First Report of Epimeletic and Acoustic Behavior in Mediterranean Common Bottlenose Dolphins (Tursiops truncatus) Carrying Dead Calves

Abstract

Epimeletic behavior toward dead calves has been frequently reported in cetaceans, mostly with females (presumed mothers) showing supportive behaviors such as carrying, lifting, or sinking, often assisted by “escort” individuals. However, information on acoustic production in such contexts is scarce. This report describes two observations of epimeletic behavior toward dead newborns in bottlenose dolphins and associated acoustic production. Data were collected at the Tiber River estuary (Rome, Mediterranean Sea, Italy) with one hydrophone for passive acoustic monitoring and two digital cameras. In both cases, an individual (presumed mother) acting as the main supporter and directly interacting with the carcass by lifting it (case 1) or sinking it (case 2) was observed. Another adult individual (escort) was present in both encounters showing standing-by and excitement behaviors (case 1) and supportive behavior (case 2). In both encounters, whistles, pulsed sounds, and bray-call elements were recorded. The consistent vocal activity observed likely conveyed context-specific information. A signature whistle in the first encounter was also recorded, likely emitted by the putative mother as a distress call. This report confirms the occurrence of epimeletic behavior in bottlenose dolphins and reports a preliminary description of the acoustic production when a dead calf is involved, providing additional information on this largely unknown topic.

First Unmanned Aerial Vehicle Observation of Epimeletic Behavior in Indo-Pacific Humpback Dolphins

“…Fetal folds displayed on the body when lifted also confirmed its very young age ( Figure 2 f). The lift-and-sink events continued throughout the sighting (video footage at , accessed 28 May 2022), which is typical of epimeletic behavior [ 20 , 29 ].…”

“…The combination of vessel-based and aerial observation is critical for unveiling the kinship of each individual and the dynamics among each member. Acoustic recording of the event, if included, may provide a further understanding of their behaviors [ 10 , 18 , 20 ].…”

“…The focal adult–offspring pair is often accompanied by other conspecifics in the same social group, which may exhibit diverse behaviors, including but not limited to standing-by, supporting, socializing, or even aggressive behavior [ 10 , 17 , 18 , 19 ]. Acoustic records associated with epimeletic behavior of the highly vocal Tursiops truncatus have been reported where the nurturant adults emitted distress calls to seek aid from conspecifics [ 18 , 20 ].…”

Bray-Call Sequences in the Mediterranean Common Bottlenose Dolphin (Tursiops truncatus) Acoustic Repertoire

“…In conclusion, this study proposed for the first time, quantification, depiction, and detailed description of common bottlenose dolphin bray-call sequences in the Mediterranean Sea, providing new and complete information about these vocalizations. Further research is needed to better understand their function(s) in feeding and social contexts (even extreme ones, like when a dead individual is present [73]), considering both their structural complexity and emission circumstances. In addition, due to the distinctiveness of the sequence structures, disruptions caused by anthropogenic (e.g., noise, fishery) and biological factors (e.g., prey type), as well as social and behavioral conditions, could be clearly revealed from the analysis of their patterns.…”

Resources and population traits modulate the association patterns in the common bottlenose dolphin living nearby the Tiber River estuary (Mediterranean Sea)

“…Bottlenose dolphin occurrence is possibly favored by the ecological conditions and heterogeneity of morphological features of the region (Ardizzone et al, 2018). Water mass circulation generates upwellings that support high productivity, making the area a suitable site for both feeding and nursing bottlenose dolphins (Pace et al, 2019;Pedrazzi et al, 2022). The study area is considered a valuable ground for the commercial fishery as well (Ardizzone et al, 2018) and is characterized by a high proportion of small-scale artisanal fishery and larger trawling vessels (Ardizzone et al, 2018).…”