PARENT SESSION

Conservation 3 -- Session Chair: Patrick Kelly-- University Center, Kate Buchanan Room

ENDANGERED GIANT KANGAROO RATS AND STOCHASTIC CLIMATIC EVENTS: DOCUMENTING THE IMPACT OF FLASH FLOODING. Patrick A. Kelly, Daniel F. Williams, Steve Messer, Darren P. Newman and Patrick L. Morrison. California State University, Stanislaus, Endangered Species Recovery Program, 1900 N. Gateway Blvd., Suite 101, Fresno, CA, USA.

ABSTRACT- A population of endangered giant kangaroo rats (Dipodomys ingens) has been tracked on two 1.44-hectare trapping grids—one ungrazed (#1) and one grazed (#2)—on the Elkhorn Plain of the Carrizo Plain National Monument, San Luis Obispo County, California since July 1987. Over that 17-year period, the population dynamics on both trapping grids has responded to long-term and short-term environmental changes. The most significant long-term response was the prolonged decline and dramatic recovery of the population during and immediately following the major drought of 1986-1991. Short-term environmental changes can also cause significant perturbations in population dynamics but such disturbances are rarely witnessed or their impacts documented. On the afternoon of July 31, 2003, the 5^th day of a 6-day census on both trapping grids, a storm cell passed directly over the grids and the Temblor Range immediately upslope from the grids. Both grids experienced surface flooding and the grazed grid (#2) was severely impacted by flash flooding; water reaching a depth of 10-15 cm flowed across parts of the grid. Only one body was recovered when the runoff subsided but captures during the remaining two nights of the July/August census and in subsequent censuses strongly suggest that the population was significantly and differentially impacted by the storm cell and the associated flash flooding. In September 2003, 30% of the giant kangaroo rats captured on grid #2 and 11% of the animals on grid #1 had never been trapped previously. Through direct mortality and displacement of individuals, the storm caused significant perturbation to population dynamics. Had the storm occurred a few days later, we would not have known of its impact and could only speculate on significant differential changes in population dynamics during the next scheduled census in spring 2004.

KEY WORDS: ingens, disturbance, Dipodomys, conservation