Cattle grazing behavior and range plant dynamics in southern Arizona.

Abstract

A 15-month study was conducted on the Santa Rita Experimental Range to evaluate the factors influencing both plants and cattle in southern Arizona. Forage biomass, nutrient value, botanical composition, and ground cover were greater in the growing season than in the dormant season. Moderate and heavy pastures had lower plant parameters than very heavy pasture, except for forage biomass and Lehmann lovegrass proportion, forage fiber and ground cover. Slopes and washes had a higher forage nutrient content and lower biomass and ground cover than the uplands. Lehmann lovegrass was more abundant on the uplands and in the washes than on the slopes and the reverse was true for native grasses and shrubs. Understory forages contained greater nutrients and forbs than open forages and the opposite occurred for shrubs and ground cover. Grazing activities, drinking, salting, defecation, urination and rumination were greater in the growing seasons, but standing and idling were greater in winter. There were no differences among pastures in major activities, but walking, drinking and salting were greater on very heavy pasture than on moderate and heavy pastures. Most grazing activities were on the uplands and resting activities were in the washes. Biting rates were similar among topographic areas. Upland and wash defecation and urination frequencies were similar and higher than slope frequencies. Grazing activities were greater in the open than under canopy and the reverse was true for resting activities. Open and canopy areas were similar in defecation and urination frequencies and biting rates. Except for resting activities, major and minor activities were more intense in the afternoon than in the morning. Morning and afternoon biting rates were similar. The weather index was the most important predictor of all cattle activities, except for the defecation frequency which mostly depended on the proportion of green forage. The forage nutrients and green proportion were the second and third important predictors of cattle activities, respectively. In conclusion, plants and animals interact and both react to environmental conditions. The recommendations for best management of a grazing land ecosystem should consider these conditions.