Skin lesion prevalence of estuarine common bottlenose dolphins (Tursiops truncatus) in North Carolina, with comparisons to other east coast study sites
J. S. Taylor, L. B. Hart, J. Adams
Bottlenose dolphins are indicators of environmental health, and skin lesions can be used to infer population health. We estimated percentages of dolphins with lesions and characterized lesions on dolphins in Roanoke Sound, NC from April 2012-October 2014 using photo-identification. Dolphin percentages with lesions varied little between years, and most lesions were observed in spring. Pale lesions were most common. Annual lesion percentages were similar to published estimates for dolphins in Charleston, SC, Brunswick, GA, and Sarasota, FL, although varied seasonally. Future studies should examine relationships between lesions and environmental variables and use stranded dolphins to investigate skin lesion etiology.
The impact of temperature at depth on estimates of thermal habitat for short‐finned pilot whales
Stephanie K. Adamczak, William A. McLellan, Andrew J. Read, Christopher L. P. Wolfe, Lesley H. Thorne
Short-finned pilot whales forage at depths up to 1,500 m. While foraging, they experience a wide range of temperatures, yet most estimates of thermal habitat use only sea surface temperature (SST) measurements. We explored how temperature at depth influenced thermal habitat estimates for short-finned pilot whales in different seasons and at different latitudes along the northeastern US seaboard. To do this we used a metric, degree-hours, to calculate the time spent at different temperatures. We found the greatest difference between estimates of thermal habitat constructed using temperature at depth and SST when SST measurements greatly differed from bottom temperature measurements.
Distributional patterns of humpback whales (Megaptera novaeangliae) along the Newfoundland East Coast reflect their main prey, capelin (Mallotus villosus)
Kelsey F. Johnson and Gail K. Davoren
Humpback whales primarily consume capelin, a small forage fish, on their Newfoundland foraging ground. As capelin populations collapsed in the early 1990s, resulting in altered timing of spawning, we examined whether humpback whale movement/distribution match these prey changes. Combining citizen science and scientific monitoring, we found that northward coastal movements of whales were associated with the initial presence of spawning capelin. In one region, initiation of capelin spawning influenced the presence of whale aggregations and photo-identification revealed a 22% return rate to capelin spawning sites, indicating that these spawning sites are important foraging areas for humpback whales in coastal Newfoundland
Interannual differences in postrelease movements of rehabilitated harbor seal pups (Phoca vitulina richardii) in the Salish Sea
Samantha Sangster, Martin Haulena, Chad Nordstrom, Joseph K. Gaydos
We compared the movements of wild and rehabilitated harbor seals and the movements of harbor seals rehabilitated in different years. Rehabilitated pups travel farther daily and cumulatively than wild pups but transmission duration is similar suggesting similar survival. Movement patterns differed across years for rehabilitated seals suggesting that individual animal factors and local environmental pressures contribute to variability.
Recommendations for estimating mark rate of cetaceans in photo‐ID research: A critique of field sampling protocols and variance estimation
Lindsay Wickman, William Rayment, Elisabeth Slooten, Stephen M. Dawson
Estimating how many individuals are present in a population is a crucial, basic question when conserving a species. One way marine mammologists estimate population size is to photograph natural markings (e.g., nicks or scars on dolphins’ dorsal fins) to identify individuals. This method can be used to estimate population size, but it also requires an estimate of the proportion of the population that has these unique markings, or mark rate. In this study we investigate how to estimate mark rate as robustly as possible. By applying our recommendations for estimating mark rate, researchers can improve their final estimate of population size.
Detailed knowledge of species’ body size and growth are imperative for successful conservation initiatives. Monitoring body condition can enable the detection of health declines ahead of significant mortality, thus potentially allowing time for a management response to prevent population decline. We trialed the use of a diver-operated stereo-video (SDOV) system for making body measurements of dwarf minke whales. We achieved significantly increased precision to previously used methods, which is desirable for monitoring growth rates and body condition. We also provide recommendations for field and analytical protocols, which may be applicable to other similarly-sized animals.
Common Bottlenose dolphins (Tursiops truncatus) in North Dalmatia, Croatia: Occurrence and demographic parameters
Grgur Pleslić, Nikolina Rako‐Gospić, Draško Holcer
The common bottlenose dolphin (Tursiops truncatus) population along the Croatian Adriatic coast is structured into discrete communities, yet many of them are unstudied. This study provides first insights into occurrence and demographic parameters of a community inhabiting the waters of North Dalmatia. Based on results, this area seems to host a mixture of resident and transient bottlenose dolphins, with the number of residents varying annually between 116 and 138 individuals. These results provide a baseline for informed management of two Sites of Community Importance, and a benchmark for future monitoring in North Dalmatian waters, an area under significant anthropogenic pressure.
Niche overlap and diet composition of three sympatric coastal dolphin species in the southwest Atlantic Ocean
Clarissa R. Teixeira, Silvina Botta, Fábio G. Daura‐Jorge, Luiza B. Pereira, Seth D. Newsome, Paulo C. Simões‐Lopes
We assess the feeding ecology of three coexisting dolphin species off southern Brazil using carbon and nitrogen stable isotopes collected from bone collagen. Specifically, we evaluated the contribution of prey sources to their diet, and temporal shifts in diet composition due to increased fishing pressure of their primary prey during the last three decades. Our results showed that the franciscana dolphin feeds mainly upon prey in the water column. In contrast, the Guiana and the Lahilles’s bottlenose dolphins feed primarily upon fish that live associated with the sea bottom and have been increasingly overexploited in southern Brazil.
Feeding ecology of the highly threatened common bottlenose dolphin of the Gulf of Ambracia, Greece, through stable isotope analysis
Asunción Borrell, Morgana Vighi, Tilen Genov, Ioannis Giovos, Joan Gonzalvo
The aim of this study was to determine the diet of bottlenose dolphins living in the Gulf of Ambracia (Greece) through the analyses of stable isotope analysis in 16 skin samples. Results suggested that the dolphin diet was based mainly on Atlantic horse mackerel, two species of sparids, and common cuttlefish, which represented together about 42% ± 15% of the biomass ingested, followed by clupeids and gobies (37% ± 17%). A better understanding of the feeding habits of these dolphins shows probable interactions with artisanal fisheries and is key for identifying adequate management measures consistent with an ecosystem-based approach.
Age‐related differences in gut microbial community composition of captive spotted seals (Phoca largha)
Jiashen Tian, Jing Du, Jiabo Han, Xinran Song, Zhichuang Lu
Captive spotted seals (Phoca largha) provide an ideal opportunity to study how age affects their gut microbiota, excluding other environmental factors, which is a challenge when monitoring wildlife. The bacterial composition of the feces of captive spotted seals from four age groups were analyzed in the present study. Firmicutes was the dominant bacteria in all measured feces; however, the composition of gut microbiota in seals of different ages was distinct. Two and 4 years of age appeared to be the most influential time nodes for variation in gut microbiota.
Passive acoustic monitoring of the distribution patterns of Irrawaddy dolphins (Orcaella brevirostris) in the middle reaches of the Ayeyarwady River, Myanmar
Zhi‐Tao Wang, Peng‐Xiang Duan, Tomonari Akamatsu, Ke‐Xiong Wang, Ding Wan
The Irrawaddy dolphin (Orcaella brevirostris) is an endangered species and its distribution in the middle reaches of the Ayeyarwady River, Myanmar, was investigated Using a towed passive acoustic monitoring device to survey between Mingun and Katha. Sixteen echolocation encounters, with a series of click trains separated by less than eight min and 26 dolphin acoustic trajectories were recorded. The mean dolphin detection rate (animals/km) progressively increased from upstream to downstream. The average interclick intervals of each click train varied significantly among river segments, indicating that the dolphins in some segments use shorter‐ranged biosonar. Future surveys with a systematic sampling track design that incorporates other factors and covering the whole distribution range along the Ayeyarwady River and at varied water levels are needed.
Occurrence, site fidelity, and associations of oceanic common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand
Jochen R. Zaeschmar, Gabriela Tezanos‐Pinto, Sarah L. Dwyer, Catherine H. Peters, Jo Berghan, David Donnelly, Anna M. Meissner, Ingrid N. Visser, Jody S. Weir, Alastair G. Judkins, Tom Brough, Marta Guerra, Lily Kozmian‐Ledward, Karen A. Stockin
Two types of bottlenose dolphin occur in New Zealand: a nationally endangered coastal type and a little-known oceanic type. This study investigated the occurrence of oceanic bottlenose dolphins using photographic records of individuals collected off the northeastern coast of North Island between 2005 and 2016. Home ranges of the two types overlap more than previously assumed yet there is little contact between them. Additionally, unlike the coastal type, oceanic bottlenose dolphins frequently associate with false killer and pilot whales and usually occur in larger groups. These findings suggest that they form two distinct populations that should be managed separately for conservation purposes.
Blowhole anomaly in pantropical spotted dolphin (Delphinidae: Stenella attenuata)
Carolina Iozzi Relvas, Michael Moore, Lucas Milmann
Corresponding Author E-mail address: firstname.lastname@example.org https://orcid.org/0000-0002-6881-3871 Ekman Serviços Ambientais e Oceanográficos, Rio de Janeiro, Brazil Correspondence Carolina Iozzi Relvas, Ekman Serviços Ambientais e Oceanográficos, Avenida das Américas, 700, bloco 1, Sala 101, Barra da Tijuca, Rio de Janeiro, RJ, 22640‐100, Brazil.
Herein we document through photos a blowhole anomaly in pantropical spotted dolphin (Stenella attenuata) in offshore waters of south eastern Brazil. It appears that two functional blowholes are present. This may be an ontogenetic anomaly since fetal development, as an opening of a second blowhole after full development of that apparatus would likely undermine its functionality. Although the modification may influence individual’s vocalization, the dolphin seemed healthy adult, and with control over the closure of the vestibular bag. We believe this is the first record of this type of anomaly in the respiratory tract of a functional odontocete.
Respiration cycle duration and seawater flux through open blowholes of humpback (Megaptera novaeangliae) and North Atlantic right (Eubalaena glacialis) whales
Maria Clara Iruzun Martins, Carolyn Miller, Phillip Hamilton, Jooke Robbins, Daniel P. Zitterbart, Michael Moore
Little is known about whale respiratory cycles, especially how blowholes function and if they interact with seawater. In this study, we described the duration of respiration cycles (exhalation/inhalation events) for North Atlantic right whales (NARWs) and humpback whales (HWs) using unoccupied aerial systems (UAS, drones). The NARWs had a mean duration of 3.07 seconds, slightly higher than HWs, 2.85 seconds. We also found seawater covering an open blowhole, potentially entering the respiratory system, in 20% of NARWs and 90% of HWs. This observation has not been described before and has implications for other fields within marine mammal science.
Gray whales hear and respond to signals from a 21–25 kHz active sonar
Adam S. Frankel and Peter J. Stein
Southbound gray whales off California were presented with 21-25 kHz sound sweeps. A research vessel moored in the migration path, transmitted the sweeps half the time, and was silent the other half. Whales had no overt or obvious response to the sound. However later statistical analyses showed that the whales slightly avoided the sound. This response demonstrates that gray whales can hear sounds in the 21-25 kHz range. These findings extend our understanding of baleen whale hearing.
Maximizing surveillance through spatial characterization of marine mammal stranding hot spots
Jennifer K. Olson, John Aschoff, Alice Goble Shawn Larson, Joseph K. Gaydos
Spatial analyses of marine mammal stranding data can be critical for improving surveillance and monitoring. We analyzed 12 years (2002-2014) of stranding data to identify carcass deposition “hot spots” for harbor seals (Phoca vitulina) in San Juan County, Washington. Carcass deposition showed a strong relationship with beaches having high proximity to public access points, suggesting increased reporting effort in those areas. Stranding frequency was also higher on beaches with longer fetch and gentle slopes. Beaches with these geomorphic characteristics would be ideal locations to actively survey to improve carcass collection during times of high expected mortality and limited resources.