Hunt, J. L.  2004.  Investigation into the decline of populations of the lesser prairie-chicken (Tympanuchus pallidicinctus Ridgway) in southeastern New Mexico.  Ph.D. dissertation, Auburn University, Auburn, Alabama, 294 pp.





John Loy Hunt

Doctor of Philosophy, December 17,2004

(B.S., University of Arkansas at Little Rock, 1996)

(M.S., Auburn University, 1999)

Directed by Troy L. Best

             Populations of lesser prairie-chickens (Tympanuchus pallidicinctus Ridgway) have declined sharply across the geographic range of the species, including southeastern New Mexico.  Suggested causes include drought, conversion of habitat to agricultural use, improper grazing management, chemical control of shinnery oak, hunting, and disturbance and fragmentation of habitat caused by petroleum development.  The Bureau of Land Management, which administers public lands that include habitat of lesser prairie-chickens, is required to manage for the conservation of the species and to ensure that their actions do not contribute to the need to list the species as threatened or endangered.  As a partial response to this requirement, the Bureau of Land Management authorized and provided support for the study documented herein.

            Lesser prairie-chickens use a breeding system in which males display at leks to attract females.  A lek is an area where males set up and defend territories on which they perform elaborate mating displays.  Most activity, including nesting and brood-rearing, takes place near the lek.  For this reason, the lek is the focal point of much research on lesser prairie-chickens.  This study compared several components of habitat at active and abandoned leks within the Carlsbad Field Office.  These components were then analyzed with factor analysis to determine which contributed most to decline in populations.  Formerly occupied areas in the Carlsbad Field Office were surveyed for breeding leks.  Management recommendations based on the findings are included.

            Several vegetative characters of active and abandoned leks of lesser prairie-chickens were measured using the line-point sampling method.  Vegetative cover and composition of active leks and associated control points were significantly different from those of abandoned leks and control points in all 3 years of the study.  Active leks and control points had significantly more Andropogon and less Sporobolus than did abandoned leks and control points.  Abandoned leks were more likely to be near Prosopis >60 cm in height than were active leks.  Vegetative structure as measured by the Robel method was not significantly different for active and abandoned leks.  Results are symptomatic of overgrazing, which is detrimental to populations of lesser prairie-chickens.

           Several aspects of petroleum development were measured at active and abandoned leks, including number of active and inactive oil wells within 1.6 km, presence or absence of power lines, and length of road within 1.6 km.  Abandoned leks had more active wells, more total wells, and greater length of road than active leks, and were more likely than active leks to be near power lines.  Effects on lesser prairie-chickens may include increased mortality due to collision with power lines, increased disturbance due to increased presence of humans, destruction of habitat due to installation of roads and drill pads, and fragmentation of habitat.  Petroleum development at intensive levels probably is not compatible with populations of lesser prairie-chickens.

Ambient sound levels were measured at 33 active leks, 39 abandoned leks, and 60 control points.  Sound levels at leks and control points were not significantly different.  Sound levels were about 4 decibels greater at abandoned leks than at active leks.  This difference, while statistically significant, is probably not great enough to explain abandonment of leks.  Instead, difference in noise levels is symptomatic of high levels of petroleum development, which contributes to abandonment through increased destruction and fragmentation of habitat and greater amounts of human-caused disturbance.

             In April 2002 and 2003, surveys were conducted in the Carlsbad Field Office to determine whether active breeding leks existed there.  Ten routes were established and surveyed three times each year.  At 0.8-km intervals on each route, observers listened for calls of lesser prairie-chickens for 3-5 minutes, for a total of 2,256 observations.  One active lek was detected in both years.  Except for this lek, near Eunice, no breeding population of lesser prairie-chickens exists on public lands in Eddy or southern Lea counties.

             Factor analysis of characters associated with active and abandoned leks was conducted to determine which potential causes are associated with decline in populations.  Two factors accounted for 50.1% of variation within the dataset.  The first factor, which loaded heavily for variables associated with petroleum development accounted for 31.5% of variation.  The second factor, which loaded heavily for variables associated with overgrazing, accounted for 18.6% of variation.  Discriminant-function analysis of these factors indicated that petroleum development was more important than overgrazing in explaining the difference between active and abandoned leks. 

             Based on these findings, the following recommendations are made:

1.      Emphasis on research and management should be shifted away from locations where breeding populations once existed to areas where they now exist and to areas relatively low in petroleum development.  Annual population surveys should be made in these areas.

2.      New petroleum development should not be allowed in areas occupied by lesser prairie-chickens, including the Sand Ranch administered by the Roswell Field Office, Lesser Prairie-Chicken Areas administered by the state, and areas in northern Lea County administered by the Carlsbad Field Office.

3.      Overgrazing should be eliminated in areas occupied by lesser prairie-chickens.

4.      Large areas with little or no petroleum development and reduced levels of grazing should be developed for reestablishment of populations.  Lesser prairie-chickens may return naturally, but could be reintroduced once the areas are established.

5.      Off-road vehicles should not be allowed in areas used by lesser prairie-chickens.

6.      Power lines should not be allowed in habitat used by lesser prairie-chickens.  Unused power lines should be removed.

7.      Cooperative agreements should be pursued with owners of private lands where lesser prairie-chickens may occur.

8.      Future research should include continued surveys of suitable habitat, study of feasibility of reintroduction, investigation into possible interaction between fragmentation of habitat and grazing, and study of effects of artificial waterers on lesser prairie-chickens and other wildlife.