44 research outputs found
pitch.mov
No full textThis is an animation of the Pitch Metric that was used to identify search events for Hawaiian monk seals. The animation shows pitch (bottom figure) for one complete
dive with concurrent dive depth (middle) and video footage (top). Video
footage shows seal RW02 foraging off the coast of Kauai. The orange line across
the pitch figure is our threshold for identifying search events (70 degrees). Time is along
the X axis in both figures with depth and pitch on the Y axes, respectively
Integrating Multiple Technologies to Understand the Foraging Behavior and Habitat Use of Monk Seals in the Main Hawaiian Islands
No full textHawaiian monk seal abundance is currently declining by about 4% per year with current population estimates around 1,100 individuals. Although the overall population continues to decline, a small sub-population in the main Hawaiian Islands (MHI) appears to be increasing by roughly 6% per year. Monk seal conservation and recovery efforts in the MHI have been hindered by the perception that seals do not belong there, and that they compete with fisheries and damage coral reefs. Education and outreach efforts describing the actual impact of monk seals in the MHI are currently underway, but we actually know very little about their at-sea behavior, especially in the MHI, even though Hawaiian monk seals have been studied extensively since the 1980s. The central objective of my dissertation was to describe monk seal behavior and develop a baseline for monk seal foraging ecology and habitat use in the MHI. To accomplish this I combined three-axis accelerometers, National Geographic Crittercams, and GPS tags to study monk seal foraging behavior. I instrumented 16 seals between 2010 and 2014 on the islands of Molokai, Kauai, and Oahu and deployed an additional 24 GPS tags without the accelerometer and Crittercam. I recovered each Crittercam/accelerometer package 3-6 days after deployment, resulting in an average of 6.14 hours of video footage per seal. The GPS tags continued to record data for 3-6 months providing long-term summaries of dive and haul-out behavior. Using a Bayesian framework I modeled monk seal behavior and habitat use, and developed a method to identify feeding events from accelerometer data. There was a high level of individual variation in the movements of monk seals, but general descriptions of their behavior were accurate at the population level. On average, foraging trips lasted 0.81 ± 1.38 days and seals traveled 28.45 ± 82.03 km per trip. Most seals began benthic dives shortly after entering the water, with most dives occurring between 20-40 m. I used kernel density estimation to define the 50% (core area) and 95% (home range) utilization distribution for each seal. The median home range and core area size for seals in the MHI was 265.62 km2 and 1,564.56 km2, respectively. The pitch axis of the accelerometer was a reliable metric, with over 70% accuracy, for identifying foraging events for monk seals. Body motion over the course of a dive, and how close the seal was to the seafloor during a dive (dive ratio) were the best predictors of these foraging events. Consequently, dive ratio was used to infer foraging in long-term telemetry records that lacked concurrent accelerometer data. Analysis of these data relative to habitat preferences revealed two distinct movement modes for monk seals in the MHI: near shore and offshore/inter-island. My research developed the first thorough understanding of monk seal movements and habitat use in the MHI and provided insight into the mechanisms contributing to the behavioral variability observed for this species. I hope that a detailed understanding of the foraging behavior of monk seals will provide insight into their true role in the ecosystem and help foster the recovery of this critically endangered species.</p
Open Tag data for Hawaiian monk seals
No full textAccelerometer data collected from Open Tags (Loggerhead Instruments) in the main Hawaiian Islands. Seals were instrumented on the islands of Molokai, Kauai, and Oahu
Fine-scale variability in harbor seal foraging behavior.
No full textUnderstanding the variability of foraging behavior within a population of predators is important for determining their role in the ecosystem and how they may respond to future ecosystem changes. However, such variability has seldom been studied in harbor seals on a fine spatial scale (<30 km). We used a combination of standard and Bayesian generalized linear mixed models to explore how environmental variables influenced the dive behavior of harbor seals. Time-depth recorders were deployed on harbor seals from two haul-out sites in the Salish Sea in 2007 (n = 18) and 2008 (n = 11). Three behavioral bout types were classified from six dive types within each bout; however, one of these bout types was related to haul-out activity and was excluded from analyses. Deep foraging bouts (Type I) were the predominant type used throughout the study; however, variation in the use of bout types was observed relative to haul-out site, season, sex, and light (day/night). The proportional use of Type I and Type II (shallow foraging/traveling) bouts differed dramatically between haul-out sites, seasons, sexes, and whether it was day or night; individual variability between seals also contributed to the observed differences. We hypothesize that this variation in dive behavior was related to habitat or prey specialization by seals from different haul-out sites, or individual variability between seals in the study area. The results highlight the potential influence of habitat and specialization on the foraging behavior of harbor seals, and may help explain the variability in diet that is observed between different haul-out site groups in this population
Movement and Corresponding Environmental Data for monk seal dives
No full textAccelerometer data, per dive, collected for Hawaiian monk seals in the main Hawaiian Islands. A GPS location for each dive was used to extract environmental data
Animation of the pitch metric to identify search events for Hawaiian monk seals in the main Hawaiian Islands
No full textThis is an animation of the Pitch Metric that was used to identify search events for Hawaiian monk seals. The animation shows pitch (bottom figure) for one complete dive with concurrent dive depth (middle) and video footage (top). Video footage shows seal RW02 foraging off the coast of Kauai. The orange line across the pitch figure is our threshold for identifying search events (70 degrees). Time is along the X axis in both figures with depth and pitch on the Y axes, respectively
Data from: Integrating multiple technologies to understand the foraging behaviour of Hawaiian monk seals
No full textThe objective of this research was to investigate and describe the foraging behaviour of monk seals in the main Hawaiian Islands. Specifically, our goal was to identify a metric to classify foraging behaviour from telemetry instruments. We deployed accelerometers, seal-mounted cameras and GPS tags on six monk seals during 2012–2014 on the islands of Molokai, Kauai and Oahu. We used pitch, calculated from the accelerometer, to identify search events and thus classify foraging dives. A search event and consequent ‘foraging dive’ occurred when the pitch was greater than or equal to 70° at a depth less than or equal to −3 m. By integrating data from the accelerometers with video and GPS, we were able to ground-truth this classification method and identify environmental variables associated with each foraging dive. We used Bayesian logistic regression to identify the variables that influenced search events. Dive depth, body motion (mean overall dynamic body acceleration during the dive) and proximity to the sea floor were the best predictors of search events for these seals. Search events typically occurred on long, deep dives, with more time spent at the bottom (more than 50% bottom time). We can now identify where monk seals are foraging in the main Hawaiian Islands (MHI) and what covariates influence foraging behaviour in this region. This increased understanding will inform management strategies and supplement outreach and recovery efforts
Integrating multiple technologies to understand the foraging behaviour of Hawaiian monk seals
No full textThe objective of this research was to investigate and describe the foraging behaviour of monk seals in the main Hawaiian Islands. Specifically, our goal was to identify a metric to classify foraging behaviour from telemetry instruments. We deployed accelerometers, seal-mounted cameras and GPS tags on six monk seals during 2012–2014 on the islands of Molokai, Kauai and Oahu. We used pitch, calculated from the accelerometer, to identify search events and thus classify foraging dives. A search event and consequent ‘foraging dive’ occurred when the pitch was greater than or equal to 70° at a depth less than or equal to −3 m. By integrating data from the accelerometers with video and GPS, we were able to ground-truth this classification method and identify environmental variables associated with each foraging dive. We used Bayesian logistic regression to identify the variables that influenced search events. Dive depth, body motion (mean overall dynamic body acceleration during the dive) and proximity to the sea floor were the best predictors of search events for these seals. Search events typically occurred on long, deep dives, with more time spent at the bottom (more than 50% bottom time). We can now identify where monk seals are foraging in the main Hawaiian Islands (MHI) and what covariates influence foraging behaviour in this region. This increased understanding will inform management strategies and supplement outreach and recovery efforts.</jats:p
