This paper presents the application of machine learning algorithms to identify pigs’ behaviors from data collected using the wireless sensor nodes mounted on pigs. The sensor node attached to a pig’s back senses the acceleration and angular velocity in three axes, and the sensed data is transmitted to a host computer wirelessly. Two video cameras, one attached to the ceiling of the pigpen and the other one to a fence, provided ground truth for data annotations. The data was collected from pigs for 131 hours over two months. As the typical behavior period depends on the behavior type, we segmented the acceleration data with different window sizes (WS) and step sizes (SS), and tested how the classification performance of different activities varied with different WS and SS. After exploring the possible combinations, we selected the optimum WS and SS. To compare performance, we used five machine learning algorithms, specifically support vector machine, k-nearest neighbors, decision tree, naïve Bayes, and random forest. Among the five algorithms, random forest achieved the highest F1 score for four major behaviors consisting of 92.36% in total. The F1 scores of the algorithm were 0.98 for ‘eating’, 0.99 for ‘lying’, 0.93 for ‘walking’, and 0.91 for ‘standing’ behaviors. The optimal WS was 7 seconds for ‘eating’ and ‘lying’, and 3 seconds for ‘walking’ and ‘standing’. The proposed work demonstrates that, based on the length of behavior, the adaptive window and step sizes increase the classification performance.