Mating patterns of dusky dolphins (Lagenorhynchus obscurus) explored using an unmanned aerial vehicle
Dara N. Orbach, Jordan Eaton, Lorenzo Fiori, Sarah Piwetz, Jody S. Weir, Melany Würsig, Bernd Würsig
We used drones to film free-swimming dusky dolphins and to characterize their mating patterns at the surface of the water. We compared patterns between dolphins that mated in isolated subgroups and those that mated within large pods to explore potential distinctions between social and procreative functions of mating. We found few differences between dolphins that mated in these two group types.
Linear skin markings in common bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon, Florida
Elizabeth Murdoch Titcomb, Jessie Stevens, Anne Sleeman, Brandy Nelson, Luke Yrastorza, Adam M. Schaefer, Gregory D. Bossart, John S. Reif, Marilyn Mazzoil
A new skin condition, which we call “linear skin markings”, was identified in wild dolphins in the Indian River Lagoon (IRL), FL. The markings are parallel, vertical lines on a dolphin’s torso varying in length and width. We investigated how many IRL dolphins have the condition, the age and sex of affected animals, where and when the condition occurred, and possible causes. 7% of the dolphins had the condition, ages ranged from 1-20 years, and the majority were female. Most cases occurred in the northern and central IRL. Once observed, the condition did not disappear, and the cause is unknown.
Age structure of strandings and growth of Lahille’s bottlenose dolphin (Tursiops truncatus gephyreus)
Rihel Venuto, Silvina Botta, André S. Barreto, Eduardo R. Secchi, Pedro F. Fruet
The Lahille’s bottlenose dolphin, endemic to the Southwest Atlantic Ocean, is vulnerable to extinction. Based on the stranding data collected over 41 years of systematic beach monitoring, we found that juveniles are more prone to bycatch in fishing nets and that females ceased their growth sooner than males but have longer lifespans than males. Our work highlights the benefit of long-term studies and will serve as baseline for future research that seek to understand mortality patterns of bottlenose dolphins elsewhere and the effects of anthropogenic threats on the survival of these animals.
Behaviorally measured tactile sensitivity in the common bottlenose dolphin, Tursiops truncatus
Madelyn G. Strahan, Dorian S. Houser, James J. Finneran, Jason Mulsow, Daniel E. Crocker
Little research has been conducted on the somatosensory system of toothed whales and it remains uncertain how tactile sensitivity varies about their bodies. In this study, tactile sensitivity to high-frequency (250-Hz) displacement of the skin was quantified in three trained adult common bottlenose dolphins (Tursiops truncatus) using a vibratory device (tactor). The greatest sensitivity was found along the rostrum, melon, and blowhole. Sensitivity decreased caudally along the body, with the dorsal fin and tip of the fluke being the least sensitive locations tested. The results support hypotheses that the follicles on the dolphin rostrum are particularly important for perception
Visual‐only assessments of skin lesions on free‐ranging common bottlenose dolphins (Tursiops truncatus): Reliability and utility of quantitative tools
Christina N. Toms, Tori Stone, Traci Och‐Adams
Scientists use photos to track individual bottlenose dolphins through time. This same technique can be used for a variety of purposes including quantifying and tracking skin lesion progression. However, this can be challenging and requires rigorous data quality control. We found that interrater reliability (i.e., the degree to which two raters give consistent results) suffers when attempting to define large numbers of skin lesions categories. Assessments using measures from the dorsal fin alone differ as much as 43% from measures using the entire visible surface of an individual. We provide recommendations for others attempting similar approaches.
Vocal repertoires and insights into social structure of sperm whales (Physeter macrocephalus) in Mauritius, southwestern Indian Ocean
Léonie A. E. Huijser, Vanessa Estrade, Imogen Webster, Laurent Mouysset, Adèle Cadinouche, Violaine Dulau-Drouot
Female and juvenile sperm whales live in social units, communicating using codas, i.e., stereotyped click sequences. Units with similar coda repertoires share vocal clan membership. Clans may exhibit differences in their social structure. To investigate vocal clan presence and social structure among sperm whales in Mauritius, we analyzed 4,767 recorded codas and investigated associations between 22 resighted individuals (out of 101 different photo-identified individuals). Differential use of about 24 detected coda types distinguished two sympatric vocal clans and social analysis revealed four candidate social units. However, more resightings are needed to confirm our results and allow for comparisons with other populations.