This paper presents a small animal body sensing and tracking system for uninterrupted and long-term activity monitoring in standard homecages. The conventional camera-based systems are not scalable and cost-effective to cover multiple animal homecages in the racks in animal facilities. The proposed scalable design, comprising a thin layer of multiple resonators (sensor unit), overcomes the limitations of the camera-based systems. It consists of a reading coil and an array of six resonators, tuned at different frequencies ranging from 100 MHz to 180 MHz, generating multiple frequency bifurcations. The shifts/changes of resonance frequencies are proportional to the changes in the electromagnetic properties of the surrounding environment of the resonators. The animal body tissue influences these properties at frequencies higher than 100 MHz and can be detected by the multi-resonator array. We have modeled the proposed sensor unit and animal body using ANSYS HFSS software to optimize the design and characterize its performance (providing a 20 mm resolution: 150 pixels), including the Specific Absorption Rate (SAR). The proposed sensing design is implemented, and the experimental results show its sensitivity and capability to detect the animal body model (Saline model) and its displacement. The measured results have illustrated significant frequency shifts (from 200 kHz to 800 kHz) for mouse model displacement over the proposed sensor unit.