Fig. 2

Examples of recent and contemporary ETDs. a CTD-SRDL archival Argos transmitter configured with CTD and Fluorometry sensors (SMRU Instrumentation, St. Andrews, United Kingdom; 105 × 72 × 60 mm, 630 g). Mid-2000s to present. Photo © by DP Costa. b Archival data logger with tri-axial jaw accelerometer and light level sensor designed for detecting bioluminescence (Little Leonardo Corp., Tokyo, Japan; 20 × 73 mm, 48 g). 2015 to present. Photo © DP Costa. c ARCGEO-13T archival data logger with temperature, depth sensors and geo-location via light levels (Lotek Wireless, St. John’s, Newfoundland, Canada; 13 × 57 mm, 12 g). Early 2000s to present. Photo © DP Costa. d Three generations of Argos-compatible satellite data transmitters commonly used as ETDs on pinnipeds made by Wildlife Computers Inc. (Redmond, WA, USA). SDR-T16 devices (top device in picture) were available through the late 1990s, measured up to 135 × 45 × 37 mm and had a mass of up to 330 g (depending on battery configurations). SPOT devices (middle) were introduced in the early 2000s. They measure up to 90 × 55 × 30 mm and have a mass up to 120 g. A different configuration for a SPOT device introduced in the mid-2000s is shown at the bottom of the image above. This form factor with smaller batteries measures 85 × 12 × 12 mm and has a mass of about 23 g. Antenna design has also changed through these years, leading to smaller and thinner yet longer lasting antennae. Photo © M Horning