By David P. Bickford
After more than two years of nearly continuous field work in the rainforests of Papua New Guinea, I have seen the greatest changes in frog calling, reproduction, density and diversity during the past three months (October - December, 1997). The last three months of 1997 coincided with the severe El Niño Southern Oscillation (ENSO) event, which caused unprecedented low rainfall, bush fires, and complete crop failure in the Western Pacific. Papua New Guinea was heavily impacted. A team of fieldworkers and I have gathered data on frog populations from 1995, 1996 and the first part of 1997 (Froglog Number 23, August 1997), and I compared frog density, distribution, and diversity as well as reproductive data to the last three months of 1997. There was an order of magnitude difference between the number of terrestrial clutches of eggs found per 5 x 5 m plot for baseline and ENSO drought data. We observed one clutch per 7.8 plots on average (81 clutches in 632 plots) for baseline conditions. During the low rainfall-ENSO period we found one terrestrial clutch per 71.25 plots (8 clutches in 570 plots). The drought conditions negatively affect terrestrial breeders and direct developing frogs in New Guinea, almost entirely shutting down reproduction. We also found more frogs during VES transects at night during the low rainfall-ENSO period compared to our baseline data. This was the result of high numbers of normally rare or uncommon arboreal species descending from their arboreal sites, presumably because the drying effects were even more pronounced in above-ground microhabitats. Frogs also appear to be at slightly higher densities near streams during the drought. Work on long-term frog monitoring has been supported by the Wildlife Conservation Society, the University of Miami, and the Biodiversity Conservation Network. I will return to Papua New Guinea and will continue to examine the on-going effects of the drought as well as other topics. I have used field assistants in 1996 and 97 and anyone interested in working with me can reach me at the following address:
David Bickford, Resident Scientist, Research and Conservation Foundation-Crater Mtn., P.O. Box 1261, Goroka, EHP, PAPUA NEW GUINEA. Tel: (675) 732-3211 Fax: (675) 732-1123 FAX rcf@dg.com.pg