High similarities in dorsal fin ratios of common bottlenose dolphins (Tursiops truncatus) in the Caribbean Sea
Carlos A. Niño-Torres, Jose A. Olvera-Gómez, Eric Ramos, Delma N. Castelblanco-Martínez, María P. Blanco-Parra, Laura J. May-Collado, Rita Sellares
Dorsal fin is the most notable features in dolphins playing an important role in swimming stability. The dorsal fin shape could change depending on where the dolphin’s lives. We compared dorsal fin across bottlenose dolphin in eight coastal regions in the Caribbean. Finding that coastal bottlenose dolphins across the Caribbean have very similar dorsal fin shape, having low and triangular shapes, two traits which are different with the oceanic dolphins. Nevertheless, differences in dorsal fin proportions were found between dolphin´s that live very close supporting the hypothesis that subgroups could be present even within extremely short geographical distances.
Vessel traffic influences distribution of Aotearoa New Zealand’s endemic dolphin (Cephalorhynchus hectori)
William Carome, William Rayment, Elisabeth Slooten, M. Hamish Bowman, Stephen M. Dawson
At Akaroa Harbor, Aotearoa New Zealand, recreational boat traffic, dolphin tourism, and cruise ship presence increased substantially between 2008 and 2020. Here, we examined relationships between levels of boat traffic and the presence of Hector’s dolphins (Cephalorhynchus hectori) during the austral summer 2019 – 2020. Statistical models revealed that increasing levels of motor vessel traffic, the presence of cruise ships, and high levels of dolphin tourism resulted in decreases in observations of dolphins. Our findings suggest that Hector’s dolphins at Akaroa Harbor were displaced from important habitat in response to each of these types of vessels.
Modeling vital rates and age-sex structure of Pacific Arctic phocids: influence on aerial survey correction factors
Paul B. Conn, Irina S. Trukhanova
Surveys of marine mammals often include corrections for the number of animals that are “unavailable” because they are under water or otherwise invisible to human observers. This study examines the implications of using correction factors that are themselves biased towards different age- or sex-classes (as when they are developed from younger animals that are easier to capture). The authors propose a solution based on age-structured population modeling and show how it can be used to achieve more accurate estimates of ice-associated seals in the Bering Sea.
Exposure and behavioral responses of tagged beluga whales (Delphinapterus leucas) to ships in the Pacific Arctic
Morgan J. Martin, William D. Halliday, Luke Storrie, John J. Citta, Jackie Dawson, Nigel E. Hussey, Francis Juanes, Lisa L. Loseto, Shannon A. MacPhee, Lisa Moore, Adrian Nicoll, Gregory O’Corry-Crowe, Stephen J. Insley
Beluga whales (Delphinapterus leucas) face many threats, including increasing underwater noise pollution from ship traffic. This study documents the behavioral responses of nine satellite-tagged belugas during encounters with ships in 2018. Individual tagged belugas’ surface movements and diving behavior were examined. Belugas’ swim speed increased when ships were nearby, showing possible changes in swim speed up to 79 km from ships. Beluga behavior was disrupted when some ships passed within 50 km. These findings match previous studies showing avoidance responses by belugas to ships at distances far beyond visual range, implying belugas react to low levels of underwater ship noise.
Towards the definition of the humpback whale population units along the Mexican and Central American coasts in the Pacific Ocean
Pamela Martínez-Loustalot,Katherina Audley,Ted Cheeseman,Joëlle De Weerdt,Astrid Frisch-Jordán,Oscar Guzón,Marilia Olio,Christian D. Ortega-Ortiz,Nicola Ransome,Francisco Villegas-Zurita,Jorge Urbán R.
Humpback whale aggregations in the Mexican Pacific were known in mainland Bahía de Banderas, the southern region of the Baja California Peninsula and the offshore Revillagigedo Archipelago, divided into coastal and offshore populations. In recent decades, humpback whales have increased their presence in the Southern Mexican Pacific. Whether these whales belong to the Mexican or Central American populations is unknown. Based on the photo-ID technique, this study found a strong relationship between the Central American population with the whales from southern Mexico. The Mexican Pacific is used by the offshore, coastal, and Central American populations.
Home ranges and diving behavior of endangered New Zealand sea lions along the Catlins coast of South Island, New Zealand
Nathan Reed, Simon Childerhouse, Bruce C. Robertson, Randall W. Davis
New Zealand sea lions have recently begun recolonizing South Island after centuries of absence. The goal of our study was to use tracking equipment attached to female sea lions to determine ranges and diving behavior along the Catlins Coast of South Island. We found that ranges were small and primarily remained close to shore, and dives were shallow and short in duration. We identified three dive types that displayed varying energy requirements and likely served different purposes. The results contrast New Zealand sea lions’ behavior in subantarctic habitats and are encouraging for future population growth on South Island.
Season, age, sex, and location impact the density of tooth rake mark and dorsal fin notch of Indo-Pacific humpback dolphins (Sousa chinensis) in the northern South China Sea
Agathe Serres, Wenzhi Lin, Binshuai Liu, Mingli Lin, Mingming Liu, Shenglan Chen, Songhai Li
The study of socio-sexual interactions in captive finless porpoises and bottlenose dolphins revealed that these interactions can range from playful/affiliative to aggressive and can play a role in the formation and maintenance of social bonds and dominance hierarchies. These interactions may play a particularly important role in the social life of captive male finless porpoises, which do not engage in much other social interactions. The characteristics of socio-sexual and agonistic interactions between males and females suggest that finless porpoises could use a scramble competition mating tactic, which needs further validation, with implications for the conservation of the endangered finless porpoises.
Low anthropogenic mortality of humpback (Megaptera novaeangliae) and killer (Orcinus orca) whales in Norwegian purse seine fisheries despite frequent entrapments
Arne Bjørge, André Moan, Kathrine A. Ryeng, Jørgen R. Wiig
Killer and humpback whales are actively approaching purse seines set for herring in Northern Norway and they are frequently entrapped. New legislation commanding fishers to open the seine if whales are entrapped, in combination with entanglement response training of the Coast Guard and the Sea Surveillance Unit of the Directorate of Fisheries, result in low anthropogenic mortality of killer and humpback whales despite frequent entrapments. Based on logbooks of fishery inspectors, average yearly mortality was approximately 0.60 killer whales and 0.39 humpback whales corresponding to 0.008% and 0.007% of the respective abundance estimates for these whale species in Norwegian waters.
Postmortem pathology investigation of the wounds from invasive tagging in belugas (Delphinapterus leucas) from Cook Inlet and Bristol Bay, Alaska
Kathleen A. Burek-Huntington, Kim E. W. Shelden, Russel D. Andrews, Caroline E. C. Goertz, Tamara L. McGuire, Sophie Dennison
Wildlife researchers need to weigh benefits to conservation goals against risks to individual animals when using implanted satellite transmitters. We examined wounds from tags on three deceased belugas from two different regions of Alaska, Cook Inlet and Bristol Bay, that were captured and released alive 4 months – over 12 years prior to their deaths. In the laboratory, we found normal healing for one whale but infection for two others. In this report, we describe these findings as well as make recommendations to reduce infections and mortality.
Factors affecting the survival of harbor (Phoca vitulina) and gray seal (Halichoerus grypus) juveniles admitted for rehabilitation in the UK and Ireland
Michal Zatrak, Sam Brittain, Lauren Himmelreich, Susie Lovick-Earle, Romain Pizzi, Kirsty J. Shaw, Robyn A. Grant, Matthew Geary
Stranded juvenile harbor and gray seals are frequently rescued and admitted for rehabilitation around the UK and Ireland. Reasons for admission included malnourishment, injuries, maternal abandonment, lethargy, and parasite infections. Gray seals were nearly five times more likely to survive than harbor seals. Heavier juvenile seals were also more likely to survive than lighter seals. This could be attributed to the importance of fat in maintaining their body temperature and keeping hydrated. Special attention should therefore be paid to the weight of juvenile seals during triage and treatment to enhance their chances of survival and consequent release to the wild.