i-iangelancis U(1), 1—ebruary 7984 11 determine the average net value of the 1000-head ranch in This information and the formulas provided with each 1982dollars. valuation technique will allow ranchers to figure their per- A capitalization rate at 12% placed the ranch value at sonal ranch value or set up a price scenario with their own $765,015, whilea capitalization rate at 10% made the ranch sales records. worth $918,020. Capitalization ratesof 75/8% and 3°kplaced "Much of this report is support data that has been availa- the ranch value at $1.2 million and $3 million. ble, but not compiled in one source," Fowler said. "It is the The federal government uses the 7 5/8% capitalization practical information necessary to figure ranch values in rates.We feel the7 5/8% or the3m/a ratesare the most reason- terms of 1982 dollars." able rates," Fowler said, "becausethese are primarily federal Report 15, "Alternative Valuation Methodsfor Cattle Ran- land ranches." ches on the White Sands Missile Range 1942-1982," is a In addition to the budgets, the report contains trends of cooperative project involving the Range ImprovementTask private and state land grazing fees per head per month and Force, and NMSU Agricultural Experiment Station and gross average livestock prices per hundredweight in New Cooperative Extension Service.The report is availablefrom Mexico between 1940and 1982. NMSU Agricultural Information Bulletin Office, Box 3A1, NMSU, Las Cruces, NM 88003; telephone 505/646-3228. •

Kangaroo Rats

Diana E. Sjoberg, James A. Young, Kent McAdoo, and Raymond A. Evans

Kangaroo rats (Dipodomys ssp.) are small, beautifully markedmammals found in thearid portionsof western north America. They are distributed from southern portions of western Canadato central Mexico, as far west as California, and east to central Kansas and Oklahoma. Kangaroo rats occupy the sparselyvegetated areas of dry steppes and even the most barren ofwestern rangelands. Recent studies ofthe Diana Sjoberg seed and seedbed ecology of such important range forage and browse species as Indian ricegrass (Oryzopsis hyme- noides) and bitterbrush (Purshia tridentata) have shown that Taxonomy seed collection and caching activities of rodents such as Kangaroo rats belong to the order Rodentia (rats, mice, kangaroo rats are essential in the regeneration of these beavers, squirrels, marmots, etc.). Thisgroup is classified as plants. such because of their upper persistently growing incisors. The kangaroo rats are strictlynocturnal. Becauseof this, a The family Hetermyidae includes kangaroo rats (Dipody- person can spend much timeon the open range withoutever mus), pocketmice (Perognathus), and kangaroomice (Micro- actually seeing them. However,loose soil revealspaw prints dipodymus). and strange curved impressions made by long balancing Kangaroo rats are sometimes confused with pack rats tails, verifying the rat's nighttime activities. Peoplecamping (Neotoma spp.). The pack rats are widely distributed on on rangelands occasionally observe kangaroo rats in the westernrangelands, especially in pinyon/juniper woodlands. eveningsaround thecampfire. The animalsapproach timidly The pack rats belong tothe family Cricetidaeso theyare not at first but become much bolder with each successive ven- closely related to the kangaroo rats. ture into the campsite, filching whatever may be found. Thefamily of heteromyids appearedin the Oligocene, but Opportunistic and swift in their nocturnal activities, kanga- kangaroo rats are known from as recent as the Pliocene roo rats reside during the day in burrows dug in soft soils. epoch when the vast deserts formed in western north Amer- ica. Of 20 identified in current taxonomic texts, Authors are undergraduateresearch assistant, Univ. Of Nevada, Reno; species only range scientist, USDA, ARS; wildlife scientist, Univ. Of Nevada, Reno; and two species are currentlythreatened with extinction. Those range scientist, USDA ARS, Reno, Nev respectively.A list of literature cit- the rat ations used indeveloping this manuscriptis available by writing theauthors. are big-eared kangaroo (Dipodomys elephantinus) About the author: Sjoberg has been an undergraduateresearch assistantat and theTexas kangaroo rat (0. &ator). Ithas beensuggested theUniversity of Nevadaworking with the USDA,Agricultural Research Ser- that the kangaroo rat is closely aligned taxonomically with vice. Raised in Nevada, she grew upwith long-establishedranching families. She received aBS degreein Wildlife Managementat the Universityof Nevada, the family Sciuridae (squirrels and chipmunks). The most Reno. While a research assistant she becamevery interestedin range man- distributed of the 21 species is agement and its importance to wildlife management. Her special research widely generally recognized interest isbitterbrush and rodent interactions. Ord's kangaroo rat (0. ordii) whichranges from Alberta and 12 RangelandS U(1), -eoruary 1gq Saskatchewan throughout the western United States. ing at approximately 17 to 22 days. By their 11th day of life the young can leap 3 to 4 inches vertically. When they are Physical Description about 3 weeks old, they begin leaving the den with their mother. Life is about 2 under natural on the rats between span typically years Depending species, kangaroo weigh conditions. 1.2 to 6.3 oz. when fully grown. The Giant kangaroo rat (D. ingens) is the largest species at4.5 to 6.3 oz (127to 179g); in Adaptations contrast, Merriam's kangaroo rat (D. merriami) weighs a Kangaroorats are highly adaptedstructurally, physiologi- mere 1.2 to 1.75 oz. The most common kangaroo rat, Ord's, cally, and behaviorally for the arid environment which they weighs 1.5 to 2.5 oz. These little mammals have a most inhabit. Physiological adaptations in the kangaroo rat result unusual body structure. The head is very large and takes up inconservation of water.Highly specialized kidneys concen- to half of the body length. The expressivedark orbital eyes tratetheir urine up to five times that of man. Kangaroo rats are placed high on the skull allowing the kangaroo rat to also have decreasedventilation in theirlungs which reduces observe around him. The placementof theseeyes have been water loss. Some species use their lower incisors to strip likened to those of snakes. Despite the large eyes, research- away thetop layers of shrub leavesto get to themost succu- ers believe their eyesight is poor. lent inner layers from which they obtain water. The rodents The forelegs of the kangaroo rats are short and not very cope with the daytime desert heat by remaining under- ground where it is cool and moist in their burrows; above- ground foraging occurs in the cool of the night. In periods of extreme cold or low food intake, the little mammals will becometorpid to reduce energy consumption. The senses of hearing and smelling are highly developed in the kangaroo rats. They have alarger expandedportion of the tympanic bone, giving them the abilityto hearextremely well. This keen hearing helps them in their escape from predators.Their excellent sense of smell is also an asset; it is important to them in relocating cached food stores, and because of their solitary nature, it is essential for finding reproductively active membersof the population. Behavior Kangaroo rats bound along at top speed of 12 mph, and their hops havebeen measuredat 28inches. The homerange foradult males averagesabout one-half acre in area. Within this areathey excavate their burrow systemswhich generally have at least three separate burrows. These additional bur- Merriam's kangaroo rat, a common rodent of western desert rows, found at the base of routes for We could not find a show- shrubs, provide escape range-lands.(Author's Note: photograph the animals. rats are in their ing the kangaroo rat's beautiful tail. When photographers photo- Usually, kangaroo solitary living graph the rat they eitherstand on the tail or attach a clip to makeit habitats, and only during mating and litter raising do they stand still and therefore never frame the tail.) share burrows. Up to 8O% of their time is spent in these burrows. strong, but are adapted for use in manipulating small food Despite their small size, the ferocity of kangaroo rats is items. The hind legs and feet are long and powerful, quite surprising. They ump on their opponents and puncture the similar to those of the Australian kangaroo for which the flesh with the toes of their powerful hind legs. Biting is also animals are named.The tail is used by the rats for balancein part of the battle. Witnesses have attested that battles the same manner as kangaroos. betweenkangaroo rats are noisy and often fatal. Researchers Kangaroo rats are considered to be among themost beau- also warn of nasty bites received fromfrightened, captured tiful of rodents. Coloration varies with the species; upper subjects, although some species can become quite tame. dark brown coat color ranges from pale yellow to shades, Natural Enemies and the underside is usually white. The very long tail is rats have enemies. the birds that dark with white on the sides and a terminal Kangaroo many Among typically stripes prey on kangaroo rats are horned owls, barn owls, and tuft of hair. great red-tailed hawks. The mammalian predators that feast on Life History these desert rodents include gray foxes, kit foxes, bobcats, Most species are reproductively active from Februaryto and coyotes. Skunksoccasionally prey on kangaroo rats, but August. They are capable of producing multiple littersannu- with limited success. Reptiles such as rattlesnakes and ally, with 2 to 3 young per litter, and an averagegestation gopher snakes also utilize the rodents in their diets. Many period of 29 to 33 days. The most common occurrence is a parasitesplague the kangaroo rats. Fleasand ticksuse them litter in early spring and another during lateor early autumn, as hosts. if fail germination of herbaceousplants occurs. in the Habitat The young are born naked in nests constructed rats are found inareas of lowrainfall and humid- burrows. The nests consist dried seed Kangaroo usually of grasses, summer and rates. and rootfibers. Thecoat of the is at 10 ity, high temperatures, high evaporation hulls, young complete inhabitareas of the and lower Sonoran to 14 and their when are 10 to 18 They usually upper days, eyesopen they days life zones. Ord's kangaroo rats seemto prefer the disturbed old. Functioning of thecheek pouches coincides with wean- Rangelands6(1), February 1984

soil of road sites where tunneling is easier.These disturbed mant, partially because of the indurate lemma and palea sites are often dominated byweeds which provide cover and whichpersist around theseed. Kangaroorats are selective in a high annual seed production used for food. Other kanga- thetypes of Indian ricegrassseeds they collect. They choose roo rats also seem to prefer loose sandy or gravelly soils primarily the forms with the best chance for germination. supporting widely spaced xerophytic shrubs. In most cases, Most importantly, beforethe rodentscache theseseeds, they loose earth is necessary for burrowing sites apparently removethe lemma and palea,thus greatly enhancing germi- becauseof the rats' weak forelegs. nation. Although the kangaroo rats then prey on emerging the to natural of Indian Food Habits seedlings, key regeneration ricegrass is this partial grazing which reduces intraspecific competi- Seeds are the primary food source for kangaroo rats, tion the in individual caches. A other among remaining seedlings although plant parts are also consumed. Insects are similar schememay exist for other speciessuch asbitterbrush. also important in the diets of Merriam's kangaroo rats, and possibly otherspecies as well. ManagementImplications The favored food items of the kangaroo rats in a California Kangaroo rats attracted interest in the 1920's and 1930's study included brome grasses(Bromus spp.), filaree (Ero- when drought and improper grazing affected many desert dium spp.), and fescues (Festuca spp.). In the Southwest, ranges. Many believed that these small mammalswere par- kangaroo rat species prefer grama grasses(Bouteloua spp.), tially at fault for the deterioration of the range. Studies on needlegrass (Stipaspp.),pigweed (Amaranthusspp.),fescues these deteriorated sites were completed by the U.S. Biologi- (Festuca spp.), and plaintain (Plantago spp.). A study in the cal Survey, now known asthe U.S. Fish and Wildlife Service, Sonoran desert showed that availability of resources influ- and many other studies have been completed since. In the encedthe patternof food utilization, but that the preferences Southwest, it was especially apparent that the bannertail of various heteromyid species determined the exact quanti- kangaroo rat (0. spectabilis)and its extensivemound system ties used. was causing a loss of forage availability due to the surface Kangaroo rats have various meansof gathering and stor- disturbance on the range.Various methodswere devised to ing food. These methods are related to the necessity of remove the offending rodent, including use of poison grain staying underground for long periods and to the seasonality similar to methods used for prairie dog control. In the of food resources. Gathering and storing activities are absenceof these animals, rangegrasses tended toreturn but further enhanced bythefunctionaluse of the cheek pouches theeconomic implication was that it was not cost effective to for transporting food items. (As mentioned previously, kan- improve degradedrangeland by this methodwhen degrada- garoo rats havean exceptional senseof smell which enables tion could have been avoided in the beginning, with sound relocation of stored food.) grazing practices and management. Caches are the most commonly known storage method With deteriorating range conditions, less desirable plant utilized by kangaroo rats. The rodents gather seeds and put species are usually the last plant utilized by grazing cattle. them in their pouches. Caching usually occurs around the Kangaroo rats can further increase the numbers of these immediate vicinity of the burrow opening or at the end of undesirable plant species through their activities. Various well-worn runways. Besides storage, another advantage of studies havealso indicated that large seededperennials are depositing seeds in thesoils is the resulting enhanced water detrimentally influenced by kangaroo rats during periods of content ofthe seeds. Kangaroo rats indicate apreference for low seed production. Becauseof the small numbers ofseeds seeds stored in soil fora time over those not cached in soil. produced, the gathering activities of the rodents can have a Seedsabsorb moisture at nighttime temperatures when the detrimental impact on plant reproduction. Also,their gather- humidityin thesoil rises. Someseeds may contain upto 30% ing of seeds on broadcast seeded areas can be especially free water and in these arid areas the additional water aggravating. becomes acritically important resource. Because therecovery The results of most studies have shown that detrimental of these seeds is by smell, the depth of burial is shallow. A effects by kangaroo rats occur in caseswhere the range is studydone on Merriam's kangaroo rat in Arizona indicated already in a deteriorated condition. Problems caused by that at a soil depth of 0.25 inches, 83% of the seeds were these rodents are considered onlyto be additiveto the exist- recovered.The lowest recovery rate (56%) was adepth of 1.0 ing situation and not due entirely to their actions. inch. On the other hand, the kangaroo rat can be very helpful in Although kangaroo rats are well known fortheir seed eat- its own way to the land that provides it a living. In good seed ing preferences,they need otheritems to balancetheir diets years, rodents favorably affect seed dispersal and germina- nutritionally. This balanceis accomplishedthrough the use tion of large seeded perennial grasses and tall, shrubby of germinated seedlings. Seeds are very low in carotene, plants. Recovery of desired range vegetation might be whereasseedlings, especially coleoptiles or cotyledons, are enhanced by the differential feeding pressure of certain very rich in this precursor ofvitamin A. Kangaroorats may be rodents. Soil quality too can be affected by kangaroo rats. deficientin vitamin A and their reproduction potential there- Theirburrowing and caching promotes water infiltration and by impaired unless theirdiet includes germinating seedlings retention,thus improving soil moisture.This favorablyaffects from their seed cache system. the survivability of seedlings in arid regions and could be Recent studies with seeds of Indian ricegrass carry this important in the natural maintenanceand improvementsof scenario a step further. Seeds of this grass are highly dor- our rangelands. S