Geology topics

Kenneth R. Whitten

Publications and source records attributed to Kenneth R. Whitten.

4 recordsLinked to original sources

USGS2017

Advancing the match-mismatch framework for large herbivores in the Arctic: Evaluating the evidence for a trophic mismatch in caribou

Climate-induced shifts in plant phenology may adversely affect animals that cannot or do not shift the timing of their reproductive cycle. The realized effect of potential trophic “mismatches” between a consumer and its food varies with the degree to which species rely on dietary income and stored capital. Large Arctic herbivores rely heavily on maternal capital to reproduce and give birth near the onset of the growing season but are they vulnerable to trophic mismatch? We evaluated the long-term changes in the temperatures and characteristics of the growing seasons (1970–2013), and compared growing conditions and dynamics of forage quality for caribou at peak parturition, peak lactation, and peak forage biomass, and plant senescence between two distinct time periods over 36 years (1977 and 2011–13). Despite advanced thaw dates (7−12 days earlier), increased growing season lengths (15−21 days longer), and consistent parturition dates, we found no decline in forage quality and therefore no evidence within this dataset for a trophic mismatch at peak parturition or peak lactation from 1977 to 2011–13. In Arctic ungulates that use stored capital for reproduction, reproductive demands are largely met by body stores deposited in the previous summer and autumn, which reduces potential adverse effects of any mismatch between food availability and timing of parturition. Climate-induced effects on forages growing in the summer and autumn ranges, however, do correspond with the demands of female caribou and their offspring to gain mass for the next reproductive cycle and winter. Therefore, we suggest the window of time to examine the match-mismatch framework in Arctic ungulates is not at parturition but in late summer-autumn, where the multiplier effects of small changes in forage quality are amplified by forage abundance, peak forage intake, and resultant mass gains in mother-offspring pairs.

Alaska↗

USGS2002

The porcupine caribou herd

Documentation of the natural range of variation in ecological, life history, and physiological characteristics of caribou ( Rangifer tarandus ) of the Porcupine caribou herd is a necessary base for detecting or predicting any potential effects of industrial development on the performance (e.g., distribution, demography, weight-gain of individuals) of the herd. To demonstrate an effect of development, post-development performance must differ from pre-development performance while accounting for any natural environmental trends. We had 2 working hypotheses for our investigations: 1) performance of the Porcupine caribou herd was associated with environmental patterns and habitat quality, and 2) access to important habitats was a key influence on demography. We sought to document the range of natural variation in habitat conditions, herd size, demography (defined here as survival and reproduction), sources and magnitude of mortality, distribution, habitat use, and weight gain and loss, and to develop an understanding of the interactions among these characteristics of the herd. In addition, we investigated ways that we could use this background information, combined with auxiliary information from the adjacent Central Arctic caribou herd, to predict the direction and magnitude of any potential effects of industrial oil development in the 1002 Area of the Arctic National Wildlife Refuge on Porcupine caribou herd calf survival on the herd's calving grounds during June.

Alaska, Northwest Territories, Yukon Territory↗

USGS2001

Effects of recent climate warming on caribou habitat and calf survival

Migratory Barren-Ground Caribou Rangifer tarandus granti are the most important subsistence resource for northern indigenous peoples. They are likely to respond to global climatic changes that affect the distribution of their forage resources and the availability of forage through the year. The Porcupine Caribou herd is a large, internationally migratory herd of about 128,000 individuals that occupies the Alaska-Canada borderlands and uses a 300,000 km 2 annual range. The calving ground is a traditionally-used portion of the annual range that comprises 23,000 km 2 at approximately 70° north. Caribou migrate several hundred kilometres from winter ranges to the calving ground, arriving in mid- to late-May each year. Calves are born during the first week of June, and cows and calves remain on the calving ground for 4-6 weeks before dispersing to late-summer, fall, and winter ranges. We measured the relative amount of green vegetation using data from polar orbiting satellites (Figure 1) to assess decade-long temporal trends in large scale habitat conditions on the calving ground and to investigate Caribou response to this habitat change. The vegetation index has shown a tendency toward earlier greening in spring and later plant senescence (dying off) in much of the northern hemisphere the 1980s, concurrent with independent estimates of climate change. High density calving was consistently located where the daily rate of increase in the amount of green plant biomass during lactation was greatest, in the period 1985-1996. This was probably because of the lactating cows' need for highly digestible new plant growth. Nutritional requirements of lactating cows are about double those during the remainder of the year.

Alaska, Yukon Territory↗

USGS1988

Applications of satellite telemetry to wildlife research and management in Alaska

Since 1984, the Alaska Fish and Wildlife Research Center, in cooperation with the Alaska Department of Fish and Game and several other agencies, has used the Argos Data Collection and Location System to address wildlife research and management problems in Alaska and other parts of North America. The use of satellite telemetry has overcome some of the logistical problems of working in remote areas in an arctic environment, where harsh weather, darkness, worker safety considerations, extensive movements by some species, and high costs of locating study animals often result in small incomplete data sets. As of September 1988, 241 satellite transmitters (PPTs) have been deployed on large mammals, including 109 on polar bears in the Bering, Beaufort and Chukchi seas; 74 on caribou in northern Alaska and northwestern Canada; 22 on brown bears in northern Alaska and Kodiak Island, Alaska; 12 on muskoxen in northeastern Alaska and Greenland; 7 on wolves in northern Alaska; 7 on walrus in the Bering and Chuckchi seas; 4 on mule deer in Idaho; 2 on elk in Wyoming; 2 on moose in southcentral Alaska; and 2 on Dall sheep int the Brooks Range of northern Alaska. The Argos DCLS has provided more than 19,000 and 66,000 locations for polar bears and caribou, respectively, and has been used to document the international ranges of these species and to address specific management questions in a cost-effective manner. The precision of locations provided by the Argos DCLS was examined using transmitters placed on the ground or on buildings and compared to the precision from that prior to deployment, presumably because of the proximity of the antenna to the animal's body. The mean error of locations for PTTs on captive animals was 954 m(+or- 1324 SD; median -553 m; n -330). Sensors for determining ambient temperature, short- and long-term indices of animal activity immersion of transmitters in saltwater, and dive depths, were developed and tested. The long-term activity index indicated animal mortality and was correlated with movement patterns for the three species we examined ; caribou, moose and mountain sheep. The short-term index was calibrated to specific activities for captive caribou, moose, mule deer and elk, and was used to determine qualitative trends in activity budgets for free-ranging caribou.

Alaska↗