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Gerald W. Garner

Publications and source records attributed to Gerald W. Garner.

17 recordsLinked to original sources
USGS2006

Immobilization of free-ranging male pacific walruses ( Odobenus rosmarus divergens ) with carfentanil citrate and naltrexone hydrochloride

The major challenges in immobilization of free-ranging walruses ( Odobenus rosmarus divergens ) are to produce a deep level of anesthesia very quickly (to avoid darted animals from entering the water and drowning), and to find a drug or drug combination that requires only a small volume to be delivered by dart, is safe, reversible, and that provides an adequate period of immobilization to permit attachment of instruments, phlebotomy, and measuring. Tiletamine-zolazepam is recommended for immobilization of pinnipeds, with inhalant anesthesia recommended for more extensive procedures requiring better analgesia (Gales 1989). Drugs that have been used on free-ranging walruses include ketamine (Hagenbeck et al . 1975), phencyclidine combined with acepromazine (DeMaster et al . 1981), etorphine (Born and Knutsen 1990, Hills 1992, Griffiths et al . 1993), tiletamine-zolazepam (Stirling and Sjare 1988, Griffiths et al . 1993), medetomidine and ketamine (Lydersen et al . 1992), and carfentanil (Hills 1992, Lanthier et al . 1999). Carfentanil but not etorphine is presently licensed and available in the United States. Forty-eight adult male walruses were immobilized with carfentanil citrate in the summers of 1995-1997 at Maggy Beach (58°57’N, 161°76’W), a land haul-out located at Cape Peirce within the Togiak National Wildlife Refuge in southwest Alaska. The number of animals present during immobilizations ranged from three to several thousand. Criteria for choosing individual walruses included good body condition, the presence of two tusks of sufficient diameter for the attachment of radio transmitters, and presence of the animal at the edge of the herd. In addition, we chose animals that were resting quietly and which had not recently hauled out (as judged by skin color). Walruses were darted from ranges of approximately 10-15 m using a Cap-Chur rifle (Palmer Chemical and Equipment Co., Douglasville, Georgia, GA 30133). Carfentanil citrate (Wildlife Pharmaceuticals, Fort Collins, CO 80524) was administered by dart with a 10-cm needle to the lumbar region. Most animals received a dose of 2.7 or 3.0 mg of carfentanil. One animal received a second dose after the first syringe apparently burst on impact. Induction times were measured as being the time at which the animal collapsed, failed to respond to external stimuli, or as the time when the darter stood up and moved towards the animal.

Marine Mammal Science↗
USGS2002

Using satellite telemetry to define spatial population structure in polar bears in the Norwegian and western Russian Arctic

1. Animal populations, defined by geographical areas within a species’ distribution where population dynamics are largely regulated by births and deaths rather than by migration from surrounding areas, may be the correct unit for wildlife management. However, in heterogeneous landscapes varying habitat quality may yield subpopulations with distinct patterns in resource use and demography significant to the dynamics of populations. 2. To define the spatial population structure of polar bears Ursus maritimus in the Norwegian and western Russian Arctic, and to assess the existence of a shared population between the two countries, we analysed satellite telemetry data obtained from 105 female polar bears over 12 years. 3. Using both cluster analyses and home-range estimation methods, we identified five population units inhabiting areas with different sea-ice characteristics and prey availability. 4. The continuous distribution of polar bear positions indicated that the different subpopulations formed one continuous polar bear population in the Norwegian and western Russian Arctic. Hence, Norway and Russia have a shared management responsibility. 5. The spatial population structure identified will provide a guide for evaluating geographical patterns in polar bear ecology, the dynamics of polar bear–seal relationships and the effects of habitat alteration due to climate change. The work illustrates the importance of defining population borders and subpopulation structure in understanding the dynamics and management of larger animals.

Arctic↗
USGS2002

Performance of a satellite-linked GPS on Pacific walruses (Odobenus rosmarus divergens)

We evaluated the utility of a satellite-linked GPS in obtaining location data from Pacific walruses ( Odobenus rosmarus divergens ). A unit was attached to one of the tusks of each of three adult male walruses in Bristol Bay, Alaska. The units were designed to relay GPS positions through the Argos Data Collection and Location System. The GPS was only minimally effective in obtaining location data. An average of only 5% of the attempts yielded a position, and only a small number of these were locations at sea. The paucity of successful attempts was probably due to infrequent and brief surfacings of the GPS, the proximity of cliffs to predominant haul-out sites in the study region, and the packing of animals when they were hauled out in herds. Argos was effective in relaying GPS positions in this study, but as GPS technology advances, and its application to marine mammal studies becomes more prevalent, it seems that the greatest challenge to the study of many species will be in data retrieval.

Polar Biology↗
USGS2002

Predators

Calving caribou ( Rangifer tarandus ) of the Central Arctic herd, Alaska, have avoided the infrastructure associated with the complex of petroleum development areas from Prudhoe Bay to Kuparuk (Cameron et al. 1992, Nellemann and Cameron 1998, and Section 4 of this document). Calving females of the Porcupine caribou herd may similarly avoid any oil field roads and pipelines developed in areas traditionally used during the calving and post-calving periods. This may displace the caribou females and calves to areas east and south of the 1002 Area of the Arctic National Wildlife Refuge. Increased calf mortality could occur if calving caribou are displaced into areas that have a higher density of predators, higher rates of predation, or where a higher proportion of the predators regularly use caribou as a food source (Whitten et al. 1992). Our study assessed predation risks to caribou calving in the 1002 Area versus calving in potential displacement areas. Due to funding constraints, our research focused on grizzly bears ( Ursus arctos ), with wolves (Camus lupus) and golden eagles ( Aquila chrysaetos ) receiving only cursory attention. Our research objectives were 1) to compare relative abundance of predators within the 1002 Area with that in adjacent peripheral areas, 2) to determine factors affecting predator abundance on the calving grounds, and 3) to quantify the use of caribou as a food source for predators and the importance of caribou to the productivity of predator populations using the coastal plain of the Arctic National Wildlife Refuge.

Alaska, Northwest Territories, Yukon Territory↗
USGS2000

Phylogeography of mitochondrial DNA variation in brown bears and polar bears

We analyzed 286 nucleotides of the middle portion of the mitochondrial cytochrome b gene of 61 brown bears from three locations in Alaska and 55 polar bears from Arctic Canada and Arctic Siberia to test our earlier observations of paraphyly between polar bears and brown bears as well as to test the extreme uniqueness of mitochondrial DNA types of brown bears on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska. We also investigated the phylogeography of brown bears of Alaska's Kenai Peninsula in relation to other Alaskan brown bears because the former are being threatened by increased human development. We predicted that: (1) mtDNA paraphyly between brown bears and polar bears would be upheld, (2) the mtDNA uniqueness of brown bears of the ABC islands would be upheld, and (3) brown bears of the Kenai Peninsula would belong to either clade II or clade III of brown bears of our earlier studies of mtDNA. All of our predictions were upheld through the analysis of these additional samples.

Alaska↗
USGS1999

Subcutaneous implantation of satellite transmitters with percutaneous antennae into male polar bears ( Ursus maritimus )

Male polar bears ( Ursus maritimus ) have not been successfully instrumented with satellite transmitters because they readily shed collar-mounted transmitters. Seven male polar bears were captured on the pack ice off the northern coast of Alaska and surgically implanted with satellite transmitters with percutaneous antennae into the subcutaneous space of the dorsal cervical region. Transmitters failed prematurely with lifetimes of 30-161 days (x̄ = 97 days). Efforts to relocate implanted bears after transmitters failed were not successful. The mean number of location solutions per transmitter was 204 (range 118-369). An average of 10% and 19% of the locations were accurate to <150 m and to 150-350 m, respectively. Our successful tracking of male polar bears, the high quality of locations obtained from transmitters with percutaneous antennae implanted in the subcutaneous space, and the low visibility of such units make further technical development worthwhile if the reason for premature failure of the transmitters can be determined.

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↗
USGS1998

Identifying and mitigating errors in satellite telemetry of polar bears

Satellite radiotelemetry is a useful method of tracking movements of animals that travel long distances or inhabit remote areas. However, the logistical constraints that encourage the use of satellite telemetry also inhibit efforts to assess accuracy of the resulting data. To investigate effectiveness of methods that might be used to improve the reliability of these data, we compared 3 sets of criteria designed to select the most plausible locations of polar bears ( Ursus maritimus ) that were tracked using satellite radiotelemetry in the Bering, Chukchi, East Siberian, Laptev, and Kara seas during 1988-93. We also evaluated several indices of location accuracy. Our results suggested that, although indices could provide information useful in evaluating location accuracy, no index or set of criteria was sufficient to identify all the implausible locations. Thus, it was necessary to examine the data and make subjective decisions about which locations to accept or reject. However, by using a formal set of selection criteria, we simplified the task of evaluating locations and ensured that decisions were made consistently. This approach also enabled us to evaluate biases that may be introduced by the criteria used to identify location errors. For our study, the best set of selection criteria comprised: (1) rejecting locations for which the distance to the nearest other point from the same day was >50 km; (2) determining the highest accuracy code (NLOC) for a particular day and rejecting locations from that day with lesser values; and (3) from the remaining locations for each day, selecting the location closest to the location chosen for the previous transmission period. Although our selection criteria seemed unlikely to bias studies of habitat use or geographic distribution, basing selection decisions on distances between points might bias studies of movement rates or distances. It is unlikely that any set of criteria will be best for all situations; to make efficient use of data and minimize bias, these rules must be tailored to specific study objectives.

Ursus↗
USGS1998

Satellite telemetry: A new tool for wildlife research and management

The U.S. Fish and Wildlife Service and the Alaska Department of Fish and Game have cooperated since 1984 to develop and evaluate satellite telemetry as a means of overcoming the high costs and logistical problems of conventional VHF (very high frequency) radiotelemetry systems. Detailed locational and behavioral data on caribou ( Rangifer tarandus ), polar bears ( Ursus maritimus ), and other large mammals in Alaska have been obtained using the Argos Data Collection and Location System (DCLS). The Argos system, a cooperative project of the Centre National d'Études Spatiales of France, the National Oceanic and Atmospheric Administration, and the National Aeronautics and Space Administration, is designed to acquire environmental data on a routine basis from anywhere on earth. Transmitters weighing 1.6-2.0 kg and functioning approximately 12-18 months operated on a frequency of 401.650 MHz. Signals from the transmitters were received by Argos DCLS instruments aboard two Tiros-N weather satellites in sun-synchronous, nearpolar orbits. Data from the satellites were received at tracking stations, transferred to processing centers in Maryland and France, and made available to users via computer tape, printouts, or telephone links. During 1985 and 1986, more than 25,000 locations and an additional 28,000 sets of sensor data (transmitter temperature and short-term and long-term indices of animal activity) were acquired for caribou and polar bears. Locations were calculated from the Doppler shift in the transmitted signal as the satellite approached and then moved away from the transmitter. The mean locational error for transmitters at known locations (n - 1,265) was 829 m; 90% of the calculated locations were within 1,700 m of the true location. Caribou transmitters provided a mean of 3.1 (+5.0. SD) locations per day during 6h of daily operation, and polar bear transmitters provided 1.7 (+6.9SD) locations during 12h of operation every third day. During the first 6 months of operation, the UHF (ultra-high frequency) signal failed on three of 32 caribou transmitters and 10 of 36 polar bear transmitters. A geographic information system (GIS) incorporating other databases (e.g., land cover, elevation, slope, aspect, hydrology, ice distribution) was used to analyze and display detailed locational and behavioral data collected via satellite. Examples of GIS applications to research projects using satellite telemetry and examples of detailed movement patterns of caribou and polar bears are presented. This report includes documentation for computer software packages for processing Argos data and presents developments, as of March 1987, in transmitter design, data retrieval using a local user terminal, computer software, and sensor development and calibration.

Resource Publication↗
USGS1998

Identification of polar bear den habitat in northern Alaska

The goal of this project is to refine the information collected previously on maternal denning, into digital maps that show where polar bears are likely to create future dens in northern Alaska. Such maps will allow a priori recommendations regarding timing and geographic locations of proposed human developments; and hence provide managers with an important mitigation and management tool.

Alaska↗
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↗
USGS1991

Inter- and intraspecific mitochondrial DNA variation in North American bears (Ursus)

We assessed mitochondrial DNA variation in North American black bears (Ursus americanus), brown bears (Ursus arctos), and polar bears (Ursus maritimus). Divergent mitochondrial DNA haplotypes (0.05 base substitutions per nucleotide) were identified in populations of black bears from Montana and Oregon. In contrast, very similar haplotypes occur in black bears across North America. This discordance of haplotype phylogeny and geographic distribution indicates that there has been maintenance of polymorphism and considerable gene flow throughout the history of the species. Intraspecific mitochondrial DNA sequence divergence in brown bears and polar bears is lower than in black bears. The two morphological forms of U. arctos, grizzly and coastal brown bears, are not in distinct mtDNA lineages. Interspecific comparisons indicate that brown bears and polar bears share similar mitochondrial DNA (0.023 base substitutions per nucleotide) which is quite divergent (0.078 base substitutions per nucleotide) from that of black bears. High mitochondrial DNA divergence within black bears and paraphyletic relationships of brown and polar bear mitochondrial DNA indicate that intraspecific variation across species' ranges should be considered in phylogenetic analyses of mitochondrial DNA.

Canadian Journal of Zoology↗
USGS1990

Seasonal movements of adult female polar bears in the Bering and Chukchi seas

Ten adult female polar bears ( Ursus maritimus ) were fitted with satellite telemetry collars during March 1986 in the Kotzebue Sound area of the Chukchi Sea. During March-April 1987, 2 of these bears were refitted with satellite telemetry collars and an additional 10 adult females were collared in the northern Bering and eastern Chukchi seas. Data for 1,560 point locations recorded through May 1988 indicated that female polar bears in the Bering and Chukchi seas were resident in western Alaskan waters from November through March, then moved northward with the receding pack ice during April and May. They remained in the northern and northwestern Chukchi Sea during June through September, often adjacent to the Soviet coastline. Satellite telemetry data indicated that 4 females marked in Alaskan waters of the Chukchi Sea apparently denned in the vicinity of Wrangel Island during winter 1987/1988. Denning in American territory of bears marked in the Chukchi and Bering seas has not been documented using satellite telemetry data. Some polar bears moved from the Chukchi Sea into the western Beaufort Sea during summer and fall, then returned to the Chukchi and Bering seas the following winter. Movements of bears from the Chukchi Sea into the central or eastern Beaufort Sea were not documented through spring 1988. These data document that polar bears occuring in the Bering and Chukchi seas are shared internationally between the United States and the Soviet Union.

Alaska↗
USGS1990

Tracking wildlife by satellite: Current systems and performance

Since 1984, the U.S. Fish and Wildlife Service has used the Argos Data Collection and Location System (DCLS) and Tiros-N series satellites to monitor movements and activities of 10 species of large mammals in Alaska and the Rocky Mountain region. Reliability of the entire system was generally high. Data were received from instrumented caribou ( Rangifer tarandus ) during 91% of 318 possible transmitter-months. Transmitters failed prematurely on 5 of 45 caribou, 2 of 6 muskoxen ( Ovibos moschatus ), and 1 of 2 gray wolves ( Canis lupus ). Failure rates were considerably higher for polar ( Ursus maritimus ) and brown ( U. arctos ) bears than for caribou ( Rangifer tarandus ). Efficiency of gathering both locational and sensor data was related to both latitude and topography. Mean error of locations was estimated to be 954 m (median = 543 m) for transmitters on captive animals; 90% of locations were <1,732 m from the true location. Argos's new location class zero processing provided many more locations than normal processing, but mean location error was much higher than locations estimated normally. Locations were biased when animals were at elevations other than those used in Argos's calculations. Long-term and short-term indices of animal activity were developed and evaluated. For several species, the long-term index was correlated with movement patterns and the short-term index was calibrated to specific activity categories (e.g., lying, feeding, walking). Data processing and sampling considerations were evaluated. Algorithms for choosing the most reliable among a series of reported locations were investigated. Applications of satellite telemetry data and problems with lack of independence among locations are discussed.

Fish and Wildlife Technical Report↗
USGS1989

Performance and utility of satellite telemetry during field studies of free-ranging polar bears in Alaska

Satellite telemetry technology has been used during field studies of polar bears in Alaska since 1985. A total of 109 Platform Transmitter Terminals (PTT) have been deployed on free-ranging female polar bears that seasonally inhabit waters adjacent to the Alaskan coast. The PTTs transmitted locational and sensor data to TIROS-N polar-orbiting satellites during a duty cycle of 12 hours on/60 hours off in 1985, 1986, and 1987. Expected battery life was 13.8 months, and collars were normally removed and replaced with new or refurbished PTTs at 11-13 month intervals. Duty cycles were altered to 7-8 hours on/64-65 hours off in 1988 to prolong expected battery life to 19-21 months. Sensor data transmitted included PTT internal temperature, short term activity counts recorded at 60 second intervals, and long term activity counts for the preceding 24 or 72-hour period. Early failures of PTTs to fix location (less than 75% of expected battery life) were as high as 53% during 198501986. Subsequent improvements in battery design, including better shock insulation, improved electronic, and an improved battery system have reduced early failures to 27% in 1987-1988. The harsh environment and the degree of abuse observed in recovered collars indicate that an unavoidable failure rate of 8-10% is inherent within 60 days after deployment on polar bears. A total of 18,000 locations and 201,000 sensor messages were received from female polar bears between May 1985 and June 1988. Polar bears that were marked in Alaskan waters have been located as far south as 60°N 168°W, and as far east as 70°N 127°W in the Beaufort Sea. Polar bears in the Beaufort Sea are shared with Canada, while polar bears in the Chukchi and Bering seas are shared with the Soviet Union. The international ranges of the two hypothesized populations have been documented. Satellite telemetry has detailed the large movement patterns of polar bear over these vast areas that were previously not available using other techniques.

Alaska↗