1997-06-13_REPORT - M1981302 (16)

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IV.Food Preferences There are few data on meadowjumping mice feeding habits in Cobradc oming. Harrington (1995)conducted preliminary feeding trials with captured mice from Roily Fiats: mice were offered a variety of plant and animal foods. Because those data were intended to guide more structured Mats,they are not reported here. Studies on food habits of Zapus hudsonius in central and eastern United States indicate that they are governed by availability more than preference(Whitaker, 1963). Grass seeds of several species are probably the mast important component of the diet,and mice will shdrto those species that have avaiable seed. Invertebrates and fungi are also readdy eaten, Wm feed on both adult and larval invertebrates, especially Coleoptera(beetles). Invertebrate feeding is very important in the spring as mica emerge from hibernation,and may consist of half of the diet at that time. Mae also feed on various species of fungi,which are often encountered during burrow"activity. As the growing season progresses, gramiraid seeds dominate the diet it is not known if jumping mice fulfill dietary water requirement from open water sources or water in vegetation. They are known to inhabit ephemeral drainages that may dry up entirely in late summer. Based on trapping records at Rocky Flats(M. Bakeman, personal commxxlcation),trapping success at some sites declines dramatically after creekflow ceases, and it is suspected that there may be a shift in habitat use when this happens. V.Sax and Age Distributions Table 2 indicates age, sex and date of capture of meadow jumping mice on the Colorado Piedmont from 1991 through 19%. These data should be interpreted with caution because of reporting inconsistencies among authors.and possible differences in field techniques. There may have been some multiple reporting of recaptured individuals, so these numbers are not definitive population sizes. Overall,about 86.0%of captures were identified as adults. The sex ratio tabulated is 51.6 males:48.4 females. Most subadults were reported from August and September(the single subadult reported from June may represent a particularly small and/or pale adult rather than early breeding), and juveniles were reported from August September and October. These data are very preliminary• Clearly. Intensive studies at particular localities will be needed to provide arty insight into the population biology of the meadow jumping mouse along the Colorado Piedmorrt and adjacent soudipastan Wyoming, studies fundamental to conservation of Zapus hudswnius pret>W VI.Habitats where Preble's Jumping Mice Are Not Found. i Surveys for jumping mice have been conducted in many habitats. One of the areas that has been extensively surveyed for small mammals is Rocky Fiats. Habitats there include: Mlesfe mired grass{ands:These habitats cover several landscape pcaidons.from the edge of the mheeic zone in riparian patches and covering gentle end steep hdskkm They are more ikely to be disturbed than most other habitats and often are Invaded by exilic plant species such as krmpweed and downy biome. They occupy more area than any other habitat type at Roddy Flab. Dominant species include Agropyron sm@hi, Bouteloua graciis,&anus japcnicus,and Alyssum minus. Xerfc mixed grasslands:These are the second most important vegetation type by area They occupy drier.more upland positions than the mesic grasslands and cover the flat piedmont tops. Dominant spades are:Bouteloua guaails. Cavex hekopftia.Muhlenbergta montane. Shpa comata. and Andmpogon gerardfi. Reclaimed grasslands: Found primarily in the southwestern comer of the site and along sections of riparian habitats. Species are primarily Bromus inermis and Agropyron intemhedium. 6