Dear all,
My co-authors and I are pleased to announce the publication of the following
research in the Journal of Mammalogy:
Mark–recapture of individually distinctive calls—a case study with signature
whistles of bottlenose dolphins (Tursiops truncatus)
Authors: Emma G Longden, Simon H Elwen, Barry McGovern, Bridget S James,
Clare B Embling, Tess Gridley
DOI: https://doi.org/10.1093/jmammal/gyaa081
This is an output of research conducted by the Sea Search group and the
associated Namibian Dolphin Project.
Abstract: Robust abundance estimates of wild animal populations are needed to
inform management policies and are often obtained through mark–recapture (MR)
studies. Visual methods are commonly used, which limits data collection to
daylight hours and good weather conditions. Passive acoustic monitoring offers
an alternative, particularly if acoustic cues are naturally produced and
individually distinctive. Here we investigate the potential of using
individually distinctive signature whistles in a MR framework and evaluate
different components of study design. We analyzed signature whistles of common
bottlenose dolphins, Tursiops truncatus, using data collected from static
acoustic monitoring devices deployed in Walvis Bay, Namibia. Signature whistle
types (SWTs) were identified using a bout analysis approach (SIGnature
IDentification [SIGID]—Janik et al. 2013). We investigated spatial variation in
capture by comparing 21 synchronized recording days across four sites, and
temporal variation from 125 recording days at one high-use site (Aphrodite
Beach). Despite dolphin vocalizations (i.e., echolocation clicks) being
detected at each site, SWTs were not detected at all sites and there was high
variability in capture rates among sites where SWTs were detected (range 0–21
SWTs detected). At Aphrodite Beach, 53 SWTs were captured over 6 months and
discovery curves showed an initial increase in newly detected SWTs, approaching
asymptote during the fourth month. A Huggins closed capture model constructed
from SWT capture histories at Aphrodite Beach estimated a population of 54–68
individuals from acoustic detection, which overlaps with the known population
size (54–76 individuals—Elwen et al. 2019). This study demonstrates the
potential power of using signature whistles as proxies for individual
occurrence and in MR abundance estimation, but also highlights challenges in
using this approach.
Kind regards,
Emma Longden
[email protected]
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