Jose Herrera

Publication Date


Document Type


First Advisor

Nicolaus, Lowell Keith

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Rodents--Food; Food poisoning


Field evaluation of the effects of 17-alpha ethinylestradiol on the food preferences of free-ranging nocturnal and diurnal rodents was conducted at sixteen independent sites in Illinois during the summer of 1988. When untreated wheat was initially provided, nocturnally active rodents, primarily white-footed mice (Peromyscus leucopus), deer mice (Peromyscus maniculatus) and meadow voles (Microtus pennsylvanicus), appeared to consume it immediately rather than to hoard substantial quantities. Diurnally active rodents, primarily thirteen-lined ground squirrels (Spermophilus tridecemlineatus), tended to hoard large quantities of wheat rather than to consume it immediately. When estrogen treated wheat was provided at treatment sites, nocturnal rodents consumed sufficient amounts to induce illness, and appeared to form a conditioned taste aversion (CTA) to the wheat. That is, compared with control sites, treatment sites were largely abandoned by these animals and so consumption was suppressed both during the remaining time that wheat contained estrogen and for several days after wheat no longer was treated. By "handling" treated wheat rather than consuming it immediately, diurnal rodents may not have met the conditions for producing CTA: consumption of a referent food followed by a severe illness. Instead, they appeared to detect the estrogen and discriminate between treated and untreated wheat. While treated wheat was present, ground squirrels in the treatment sites removed substantially less than did those at control sites, but they continued to visit sites and sample wheat rather than to abandon it. When untreated wheat was again offered, ground squirrels at some sites resumed removing it immediately; at other sites, removal remained suppressed for a time before resuming. Because rodents that store potentially toxic foods rather than consume them immediately may detect toxins before consuming illnessinducing amounts, additional experiments were conducted with laboratory hamsters (Mesocricetus auratus) and with free-ranging ground squirrels. These studies tended to confirm that food handling provides a safe means for detecting toxins and for regulating the amount of toxic food that may be safely handled and consumed.


Includes bibliographical references (pages [83]-94)


ix, 94 pages




Northern Illinois University

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