Morrow, M.E., Griffin, C.P., Peterson, M.J. & Silvy, N.J. 1997: Attwater's prairie-chicken Tympanuchus cupido attwateri - status, limiting factors and future. - Wildl. Biol. 3: 275.
The number of endangered Attwater's prairie-chicken (APC) Tympanuchus cupido attwateri has decreased dramatically since the last published status report 16 years ago. The 1980-population estimate of 1,584 individuals decreased to an estimated 42 individuals in the wild as of spring 1996. Of the 10 counties inhabited by APC in 1980, only three supported APC in spring 1996. As predicted in 1980, habitat loss has gradually reduced numbers, however, the dramatic decrease in numbers during the last four years cannot be attributed solely to habitat loss. Reduced environmental quality, disease, inbreeding, and environmental stochasticity may have contributed to this rapid decline. Environmental stochasticity is an important factor affecting low populations of r-selected species. Previous studies have documented the relationship between prairie grouse nesting success and subsequent population changes. Computer simulations were used to estimate the minimum population size of APC that would be able to withstand the impacts of environmental stochasticity on nesting success with minimal (5%) risk of extinction. Extinction risks for populations of 100, 200, and 225 individuals were estimated at 13, 8, and 3%, respectively. Carrying capacity was particularly important to the resilience of a population with respect to environmental stochasticity. Captive breeding is currently underway to supplement existing populations. Without supplementation, the wild population is predicted to be extinct by the year 2000. Consideration of the risks of extinction associated with environmental stochasticity should have an integral part in recovery planning for this endangered species.
Key words: Attwater's prairie-chicken, carrying capacity, extinction, environmental stochasticity, limiting factors, status, Tympanuchus cupido attwateri
Michael E. Morrow, Attwater Prairie-Chicken National Wildlife Refuge, Eagle Lake, Texas 77434, USA
Clifton P. Griffin, Markus J. Peterson & Nova J. Silvy, Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas 77843, USA