<p>Animals obtain and use energy for vital functions, and intestinal tract length and enzymatic activity influence energy processing, among other internal factors. In vertebrates, it has been observed that body mass correlates with intestinal tract length and nominal surface area, and larger animals are generally expected to exhibit higher enzymatic activity for digestion. In bats, there is a positive relationship between body mass and intestinal length. However, smaller vespertilionid bats exhibit higher apparent dry matter digestibility —likely linked with greater enzyme activity— than larger species. Interestingly, published data suggests a negative interspecific relationship between body mass and/or intestinal length and enzymatic activity standardized by nominal area in some bat species. This pattern supports the idea that, in species with reduced intestinal size, enzymatic activity may increase as a compensatory functional response to morphological limitations. To test this hypothesis, we analyzed the relationship between intestinal tract length and enzymatic activity of aminopeptidase-N and lipase in 10 species of vespertilionid bats differing in body mass from central Mexico. Using a phylogenetic approach, we observed a positive relationship between intestinal tract length and body mass. According to our prediction, we found a negative relationship between intestinal length and enzymatic activity for both enzymes across species. These findings suggest a trade-off: species with larger intestines improve absorption capacity, while smaller bats compensate for reduced intestinal size and shorter transit times by increasing enzymatic activity. This study highlights the adaptive digestive strategies in bats and provides new insights into the interaction between body mass, intestinal morphology, and enzymatic function in insectivorous bats.</p>