Experts at Newcastle University analysed signature whistles produced by bottlenose dolphins (Tursiops truncatus) recorded off the Northumberland coast in north-east England and compared it to using photo-ID data of the species (a more labour-intensive method that requires photographically identifying dolphins during boat surveys). A total of 26 surveys were conducted and 5,771 hours of acoustic data were recorded across three sites from anchored recorders. The team found that the distinctive signature whistles offer a reliable method for estimating the abundance for the species that matches the accuracy of photo ID data.

Published in the journal Marine Mammal Science, the study also provides the first abundance (number of individuals in a defined area) estimates for the species of approximately 60 individuals off Northumberland, United Kingdom. The results suggest that the Northumberland coast serves as an important habitat for a substantial portion of the East Coast bottlenose dolphin population, with approximately 30% of the total population frequenting the area during summer months.

Benefits of using signature whistles

Dr Matt Sharpe, PhD graduate at Newcastle University, said: “Using signature whistles to estimate abundance offers several benefits. The main advantage is that collecting data is less resource intensive than conventional methods, such as transect sampling and capture-recapture based on photo-ID, which typically use data collected during boat-based surveys.”

Senior author, Per Berggren, Professor of Marine Megafauna Conservation, School of Natural and Environmental Sciences, Newcastle University, said:

“This study not only reinforces the feasibility of using signature whistles for abundance estimation but also provides a foundation for future research using low-cost acoustic methods that can be applied regardless of location, weather and light conditions. Long-term monitoring using signature whistle analysis, could inform conservation strategies and improve understanding of the population’s spatial and temporal dynamics.”

Reference: Sharpe, M., & Berggren, P. (2024). A comparison of photo-ID and signature whistle based capture-recapture abundance estimates of common bottlenose dolphin. Marine Mammal Science, e13218. https://doi.org/10.1111/mms.13218