Thinking small: Next-generation sensor networks close the size gap in vertebrate biologging

Abstract

Recent advances in animal tracking technology have ushered in a new era in biologging. However, the considerable size of many sophisticated biologging devices restricts their application to larger animals, whereas older techniques often still represent the state-of-theart for studying small vertebrates. In industrial applications, low-power wireless sensor networks (WSNs) fulfill requirements similar to those needed to monitor animal behavior at high resolution and at low tag mass. We developed a wireless biologging network (WBN), which enables simultaneous direct proximity sensing, high-resolution tracking, and long-range remote data download at tag masses of 1 to 2 g. Deployments to study wild bats created social networks and flight trajectories of unprecedented quality. Our developments highlight the vast capabilities of WBNs and their potential to close an important gap in biologging: fully automated tracking and proximity sensing of small animals, even in closed habitats, at high spatial and temporal resolution.

Simultaneous monitoring of the same animals with PIT-tags and sensor nodes causes no system interference

“…The combination of long-term monitoring with PIT tags and short-term tracking with biologging sensor nodes creates exciting new opportunities to gather rich data from individuals when they are not present at RFID reader stations, e.g. (Ripperger et al 2019c).…”

“…5.5 cm in diameter, Figure 1C) connected to a reader (Euro ID LID 665 Multi reader powered by a 12V motorcycle battery). For the second biologging device, we tested two versions of recently developed sensor nodes (part of the BATS wireless biologging network (Duda et al 2018; Ripperger et al 2019c); see Figure 1). These sensor nodes contain an accelerometer, a magnetometer and an air pressure sensor which continuously sampled data and wirelessly transmitted them to a receiver unit.…”

“…A more complete picture of individual behaviour can be gained from increasingly powerful animal-borne biologging tags, such as GPS-loggers or proximity sensors. Recent technological advances have led to the miniaturization of these devices, creating new opportunities for studies of small animals (Ripperger et al 2019c). Another key advance in ‘next-generation’ biologgers is a diverse array of sensors such as accelerometers, magnetometers, or air pressure sensors, which autonomously collect and process data and give additional insights into the animal’s behaviour, performance, body posture, or flight height (O’Mara et al 2019; Williams et al 2017), which can be useful for studying foraging (Conenna et al 2019; Egert-Berg et al 2018; O’Mara et al 2019) or social behaviour (Ripperger et al 2019a; Ripperger et al 2019b).…”

“…Still, these short-term studies can answer new questions beyond the reach of traditional methods. In particular, the combination of digital biologgers and long-term monitoring of generations of PIT-tagged individuals provides extraordinary opportunities to answer long-standing questions (Ripperger et al 2019c).…”

“…Another concern is whether the magnetic field from the RFID-antenna will affect the functionality of this second device. In this study, we test for interference between a popular RFID-system and sensor nodes from a novel wireless biologging network (Ripperger et al 2019c). We found that when a biologging sensor node was attached to the skin directly on top of a subcutaneous PIT tag, data transmission was not reduced in either system.…”