Rodent communities in a grazed and ungrazed Arizona grassland, and a model of habitat relationships among rodents in southwestern grass/shrublands
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Authors: Z. F. Jones, C. E. Bock, and J. H. Bock
Date: 2003
Journal: The American Midland Naturalist
Volume: 149
Number: 2
Pages: 384-394
Summary of Methods: Rodent numbers within paired grazed vs. ungrazed treatments in Sonoita Valley, Arizona were calculated and compared to a previous rodent survey conducted 17 years earlier. Rodents were sampled twice, at least 6 months apart over the course of a year beginning in November. Vegetation measurements were recorded in December of that year.
Article Summary / Main Points: Fourteen rodent species were captured (belonging to two families: Heteromydiae and Muridae). None of the rodent species was more abundant on grazed sites, while four species were more abundant on ungrazed sites. The Heteromydae rodents as a whole were more abundant on grazed sites. Compared to the previous study, vegetation was taller on both treatments in the recent survey. Heteromydae occurrence percentages were similar on the grazed sites, but lower on the ungrazed site when the current method was compared to the older method. The percentage of Muridae found, except the genus (Peromyscus), was higher on both treatments in the current study. Kangaroo rats (Dipodomys merriami) known for their stable populations, had severely reduced numbers in the current survey compared to the earlier survey.
Vegetation Types: Desert Grasslands
MLRA Ecoregions: 41 Southeastern Arizona Basin and Range
Agrovoc Control Words: Grazing systems Rangelands Rodents
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: heteromydae, muridae, habitat structure, grazing, fire
Annotation: This one year replicated study and its findings apply only to southwestern desert grasslands. As noted by the authors, the difference in rodent numbers between surveys may occur by chance. Thus, more rodent population data needs to be collected to determine the long time trend effects of grazing on rodent populations. Comparing different survey methods has many limitations because the methods are not truly replicated. The Hetermydae group (including Dipodomys species) as a whole preferred heavier grazed sites in this study in southeast Arizona and in a study by Jones and Longland (1999, Amer. Mid. Nat. 141:1-11) in the Salt Desert Shrubland of the Great Basin, while Perognathus preferred lightly grazed areas in both studies. As is true for all grazing research, the results are most directly applicable to areas with similar landscapes, type of ungulate and rodent species, weather conditions and season of use.
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