A growing body of research demonstrates that humans can accurately perceive the emotional states of animals solely by listening to their calls, highlighting shared evolutionary ancestry. Yet, the cognitive and perceptual mechanisms underlying heterospecific emotion perception have remained open to investigation. One hypothesis is that humans rely on simple acoustic heuristics to make such judgments, for example, perceiving higher-pitched calls as reflecting heightened emotional arousal (the "pitch rule"). This could lead to accurate judgments of emotion since in most mammals, as in humans, vocal fundamental frequency (the acoustic determinant of the pitch percept) does objectively correlate with emotional arousal. In the present study, we used digital pitch manipulation to create pairs of animal calls that were perceptually identical except for pitch, and we measured human perceptions of the caller's emotional arousal using an online survey. Calls of six phylogenetically diverse species were included as stimuli. Participants attributed slightly but statistically significantly higher arousal to higher-pitched versions of the same calls. Variation in application of the pitch rule across species was not well explained by familiarity, and prior experience with cats did not significantly predict sensitivity to pitch in cat vocalizations. Cross-species variation also did not align with phylogenetic distance from humans, or the hypothetical usefulness of pitch for making accurate judgments. Thus, the pitch rule may be a "mammalomorphic" heuristic leading to accurate emotion judgments in some taxa and call types and erroneous judgments in others, depending in part on phylogenetic distance and the mechanisms of call production. (PsycInfo Database Record (c) 2023 APA, all rights reserved).