Pronghorn Decline on Multiple fronts
Arizona’s American Pronghorn (Antilocapra americana americana) have
suffered a significant decline in recent years, as survey estimates dropped
from 12,000 in 1987 to 8,000 by 2000. Particularly hard hit areas, such
as Anderson Mesa near Flagstaff, are of special concern. Habitat loss and
the more recent severe drought in our rapidly developing state continue
to reduce pronghorn population size and viability. There is little management
can do to mitigate the effects of drought, however, the Research Branch
initiated a project in 2002 to determine how 9 potentially limiting factors
contribute to low recruitment (the survival of a fawn to adulthood) that
might be improved with additional management.
Fences, encroachment of trees and shrubs into grassland, and human recreational
activity can decrease mobility and increase stress. Malnutrition, water
shortages, and diseases can directly impact populations, or cause infertility,
terminate pregnancies, and impede fawn development, affecting populations
in an indirect manner. Predation of fawns, particularly by coyotes, is
a leading cause of fawn mortality, and lack of fawn hiding cover contributes
to predation. The Research Branch is investigating how each of the above
limiting factors may cause low fawn recruitment in several sites in Arizona.
The goal is to identify how a series of variables can work in concert with
one another to decrease or increase fawn recruitment and make subsequent
recommendations to provide environments in which pronghorn herds can flourish.
In order to gain a comprehensive view of how
variables function throughout the state, study
locations were selected in different habitat
types. Pairs of study sites were selected in
different regions, with one site representing
consistently low fawn recruitment, the other
consistently higher recruitment areas. Site
pairs near Prescott, Flagstaff, and Springerville,
are representative of higher elevations in
central, northern , and eastern Arizona. We
are also analyzing data on pronghorn in two
sites located in southern Arizona desert grasslands.
Most of the fieldwork takes place over the spring and summer months, when
fawns are born and nursed. Water sources and recreational traffic are monitored
regularly, and pronghorn nutrition is examined during several critical
periods in the reproductive cycle. Relative abundance of predators, and
cover for fawn bed sites are measured every spring. In the fall, data on
disease exposure (using hunter-harvested animals) are collected and soil
health indices are measured. Fences and tree/shrub encroachment are measured
during the off-season.
collecting data, comparisons between high and low recruitment sites will
be made to determine the individual significance of each factor and its
distribution over the habitat types. Analyses will also investigate correlations
between variables to derive combinations that have compounded effects.
Data collection will come to a close in August 2004, and the completion
date for the final report is 30 June 2005.
Results from this study will identify potential causes of low fawn recruitment
and guide AZGFD in managing pronghorn statewide by showing general trends
affecting recruitment levels. Most importantly, it will demonstrate the
relationships between different factors and allow the development of comprehensive
management plans that address the combination of conditions, rather than
attempting to counteract individual issues.
For more information
Stan Cunningham, Arizona Game and Fish Department, 5000 W. Carefree Highway Phoenix, AZ 85086-5000
Phone: (623) 236-7661 E-mail: firstname.lastname@example.org
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