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.
Seasonal acoustic occurrence, diel‐vocalizing patterns, and bioduck call‐type composition of Antarctic minke whales off the west coast of South Africa and the Maud Rise, Antarctica
Fannie W. Shabangu, Ken Findlay, Kathleen M. Stafford
This study listened for minke whale “bioduck” sounds to document the seasonal acoustic occurrence and calling behavior of Antarctic minke whales off the west coast of South Africa, and in the eastern Weddell Sea. Minke whale sounds were heard in Antarctica in January and continuously from April through September, with more calls being heard during the day than night. In South African waters, minke whale sounds were only heard from August through February, and no diurnal calling pattern was observed. A new minke whale bioduck call type is described in this study.
Calving rate decline in humpback whales (Megaptera novaeangliae) of northern British Columbia, Canada
Janie Wray and Eric M. Keen
A 15-year study along the north coast of British Columbia, Canada, observed an alarming decline in newborn humpback whales. The number of mothers with calves has declined from 2013 to 2018 at an annual rate of 13%. This new trend may indicate that the Hawaii breeding population of humpback whales has increased to its carrying capacity, but it also coincides with a decade of unusual climate events, increased shipping activity, natural disasters, and fishing activity. As this shift was occurring, federal protections for this population were removed and new shipping lanes were slated for the whale habitat in this study.
Mature hematology in neonatal walruses supports diving alongside their mothers
Shawn R. Noren, Matthew S. Edwards
Walruses have altered foraging and distribution patterns in response to climate change. Quantifying physiological capacities improves our ability to determine the environmental conditions under which an animal can persist; for marine mammals quantifying breath-hold capacities is important because this constrains foraging and habitat utilization patterns. We quantified the blood oxygen stores that support breath-holding, and found that, unlike other marine mammals, blood hematology changed little after birth. Despite having mature body oxygen stores early in life, immature walrus diving capacity remains limited compared to adults due to body size, making immature walruses most vulnerable to environmental perturbations. #walrus #climate change
Abundance and residency dynamics of the Indo‐Pacific humpback dolphin, Sousa chinensis, in the Dafengjiang River Estuary, China
Chongwei Peng, Haiping Wu, Xianyan Wang, Qian Zhu, Thomas A. Jefferson, Chun‐Chieh Wang, Youhou Xu, Jian Li, Hu Huang, Mo Chen, Shiang‐Lin Huang
Abundance and residency dynamics are baselines essential for informing population status and habitat uses. In the Dafengjiang River Estuary, one of the key habitats in the northern Beibu Gulf, China, a total of 353–430 Indo-Pacific humpback dolphins (Sousa chinensis) were involved in a fluid residency dynamic that lasted, on average, 78.5 days inside and 46.9 days outside the habitat. Strong seasonality in abundance and emigration implied a strong association between habitat use and prey resources. These baselines are seldom considered in conservation planning for the humpback dolphins, which can be addressed by genetic analyses and cross-matching photo-identification records.
Seasonal variation in Arctic marine mammal acoustic detection in the northern Bering Sea
Emily Chou, Ricardo Antunes, Stephanie Sardelis, Kathleen M. Stafford, Leigh West, Christopher Spagnoli, Brandon L. Southall, Martin Robards, Howard C. Rosenbaum
With climate change and melting sea ice, human activity in the Arctic is increasing, potentially impacting Arctic marine mammal species. In this study, we recorded and examined the underwater vocalizations of different whale, walrus, and seal species in the Bering Strait and northern Bering Sea – the Pacific gateway to the Arctic. We found that presence of calling is most influenced by time of year, where calling was most common during the winter and spring months. We also investigated changes in call presence between different recording sites, providing important information on species living in a rapidly changing Arctic.
Skin in the Game: Epidermal Molt as a Driver of Long-Distance Migration in Whales
Robert L. Pitman, John W. Durban, Trevor Joyce, Holly Fearnbach, Simone Panigada, and Giancarlo Lauriano
Why whales that feed in near-freezing waters in high latitudes, subsequently migrate thousands of miles to breed in the tropics has never been adequately explained. We satellite-tagged 62 killer whales in Antarctica and showed that they made long-distance, essentially nonstop, migrations to warm waters (20-24˚C), and back. We suggest that they could conserve body heat in subfreezing waters by reducing blood flow to their skin, thus precluding normal (continuous) epidermal molt and necessitating periodic trips to warm waters for skin maintenance. We further suggest that this ‘skin molt migration’ hypothesis could also explain long distance migration for all large whales.
Residency and abundance of sperm whales (Physeter macrocephalus) in Nemuro Strait, Hokkaido, Japan
Hayao Kobayashi, Masao Amano
We examined the trend in residence patterns and abundance of male sperm whales in Nemuro Strait, Japan, based on long-term photo identification. These findings along with previous studies suggest that males move from one breeding area to another neighboring area every several weeks, shifting their home ranges gradually over a period of a few years. The abundance of sperm whales in Nemuro Strait varied greatly from year to year. This study provides important knowledge of abundance and residency on a local scale, information which will contribute to further research on the social structure and movement pattern of male sperm whales.
Morphology of the vertebral centra in dolphins from the southwestern South Atlantic: A 3D morphometric approach and functional implications
María C. Marchesi, Claudia C. Boy, Silvana L. Dans, Matías S. Mora, Rolando González‐José
First published: 05 December 2019 https://doi.org/10.1111/mms.12660
The Commerson’s (Cephalorhynchus commersonii), Peale’s (Lagenorhynchus australis), dusky (Lagenorhynchus obscurus), and hourglass dolphins (Lagenorhynchus cruciger) are closely related species inhabiting the Southern Hemisphere that have diverse prey and habitat preferences. We applied 3D geometric morphometrics to describe differences in centrum shape along the vertebral columns of these species, and hypothesize how these differences may affect swimming. These species may be partially sympatric but they have important differences in foraging ecology and habitat preferences that could be related to differences in centrum shape along the vertebral column.
Social dynamics and sexual segregation of Australian humpback dolphins (Sousa sahulensis) in Moreton Bay, Queensland
Elizabeth R. Hawkins, Lara Pogson‐Manning, Christian Jaehnichen, Justin J. Meager
The social dynamics in a population of Australian humpback dolphins (Sousa sahulensis) inhabiting the near-urban embayment of Moreton Bay, Queensland, Australia were investigated. Between 2014 and 2017, 148 adults were photographically identified. The society was sexually segregated with females being more gregarious than males and maintaining larger networks of associates based on preferred companionships. Males had relatively few associates; however, strongly bonded male pairs were evident. Five distinct social clusters were detected with individuals unlikely to associate with others from different clusters. This highly fragmented social network implies that the population may be vulnerable to social disruptions from human impacts.
Sexual differences in the foraging ecology of 19th century beluga whales (Delphinapterus leucas) from the Canadian High Arctic
Paul Szpak, Marie‐Hélène Julien, Thomas C. A. Royle, James M. Savelle, Dongya Y. Yang, Michael P. Richards
It is very difficult to determine the sex of an animal by looking at its bones. We analyzed the DNA in beluga whale bones from a 19th century whaling site in the Canadian Arctic to determine the sex of the animals. Then, by analyzing the stable isotopes of carbon and nitrogen in the protein preserved in the bones, we found that the diets of male and female belugas differed, with males consuming a wider variety of prey than females.
Acanthocephalan parasites in sea otters: Why we need to look beyond associated mortality
Kyle M. Shanebeck and Clement Lagrue
Research often focuses on parasites that kill sea otters but we know nothing about the nonlethal significance of their most common parasite. Intestinal parasites can have many different effects in animals, such as, lowering immune response (increasing the severity of other infections), lowering metabolism and body condition (which could be important for sea otters who need an enormous amount of calories to stay warm), or changing the behavior of intermediate hosts such as crabs (affecting whole ecosystems and fisheries). In this review, we explore the idea that what does not kill a sea otter… might not make it stronger.
A citizen science approach to long‐term monitoring of humpback whales (Megaptera novaeangliae) off Sydney, Australia
Vanessa Pirotta, Wayne Reynolds, Geoffrey Ross, Ian Jonsen, Alana Grech, David Slip, Robert Harcourt
Citizen scientists from the Cape Solander Whale Migration Study compiled a 20-year data set (1997-2017) of shore-based observations from Cape Solander, Sydney, Australia. This long-term data set was used to estimate the recovery of a humpback whale population trend post-exploitation. An estimated exponential growth rate of 0.099 (95% CI = 0.079-0.119) was produced using a generalized linear model, based on observer effort (number of observation days) and number of whales observed, equating to 10% per annum growth in sightings since 1997. This highlights citizen science as low-cost approach to monitoring wildlife over time necessary to detect change in a population
Distribution, habitat use, and abundance of the endangered franciscana in southeastern and southern Brazil
Federico Sucunza, Daniel Danilewicz, Artur Andriolo, Alexandre F. Azevedo, Eduardo R. Secchi, Alexandre N. Zerbini
The franciscana (Pontoporia blainvillei) is a small dolphin found only in coastal waters of the western South Atlantic Ocean. The species is regarded as one of the most threatened cetaceans in South America mainly because of incidental mortality in fishing nets (“bycatch”). In the late 2000s, aerial surveys were conducted off southern Brazil to understand the distribution and to estimate the size of the franciscana population. Groups of franciscanas were seen in shallow coastal habitats, and ~6,800 individuals were estimated in the area. These estimates suggest that bycatch is unsustainable and a threat to the long-term survival of the franciscana.
Reproductive status of female beluga whales from the endangered Cook Inlet population
Kim E. W. Shelden, John J. Burns, Tamara L. McGuire, Kathleen A. Burek‐Huntington, Daniel J. Vos, Caroline E. C. Goertz, Gregory O’Corry‐Crowe, Barbara A. Mahoney
Beluga whales in Cook Inlet, Alaska, are endangered and isolated from other beluga populations. Aspects of their life history are poorly understood and important to their recovery. In this study, we investigated when mating and calving occurs by comparing measurements (body length/circumference) from living fetuses in pregnant, captive belugas to measurements from deceased Cook Inlet fetuses and newborns. We found most Cook Inlet whales were conceived in March-May (58%-94% depending on measurement used), and born in July-October (44%-81%). These periods match to when most captive females were ovulating/conceiving, and to when researchers saw recently born belugas during photo-identification surveys