Date of Award:

5-1-1990

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology Ecology

Committee Chair(s)

James A. MacMahon

Committee

James A. MacMahon

Committee

Frank Messina

Committee

Fred Provenza

Abstract

Field and laboratory experiments were conducted during the 1989 growing season to examine the seed preferences of two geographically distinct deer mouse (Peromyscus maniculatus) populations. Of the ten seed species offered, balsam root (Balsamorhiza sagittata (Pursh)Nutt.), Indian rice grass (Oryzopsis hymenoides (R. & S.) Ricker), millet (Panicurn miliaceum L.), and antelope bitterbrush (Purshia tridentata (Pursh) DC.) seeds were more preferred than big sagebrush (Artemisia tridentata Nutt.), yarrow (Achillea millefolium L.), shadscale (Atriplex confertifolia (Torr. & Frems.) Watts.), wild rye (Elymus cinereus Scribn. & Merr.), western wheat grass (Pascopyrum smithii (Rydb.) Love), and green needle grass (Stipa viridula Trin). The relationship between preference and nutritional attributes of the seeds was examined. Preference was significantly correlated with nine nutritional seed qualities. Preferences were inversely correlated with acid soluble ash, calories/gram, non-nutritive matter, protein, solvent extract, and structural carbohydrate. Preferences were positively correlated with cell contents, moisture, and soluble carbohydrate. The correlations were in agreement with Frank's (1988a,b) observations that desert rodents choose seeds high in free water or seeds with nutrients that have high net metabolic water yields. Potential sources of preference variation were examined as the seed selection data were collected. Field preferences varied significantly between two microhabitats and between two times during the growing season. Preferences also varied between the two populations. Under laboratory conditions, preferences were different among individuals but not for one individual over a series of trials. Comparison of laboratory and field preferences indicated that laboratory preferences did not always reflect field preferences. Variability in the data implied that extrapolation of seed preferences from the population level to species level and from laboratory individuals to field populations may not always be valid.

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