet to be captured or further identified.

Eastern Gray Squirrel (Sciurus carolinensis) - Habitat: Dense hammocks of live or water oak / also deep swampy areas. Sometimes found occurring in well-drained bottomlands of post or red oak, hackberries, bumelia and pecan. Den: Hollow trees or in nests constructed of leaves and twigs. Runs: Trees. Scat: Elongated, often with a ‘tail’ ~10mm. Food: Mainly nuts, also some insects. N/D?: Diurnal - usually feeding in early morning and late afternoon. Comments: Mainly found in sandy regions east of us.

Eastern Flying Squirrel (Glaucomys volans) - Habitat: Forest, especially along rivers/streams - prefers areas with Spanish moss. Den: Holes in stumps, esp. abandoned woodpecker nests. Runs: Trees. Scat: Elongated, irregular, ~5-8mm. Food: Nuts and acorns, persimmons, also insect larvae, beetles, bird eggs and young. Very fond of flesh. Tracks: Look for disturbed patches of ground where the squirrel has landed. Comments: Sociable - lives together in groups. Listed as occurring throughout North Central Texas though no longer clearly apparent. Over the years several have been brought in to the Plano Living Materials Center, but Jim Dunlap suspects they were all released into the wild by people who purchased them at pet shops.

Subterranean Rodents (moles and gophers)

Exceedingly Remote Possibilities

Plains Pocket Gopher (Geomys bursarius) - Habitat: Loose sandy soil in fields and forests. Den: Labyrinthine burrows marked by mounds 30-40cm wide and ~8cm high, crescent shaped with the entrance noticeable, though plugged. Tunnels are created while foraging and average ~6 cm in dia. Runs: Stays underground, runs absent. Scat: Deposited in a toilet underground. Food: Underground roots and stems, grubs. Comments: Farmers have waged a long battle to destroy gophers and have largely succeeded.

Eastern Mole (Scalopus aquaticus) - Habitat: Mainly in moist (not wet) sandy soils. Den: Deep burrows marked by large conical mounds of excavated earth that resemble an eruption. The burrow entrance is blocked and not apparent. Runs: Shallow meandering burrows just below the surface that produce a noticeable hump as the mole swims through the loose topsoil. Food: Mainly earthworms & grubs, also beetles, spiders, & an occasional mouse.

Reference:

Clay, Marcus. (Currently writing a booklet on mammals for Cedar Hill State Park) Interview, March 21, 1996

Davis, William B. & Schmidly, David J. The Mammals of Texas. Austin, Texas: Texas Parks and Wildlife Department - Nongame And Urban Program, 1994

Dunlap, Jim. (Author, Animal Rehabilitator, Director of Plano I.S.D. Living Materials Center) Telephone interview, April 24, 1996

Griffith, Corey. (Interpretive Director - Cedar Hill State Park) Personal interview, November 7, 1995.

Meeks, Steven. (Animal Damage Control) Telephone interview, April 5, 1996

Murie, O.J. A Field Guide to Animal Tracks. Peterson Field Guide Series No. 9. Boston, Mass.: Houghton Mifflin Co., 1954.

Stall, Chris. Animal Tracks of Texas. Seattle, Washington: The Mountaineers, 1990.

Whitney, Ray. (Urban Fish & Wildlife Dept. - Cedar Hill State Park) Interview, January 10, 1996

Natural History of North Central Texas Index
 

Royce & LuCretia Milam Copyright © March 1996 Wild Vision. All rights reserved.