Geology topics

Lyman L. McDonald

Publications and source records attributed to Lyman L. McDonald.

6 recordsLinked to original sources

USGS2011

Recommended methods for range-wide monitoring of prairie dogs in the United States

One of the greatest challenges for conserving grassland, prairie scrub, and shrub-steppe ecosystems is maintaining prairie dog populations across the landscape. Of the four species of prairie dogs found in the United States, the Utah prairie dog (Cynomys parvidens) is listed under the Endangered Species Act (ESA) as threatened, the Gunnison's prairie dog (C. gunnisoni) is a candidate for listing in a portion of its range, and the black-tailed prairie dog (C. ludovicianus) and white-tailed prairie dog (C. leucurus) have each been petitioned for listing at least once in recent history. Although the U.S. Fish and Wildlife Service (USFWS) determined listing is not warranted for either the black-tailed prairie dog or white-tailed prairie dog, the petitions and associated reviews demonstrated the need for the States to monitor and manage for self-sustaining populations. In response to these findings, a multi-State conservation effort was initiated for the nonlisted species which included the following proposed actions: (1) completing an assessment of each prairie dog species in each State, (2) developing a range-wide monitoring protocol for each species using a statistically valid sampling procedure that would allow comparable analyses across States, and (3) monitoring prairie dog status every 3-5 years depending upon the species. To date, each State has completed an assessment and currently is monitoring prairie dog status; however, for some species, the inconsistency in survey methodology has made it difficult to compare data year-to-year or State-to-State. At the Prairie Dog Conservation Team meeting held in November 2008, there was discussion regarding the use of different methods to survey prairie dogs. A recommendation from this meeting was to convene a panel in a workshop-type forum and have the panel review the different methods being used and provide recommendations for range-wide monitoring protocols for each species of prairie dog. Consequently, the Western Association of Fish and Wildlife Agencies (WAFWA), in coordination with USFWS and U.S. Geological Survey (USGS), hosted a prairie dog species survey methodology workshop January 25-28, 2010 in Fort Collins, Colorado. The workshop provided all WAFWA partners and interested parties the opportunity to present their survey methodology to a review panel made up of experts in the fields of quantitative biology, population biology, species biology, and biostatistics. This report presents the panel's survey methodology recommendations for each of the four species of prairie dogs found in the United States and, for the black-tailed prairie dog, a list of action items to facilitate implementation of the recommended methodology.

Scientific Investigations Report↗

USGS2002

Sea otter ( Enhydra lutris ) perspective: Part A. Sea otter population status and the process of recovery from the 1989 Exxon Valdez oil spill

Sea otter ( Enhydra lutris ) populations were severely affected by the 1989 Exxon Valdez oil spill in western Prince William Sound, AK, and had not fully recovered by 2000. Here we present results of population surveys and incorporate findings from related studies to identify current population status and factors affecting recovery. Between 1993 and 2000, the number of sea otters in the spill-area of Prince William Sound increased by about 600 to nearly 2700. However, at Knight Island, where oil exposure and sea otter mortality in 1989 approached 0.90, no increase has been observed. Sea otter reproduction was not impaired and the age and sex structure of animals captured are consistent with both intrinsic reproduction and immigration contributing to recovery. However, low resighting rates of marked animals at Knight Island compared to an unoiled reference area, and a high proportion of young animals in beach cast carcasses through 1998, suggest that the lack of recovery was caused by relatively poor survival or emigration of potential recruits. Significantly higher levels of cytochrome P4501A (CYP1A), a biomarker of hydrocarbons, were found in sea otters at Knight Island in 1996-98 compared to unoiled Montague Island, implicating oil effects in the lack of recovery at Knight Island. Delayed recovery does not appear to be directly related to food limitation. Although food availability was relatively low at both oiled and unoiled areas, we detected significant increases in sea otter abundance only at Montague Island, a finding inconsistent with food as a principal limiting factor. Persistent oil in habitats and prey provides a source of continued oil exposure and, combined with relatively low prey densities, suggests a potential interaction between oil and food. However, sea otters foraged more successfully at Knight Island and young females were in better condition than those at Montague Island. We conclude that progress toward recovery of sea otters in Prince William Sound is evident, but that in areas where initial oil effects were greatest, recovery may be constrained by residual spill effects, resulting in elevated mortality and emigration. It is evident that internal reproduction and immigration of juveniles has been the primary means of population recovery, as opposed to broad scale redistribution of adults from outside affected areas. The result is a recovery period protracted by long-term spill effects on survival and emigration and intrinsic limits to population growth.

Alaska↗

USGS2000

Densities of Barrow's goldeneyes during winter in Prince William Sound, Alaska in relation to habitat, food, and history of oil contamination

We evaluated variation in densities of Barrow's Goldeneyes ( Bucephala islandica ) during winter at 214 sites within oiled and unoiled study areas in Prince William Sound, Alaska in relation to physical habitat attributes, prey biomass, and history of habitat contamination by the 1989 Exxon Valdez oil spill. Using general linear model analyses, we found that goldeneye densities were positively associated with occurrence of a stream within 200 m, lack of exposure to wind and waves, and mixed (versus rocky) substrate. We speculate that these associations relate to habitat profitability via selection of beneficial attributes and avoidance of detrimental features. We also determined that biomass of blue mussels ( Mytilus trossulus ), the primary prey, was not related to Barrow's Goldeneye densities; we suggest that mussel standing stock exceeds predation demands in our study areas and, thus, does not dictate goldeneye distribution. After accounting for habitat effects, we detected no effect of history of oil contamination on Barrow's Goldeneye densities, suggesting that populations have recovered from the oil spill. Although other studies documented hydrocarbon exposure in Barrow's Goldeneyes through at least 1997, either the level of exposure did not affect populations via reductions in survival, or effects of oil exposure were offset by immigration.

Alaska↗

USGS1999

Comparison of aerial survey procedures for estimating polar bear density: Results of pilot studies in northern Alaska

The U.S. Marine Mammal Protection Act (MMPA) and International Agreement on the Conservation of Polar Bears mandate that boundaries and sizes of polar bear ( Ursus maritimus ) populations be known so they can be managed at optimum sustainable levels. However, data to estimate polar bear numbers for the Chukchi/Bering Sea and Beaufort Sea populations in Alaska are limited. We evaluated aerial line transect methodology for assessing the size of these Alaskan polar bear populations during pilot studies in spring 1987 and summer 1994. In April and May 1987 we flew 12.239 km of transect lines in the northern Bering, Chukchi, and western Beaufort seas. In June 1994 we flew 6.244 km of transect lines in a primary survey unit using a helicopter, and 5,701 km of transect lines in a secondary survey unit using a fixed-wing aircraft in the Beaufort Sea. We examined visibility bias in aerial transect surveys, double counts by independent observers, single-season mark-resight methods, the suitability of using polar bear sign to stratify the study area, and adaptive sampling methods. Fifteen polar bear groups were observed during the 1987 study. Probability of detecting bears decreased with increasing perpendicular distance from the transect line, and probability of detecting polar bear groups likely increased with increasing group size. We estimated population density in high density areas to be 446 km 2 /bear. In 1994, 15 polar bear groups were observed by independent front and rear seat observers on transect lines in the primary survey unit. Density estimates ranged from 284 km 2 /bear to 197 km 2 /bear depending on the model selected. Low polar bear numbers scattered over large areas of polar ice in 1987 indicated that spring is a poor time to conduct aerial surveys. Based on the 1994 survey we determined that ship-based helicopter or land-based fixed-wing aerial surveys conducted at the ice-edge in late summer-early fall may produce robust density estimates for polar bear populations in the Chukchi/Bering and Beaufort seas.

Conference Paper↗

USGS1996

Maximum likelihood estimation for the double-count method with independent observers

Data collected under a double-count protocol during line transect surveys were analyzed using new maximum likelihood methods combined with Akaike's information criterion to provide estimates of the abundance of polar bear ( Ursus maritimus Phipps) in a pilot study off the coast of Alaska. Visibility biases were corrected by modeling the detection probabilities using logistic regression functions. Independent variables that influenced the detection probabilities included perpendicular distance of bear groups from the flight line and the number of individuals in the groups. A series of models were considered which vary from (1) the simplest, where the probability of detection was the same for both observers and was not affected by either distance from the flight line or group size, to (2) models where probability of detection is different for the two observers and depends on both distance from the transect and group size. Estimation procedures are developed for the case when additional variables may affect detection probabilities. The methods are illustrated using data from the pilot polar bear survey and some recommendations are given for design of a survey over the larger Chukchi Sea between Russia and the United States.

Alaska↗

USGS1996

Assessing habitat selection when availability changes

We present a method of comparing data on habitat use and availability that allows availability to differ among observations. This method is applicable when habitats change over time and when animals are unable to move throughout a predetermined study area between observations. We used maximum—likelihood techniques to derive an index that estimates the probability that each habitat type would be used if all were equally available. We also demonstrate how these indices can be used to compare relative use of available habitats, assign them ranks, and assess statistical differences between pairs of indices. The set of these indices for all habitats can be compared between groups of animals that represent different seasons, sex or age classes, or experimental treatments. This method allows quantitative comparisons among types and is not affected by arbitrary decisions about which habitats to include in the study. We provide an example by comparing the availability of four categories of sea ice concentration to their use by adult female polar bears (Ursus maritimus), whose movements were monitored by satellite radio tracking in the Bering and Chukchi Seas during 1990. Use of ice categories by bears was nonrandom, and the pattern of use differed between spring and late summer seasons.

Ecology↗