Impact of forest management on the communication distance of an endangered tree squirrel

• Published in: The Journal of wildlife management 2024-11
• Main Authors: Brzozowski, Ryan, Mahoney, Sean M., Combrink, Hendrik J., Hefty, Kira L., Pasch, Bret
• Format: Article
• Language: English
• ISSN: 0022-541X; 1937-2817
• DOI: 10.1002/jwmg.22689

Long‐distance acoustic signals mediate important social interactions between animals, and the structure of the environment can influence sound transmission to affect communication distance. Anthropogenic disturbances such as fire suppression alter forest structure and can potentially affect acoustic interactions by altering sound attenuation patterns. In the spruce‐fir and mixed‐conifer forests of the Pinaleño Mountains, Arizona, USA, that harbor endangered Mount Graham red squirrels ( Tamiasciurus fremonti grahamensis ), numerous historical anthropogenic disturbances have altered forest characteristics and contributed to habitat degradation and loss. In this study, we assessed how recent forest management treatments influenced the attenuation of red squirrel territorial rattle vocalizations. In June 2023–August 2023, we broadcast and recorded rattles 5.4 m above the forest floor at various distances (1, 10, 20, and 40 m) to mimic hypothetical senders and receivers. We used on‐the‐ground measurements and lidar to quantify forest structure relative to patterns of sound attenuation in 3 treatments: thinning, understory fuel reduction, and untreated control plots. Across all treatments, we found that increasing tree basal area resulted in higher attenuation, with rattles being approximately 6 dB lower in amplitude in the most dense compared to the least dense plots, equivalent to a doubling in squirrel communication distance. Additionally, rattles on untreated control plots experienced more attenuation than thinned (~3 dB) and fuel‐reduced (~1.5 dB) plots. A lidar‐derived measure of canopy structure was a better predictor of rattle attenuation than lower resolution on‐the‐ground measurements. In the short‐term, forest thinning may facilitate development of acoustic social neighborhoods that increase squirrel fitness, though alternative costs of more open forests exist. More generally, our results indicate that forest management can affect the efficacy of acoustic communication and that integration of signaling and sensory ecology with remote sensing can inform wildlife conservation.