Publications

The Brown Tree Snake, Boiga irregularis, is an introduced species on Guam where it causes frequent electrical power outages. The snake's high abundance, its propensity for climbing, and use of disturbed habitats all contribute to interruption of Guam's electrical service and the activities that depend on electrical power. Snakes have caused more than 1600 power outages in the 20-yr...

We examined the phylogeography and history of giant Galápagos tortoise populations based on mitochondrial DNA sequence data from 161 individuals from 21 sampling sites representing the 11 currently recognized extant taxa. Molecular clock and geological considerations indicate a founding of the monophyletic Galápagos lineage around 2–3 million years ago, which would allow for all the

There are a growing number of contrasting theories about plant invasions, but most are only weakly supported by small-scale field experiments, observational studies, and mathematical models. Among the most contentious theories is that species-rich habitats should be less vulnerable to plant invasion than species-poor sites, stemming from earlier theories that competition is a major force...

Basic information on where nonnative plant species have successfully invaded is lacking. We assessed the vulnerability of 22 vegetation types (25 sets of four plots in nine study areas) to nonnative plant invasions in the north–central United States. In general, habitats with high native species richness were more heavily invaded than species-poor habitats, low-elevation areas were more...

In response to a request from the United States Fish and Wildlife Service, we examined the likelihood of visitors changing their plans for future visits to National Wildlife Refuges (NWR) because of changes in entrance or use fees. We obtained data for this study from 3,173 respondents from 14 NWRs between 1998 and 2000. Overall, only 8% of all respondents reported potential displacement...

Was the pre-European Southwest a region of wild landscapes, shaped primarily by natural processes like lightning-ignited fire, or did people substantially mold these lands into regional-scale artifacts through their use of fire and other means? Perspectives on this question have varied markedly through time and between scholars, as evident from the quotes interspersed through this...

No abstract available.

No abstract available.

During the fall of 1998, scientists from the Midcontinent Ecological Science Center (MESC) of the U.S. Geological Survey (USGS) a?? sent a survey by mail to residents in southwest Colorado and northwest New Mexico to better understand quality of life issues in this area of the Colorado Plateau. Collaborators in this study included the Bureau of Land Management and U.S. Forest Service...

Researchers examined the fish communities of the Colorado and San Juan river interface zones of Lake Powell during 1999 and 2000. The objectives were to: (1) search for young razorback sucker and Colorado pikeminnow and, if found, RIT tag them; (2) examine the effectiveness of the various collection techniques on juvenile native fish; and (3) describe the fish communities found in these

Long-term ecosystem research and monitoring was begun in the Loch Vale watershed of Rocky Mountain National Park in 1983, after extensive survey work to identify the best location. Then, as now, our scientific objectives were to understand natural biogeochemical cycles and variability, so that we could differentiate ecosystem changes from human-caused disturbances, such as atmospheric...

The vocal signatures of the primary song form (“fitz-bew”) of the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus) and its northern counterpart, E. t. adastus, are distinctive. Songs of the extimus subspecies are longer (total song, note, internote) and frequencies at maximum amplitude are lower than those of adastus. I used vocal evidence to clarify the...