A 8.300Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE
Determining the location of marine mammals at sea is a challenge that must be overcome in order to study many aspects of their behaviour. There are a number of methods that biologists employ to determine marine mammal locations, which include deploying satellite transmitters affixed to animals of interest and boat-based surveys. While these methods have the potential to yield high-quality location data, both are expensive and may disturb the study animals. Using a theodolite from an elevated shore-based station is an alternative method to collect marine mammal location data that is relatively inexpensive, efficient, and non-invasive. Theodolites have been used to study many species of whales and dolphins since 1972.
LGL Limited, one of North America’s leading ecological research consulting companies, currently has two projects that utilize a Sokkia CX total station and Mesa tablet running MAGNET field data collection software to collect and record marine mammal location data. The data logger is key to allowing researchers to collect multiple fixes on moving marine mammals quickly and accurately. In these applications, the CX-105 is run in the reflectorless mode because the targets (i.e., marine mammals) are typically moving, at distances greater than 500 m, and spend little time at the water’s surface. The horizontal and vertical angles measured by the CX-105 are used, along with known locations of a few reference points (a false north and a shoreline point used to determine an accurate elevation of the total station above sea level), to calculate locations of the marine mammals being studied. Calculations account for the earth being an oblate spheroid, and incorporate output from a tidal elevation model (WebTide Tidal Prediction Model (v0.7.1); http://www.bio.gc.ca/ science/research-recherche/ocean/webtide/ index-eng.php) to offset changes in total station elevation with changes in tide level.
The first project to use the CX-105 was initially conducted on the Cape Race Lightstation lands, approximately 160 km south of St. John’s, Newfoundland. LGL is collaborating on this project with researchers from the Alfred-Wegener Institute in Germany (www.awi.de/en.html). One of the objectives is to optimize an automated thermal-infrared (IR) marine mammal detection system, developed by AWI researchers for use in polar waters, for use in the thermal regime off Atlantic Canada.
The first step in this optimization required that locations were determined for all marine mammals sighted by observers scanning the water’s surface using either the naked eye or binoculars from our shore-based station at Cape Race. These sightings were then compared with thermal anomalies detected in data simultaneously collected by a rotating thermal-IR camera. Matches and missed detections were then studied and thermal-IR data were used to modify the detection software. During 30 (often foggy) days in July and August 2014, a total of 1114 fixes were made on marine mammals. The majority of fixes were made on humpback whales, though minke whales and harbour porpoises were also observed.
The next phase of this project involves comparing detections made by visual observers and the newly optimized thermal-IR detection system while aboard a vessel. A total station will not be used for the next phase of the project because keeping the instrument level while at sea is not practical.
The second project that utilized the CX-105 was conducted at the southern end of Milne Inlet on northern Baffin Island in Nunavut. Since 2013, a study team composed of LGL biologists and Inuit observers from nearby communities have spent the ice-free portion of the summer, roughly six weeks from late July to very early September, making observations of narwhals from a cliff-top observation platform perched approximately 215 m above sea level. Narwhals, also known as the "unicorns of the sea" because of the single long tusk possessed by most male narwhals, are the focus of this research because they are an important subsistence resource for local Inuit and it is unknown how narwhals will respond to increasing shipping traffic in the area. The study team uses the CX-105 to record locations of narwhals, vessels, and other marine mammals in the study area. These location data will allow us to describe how the southern portion of the inlet is being used by marine mammals and vessels in general (i.e., by identifying areas commonly used by marine mammals and routes taken by small and large vessel traffic), as well as how narwhal behaviour changes at a finer scale in response to changes in their environment (e.g., tide, sea state, vessel presence).
This finer scale analysis involves using the CX-105 to continuously track a "focal" narwhal, or group of narwhals, for as long as possible (usually less than five minutes because narwhals will dive below the surface or move out of the observable area). Fixes are made at 5-10 second intervals, and the resulting location data are used to calculate metrics that describe the swimming behaviour of the narwhals in terms of speed and linearity of route.
Though a basic theodolite has been a valuable tool in the study of marine mammal behaviour since the early 1970’s, the modern CX series total station and Mesa data logger are vast improvements on earlier applications of this methodology since they allow us to collect a relatively large amount of high-quality data in a very efficient manner. This improved data collection ability allows us, in turn, to address more complex research questions about marine mammals not previously attempted. A key component of LGL Limited’s success is ensuring we conduct environmental research in a scientifically defensible manner–this is in part achieved by using advanced and technically proven equipment like the CX-105 total station.
Heather Smith, Ph.D., is a Senior Marine Ecologist with LGL Limited with expertise in marine mammal studies. LGL Limited provides a wide range of environmental services across Canada, the U.S., and internationally. For more information visit: www.lgl.com.
A 8.300Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE