Date of Award:

8-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Advisor/Chair:

Michael R. Conover

Abstract

In Utah, farmers are concerned that ungulates are damaging safflower (Carthamus tinctorius) fields. I examined elk (Cervus elaphus) and mule deer (Odocoileus hemionus) damage to safflower production in San Juan County, Utah during 2009 and 2010. Data on damaged safflower plants were collected within 28 fields, totaling 1,581 ha (13 fields totaling 963 ha during 2009; 15 fields totaling 618 ha during 2010). I compared 3 methods to assess losses: ungulate-proof exclosures, adjacent plant compensation method, and counting the number of damaged plants in 50-m transects (safflower count method). Exclosures were of limited use because they could not be erected until farmers stopped using cultivating their fields. Hence, this method did not account for ungulate damage to young plants. The adjacent plant compensation method assessed yields within 1 m of a randomly-selected damaged plant to account for any compensatory growth of neighboring plants but this method proved inaccurate because ungulate herbivory was concentrated so that a browsed plant was often surrounded by other browsed plants so no compensatory growth by surrounding plants occurred. The most accurate method was the safflower count method which determined the number of damaged plants within a field and then multiplied this number by the decrease in yield from an average damaged plant. I used this method to examine 981,000 plants for damage. Deer and elk damaged or killed 7.2% of safflower plants during 2009 and 1.4% of plants during 2010. Overall yield reduction was 2.9% during 2009 and 0.6% in 2010. The total value of safflower loss within all surveyed fields in 2009 was $9,023 for a loss of $9.42 / ha. The loss of value within surveyed fields in 2010 was $2,330, or $3.77 / ha. The best model for predicting ungulate damage in 2009 included distance to canyon from field edge and the percent of a field bordered by a fallow field, while the best model for 2010 included distance to canyon from field edge and the percent of a field bordered by a wheat field. Safflower farmers were surveyed in the spring of 2010 to compare perceived losses in their fields during 2009 to those measured in this study. Farmers believed that damage by deer and elk reduced their yields by 20% with most damage caused by elk (x¯ =12% by elk, 7% by deer, 1% by other wildlife). On average, perceptions of damage were 5.2 times higher than the actual levels I measured during 2009. This was not surprising because farmers usually surveyed their field from the field’s edge and ungulate damage was concentrated along the edge of the fields.

Comments

This work was made publicly available electronically on September 29, 2011.

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