STELLER SEA LION RESEARCH

CAPTIVE STUDIES RELATED PUBLICATIONS

NEW TECHNOLOGIES


2017
 
On the utility of accelerometers to predict stroke rate using captive fur seals and sea lions.
Ladds, M. A., D. A. S. Rosen, D. J. Slip and R. G. Harcourt. 2017.
Biology Open 6:1396-1400.
abstract
Energy expenditure of free-living fur seals and sea lions is difficult to measure directly, but may be indirectly derived from flipper stroke rate. We filmed 10 captive otariids swimming with accelerometers either attached to a harness (Daily Diary: sampling frequency 32Hz, N = 4) or taped to the fur (G6a+: 25Hz, N = 6). We used down sampling to derive four recording rates from each accelerometer (Daily Diary: 32, 16, 8, 4Hz; G6a+: 25, 20, 10, 5Hz). For each of these sampling frequencies we derived 20 combinations of two parameters (RMW - the window size used to calculate the running mean, and m – the minimum number of points smaller than the local maxima used to detect a peak), from the dynamic acceleration of x, z and x+z, to estimate stroke rate from the accelerometers. These estimates differed by up to ~20% in comparison to the actual number of foreflipper strokes counted from videos. RMW had little effect on the overall differences, nor did the choice of axis used to make the calculations (x, z or x+z), though the variability was reduced when using x+z. The best m varied depending on the axis used and the sampling frequency, where a larger m was needed for higher sampling frequencies. This study demonstrates that when parameters are appropriately tuned, accelerometers are a simple yet valid tool for estimating the stroke rates of swimming otariids.

keywords     otariid, swim mechanics, stroke rate, accelerometer, energetics, biologger
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2016
 
Transiting to depth disrupts the relationship between overall dynamic body acceleration and oxygen consumption in freely diving Steller sea lions.
Volpov, B.L., E.T. Goundie, D.A.S. Rosen, A.W. Trites and J.P.Y. Arnould. 2016.
Marine Ecology Progress Series 562:221-236.
abstract
Previous research has presented contradictory evidence on the ability of overall dynamic body acceleration (ODBA) to predict oxygen consumption (sV̇O2) in air-breathing diving vertebrates. We investigated a potential source of these discrepancies by partitioning the ODBA: sV̇O2 relationship over 3 phases of the dive cycle (transiting to and from depth, bottom time, and post-dive surface interval). Trained Steller sea lions (Eumetopias jubatus) executed 4 types of dives to 40 m (single dives, long-duration dive bouts of 4-6 dives, short-duration dive bouts of 10 or 12 dives, and transit dives with minimal bottom duration). Partitioning single dives by dive phase showed differing patterns in the ODBA: sV̇O2 relationship among dive phases, but no significant linear relationships were observed. The proportion of the dive cycle spent transiting to and from the surface was a significant predictive factor in the ODBA: sV̇O2 relationship, while bottom duration or post-dive surface interval had no effect. ODBA only predicted sV̇O2 for dives when the proportion of time spent transiting was small. The apparent inability of ODBA to reliably predict sV̇O2 reflects differences in the inherent relationships between ODBA and sV̇O2 during different phases of the dive. These results support the growing body of evidence that ODBA on its own is not a reliable field predictor of energy expenditure at the level of the single dive or dive bout in air-breathing diving vertebrates likely because ODBA (a physical measure) cannot account for physiological changes in sV̇O2 that occur during the different phases of a dive cycle.

keywords     diving behaviour, metabolic rate, ODBA, dive phase, pinniped
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Averaged propulsive body acceleration (APBA) can be calculated from biologging tags that incorporate gyroscopes and accelerometers to estimate swimming speed, hydrodynamic drag and energy expenditure for Steller sea lions.
Ware, C., A. W. Trites, D. A. S. Rosen and J. Potvin. 2016.
PLoS ONE 11(6): e0157326
abstract
Forces due to propulsion should approximate forces due to hydrodynamic drag for animals horizontally swimming at a constant speed with negligible buoyancy forces. Propulsive forces should also correlate with energy expenditures associated with locomotion預n important cost of foraging. As such, biologging tags containing accelerometers are being used to generate proxies for animal energy expenditures despite being unable to distinguish rotational movements from linear movements. However, recent miniaturizations of gyroscopes offer the possibility of resolving this shortcoming and obtaining better estimates of body accelerations of swimming animals. We derived accelerations using gyroscope data for swimming Steller sea lions (Eumetopias jubatus), and determined how well the measured accelerations correlated with actual swimming speeds and with theoretical drag. We also compared dive averaged dynamic body acceleration estimates that incorporate gyroscope data, with the widely used Overa ll Dynamic Body Acceleration (ODBA) metric, which does not use gyroscope data. Four Steller sea lions equipped with biologging tags were trained to swim alongside a boat cruising at steady speeds in the range of 4 to 10 kph. At each speed, and for each dive, we computed a measure called Gyro-Informed Dynamic Acceleration (GIDA) using a method incorporating gyroscope data with accelerometer data. We derived a new metric輸veraged Propulsive Body Acceleration (APBA), which is the average gain in speed per flipper stroke divided by mean stroke cycle duration. Our results show that the gyro-based measure (APBA) is a better predictor of speed than ODBA. We also found that APBA can estimate average thrust production during a single stroke-glide cycle, and can be used to estimate energy expended during swimming. The gyroscope-derived methods we describe should be generally applicable in swimming animals where propulsive accelerations can be clearly identified in the signal預nd they should also prove useful for dead-reckoning and improving estimates of energy expenditures from locomotion.

keywords     biologging, ODBA, accelerometer, gyroscope, swimming, speed, energy expenditure, drag, stroke
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2015
 
Stable carbon and nitrogen isotope trophic enrichment factors for Steller sea lion vibrissae relative to milk and fish/invertebrate diets.
Stricker, C.A., A.M. Christ, M.B. Wunder, A.C. Doll, S.D. Farley, L.D. Rea, D.A.S. Rosen, R.D. Scherer and D.J. Tollit. 2015.
Marine Ecology Progress Series. 523:255-266.
abstract
Nutritional constraints have been proposed as a contributor to population declines in the endangered Steller sea lion Eumetopias jubatus in some regions of the North Pacific. Isotopic analysis of vibrissae (whiskers) is a potentially useful approach to resolving the nutritional ecology of this species because long-term (up to 8 yr) dietary information is sequentially recorded and metabolically inert once formed. Additionally, vibrissae are grown in utero, potentially offering indirect inference on maternal diet. However, diet reconstruction using isotopic techniques requires a priori knowledge of trophic enrichment factors (TEFs), which can vary relative to diet quality and among animal species. In this study, we provide new TEF estimates for (1) maternal relative to pup vibrissae during both gestation and nursing and (2) adult vibrissae relative to a complex diet. Further, we refine vibrissa−milk TEFs based on an additional 76 animals with an age distribution ranging from 1 to 20 mo. Mother−pup vibrissae TEF values during gestation and nursing were near zero for δ13C and averaged 0.8 and 1.6‰, respectively, for δ15N. In contrast, vibrissa− fish/invertebrate TEFs averaged 3.3 (± 0.3 SD) and 3.7‰ (±0.3) for lipid-free δ13C and δ15N, respectively. Average lipid-free δ13C and δ15N vibrissa−milk TEFs were 2.5 (±0.9) and 1.8‰ (±0.8), respectively, and did not differ among metapopulations. Empirically determined TEFs are critical for accurate retrospective diet modeling, particularly for evaluating the hypothesis of nutritional deficiency contributing to the lack of Steller sea lion population recovery in some regions of Alaska.
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Identification of prey captures in Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted accelerometers: Field validation with animal-borne video cameras.
Volpov, B.L., A.J. Hoskins, B. Battaile, M. Viviant, K.E. Wheatley, G.J. Marshall, K. Abernathy and J.P.Y. Arnould. 2015.
PloS One Vol 10(6): e0128789
abstract
This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, stingray) or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate) on individual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP) rate ranged from 15-67% individually in the testing subset, and 26-59% averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration variance did not always equate to an individual prey item. The results of the present study indicate that head-mounted accelerometers provide a complementary tool for investigating foraging behaviour in pinnipeds, but that detection and FP correction factors need to be applied for reliable field application.

keywords     Arctocephalus pusillus doriferus, accelerometer, prey capture success, foraging behavior, foraging success, pinniped
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2012
 
Mechanical reliability of devices subdermally implanted into the young of long lived and endangered wildlife.
Hori, B., R.J. Petrell, G. Fernlund and A.W. Trites. 2012.
Journal of Materials Engineering and Performance. 21:1924-1931.
abstract
Service data does not exist for the strength of enclosures for subdermally implanted biotelemetry devices intended for young wild animals. Developing adequate tests especially for implants intended for endangered species is difficult due to the very limited availability of live animals and cadaverous tissue, ethical concerns about using them, and high enclosure costs. In this research, these limitations were overcome by taking a conservative approach to design and testing. Reliability tests were developed and performed to establish the likelihood that a thin subdermally and cranially implanted alumina enclosure would fail due to typical external forces related to diving, fights, and falls over the expected 30-year life time of sea lions. Cyclic fatigue tests indicative of deep dives performed out of tissue and at the 90% reliability level indicated no failure after 70,000 stress cycles at stresses of approximately 15 MPa; dynamic fatigue tests indicated a 5% probability of failure at 250 MPa; and puncture tests indicative of fight bites showed a 5% probability of failure at 1500 N. These values were far outside of what the animals might expect to encounter in real life. On the other hand, the response of the enclosure to impact outside of the tissue was failure at a mean energy level of 6.7 J. Modeling results predict that head impacts due to trampling by fighting sea lion males and falls over 1 m onto a rocky ledge typical of haul out environments would likely fracture an infant‚s head as well as the implant. The device can be implanted under an impact absorbing 1 cm blubber layer for extra protection. More service data for enclosures can be made more available despite limited availability of test animals if a conservative approach to testing is taken.

keywords     alumina, biomaterials, biotelemetry, mechanical testing, Sea Lion, structural ceramics
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2011
 
Environment and feeding change the ability of heart rate to predict metabolism in resting Steller sea lions (Eumetopias jubatus).
Young, B. L., D.A.S. Rosen, M. Haulena, A. G. Hindle and A.W. Trites. 2011.
Journal of Comparative Physiology-B 118:105-116.
abstract
The ability to use heart rate (fh) to predict oxygen consumption rates (VO2) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established fh:VO2 relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed whether fh could accurately predict VO2 in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations to describe the fh:VO2 relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh:VO2 relationship on land. However, Steller sea lions in water displayed a different fh:VO2 relationship after consuming a 4 kg meal compared to the fasting condition. Incorporating comparable published fh:VO2 data from Steller sea lions showed a distinct effect of feeding after a 6 kg meal. Ultimately, our study illustrated that both feeding and physical environment are statistically relevant when deriving VO2 from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current bioenergetic models with data gathered using these predictive fh:VO2 equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological, behavioral, and environmental states.
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2010
 
Prey capture attempts can be detected in Steller sea lions and other marine predators using accelerometers.
Viviant, M., A.W. Trites, D.A.S. Rosen, P. Monestiez and C. Guinet. 2010.
Polar Biology 33:713-719.
abstract
We attached accelerometers to the head and jaw of a Steller sea lion (Eumetopias jubatus) to determine whether feeding attempts in a controlled setting could be quantified by acceleration features characteristic of head and jaw movements. Most of the 19 experimental feeding events that occurred during the 51 dives recorded resulted in specific acceleration patterns that were clearly distinguishable from swimming accelerations. The differential acceleration between the head-mounted and jaw-mounted accelerometers detected 84% of prey captures on the vertical axis and 89% on the horizontal axis. However, the jaw-mounted accelerometer alone proved to be equally effective at detecting prey capture attempts. Acceleration along the horizontal (surge)-axis appeared to be particularly efficient in detecting prey captures, and suggests that a single accelerometer placed under the jaw of a pinniped is a promising and easily implemented means of recording prey capture attempts.
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Non-invasive measurement of thyroid hormone in feces of a diverse array of avian and mammalian species.
Wasser, S. K., J. C. Azkarate, R. K. Booth, L. Hayward, K. Hunt, K. Ayres, C. Vynne and K Gobush. 2010.
General and Comparative Endocrinology 168:1-7.
abstract
We developed and validated a non-invasive thyroid hormone measure in feces of a diverse array of birds and mammals. An I-131 radiolabel ingestion study in domestic dogs coupled with High Pressure Liquid Chromatography (HPLC) analysis, showed that peak excretion in feces occurred at 24-48 h post-ingestion, with I-131-labelled thyroid hormone metabolites excreted primarily as triiodothyronine (T3) and relatively little thyroxine (T4), at all excretion times examined. The immunoreactive T3 profile across these same HPLC fractions closely corresponded with the I-131 radioactive profile. By contrast, the T4 immuno-reactive profile was disproportionately high, suggesting that T4 excretion included a high percentage of T4 stores. We optimized and validated T3 and T4 extraction and assay methods in feces of wild northern spotted owls, African elephants, howler monkeys, caribou, moose, wolf, maned wolf, killer whales and Steller sea lions. We explained 99% of the variance in high and low T3 concentrations derived from species-specific sample pools, after controlling for species and the various extraction methods tested. Fecal T3 reflected nutritional deficits in two male and three female howler monkeys held in captivity for translocation from a highly degraded habitat. Results suggest that thyroid hormone can be accurately and reliably measured in feces, providing important indices for environmental physiology across a diverse array of birds and mammals.
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2009
 
Evaluation of a new radio frequency identification tag for subdermal implantation.
Azad, F. 2009.
MSc thesis, University of British Columbia, Vancouver, B.C. 146 pages
abstract
This research was aimed at examining the readiness of a prototype implantable tag of dimensions 39 mm x 24 mm x 4.1 mm designed to operate at 915 MHz for monitoring the movement of young sea lions and seals. Several issues had to be resolved, and they include developing and testing a suitable communication protocol between the base station and tag, and way of providing power to the tag. Engineering issues related to longevity of the implantable tag, and power radiated by the loop antenna of the implantable tag in its alumina enclosure, under skin and under the fat underlying the skin, also, had to be addressed. Finally issues related to how data from the tag could be best recorded at haul outs and rookeries were examined. A working prototype of an implantable tag was obtained by reducing the height of the loop antenna by 2 mm and changing the capacitor values in the matching network to 0.2 pF. Field tests using a base station that accepted signal strengths up to -60 dBm indicated that the tag‚s range was a maximum of 500 m when it was operated out of a body at a data rate of 1 kbps and the height of the base station antenna was more than 5 m. When the prototype was implanted within its alumina housing under the skin of cavernous tissue, the range of the device fell to an acceptable 180 m. A lifetime model indicated that the longevity of the tag would meet the three year target if it were to be operated using a data rate of 1 kbps, transmission interval of 15 min, packet size of 104 bits and battery capacity of 72 mAh. The lifetime model was verified at the same temperature as a sea lion. A link budget model was developed for the prototype tag, and was used to estimate the performance of the implantable in the sea lion‚s environment.
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2007
 
Elemental analysis of otoliths and eye lenses in the assessment of Steller sea lion diets.
Ferenbaugh, J. 2007.
PhD, Texas Tech University. 135 pages
abstract
Steller sea lions (Eumetopias jubatus) have historically ranged along the North Pacific Rim from the coast of California to Japan, but the population has dramatically declined since the 1960s. Research has indicated that nutritional stress is likely to be the main cause of the decline. Scat analysis is the preferred technique for dietary analysis of Steller sea lions, and fish otoliths and eye lenses are routinely recovered from pinniped scat. Fisheries scientists use elemental analysis of otoliths and eye lenses to provide information on fish biology, but marine mammalogists have not incorporated this technique to study prey fish or foraging behavior. In this dissertation, I examined the use of elemental analysis of prey fish otoliths and eye lenses in dietary studies for Steller sea lions. I first examined the use of otoliths as indicators of total body burdens of metal contaminants in the fish. Then, I assessed the effects of Steller sea lion digestion on the microchemistry of otoliths. Third, I examined the microchemistry of fish eye lenses, the effects of digestion on eye lenses, and their potential use in dietary analysis. Concentrations of some metals, such as zinc and barium, in undigested otoliths are significantly correlated with concentrations found in homogenized tissues, but several factors affect this relationship, such as fish species, sampling site on the otolith, and the specific metal being analyzed. The degradation of an otolith in the sea lion digestive tract is also likely to affect correlations between otolith and tissue metal concentrations. Steller sea lion digestion has significant effects on otolith microchemistry. These effects do not prohibit the use of digested otoliths in species determination for dietary analysis, but they may preclude using otoliths recovered from sea lion scat for fish stock separation, determination of foraging locations, and fish life history analyses. Eye lenses appear to be resistant to sea lion digestion, and they form sequential growth layers that can be used to age fish. The fibrous structure of the layers may inhibit symmetrical distributions across the lens for some elements, but the distinct elemental distributions across the lens may be useful in distinguishing fish species, discriminating between fish stocks, and tracking fish movements and spatial locations.
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A study of the loop as a compact antenna.
Lea, A. 2007.
MSc thesis, Simon Fraser University, Burnaby, B.C. 101 pages
abstract
This thesis examines the suitability of the loop antenna for use as a compact radiating element. The derivation of the loop equation is reviewed, and a summary of the significant research on the electrically large loop antenna over the past century is presented. The theoretical radiation efficiency for the electrically large loop is derived. This analysis shows that the radiation efficiency of the loop antenna is drastically improved by increasing the electrical size of the loop. The theoretical input impedance is used to calculate the quality factor and bandwidth of the tuned loop antenna, and a suitable impedance matching technique is presented to attain this bandwidth. Several loop antennas were constructed, and a Wheeler cap was used to measure the radiation efficiency of these antennas. This measured radiation efficiency is shown to agree reasonably well with the theoretically predicted values.
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Link analysis of a prototype wireless implanted tracking tag.
Lea, A., R. Vaughan, W.G. Dunford, R.J. Petrell and A.W and Trites. 2007.
In 20th Canadian Conference on Electrical and Computer Engineering. pp. 920-923.
abstract
A team of researchers from Simon Fraser University and the University of British Columbia have designed and built a prototype implanted wireless tag for monitoring Steller sea lions. This paper reviews the system level RF design aspects, and estimates the RF link range.
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2006
 
Long term soft tissue fixation and mechanical reliability of a ceramic housing for a new radio frequency transmitter.
Hori, B.D. 2006.
University of British Columbia, Vancouver. 200 pages
abstract
This project was focused on the design and suitability of the housing component of a new telemetry device to be implanted into young Steller sea lions. The housings suitability is assessed on its long term performance for stable implantation for lifetimes of up to 30 years. An aluminum oxide ceramic material is selected as the housing material as it meets radio frequency, biocompatibility and strength requirements. The housing design consists of a solid base and porous top surface with an inner cavity for electronics potted in epoxy. Aptness of the design for implantation involved investigating the response of the housing to biological and mechanical factors. Biological response was examined by assessing tissue fixation of porous aluminum oxide. Disc implants (36), with a top porous surface of pore size 32 μm and thicknesses of 0.5 mm and 1.0 mm, were sub-dermally implanted into the backs of young rabbits. Due to surgical complications, 33 tags were inserted under the cutaneous trunci muscle, while the remaining were inserted above it. A favourable tissue reaction was assessed in all cases. All implants migrated with the skin growth a distance of 4.69 ± 1.48cm. Half of the implants moved an additional 1.74 ± 1.93cm caused by a combination of externally applied forces and loose tissue attachment. Loose tissue attachment was a result of implantation into subcutaneous fat tissue and the inability of implant encapsulated tissue in integrating with the fat layers. The response of the housing to me! chanical factors was examined by applying loading conditions (cyclic fatigue, compression, puncture and impact) that simulate what is expected in-service. Implants were able to resist fracture due to compression and puncture while impact suitability is achieved when considering energy absorption by the surrounding tissue. The derived housing design has good potential for future implantation into Steller sea-lions. Further research is required to examine implant fixation and migration in dermal tissue compared to subcutaneous tissue. As the implants will move from the insertion location in growing skin, cranial skin growth patterns should be considered prior to implantation into Steller sea lions.
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Techniques for real-time, active tracking of sea lions.
Lea, M.A., and B. Wilson. 2006.
In A.W. Trites, S. Atkinson, D.P. DeMaster, L.W. Fritz, T.S. Gelatt, L.D. Rea and K. Wynne (eds), Sea Lions of the World. Alaska Sea Grant College Program, University of Alaska, Fairbanks. pp. 235-253.
abstract
The movements of otariids at sea are generally studied by satellite telemetry. At fine scales (1-20km), however, the level of precision provided by this technique (+- mean 1.5-19 km) may be insufficient to accurately reconstruct the track of an individual and/or integrate such movement data with habitat and environmental features. An alternative technique is the boat-based active tracking of individuals by very high frequency (VHF) or acoustic telemetry. By following an individual equipped with transmitters, detailed observations of habitat use, predator occurrence, social context, behavioral state, and prey availability may be integrated to provide a real-time context in which to place the animals? movements. For species such as the Steller sea lion (Eumetopias jubatus), which are difficult to recapture, such techniques enable the collection of much needed contextual information. Here we describe the methods we applied to actively track Steller sea lions. Twenty-o! ne juveniles were captured in southeast Alaska during October 2003 and February 2004. They were fitted with a variety of VHF, satellite, and/or acoustic tags and were tracked through the winter and spring of 2003-2004. The use of ship-based VHF telemetry in conjunction with real time navigation plotting software was highly successful and provided 37 fine-scale tracks of coastal and pelagic sea lion movements covering a total distance of 482 km. Acoustic telemetry techniques were less successful because of the suspected overlap in tag transmission frequency and sea lion hearing. The study represents the first active tracking of a sea lion species, highlighting the high-resolution tracks and contextual behavioral and habitat information that can be obtained using VHF telemetry at sea.
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An approach to improving battery life time in a PV application using high energy density double layer capacitors.
Majaess, D. 2006.
MSc thesis, University of British Columbia, Vancouver, B.C. 151 pages
abstract
An application to monitor Steller sea lions using a sub dermal sensor requires a power supply to provide energy for wildlife monitoring base stations. The base stations are positioned near the habitats of the North Pacific Steller sea lions in isolated coastal areas of North British Columbia and South Alaska. The locations expose the base station to high winds, storms, ice, snow, debris, impacts from ocean waves, salt corrosion, and wide temperature swings. Furthermore, due to the remote distance, there is limited infrastructure; connection to the electrical grid is impossible and installation/maintenance is costly. The project requires a ruggedized, autonomous power supply requiring minimum maintenance and a long operating life. Therefore, the thesis propose a unique power supply design incorporating high energy density double layer capacitors, (ultracapacitors) that extends serviceability and improves immunity to cold comates Finally, the researchers working on the Steller sea lion project have a limited economic budget and require a low cost system that is simple to transport and easy to install. The purpose of this research is to extend the battery‚s service life and improve the base station‚s immunity to cold climates. In this thesis, two methods are used to accomplish the objective. The first undertaking is to extensively research, design and implement high efficient components to minimize battery demand. As a result, the input source, its electronics and the load are well matched for the application. The next task is to incorporate a battery/capacitor bank to store energy. By integrating ultracapacitor technology to create a hybrid energy storage system, the battery cycling is minimized.
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2005
 
The dielectric properties of the cranial skin of five young captive Stellar sea sea lions (Eumetopias jubatus) and a similar number of young domestic pigs (Sus scrofa) and sheep (Ovis aries) between 0.1 and 10 GHz.
Olawale, K.O., R.J. Petrell, D.G. Michelson and A.W. Trites. 2005.
Physiological Measurement 26:626-637.
abstract
To aid in the development of a long-range subcutaneous radio frequency identification tag to monitor the fate sea lion pups, the dielectric properties of the cranial skin of young female otariids, and possible test subjects of similar size and age, or pigs (Sus scrofa) and sheep (Ovis aries)were obtained over a frequency range of 0.1 to 10 GHz at the base of their heads where the tag will be implanted. The resulting curves were similar in shape to adult human skin data, but the values were generally lower. Between ubjects, variations were noted in all the species. Circuitry for the RF-ID tag is being designed to account for antenna detuning as a result of the lossy media or skin and he variation in dielectric properties.

keywords     Keywords: dielectric constant, dielectric loss, skin thickness,
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A novel approach to measuring heat flux in swimming animals.
Willis, K. , Horning, M. 2005.
Journal of Experimental Marine Biology and Ecology 315:147-162.
abstract
We present a design for long-term or removable attachment of heat flux sensors (HFSs) to stationary or swimming animals in water that enables collection of heat flux data on both captive and free-ranging pinnipeds. HFSs were modified to allow for independent, continuous, and long-term or removable attachment to study animals. The design was tested for effects of HFSs and the attachment mechanism on resultant heat flux. Effects were insulative and consistent across water temperatures and flow speeds, resulting in a correction factor of 3.42. This correction factor was applied to all measurements of heat flux from animal experiments to account for the thermal resistance of HFSs and insulative effects of the attachment mechanism. Heat flux and skin temperature data were collected from two captive Steller sea lions (Eumetopias jubatus) as they swam in a large habitat tank over time periods ranging from approximately 4 to 9 min. Of the 72 HFSs deployed using the attachm! ent mechanism, data were successfully retrieved from 70. The HFS attachment mechanism was also used on two wild free-ranging Weddell seals (Leptonychotes weddellii) off Ross Island, Antarctica, for up to 7 days. Heat flux data were retrieved from all eight sensors deployed. These results, along with those from Steller sea lions, suggest that HFSs can be deployed with success on captive and wild animals using the designed attachment mechanism.
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2003
 
Predicting metabolic rate from heart rate for juvenile Steller sea lions Eumetopias jubatus.
McPhee, J.M., D.A.S. Rosen, R.D. Andrews and A.W. Trites. 2003.
Journal of Experimental Biology 206:1941-1951.
abstract
The validity of using heart rate to estimate energy expenditure in free-ranging Steller sea lions Eumetopias jubatus was investigated by establishing whether there is a relationship between heart rate (fH) and oxygen consumption rate (V . O·) in captive sea lions while swimming and resting. Four trained Steller sea lions (2 males and 2 females; mass 87.4–194.4·kg; age 16 months– 3 years) were each equipped with a datalogger and two dorsal subcutaneous electrodes to record electrocardiograms from which fH was calculated. V . O· (measured using open-circuit respirometry) was simultaneously recorded while the previously fasted animals were at rest within an enclosed dry metabolic chamber or while they swam in an enclosed swim mill against water currents of various speeds (0–1.5·m·s –1 ). The mean regression equation describing the relationship between fH (beats·min –1 ) and V . O· (ml·h –1 ·kg –0.60 ) for all four animals was V . O·=(71.3fH±4.3)–(1138.5±369.6) (means ± S.E.M.) (r 2 =0.69, P<0.01). The relationship demonstrated between fH and V . O· while fasting suggests that heart rate can potentially be used to monitor energy consumption in free-ranging Steller sea lions. However, a short-term feeding experiment revealed no significant increase in heart rate following a 6·kg or 12·kg meal to match the observed increase in rate of oxygen consumption. This suggests that heart rate may not accurately reflect energy consumption during digestion events. Additional research should be conducted to further elucidate how the relationship between heart rate and oxygen consumption is affected by such factors as digestive state, stress and age.
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2002
 
Acoustic identification of female Steller sea lions (Eumetopias jubatus).
Campbell, G.S., R.C. Gisiner, D.A. Helweg and L.L. Milette. 2002.
Journal of the Acoustical Society of America. 111:2920-2928.
abstract
Steller sea lion Eumetopias jubatus mothers and pups establish and maintain contact with individually distinctive vocalizations. Our objective was to develop a robust neural network to classify females based on their mother-pup contact calls. We catalogued 573 contact calls from 25 females in 1998 and 1323 calls from 46 females in 1999. From this database, a subset of 26 females with sufficient samples of calls was selected for further study. Each female was identified visually by marking patterns, which provided the verification for acoustic identification. Average logarithmic spectra were extracted for each call, and standardized training and generalization datasets created for the neural network classifier. A family of backpropagation networks was generated to assess relative contribution of spectral input bandwidth, frequency resolution, and network architectural variables to classification accuracy. The network with best overall generalization accuracy 71% used an input representation of 0–3 kHz of bandwidth at 10.77 Hz/bin frequency resolution, and a 2:1 hidden:output layer neural ratio. The network was analyzed to reveal which portions of the call spectra were most influential for identification of each female. Acoustical identification of distinctive female acoustic signatures has several potentially important conservation applications for this endangered species, such as rapid survey of females present on a rookery.
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2001
 
Growth rates of vibrissae of harbor seals (Phoca vitulina) and Steller sea lions (Eumetopias jubatus).
Hirons, A.C., D.M. Schell and D.J. St.Aubin. 2001.
Canadian Journal of Zoology 79:1053-1061.
abstract
Growth rates of vibrissae (whiskers), which act as a temporal record of feeding in harbor seals (Phoca vitulina) and Steller sea lions (Eumetopias jubatus), were estimated using 13 C- and 15 N-labeled glycine followed by stable-isotope analysis. The labeled glycine was incorporated into keratin and served as a temporal marker for growth-rate calculation. One captive harbor seal received two doses 147 days apart, while a second seal received one dose; vibrissae were analyzed after 86 and 154 days. The peak positions indicated that growth began in the fall, continued into spring, but ceased in June, with active growth rates of 0.33 mm/day. Two adult captive Steller sea lions each re-ceived two labeled doses during a 308-day period. After 427 days vibrissae in both sea lions showed two peaks corre-sponding to the markers; growth rates were calculated as 0.05–0.07 mm/day. Growth rates in captive juvenile and wild adult Steller sea lions, 0.10–0.17 mm/day, supported the assumption that major isotopic oscillations in vibrissae of wild sea lions were annual. The multiyear records imply that Steller sea lions retain their vibrissae; harbor seal vibrissae, in contrast, have periods of rapid growth and appear to be shed, at least in part, annually.
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1998
 
Remotely releasable instruments for monitoring the foraging behaviour of pinnipeds.
Andrews, R.D. 1998.
Marine Ecology Progress Series 175:289-294.
abstract
The use of stomach temperature data loggers to record prey ingestion has proven to be very valuable when combined with time-depth recorders and satellite tracking devices in studies of seabird foraging ecology. This paper presents a similar system that will allow biologists to determine the precise timing and location of foraging by pinnipeds. The system includes a stomach temperature transmitter and an animal-mounted instrument package. The instrument package contains a satellite transmitter, for remote tracking of movements, and a data logger, for recording dive depth, swim speed, water temperature, and stomach temperature (made possible by an incorporated telemetry receiver). The instrument package can be remotely released upon command to allow data recovery without animal recapture. The system was tested on 6 Steller sea lions Eumetopias jubatus in Southeast Alaska and found to be a powerful tool for quantifying foraging behaviour, although some suggestions for improvement are presented.

keywords     swimming, telemetry, foraging, food, Steller sea lion
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1994
 
Final report on an investigation of image processing techniques for the problem of automatic counting of sea lions from aerial video.
Gosine, R.G. and L. Gamage. 1994.
University of British Columbia, Industrial Automation Laboratory, Department of Mechanical Engineering, 2324 Main Mall, Vancouver, B.C. V6T 1Z4, Vancouver, B.C. V6T 1Z4.
abstract
A coalition of North Pacific fishing industry groups has been working to address pending restrictions on the Gulf of Alaska and Eastern Bering Sea commercial fishery as a result of possible decline of the Steller sea lion population. A component of the resea.rch into this problem is the investigataioonf techniques to automate the counting of sea lions from aerial video of the Alaska coast. Currently, sea-lion counts are completed mmually from 35mm slides, and there is some concern regarding t,he accuracy and repeatabilityof such an approach. It is proposed that computer-assisted counting from video tape or digitised slides (CDROM) could provide a better alternative to manual counting in terms of improved spatial coverage, improved reliability/consistency and reduced labour costs.
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