Managing cattle on south Texas rangelands also means managing a habitat that includes pests such as ticks and horn flies and brush such as mesquite. The traditional approach of treating cattle with pesticides to manage tick and horn fly infestation can mean high costs and can add the risk of residues in meat or pesticide resistance.

Brush management tactics have proved to be a successful component of a ranching enterprise's IPM program. The effectiveness of brush management, however, depends on whether parasites are subsequently brought in from untreated areas, especially by the grazing cattle, so it is important where cattle graze in relation to where brush management is used.
    It has not been clear in the past exactly how cattle use various rangeland habitats. There have been no quantitative measurements of how much time cattle spend foraging in uncanopied environments versus the canopied vegetation communities that provide optimal conditions for ticks to thrive, or whether time spent in canopied areas increases the number of ticks cows pick up. It also has been unclear whether cattle make substantial habitat shifts with the seasons or when drought occurs.
    Researchers at Texas A&M University have adapted GIS technology to analyze the relationship between pest management and grazing environments, and research results indicate that controlling where and when cattle graze can be an effective tick management strategy.
 

Funding Allowed Technology Adaptation

Technology has not previously been available to precisely track animals in relation to landscape characteristics in order to evaluate the effect of habitat on tick infestation, but funding from the Southern Region IPM Grants Program enabled an interdisciplinary team at Texas A&M University, led by Pete D. Teel, to examine this complex problem by adapting and using new technologies.
    Researchers in entomology, rangeland ecology and management, statistics, and mapping sciences at the Texas Agricultural Experiment Station adapted Differential Global Positioning System (DGPS) instruments and battery packs to harnesses that could be worn by cows. The harnesses were placed on 16 cows in a herd grazing 400 acres of south Texas rangeland in brush habitat and interstitial grass zones.
 

Cattle Movement Patterns Studied

From the GPS unit, each cow's movement was monitored at two-minute intervals over a four-day grazing period. A radio in the harness transmitted each animal's position to a computer at ranch headquarters. Data sets were collected over several seasons so that changes in forage conditions and weather factors could be evaluated. The amount of time each animal spent in different areas was obtained by linking the cow's position with computer maps of the vegetation types defined from aerial-infrared photographs of the pastures. The data were analyzed using Geographic Information Systems software.
    Researchers evaluated the amount of time each monitored animal spent in different habitat types for:

• landscape use patterns
• the number of adult and nymphal ticks that attached to the animal during the graze period
• the number of ticks estimated to be present in each habitat type using carbon-dioxide traps.

Results showed a positive relationship between the amount of time spent in different canopied habitats and the number of ticks which attached to the animals. Brush habitats in drainage zones appeared to result in more ticks than other habitat types.
    Because we know more about how habitat type and the amount of time spent in them affects the rate at which cows are infested with ticks, the potential of scheduled rotational grazing as a pest management strategy is more clearly understood.
    Patterns of cow movement among and between the different habitat types and brush-dominated corridors suggest that selective brush management tactics could be targeted to alter landscape use by cattle and reduce tick burden.
    This research focused on ticks, but horn flies, which develop in manure and then seek cattle for blood, also may be effectively managed by scheduled rotational grazing.
 

Drought Conditions Could Affect Tick Populations

These studies were conducted during one of the most severe droughts to occur in this region (1995-96). As forage became short during the drought, the cattle consumed as much as five times more browse to fill their nutritional needs than when forage is abundant. Canopied areas with woody plants were a source of nutritional sustenance and heat relief, and they brought the animals in contact with ticks.
    Therefore, changes in landscape use by cattle and other vertebrate herbivores during drought conditions may be an important factor in perpetuating tick populations on rangelands.
 
 
 

	Information transmitted by the radios was analyzed using Geographic information Systems software.
	A radio in the harness communicated each animal's position to a computer at ranch headquarters.

 

For more information contact:

Tom Fuchs  Texas Agricultural Extension Service  7887 U.S. Highway 87 N.  San Angelo, TX 76901

Jim Starr  Department of Plant Pathology and Microbiology  Texas A&M University  College Station, TX 77843-2132  (409)845-8278