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At the onset of this project in 2001, one of the leading hypotheses for the historic and continuing decline of Steller sea lions in the Aleutian Islands (AI) and Gulf of Alaska (GoA), was a decrease in juvenile survival by 10 - 20% (York 1994, Pascual & Adkison 1994, York et al. 1996, Gerber & Van Blaricom 2001, see also NRC 2003, Holmes & York 2003, Eberhardt et al. 2005, NMFS 2008). Nutritional stress related to a reduced juvenile foraging efficiency had been hypothesized as one possible cause for reduced juvenile survival, though some authors had later proposed predation by killer whales as a major contributor to pup and juvenile mortality (see Springer et al. 2003, Fritz & Hinckley 2005, Trites et al. 2007, Atkinson et al. 2008). The hypothesized reduction in juvenile survival, however, was derived from a model based on a Leslie population matrix (York 1994). This matrix was in turn based on observed rates of decline, observed changes in average age of adult females, and estimates of age-specific fecundity. The proposed top-down effects from predation were similarly based on indirect evidence, rather than a direct quantification of predation on juvenile sea lions (Springer et al. 2003). The hypothesized reduction in juvenile survival, resulting in a reduced recruitment into the reproductively active rookery population, has been used to focus investigative efforts relating to the Steller sea lion decline primarily on juvenile animals (NRC 2003; see NMFS 2008). More recently, modeling efforts have been used to suggest a decline in natality, and more specifically in female fecundity as a possible major factor in driving current population trajectories, during a period when the rate of decline has slowed when averaged for the entire western DPS (Holmes et al. 2007). It is unclear whether the postulated recent decline in natality is driven by bottom-up effects (i.e. nutritional stress) or forcing neutral factors (i.e. effects of pollutants on fertility), or possibly a result of changing sea lion demographics: a shift towards a larger proportion of older animals has been suggested through modeling efforts. Though no data on age-specific fecundity exists for Steller sea lions, extant studies on other otariid species have shown a decline in natality with parity in older females (Lunn et al. 1994, Beauplet et al. 2006). Thus, the postulated decline in current natality could be driven in part by formerly high levels of juvenile mortality, through reduced recruitment. Determining juvenile survival rates, and specific causes of mortality, therefore remains of high importance in determining forcing of past and present Steller sea lion population trajectories.
Mortality figures are key indicators of future population trends, and are crucial data for the management of endangered species and those potentially exposed to detrimental ecological and anthropogenic environmental changes, or climate related regime shifts (Gerrodette 1987, Barker 1997, Schwarz 2001). In addition, data on individual survivorship is needed to assess the efficacy of programs designed to mitigate the impact of such changes and shifts (NMFS 2008). Survival of juvenile animals is bound to impact recruitment and thus reproductive output of rookeries (Gerber & Van Blaricom 2001, Holmes & York 2003, Holmes et al 2007). On a population level, survival figures are integrators over several possible proximate effects that could contribute to the population decline, such as disease and pollution, predation as well as a reduction in foraging efficiency due to changes in prey abundance and/or quality. Thus, survival figures can be utilized to monitor a population, irrespective of which proximate causes contribute (with some exceptions) to the population decline. Furthermore, mortality rates are expected to reflect predation, nutritional stress or other proximate factors detrimental to a population several years before ultimate effects such as reduced pupping rates / pup counts become apparent (the latter presumably through a drop in recruitment).
To measure juvenile survival rates, and provide information on actual causes of mortality, we specifically developed the implantable Life History Transmitter, or LHX tag (Horning & Hill 2005). The LHX tag is a modified mortality transmitter. Mortality transmitters are a well established technique to determine survival rates in wild animals. Our approach is new in that conventional mortality transmitters are externally attached and typically utilize VHF radio transmission. Several problems are associated with such devices: on pinnipeds and seabirds, external units do not remain attached beyond the annual molt, limiting tracking to a maximum of one year. Battery-size and -capacity constraints also limit the life span of such units. Implanting mortality transmitters avoids long-term attachment problems. Implanted telemetry devices have been successfully used on a wide range of marine endotherms, and circumvent external attachment limitations. However, reception range and thus area coverage from VHF implants is reduced compared to external devices. Transmitting life span is still limited to 2-3 years.
Our solution to extend coverage range for mortality transmitters is the use of satellite-linked devices. Satellite-linked data loggers, using the Service ARGOS system aboard NOAA satellites for obtaining location fixes and transmission of stored data have been successfully and extensively used on oceanic vertebrates. At present however, transmission to a satellite from implanted devices is not feasible. LHX tags circumvent this problem, by continuously monitoring up to five built-in sensors to determine the state of an instrumented animal, then store time and date of death in memory, once this is detected. Subsequently, LHX tags transmit this and other previously stored data to an orbiting ARGOS satellite, once the positively buoyant device has been released from the decomposing or partially consumed body. Through the absence of any transmissions, until after death and release of the device, battery life is greatly extended to well beyond five years, typically 8-10 years, or even more. One complication resulting from the reliance on end-of-life transmissions for all data recovery is the inability to transmit periodic ‘alive’ signals that are used in conventional mortality transmitters to verify proper transmitter operations. This necessitates accurately determining tag failure rates. To determine failure rates, dual LHX tags are deployed in implanted animals. In addition to increasing data recovery likelihood, the ratio of single to dual tag returns will allow the estimation of tag failure rates.
LHX tags allow the application of new experimental paradigms, by analyzing differences between survivors and non-survivors, rather than through the application of the classic regional comparison between stable and declining DPSs. The regional comparison is based on different likelihoods of sampling survivors versus on-survivors, whereas the LHX design allows for a direct comparison between such groups. This may lead to reduced sample size requirements for the testing of certain hypotheses.
A reduction in juvenile Steller sea lion (Eumetopias jubatus) survival, possibly linked to reduced foraging efficiency and increased nutritional stress, or high levels of predation by killer whales (Orcinus orca), has been hypothesized to contribute to the continuing decline of this mesopredator in the North Pacific and Bering Sea ecosystems. To date, this hypothesis has not been tested. As a central part of the Steller LHX Project, we will determine survival rates of juvenile Steller sea lions, using long-term, implanted satellite-linked life history transmitters. For the first time, this project will provide a direct measure of predation and deliver information on causes of individual animal mortality.
In addition, we are collecting longitudinal, multi-year dive effort data from individual, free-ranging marine mammals. In a new experimental paradigm, we will directly assess the influences of proximate effects such as condition, health, pollutants and immuno-competence on survival of individual sea lions. This approach represents a departure from the classic regional comparison paradigm, comparing stable and declining populations. The LHX project is based on the development and application of a new generation of life-long archival satellite transmitters, the Life History Transmitter. LHX transmitters were developed in collaboration with Wildlife Computers, and are described in:
Horning, M. and R.D. Hill. 2005. Designing an archival satellite transmitter for life-long deployments on oceanic vertebrates: The Life History Transmitter. IEEE Journal of Oceanic Engineering. 30: 807-817.
The implantation of LHX transmitters is described in:
Horning, M., M. Haulena, P.A. Tuomi and J.E. Mellish. 2008. Intraperitoneal implantation of life-long telemetry transmitters in otariids. BMC Veterinary Research. 4:51. [pdf]
For additional publications from this project, please check the update section of these pages.
This project is directed by the Pinniped Ecology Applied Research Laboratory in cooperation with the Alaska SeaLife Center, the National Marine Mammal Laboratory (NMFS), and the Alaska Department of Fish & Game.
The LHX Project has received support from:
North Pacific Marine Research Board NOAA's National Marine Fisheries Service Pollock Conservation Cooperative Research Center The Alaska SeaLife Center
This research is carried out under NMFS Permits #881-1668; 881-1890, 1034-1685 and 1034-1887.
Data on survivorship is crucial for the effective monitoring and management of many species of marine endotherms, in particular endangered species and those potentially exposed to detrimental ecological and anthropogenic environmental changes, or climate related regime shifts. In addition, data on individual survivorship is needed to assess the efficacy of programs designed to ameliorate the impact of such changes and shifts.
Due to wide dispersal or migrations, and the open ocean ranging of marine endotherms, such data is extremely difficult to obtain. Survival of free-ranging animals is typically assessed through mark and recapture studies, or through the use of mortality transmitters. Mark and recapture studies are expensive and logistically complex to conduct, and highly disruptive in the rookeries of shy species such as Stellers. In addition, such studies cannot directly distinguish between dispersal / emigration, and mortality. Conventional mortality transmitters are externally attached VHF transmitters. Several problems are associated with such devices: on pinnipeds and seabirds, external units typically do not remain attached beyond the annual molt, limiting tracking to a maximum of one year. Battery-size and -capacity constraints also limit the life span of such units. Implanting mortality transmitters would avoid such problems. Implanted devices have been successfully used on a wide range of marine endotherms. However, reception range and thus area coverage from implants is reduced compared to external devices. Transmitting life span is still limited to 2-3 years.
A possible solution to extend coverage range for mortality transmitters is the use of satellite-linked devices. Satellite-linked data loggers, using theArgos system aboard NOAA satellites (accessible through Service Argos) for obtaining location fixes and transmission of stored data have been successfully and extensively used on oceanic vertebrates. At present however, transmission to a satellite from implanted devices is not feasible (Horning et al. 1999).
To circumvent this problem, the concept of implanted, delayed transmission, Satellite-linked Life History Transmitters (LHX) was developed in the Laboratory for Applied Biotelemetry & Biotechnology at Texas A&M University. Under funding from the North Pacific Marine Research Program, LHX devices are being developed by Wildlife Computers, in cooperation with our lab. The LHX units consist of an ARGOS-compatible transmitter, a microprocessor driven controller, and five sensors for pressure, temperature, motion, light-level and conductivity. These LHX devices continuously monitor these built-in sensors to establish death of an instrumented animal, then store time and date of death in memory. Subsequently, the LHX devices will transmit this data to an orbiting ARGOS satellite, once the positively buoyant device has been released from the decomposing or consumed body. Through the absence of any transmissions, until after death, battery life is greatly extended to well beyond five years.
One of the problems associated with this concept of "delayed-transmission" satellite-linked mortality transmitters, is the impossibility of periodically transmitting an 'alive' signal, which is traditionally used to verify continued operation of the transmitter, and to guarantee the quality of the data obtained. In the absence of such transmissions of 'alive' signals, the accurate assessment of the transmission failure rate of implanted mortality transmitters becomes crucial. Mortality data obtained in form of positive 'deceased' signals needs to be corrected by estimates of failure rates. In the LHX project, the use of dual redundant implants is one of several approaches used to quantitatively assess instrument and transmission failure rates. Cumulative system failure rates are determined by comparing the ratio of dual versus single hits from two redundant LHX devices implanted into each study animal.
A required step before we can consider implanting LHX devices into free-ranging Steller sea lions - a declining and endangered species - is the validation of the LHX concept under highly controlled conditions, on captive animals.
This validation will consist of two steps:
We will accomplish these validations through a combination of tests. We will initially test LHX devices on carcasses of California sea lions, to ascertain technical functionality and operation of the units. Next, we will impant dual redundant LHX devices into rehabilitated California sea lions at The Marine Mammal Center, for the next five years. (TMMC) at Sausalito, CA - a major marine mammal rehabilitation organization. TMMC is highly interested in the LHX project. Our technology - if validated - will allow rehabilitation centers such as TMMC to accurately assess the success rates of their rehab & release programs, through long-term post-release tracking and survival monitoring of rehabilitated animals. After implantation of two redundant LHX devices into rehabilitated California sea lions, the animals will be kept under close observation for periods from two to eight weeks, and will then be released along the California coast. We will then monitor for a signal from the LHX implants, through.
The concept of a satellite-linked, delayed transmission mortality tag represents a new experimental paradigm in the study of ocean-ranging marine endotherms. Through the use of LHX technology, we can directly assess effects of a large number of proximate causes on the survival of individual animals. For the testing of hypotheses pertinent to proximate causes of Steller sea lion decline, our new paradigm will offer a greater resolution, and will be able to detect smaller effects, than the classic regional comparison between stable and declining populations. In the LHX project, we expect to test predictive powers on future survival, of parameters that can be measured in juvenile animals when they are most accessible, prior to weaning. This could become an important tool in predicting future population trends several years before these trends become apparent at the census level. The LHX project will likely enhance future capabilities of modeling the response of an apex predator population to a variety of environmental changes - whether manmade or associated with non-anthropogenic environmental variability. In providing - for the first time in a marine mammal - long-term, multi-year dive effort data, LHX technology will provide the means to relate short-term (seasonal) and long-term (inter annual, ontogenetic) variability in survival and foraging behavior to environmental variability along multiple temporal and spatial scales. In addition, LHX technology will be a valuable tool for long-term population monitoring, when applied to other age groups including adults. The LHX project follows specific recommendations by the Bering Sea Ecosystem Research Plan Draft (BSERP 1998), and several Steller Sea Lion Recovery Team Research Peer Review Workshops (Didier, ed. 1997a,b; Springer et al. 1999; Williams et al 1999).
This study will address these primary questions:
The specific objectives of the LHX Project are to:
Six more juveniles with LHX tag implants were successfully released from the Alaska SeaLife Center in November 2008. This brings the total number of juvenile Steller sea lions released with implants to 21 animals since November 2005. To date, we have received returns from 5 sea lions. Check back with us soon for updates on what happened to these five animals in the next episode of "Marine Mammal CSI from Space."
Here is the most recent list of publications and reports on the LHX project:
August 21st, 2008
Since November 2005, a total of 15 Steller sea lions have been successfully released with LHX tag implants.
We have received the first data returns from several LHX transmitters. While this is sad news - it means that animals have died - it confirms the functionality of LHX transmitters for uplinking post-mortem data from monitored sea lions. Check back with us soon for updates on "Marine Mammal CSI from Space" with new publications and the first results from our LHX tag returns.
January 31st, 2008 Here is a summary of publications resulting from or related to the LHX project:
October 31st, 2007 Five juvenile Steller sea lions that had previously received dual LHX tag implants were successfully released into the wild and are currently being tracked via external satellite transmitters.
September 14th, 2007
Five more juvenile Steller sea lions received dual LHX tag implants in early September, at the Alaska Sea Life Center.
April 28th, 2006
On April 19th, four juvenile Steller sea lions were released in Resurrection Bay, AK, that received dual Life History Transmitter (LHX) implants. The animals are now being tracked via externally attached satellite transmitters. This brings the number of Steller sea lions that have been successfully released with LHX tag implants, to six. The external transmitters on the first two implanted animals have recently fallen off, though the animals have been resighted since.
February 10th, 2006
As of February 10th, 2006, we are still receiving uplinks via the ARGOS system, from the external satellite transmitters carried by the three most recently released juvenile Steller sea lions, including two animals with implanted Life History Transmitters. Almost three months have passed since the release of the animals, and about four months since the implant procedures.
December 22nd, 2005
We are continuing to track the three juvenile Steller sea lions that were released from the Alaska Sea Life Center via the external satellite transmitters. Two of these animals were the first ever Steller sea lions that received Life History Transmitter implants prior to release. As of December 22nd all three animals are doing well, one month after their release, and almost 2.5 and 3 months after receiving the LHX implants, respectively.
The following contributions about aspects of the LHX project and the Transient Juvenile Project were given at the XVI Biennial Conference on the Biology of Marine Mammals held Dec. 12-16, 2005 at San Diego, CA.
December 1st, 2005
We have reached an exciting new milestone in the LHX project:
The two very first juvenile Steller sea lions with Life History Transmitter implants were successfully released back into the wild in Resurrection Bay, Alaska, on November 22nd, 2005. The image below shows the two animals with LHX tags swimming in the water immediately after their release. On one of the two animals, the external satellite transmitter that is used for post-release tracking is visible. A third juvenile that had not received an LHX implant, was also released at that time.
This research is being conducted under permit #881-1668-05 by the NMFS.
April 5th, 2005
We are continuing to monitor all LHX transmittters deployed in 2004. To date, we have not received any signals from any of the six transmitters released in four animals, and we are assuming that these animals are continuing to do well.
We will be giving the following two presentations at conferences, on aspects of the LHX project:
October 18th, 2004
On October 13th, Eisenhower, the second rehabilitated California sea lion to have received dual Life History Transmitter implants at The Marine Mammal Center, was released into the Ocean after completing the mandatory 6-week post-procedure observation period. The release went well, and 'Howie' is now being tracked via an externally attached satellite data transmitter. This successful release brings the total number of rehabilitated sea lions with Life History Transmitters that have been released, to four. The first two animals were released with single LHX tag implants, the second two with dual LHX tag implants. (October 18th, 2004)
September 30th, 2004
On September 16th, D-Day was released into the Pacific Ocean, and is now the first rehabilitated California sea lion to be released into the wild with dual Life History Transmitter implants. Eisenhower as the second animal to have received dual implants is currently undergoing the mandatory 6 week observation period following the procedure, and is continuing to do well.
September 1st, 2004
As of Sept. 1st we have implanted LHX tags into four animals, Rory and Pia both received single tag implants. Both were released and tracked with external tags after their release. They were diving well for as long as their external tags lasted. As is typical for such external tags, we were able to track them for one month or less, one reason for developing the LHX tags! D-Day and Eisenhower both received dual LHX tag implants. Both are still at The Marine Mammal Center for their extended post-procedure observation period, and both are continuing to do well. They will eventually be released just like Rory and Pia, and will be tracked by means of external satellite tracking units. We are of course monitoring the ARGOS frequencies of the LHX tags for Rory and Pia, and will do the same for all other animals that will be released.
August 26th, 2004
On August 26th Eisenhower was the second animal to receive two LHX tag implants. His procedure also went very well, and he is recovering well.
July 12th, 2004
Pia was released on July 9th. Pia is the second animal to carry a Life History Transmitter in the wild. In the image below, you can see Pia carrying an external Satellite-linked Data Recorder. This instrument allows us to obtain data about the diving behavior and locations of the animal for the next 4 - 8 weeks.
July 7th, 2004
On July 7th, D-Day was the first animal to receive two LHX implants. D-Day is a large male California sea lion of about 195 kg. The procedure went well, and D-Day has recovered very well. He is currently at The Marine Mammal Center for the extended post-procedure observation period mandated by our MMPA permit. The image below shows an x-ray radiograph of the two implants, taken after the procedure. One can see the vertebral column, the last few ribs on the left side of the image, the hip and two femurs towards the right, and the two LHX tags, of a size comparable to two vertebrae each:
July 1st, 2004:
Rory was released on June 29th, and is once again roaming the oceans. She is the first animal to carry a Life History Transmitter in the wild.
May 25th, 2004:
On May 25th, we performed the second implant procedure at The Marine Mammal Center, on a larger male California sea lion from the rehabilitation program - Pia. The image below shows a radiograph of the intraperitoneally implanted transmitter, taken at the end of the implant procedure. Pia is also doing very well.
May 11th, 2004:
On May 11th, we performed the first ever LHX tag implant procedure on Rory, a female California sea lion that had recently undergone a rehabilitation program for stranded animals at The Marine Mammal Center, and under funding from the Pollock Conservation Cooperative Research Center. The image below shows Rory one week after the procedure. She is continuing to do very well.
In 2001 under funding from the North Pacific Marine Research Program, we completed the development of the first generation LHX tags at Wildlife Computers. These early standard LHX tags consisted of the Wildlife Computers controller board, piggybacked onto an Argos-compatible transmitter board. We used a helical antenna instead of the standard whip antenna, to reduce the size of the LHX tag. This first functional transmitter operated at a power output level of 1 Watt. The helical antenna intrinsically has a reduced efficiency compared to the straight whip. This results in an actual transmission power comparable to a 1/2 Watt transmitter with a straight whip antenna. A single large battery and a float with a large waist that served as the antenna cover completed the package.
The composite image below shows the very first functional prototype LHX tag housed in a positively buoyant package in the upper part of the image, above a pocket knife for size comparison.
This first functional tag was used for extensive simulation and uplink testing, but was still too large to use in an animal. In addition, our goal was to produce a different shape more suitable for implantation. We accomplished that in 2003 and now have a fully functional LHX tag that meets all our size, shape and design criteria, and has passed all simulation testing. This tag is shown in the above image below the pocket knife, but to a different scale than the first functional tag. The actual size of our final tag design is outlined above the first functional tag, for comparison. While the first functional prototype was still over 190mm long and 50mm in diameter, the final design of the LHX tag is housed in a significantly smaller package of 42mm diameter and 120mm in length. This tag has a single integrated controller and transmitter board, a different type of helical antenna, two batteries, and the floatation properties are a function of the entire tag. The tag is coated in a class VI USP certified physiological resin compatible with implantation.
For the health assessments that are part of the LHX project, we are using our new portable hematology and clinical chemistry analyzers to collect baseline data on blood values for healthy animals. These same units will later be used in the field to determine the health status of juvenile Steller sea lions that will receive LHX implants, based on small blood samples.
The unit shown in the image below is a VetScan HMT hematology analyzer by Abaxis. The unit determines a large variety of hematological parameters including hematocrit, RBC count, hemoglobin concentrations and many more from a 10-microliter sample of whole blood, in just a few minutes. The unit uses a separate package of test reagents in the cardboard box to the left.
In addition to the HMT hematology analyzer, we use a small, portable VetScan Clinical Chemistry Analyzer. This machine uses a 90 micro-liter sample of whole blood to determine up to 29 different parameters such as glucose, BUN (Blood Urea Nitrogen) and bilirubin, in just a few minutes.
To determine the thickness of the subcutaneous blubber layer and body condition of the sea lions, we use a portable, high resolution ultrasound imaging system by SonoSite:
One of the images recorded by the SonoSite 180. This is a scan of Sugar, an 8 year old female Steller sea lion at the Alaska Sea Life Center at Seward, AK. At the top of the image is the skin with subdermal tissue. The blubber layer is highlighted by the dotted white line, and in this image is about 17 mm thick. Embedded in the blubber layer are strands of muscle tissue. This makes the application of non-visual ultrasonic blubber thickness probes such as the ScanProbe problematic, a visual control of the blubber layer delivers more reliable results.