Animal dietary preferences have been studied by feeding-site
examinations, animal observation, and stomach and esophageal collections.
Analysis of fecal material for undigested plant cuticle is
another means for obtaining the same information.
This study was conducted to: (1) prepare a microscope slide
series depicting the surface features of leaves and current annual
growth of stems of selected plants, (2) evaluate methods for preparing
plant and fecal material for cuticle examination, and (3) develop
a key for identification of these plant surfaces.
Plants were collected and identified by personnel of the PNW
Forest and Range Experiment Station. All other work was conducted
at Oregon State University, Corvallis, Oregon.
Reference slides were prepared by three techniques: scraping,
maceration and replication. All were appropriate for fresh or herbarium plant material. Scraping was a tedious method which
provided pieces of cuticle representing the surface where other
methods were unsuitable. Maceration yielded cuticle fragments
strong enough to withstand the acid treatment, but was not adaptable
to some plant surfaces. Replication techniques were easiest, but
only half of the plant surfaces were acceptably represented in this
manner and these caused additional problems during photomicrography.
Fecal material was prepared for analysis by a macerating
technique.
Photomicrographs of reference slides were prepared for use
in subsequent key development. Pictures were taken with a Makam
camera mounted on a Wild M20 binocular microscope equipped with
photo tube, using Kodak Contrast Process Panchromatic 3-1/4 x
4-1/4 sheet film.
The key was developed using epidermal cell arrangement,
trichome characteristics, stomata subsidiary cell arrangement, and
silica bodies as dependable characters. Secondary characters included
hair lengths, stomata size and cell outline.
Differential digestion attributable to plant and (or) animal differences
is a variable in analyzing cuticle fragments in fecal material
not tested in this study. However, the key, a first approximation
to cuticular identification of these selected plants, appears to handle
this variability for most species studied. Successful use of the key is dependent upon a comprehensive
assessment of the vegetation in the study area and the biology of
the animal under study. This perspective is necessary to restrict
the variables which would otherwise decrease the effectiveness of
identification of cuticular fragments in fecal material
