Mataki-LITE: lessons learned from petrel tracking (Part I: GPS loggers)

Dear colleagues,

I recently used Mataki-LITE GPS tags (Debug Innovations, Cambridge, UK) and I thought it would be helpful to share the set-up and configuration I used, as well as lessons learned. This is a lot of text so I'll publish it as replies. 

Deployment: From April 10 to 25, I partnered with Grupo Jaragua, a Dominican conservation NGO, to track the foraging movements of Black-capped Petrel (Diablotin, Pterodroma hasitata) through a conservation grant by the Neotropical Bird Club. I powered the Mataki-LITE with a 150mAh lithium-ion battery (TinyCircuits, Akron, USA; 3.8g) and waterproofed them with light-weight heatshrink tubing (F4(Z),, Ogden, USA). The total mass of the waterproofed devices were ~ 8g. I attached them at the base of the tail with 2-part epoxy and 3 strips of TESA cloth tape, to the underside of the 4 central rectrices. I finally secured the whole with a 0.2mm zip-tie. We deployed LITE loggers on 9 petrels. The handling process lasted less than 15 minutes and all birds were returned to their burrows.  

Logging schedule: To avoid draining the battery underground, I programmed the devices to turn on 24h after deployment, when the birds were back at sea. Based on previous results, we expected foraging trips to last 10-15 days thus GPS loggers were set to record GPS locations every 30 minutes in normal power mode to allow for a battery life of ca. 21 days. Upon return to the nest, loggers were set to upload tracking data to base-stations placed within 200m of clusters of burrows (See base-stations details in this other Wildlabs post).

Logging script: Mataki-LITE loggers are coded in BASIC language and I adapted a sample script provided by Debug Innovations. The script is attached (Appendix A). Briefly, I wrote the logging script to optimize power consumption by the GPS logger in two ways. First, I created two geofences (of respective 25 km and 150 km radius from the colony) to control the frequency of UHF communication “heartbeats” (which let the base-station know that a tag is near): a heartbeat was sent every 2 minutes when inside the 25 km geofence (based on the coordinates of the last recorded GPS location), every 10 minutes when inside the 150 km geofence, and no heartbeat was sent when more than 150 km away from the colony (Table B.1). Then, when the battery power decreased below a threshold of 3.5 V, a simple “low voltage” loop reduced the GPS logging schedule from every 30 minutes to every 180 minutes, and the frequency of UHF heartbeats was scheduled to every 10 minutes disregarding of the distance to the colony. Stationary tests were performed before deployment to debug the script and estimate battery life.

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