Geoscience Reference
In-Depth Information
Figure 5.5
Information content (ranging from relative use to estimated biomass consumed) and
sample resolution (individual animal or population) of common methods used to investigate verte-
brate food habits.
mately 1 (identical diet; Krebs 1989; Litvaitis 1992). During an investigation
of carnivore interactions (Litvaitis 1992), the overlap between coyotes (
Canis
latrans
) and bobcats (
Felis rufus
) was 0.83. Because adult male bobcats are
50-100 percent larger than adult females, male bobcats are able to exploit
larger prey and thus may be more similar to coyotes, which are substantially
larger than female bobcats. To examine this possibility, samples from bobcats
were separated into two classes based on body mass and diet; overlap between
each size class of bobcats and coyotes was calculated. As suspected, overlap was
substantially greater between adult male bobcats and coyotes (0.95) than
between coyotes and female and juvenile bobcats (0.78) (Litvaitis unpublished
data). This example suggests the benefits of obtaining greater sample resolu-
tion and not averaging samples from a population where resource segregation
has occurred.
IMPROVING SAMPLE RESOLUTION AND INFORMATION CONTENT
There may be ways to enhance the information obtained from conventional
approaches to examining food habits. Fecal samples are still the most conven-
ient, nonintrusive method to examine food habits of vertebrates. Methods are
currently available and others are being developed that may increase the infor-
