Initial results on the variation of whistle characteristics of bottlenose dolphins from two neighbouring regions of the Mediterranean Sea: Northern Ionian and Southern Adriatic Sea

Bottlenose dolphins have a complex vocal repertoire that varies depending on behavioral context, social structure, group composition, and anthropogenic pressures. This current study describes the whistle characteristics of bottlenose dolphins for the first time in the South Adriatic Sea while assessing the potential differences between whistle characteristics of geographically separated dolphins within neighbouring waters of the North Ionian Sea. The results show that whistle characteristics were similar between Taranto Gulf (Italy) and Boka Bay (Montenegro), despite their spatial differences. The mean peak frequency was 10kHz for each study location while the mean minimum and maximum frequency ranged from 7 to 14kHz. The average duration of whistles was 500 milliseconds. These results share similarities with previous literature, although several studies reported slightly different mean peak frequencies, ranging up to 15kHz in the neighbouring waters of Croatia and Italy. Further, harmonics were produced and formed in 40% of the whistles in Taranto Gulf and 30% of the whistles in Boka Bay. A high incidence of harmonics has previously been associated with behavioral states (i.e., travelling) and with certain types of marine traffic (i.e., fishing vessels). Therefore, it is important to collect simultaneous data on the visual behavior of the focal group as well as document the type and density of marine traffic within the proximity of the dolphins to have an in-depth understanding of vocal behavior. Despite the similarities of whistle characteristics of Taranto and Boka Bay, the whistle contours showed notable variations. Upsweep whistles were the most regularly produced whistle type in each location, which coincides with previous studies in the Mediterranean Sea. However, the least produced whistle had a concave contour in Taranto and was flat in Boka Bay. Previous studies have confirmed that flat whistles account for the least produced whistle contour in the Mediterranean Basin. Examining the whistle characteristics and the variation in whistle contours provides an in-depth understanding of the behavioral complexity as well as its plasticity in the presence of pressure. Therefore, future studies need to include behavior, group composition, noise levels, and human presence to enable an effective understanding of variation in whistle characteristics of bottlenose dolphins

Social Structure and Temporal Distribution of Tursiops truncatus in the Gulf of Taranto (Central Mediterranean Sea)

This study aims to provide information on the site fidelity, residency patterns and the social structures of bottlenose dolphins occurring in the Gulf of Taranto in order to supply effective indications supporting the future management and conservation measures of the species. Out of 141 photo-identified individuals about 76% were re-sighted from 2 up to 31 times. The site fidelity analysis of photo-identified individuals highlighted the occurrence of 20 seasonal residents, 62 visitors and 59 transient individuals that were included in a local population in which emigration and reimmigration events occurred, as suggested by the residency-pattern analysis. The association pattern, performed using SOCPROG 2.9, highlighted a relatively low mean value of the overall half-weight association index (0.11 ± 0.04). However, the test for the null hypothesis of ‘random association’ was rejected and the temporal analysis made with SLAR suggested the presence of both extremely fluid and stable associations between individuals, describing a fission fusion social structure with a certain degree of social organization. Moreover, the cluster and social network analysis showed two geographically and socially segregated units. Thus, more investigations are needed and the development of a specific conservation plan for bottlenose dolphins in the whole area is required

Site fidelity, residency and habitat use of the Risso's dolphin Grampus griseus in the Gulf of Taranto (Northern Ionian Sea, Central-eastern Mediterranean Sea) by photo-identification

A photo-identification tool was applied to identify and create a catalogue of photo from Risso's dolphins providing evidence of its site fidelity, residency and habitat use in the Gulf of Taranto (Northern Ionian Sea, Central-eastern Mediterranean Sea). Sightings carried out from 2013 to 2016, occurred in a depth range from 436 to 1000 m with a mean depth value of 762 +/- 217 m. A total of 215 specimens of G. griseus were observed including 206 adults and juveniles, 7 calves and 2 new-borns. The evidence of calving and nursering females was inferred from calf association without any other sex information. Group size varied between 2 and 30 dolphin specimens, with a mean value of 13 +/- 7 specimens. A total of 54 Risso's dolphins were identified as distinctly marked. Among these, 34 specimens (63%) were sighted only once and 20 specimens (37%) were re-sighted up to 4 times. Rates of re-sighting within single year were relatively high, reaching 23, 18 and 43% during 2013 (3 re-sighted/13 dolphins), 2014 (4 re-sighted/22 dolphins) and 2016 (12 re-sighted/28 dolphins), respectively. The site fidelity reached 0.50, with a mean value of 0.13 0.18. The monthly residency rate varied between 0.11 and 0.44, with a mean value of 0.17 0.09. Among a total of 9 Risso's dolphins considered as "multi-year residents", 7 specimens were re-sighted in two consecutive years and 2 were re-sighted in a period of two non-consecutive years. Although results suggest the need for further studies implementing the photo-identification catalogue for the Risso's dolphin and allowing possible reconstruction of its migration patterns on the Mediterranean and global scale, the Taranto Valley canyon system seems to be a critical habitat to enforce specific conservation measures for the effective protection of the species

Individuals size estimations of the sperm whales from the Gulf of Taranto (Northern Ionian Sea, Central Mediterranean Sea) employing clicks’ Inter-Pulse-Interval (IPI) measurements

For the purpose of conserving vulnerable species included in the Habitats Directive as well as species indicating the state of ecosystem health, according to the Marine Strategy Framework Directive, regular basis information on their populations and demography trends are necessary. In this study, an indirect assessment of the individual size and age of sperm whales sighted in the Gulf of Taranto (Northern Ionian Sea, Central Mediterranean Sea) was carried out by means of acoustic analysis of the Inter-Pulse-Interval (IPI) values of the clicks recorded from June to November 2020. The open software CABLE was employed to calculate first the IPI of the animals, then their body length, using two different equations. The obtained size estimates were then compared with ones visually made by observers on the field. The results show that, except for two individuals of 13 m and 14 m in length, most of the recorded animals are individuals of 8 m-10 m in length, corresponding to the age class of mature females or young males. An evaluation of IPIs of sperm whales recorded in different Mediterranean areas will allow verifying if most Mediterranean sperm whales belong to younger age classes indicating that the population is still recovering from the past centuries of direct catch

Generalized additive models for Risso's dolphin group size estimation in the Gulf of Taranto (Northern Ionian Sea, Central-eastern Mediterranean Sea)

Cetaceans are species indicator of the ecosystem health status. It is necessary to increase knowledge on them to support the conservation of these species and their habitat. New strategy, based on machine learning techniques, has been adopted to estimate cetacean group size. Starting from Risso’s dolphin sighting data in the Ionian Sea collected between 2009 and 2019, the aim of this work is to build a correlative model which can help in estimating Risso’s dolphin group size, by using a set of physical and biogeochemical features

The Social Role of Vocal Complexity in Striped Dolphins

Many gregarious species require complex patterns of communication for maintaining coordinated behaviors, articulated social structure and group cohesion. In mammal species, social complexity has been considered the driving force for the development of advanced acoustic communication systems. Striped dolphins are highly social, showing large group size with females maintaining strong bonds with kin. Here, we tested the hypothesis that more complex acoustic pattern plays a key role in social activity in the striped dolphins. The production rate of clicks, whistles and burst pulses, and the acoustic features of whistles have been related to the activity context (feeding, traveling, resting, and socializing). Furthermore, complex calls, consisting of a combination of frequency-modulated, and/or pulsed components were detected. Higher whistles and burst pulses production rates were recorded during socializing. Also, the social activity can be discriminated basing on the modulation of the whistle contour. Biphonic calls were especially recorded during social interaction events, suggesting that these phenomena can encode information about individual or group identity to conspecifics. Outcomes indicate the pivotal role of vocal complexity during social context and elicit further investigations of the communication system of small odontocetes from local to wider spatial scale

AS-OCT and Ocular Hygrometer as Innovative Tools in Dry Eye Disease Diagnosis

Dry eye disease (DED) is one of the conditions that most commonly leads patients to visit an ophthalmologist. Fast and accurate diagnosis relieves patient discomfort and spares them from long-term effects on the ocular surface. Many tests used in the diagnosis of DED may be considered subjective as they rely on an experienced observer for image interpretation, resulting in variations in diagnosis. On one hand, the non-contact nature of the anterior segment optical coherence tomography (AS-OCT) device and its rapid image acquisition enable the measurement of the tear meniscus parameter without reflex tearing. On the other hand, an ocular hygrometer allows a rapid, safe, but also efficient, analysis and is associated with low costs and the repeatability of the procedure