One of the objectives of the wolf-livestock interaction study is to quantify the influence of wolf presence on cattle performance and grazing behavior across herds of cattle grazing on rangelands. In order to accomplish this, cattle will be randomly selected from wolf-affected and control herds to be fitted with a GPS collar that will track their movement during the summer (June - October) grazing season. 

On-board animal/livestock tracking technology has proliferated recently; creating a myraid of hardware options to select from. In this blog post, we will provide details on the units we selected to deploy for this project and the configuration changes and connectivity augments we made in order to preserve battery life and collect data over for the duration that cattle were out for the summer grazing season. Cost, durability, and ease of use were also paramount in our decision-making process.

The GPS Tracker

After much research and discussion with other researchers in the livestock-tracking space, we decided to partner with Lonestar Tracking for procuring GPS units, cellular subscriptions, and configuration support services. We purchased the Oyster3 tracking devices given that they are battery operated, encased in a rugged plastic container, waterproof, and have on-board data storage and cellular real-time tracking capabilities. Each unit was priced at $149.99 with quantity discounts available. There is a subscription service fee of $99/unit per year that facilitates cellular-based tracking and a web interface. 

Each unit, in its case, is 3 inches wide and 4 inches long. The case protects the circuit board, batteries, and on-board storage. 

Configuration and Battery Life Considerations

The Oyster3 GPS units, like all real-time tracking equipment, anticipate having cellular connectivity and/or satellite connectivity when making projections about battery life. However, many of the cattle in the wolf-affected and control herds will not be in areas where a cell signal is available. The GPS unit can use a tremendous amount of battery life continually trying to connect to cellular and upload data. As such, we worked with Lonestar Tracking to modify each unit's software configuration to preserve battery life. The units that we are deploying have the following settings:

• Record a latitude. longitude, and altitude coordinate every 30 minutes;
• Attempt to connect to cellular service once daily;
• If attempt to connect to cellular fails, do not attempt again for another 24 hours;
• When/if a cellular connection is established, download all existing data collected;
• If a cellular connection is never established, store all data recorded. 

Based on the best available data on Oyster3 battery performance, these augmentations to each unit's software should get us roughly 6 months of battery life; i.e., the units would collect data for the duration of the summer grazing season.

The next blog in the series will describe how collars, to connect the GPS units to the cows, are built.