# May the Extensive Farming System of Small Ruminants Be Smart?
## 3 Results
### Wearable Sensors
#### 3.2.4 Sensors to Measure Behaviour  
Sensors play an essential role in PLF technology by gathering real-time data across various aspects of livestock production including animal behaviour, health status, and environmental conditions [3]. In particular, they can record movement and resting patterns, feeding behaviour, and social interactions between animals and thus observe animal behaviour. These sensors can also provide valuable information about the health statuses of the animals as they record vital signs such as the body temperature, heart rate, respiratory rate, and activity levels to detect signs of illness or stress. Monitoring animal behaviour facilitates the collection of information related to farm management such as heat, childbirth, rumination, illnesses, or relationship problems. Commercially available sensors are accelerometers, usually placed on the neck or paws, or in-ear tags or boluses. Depending on where the sensor is located, different behaviours can be correlated to the accelerometer signals, and, therefore, the behaviours can be quantified. Several studies have been conducted to classify cattle behaviour compared to sheep behaviour [25; 42]. Eating, grazing, stationary, walking, running, active behaviour (walking and scratching), and inactive behaviour (standing and resting) have been studied. More complex behaviours, such as rumination, kicking and foot movements, grazing, standing, walking, lying down, and running, have been successfully classified using accelerometers [33]. Sensors attached to the animal's neck or ear often provide information only on activity, i.e., the total amount of movement [44]. The sensors applied around the animal's paws can also provide information on the number of steps and rest times [44]. [PERSON] et al. [45] demonstrated that accelerometers can indicate variation in behaviours among grazing sheep: in their study, most of the sheep's time was spent grazing, ruminating, and idling while smaller amounts of time were spent walking, licking, and in other behaviours, and the time spent by an animal in each activity varied during the day. Males and females showed differences in the time spent grazing. [PERSON] et al. [36] reported that they could provide information on rumination time, the number of chewing movements, and feed and water intake. Accelerometers were also tested to evaluate their ability to discriminate between sheep's biting and chewing activities during grazing [52]. [PERSON] et al. [59] showed that the spatial distribution of grazing Churra sheep was non-random because the animals seemed to develop common behavioural patterns. Notably, airborne data related to vegetation height, slope, and aspect showed the most significant effect on the location of sheep grazing. Moreover, sheep chose the grazing areas that offered the freshest and most nutritious food. The application of the 3D accelerometer technology has proven to be very useful in the rationalisation of reproductive aspects, such as in the onset of parturition [49; 50; 51], in identifying behavioural changes in ewes during parturition [43], or in the estimation of the serving capacity of rams [48]. Sensor systems can detect infectious diseases, metabolic disorders, and lameness [46; 65]. Many conditions can also be detected earlier than through manual monitoring, even before the appearance of clinical signs, with the analysis of data collected and the results of the processing software connected to the farmer's smartphone [59]. Data transmission and energy supply limitations are the main obstacles to using sensor-assisted monitoring in extensive and remote rangelands. Accelerometers record a lot of data, but with difficulty in analysis and interpretation, they require suitable algorithms for data processing [37; 79].