Geology topics

Harold D. Picton

Publications and source records attributed to Harold D. Picton.

4 recordsLinked to original sources

USGS1994

Chromatographic (TLC) differentiation of grizzly bear and black bear scats

While past work concluded that thin-layer chromatography (TLC) was inadequate for the separation of grizzly ( Ursus arctos horribilis ) and black bear ( U. americanus ) scats, our study found differences adequate for species separation. A key was constructed using 19 of 40 data points recorded on each( N )=356 profiles of 178) know-species scat. Accuracy was best for late summer scats (94%). Methods for specimen preparation, analysis, and reading the TLC profiles are discussed. Factors involved in scat variation were tested.

Bears: Their Biology and Management↗

USGS1990

Fluctuating asymmetry and testing isolation of Montana grizzly bear populations

Fluctuating asymmetry of adult skulls was used to test he genetic isolation of the Yellowstone grizzly bear population from its nearest neighbor. An overall summary statistic was used in addition to 16 other parameters. Tests found the males of the Yellowstone populaion to be more vaiable than those of the North Conitinental Divide Exosystem. Evidence for precipitaiton effects is also included. This test tends to support the existing management haypothesis that the Yellowstone population is isolatied.

Yellowstone National Park↗

USGS1986

Using climate data to predict grizzly bear litter size

A 5-year double-bind test was conducted to test the predictive capability of a previously published (Picton 1978) regression (Y= 2.01 + 0.042 x ), which described the relationship between the littler size of grizzly bears ( Ursus arctos horribilis ) and an index of climate plus carrion availability (climate-carrion index). This regression showed an efficient in excess of 99% in predicting the observed grizzly bear littler size. The predictions made using the climate-carrion index had a mean absolute error of less than 25% of forecasts using other methods. The updated climate-carrion index regression, which includes all of the 16 years for which data are available, is Y= 2.009 + 0.042 x ( r = 0.078; P < 0.01; N = 16). We concluded that the climate-carrion index can be a helpful tool in predicting grizzly bear littler size. The relation of this information to the effects of the closure of Yellowstone Park garbage dumps is discussed.

Bears: Their Biology and Management↗

USGS1978

Climate and reproduction of grizzly bears in Yellowstone National Park

Controversy surrounds the conflicts between the requirements of human safety and the preservation of grizzly bears ( Ursus arctos horribilis ) in western North America. It has been difficult to separate the effect of factors such as the closure of garbage dumps from that of the climate. It has also proved difficult to relate climatic data to changes in the populations of large mammals. I report here a correlation of climatic change with fluctuations in the sizes of litters of grizzly bears born in Yellowstone National Park, Wyoming, during 1958–1976. The decrease in litter sizes observed since the closure of garbage dumps seems to be largely a consequence of unfavourable weather during the periods of the final fattening of the mother, winter sleep, birth, lactation and early spring foraging. This study represents one of the few times that the effects of climate have been demonstrated for large omnivorous or carnivorous mammals.

Wyoming↗