A paper on the first survey of the critically endangered Saharan cheetah Acinonyx jubatus hecki was recently published in the Journal PlOS ONE. The study was carried out over two field seasons (August-October 2008 and August-November 2010) in Ahaggar Cultural Park, South Central Algeria by Farid Belbachir and his colleagues.
A rectangular trapping grid was designed and overlaid on a satellite image of the study area using 40 camera trap locations, spaced 10 km apart, covering a total area of 2,551 km2. The survey used camera-traps which use passive infra-red motion detectors that trigger a photograph when animals pass in front of the camera.
Cameras were usually placed under the nearest tree within 1km of each pre-allocated grid point. Trees were selected as they were likely to be attractive to passing cheetah; however they had the added advantage of providing shade for the camera traps, protecting them from the heat of the day.
Photographs were obtained from 15 captures of cheetah in 2008 and 17 captures in 2010. The data in 2008 and 2010 yielded captures of four adult cheetah (3 males and 1 of unidentified sex) and two adult cheetah (2 males) and one subadult (unidentified sex) respectively. Camera-trap effort totaled 1862 trap-days in 2008 and 3367 trap-days in 2010. Overall, an average of 124.1 and 198.1 trap-days were necessary to capture a single cheetah picture in 2008 and 2010, respectively. Continue reading
by Roberta Kwok
When a country goes into economic freefall, the resulting chaos can trigger a host of environmental changes. Wildlife regulation often falls by the wayside, and poaching rises — but activities such as logging may drop. “Thus, socioeconomic shocks may hinder or help conservation,” researchers write in Conservation Biology. In the case of the 1991 Soviet Union collapse, which was it? The team studied population trends for 8 mammal species in Russia, including deer, bears, lynxes, and grey wolves. For data, they turned to the Russian Federal Agency of Game Mammal Monitoring’s records. That database contains annual tallies for mammal species, obtained by methods such as counting tracks in the winter and surveying hunters. The researchers studied data from 1981 to 2010, covering the decade before the collapse and the two following decades. Continue reading
The number of passenger pigeons went from billions to zero in mere decades, in contrast to conventional wisdom that enormous population size provides a buffer against extinction. Our understanding of the passenger pigeon’s extinction, however, has been limited by a lack of knowledge of its long-term population history. Here we use both genomic and ecological analyses to show that the passenger pigeon was not always super abundant, but experienced dramatic population fluctuations, which could increase its vulnerability to human exploitation. Our study demonstrates that high-throughput–based ancient DNA analyses combined with ecological niche modeling can provide evidence allowing us to assess factors that led to the surprisingly rapid demise of the passenger pigeon.
To assess the role of human disturbances in species’ extinction requires an understanding of the species population history before human impact. The passenger pigeon was once the most abundant bird in the world, with a population size estimated at 3–5 billion in the 1800s; its abrupt extinction in 1914 raises the question of how such an abundant bird could have been driven to extinction in mere decades. Although human exploitation is often blamed, the role of natural population dynamics in the passenger pigeon’s extinction remains unexplored. Applying high-throughput sequencing technologies to obtain sequences from most of the genome, we calculated that the passenger pigeon’s effective population size throughout the last million years was persistently about 1/10,000 of the 1800’s estimated number of individuals, a ratio 1,000-times lower than typically found. This result suggests that the passenger pigeon was not always super abundant but experienced dramatic population fluctuations, resembling those of an “outbreak” species. Ecological niche models supported inference of drastic changes in the extent of its breeding range over the last glacial–interglacial cycle. An estimate of acorn-based carrying capacity during the past 21,000 y showed great year-to-year variations. Based on our results, we hypothesize that ecological conditions that dramatically reduced population size under natural conditions could have interacted with human exploitation in causing the passenger pigeon’s rapid demise. Our study illustrates that even species as abundant as the passenger pigeon can be vulnerable to human threats if they are subject to dramatic population fluctuations, and provides a new perspective on the greatest human-caused extinction in recorded history.
This article contains supporting information online at http://www.pnas.org/content/suppl/2014/06/13/1401526111.DCSupplemental/pnas.1401526111.sapp.pdf
, ,, ,, ,
Drastic population fluctuations explain the rapid extinction of the passenger pigeon PNAS 2014 ; published ahead of printJune 16, 2014,