# The Design of an Energy Harvesting Wireless Sensor Node for Tracking Pink Iguanas
## 1 Introduction  
Tracking devices are fundamental tools to study the behavior of wild animals in relation to their natural environment. Retrieved information can guide the design of effective strategies and actions aimed at protecting endangered species and optimizing ecosystem management. Thus, in the last years, such rationale has prompted the design and the development of a plethora of non-commercial and commercial monitoring devices, each characterized by a trade off between biological requirements and technical limitations [1]. The selection of suited technologies requires a tight collaboration between engineers and wildlife conservationists: for instance, the choice of a specific network technology may have strong implications on the size of the device, and power consumption which may have a reflection on the weight and size of the battery loaded on the animal. This ultimately affects the duration of monitoring. In the last years, technological advances enabled the development of a new generation of tracking devices: smaller, more energetically efficient, more ecologically sound (\"green\"), and thus best suited to monitor animals in the wild. In this work we present some design aspects of a device aimed at characterizing the long-term behaviour of Galapagos pink land iguanas (_Conolophus marthae_, hereafter pink iguanas): a recently discovered species of iguana [2] that is assessed as _Critically Endangered_. Prior attempts to investigate the behavior of this animal were ineffective due to a combination of the difficulty of the terrain and hard logistics that limits the duration of field trips, lack of suitable tracking devices, and absenceof a network infrastructure in the interested area. The harsh environmental conditions require a environmental-friendly, water-resistant, low-power, wireless system. For these reasons, we developed a wireless sensor node that integrates several elementary sensors, a GPS receiver and storage capabilities. The device is powered by an energy harvesting circuit composed by a small-size solar cell combined with a super-capacitor in order to power the energy-consuming GPS receiver. The system is complemented by an high power long range communication transmitter. The combination of energy harvesting and long-range communication should theoretically enable a perpetual monitoring [3]. The optimization of the energy requirement and harvesting can balance the need to limit the size of the device (to avoid interference with animal habits) and the opportunity to collect, alongside GPS data, environmental parameters such as temperature, humidity, UVB radiation, etc. We also pursued a green engineering approach by using processes and products to minimize potential hazards and toxicity, including, for example, super-capacitors that have an impact on the environment lower than Li-Ion batteries [4]. This objective represents an important advance in this field and it is of paramount importance in this application where devices are going to be deployed in natural sanctuaries and remote settings where the probability of not recollection is high. The main goal of the paper is to demonstrate how current sensor technology can be effectively used to solve a real zoology problem such as tracking the pink isquana in a harsh environment. The main contributions of this work are:  
* The description of the tracking problem in an harsh environment with a specific reference to the Galapagos Pink Iguana;
* The energy harvesting and power architecture solution, that enables long distance communication by powering both an high current demanding RF booster and the energy demanding GPS module;
* The description of the device packaging and of the real deployment on the field;
* An analysis of power consumption, sensors calibration and GPS fixing performance.