Posts

Posted on

Autumn movements of fin whales (Balaenoptera physalus) from Svalbard, Norway, revealed by satellite tracking

Lydersen and colleagues set out to investigate fin whales and their migratory paths using satellite tracking. Tags were deployed on 25 fin whales and stayed attached for a range of 6 to 95 days with an average duration of 33. It was found that 10 of the 25 individuals stayed within the study region, and 15 individuals travelled out of the immediate study area and tracks varied among individuals. Environmental variables such as ocean depth, sea surface temperature, and distance to the nearest coast were extracted from geodatabases given the location of the whales. In this case, Lydersen extracted bathymetry data from the ETOPO 1 Arc-Minute global relief data set from the National Geophysical Data Center, NOAA, sea surface temperature from the Extended Reconstructed Sea Surface Temperature (ERSST) v5, and finally distance to the nearest coast from the land file (1:10 m) from www.naturalearthdata.com.

Track maps of whales are an incredible tool in both visualizing and analyzing whale movements. These tracks provide important information on foraging behavior, activity level, and migratory destinations or lack thereof. The locations that satellite tags transmit allow for extraction of environmental variables from a variety of geodatabases, such as those listed above, that can provide further insight into whale behavior and foraging strategies.

Lydersen, C., Vacquié-Garcia, J., Heide-Jørgensen, M.P., Øien, N., Guinet, C. & Kovacs, K.M. (2020) Autumn movements of fin whales (Balaenoptera physalus) from Svalbard, Norway, revealed by satellite tracking. Scientific Reports, 10, 16966.

Posted on

Behavior and social structure of the sperm whales of Dominica, West Indies

This long-term study took place during the years 2005 to 2012 and focused on data collection on Caribbean sperm whales with the goal of general investigation of this understudied population. Through use of photo ID and behavioral observations, social units of sperm whales were identified, and locations of encounters were recorded. Using Spatial Analyst Tools in ArcGIS10, the researchers were able to determine the distance from shore, and from a 100 by100 m resolution bathymetric model (IFREMER), the researchers were able to estimate the depth of ocean that the whales were sighted.

Although this study focused primarily on individual identification through photo ID and determination of social units, this study exemplified the simple yet effective use of GIS to extract pertinent information such as distance from shore and ocean depth from simple lat/long coordinates. My own dataset does not include depth or distance from shore but may benefit from these metrics by providing additional clues to identify potential foraging behavior and prey preferences based on depth of occurrence and location.

Gero, S., Milligan, M., Rinaldi, C., Francis, P., Gordon, J., Carlson, C., Steffen, A., Tyack, P., Evans, P. & Whitehead, H. (2014) Behavior and social structure of the sperm whales of Dominica, West Indies. Marine Mammal Science, 30, 905–922.

Posted on

The Application of GIS and Spatiotemporal Analyses to Investigations of Unusual Marine Mammal Strandings and Mortality Events

This study investigated unusual mortality events (UME) of marine mammals using harbor porpoises as a model. An unusually high number of porpoise strandings within the Pacific Northwest, later classified as a UME, occurred in the years 2007-2008. Upon investigation of the stranded carcasses, location data was taken (lat/long) and a spatiotemporal cluster detection test (Knox test) was performed. The study found interesting patterns when investigating the age class, as there were a higher proportion of stranded calves relative to more mature individuals. This study exemplifies the use of spatiotemporal analyses on marine mammals to study stranding events and tracking of disease and other health related metrics.

Using location data to investigate stranding events can help researchers perform impact assessments of events such as oil spills. With events such as Deepwater Horizon, we may be interested in investigating the spatial patterns of stranded individuals and the populations from which they originate. The ability to analyze location data along with data such as sex and age class could help to understand the geographic patterns in strandings.

Norman, Stephanie A., et al. “The Application of GIS and Spatiotemporal Analyses to Investigations of Unusual Marine Mammal Strandings and Mortality Events.” Marine Mammal Science, vol. 28, no. 3, July 2012, pp. E251–66. DOI.org (Crossref), https://doi.org/10.1111/j.1748-7692.2011.00507.x.

Posted on

Statistical modeling of North Atlantic right whale migration along the mid-Atlantic region of the eastern seaboard of the United States

Many whale species exhibit long migrations during which data collection events become limited, but statistic modeling can help to fill in the gaps of sighting data. Firestone and colleagues created a model to predict the time and location that right whales occur within the eastern US waters. Firestone makes use of the International Comprehensive Ocean–Atmosphere Data Set (ICOADS) which is a publicly available georeference to map traffic intensity and port volume statistics. This data is important in predicting the probability of vessel strikes and entanglements within this region which could pose conservation concerns to this species. This study was able to use this model and subsequent predictions to inform further survey efforts and management regulations to help reduce the likelihood of vessel strikes and entanglements along the right whale migratory corridor.

This study implemented GIS by mapping the ship traffic intensity, as measured by a heat map, overlayed with the right whale migratory corridor. Here we can visually assess the impact that certain shipping corridors may have on whales during certain times of the year. Mapping anthropogenic impacts with wildlife occurrences can help manage global populations, including my own study species in the Gulf of Mexico (GoM). I could use techniques such as this to measure the overlap of the Deepwater Horizon oil spill on the sperm whale population in the GoM.

Firestone, J., Lyons, S.B., Wang, C. & Corbett, J.J. (2008) Statistical modeling of North Atlantic right whale migration along the mid-Atlantic region of the eastern seaboard of the United States. Biological Conservation, 141, 221–232.

Posted on

Diving behavior of sperm whales in relation to behavior of a major prey species, the jumbo squid, in the Gulf of California, Mexico

Sperm whales in the Gulf of California prey heavily upon jumbo squid, which has been verified through stomach content analysis and stable isotope analysis, although sperm whale hunting behavior has remained understudied. Davis and colleagues attached satellite dive recorders to 5 sperm whales and 3 jumbo squid to investigate the diving behavior of these two mesopelagic predators. This study found that sperm whales dive and hunt within the same depth ranges that jumbo squid persist, around 100 to 500 meters deep. Results also indicate that squid may be more susceptible to predation following surfacing events in which they feed, and at depths of greater than 250 meters where oxygen content of the water is decreased.

This study showed the use of geographic data to analyze the predator-prey interactions in a marine environment. Maps within the paper, which show bathymetry layered beneath whale tracks, exemplify the use of GIS software ArcView to show the spatial content of both species within the study region of the Guaymas Basin of Baja California. Annotated maps implemented both spatial and temporal data to show the tracks of the 5 sperm whales over the duration of the study. Although this study did not make use geographic information science, the use of maps and visual context is vital to investigating species behavior and movement trends. Tracks such as these are directly applicable to data I am working with, but at a shorter temporal scale.

Davis, R., Jaquet, N., Gendron, D., Markaida, U., Bazzino, G. & Gilly, W. (2007) Diving behavior of sperm whales in relation to behavior of a major prey species, the jumbo squid, in the Gulf of California, Mexico. Marine Ecology Progress Series, 333, 291–302.