Heard but not seen: Occurrence of Kogia spp. along the western North Atlantic shelf break
Lynne E. W. Hodge, Simone Baumann‐Pickering, John A. Hildebrand, Joel T. Bell, Erin W. Cummings, Heather J. Foley, Ryan J. McAlarney, William A. McLellan, D. Ann Pabst, Zachary T. Swaim, Danielle M. Waples and Andrew J. Read
Dwarf and pygmy sperm whales strand frequently along the southeastern U.S. but are rarely detected during visual surveys. These relatively small whales often lie motionless at the surface and dive without showing their tails. To better understand their distribution, we compared detections of these two species along the Atlantic shelf break using visual survey and passive acoustics methods. Our results demonstrate that these animals are much more common along the Atlantic shelf break and slope waters than suggested by visual surveys, highlighting the value of passive acoustic monitoring for describing the occurrence and distribution of cryptic species.
Large dugong (Dugong dugon) aggregations persist in coastal Qatar
Christopher D. Marshall, Mehsin Al Ansi, Jennifer Dupont, Christopher Warren, Ismail Al Shaikh and Joshua Cullen
A gulf-wide survey conducted in 1986 for dugongs, or sea cows, in the Arabian Gulf discovered the largest population outside Australia. The largest group of dugongs ever recorded was found during these surveys between Qatar and Bahrain. Our team rediscovered several large herds of sea cows in this region. The largest group size we report is 508 individuals, but helicopter surveys also detected large herds of 226 and 166 individuals each. Large groups of dugongs still frequent coastal waters of Qatar during the winter months. These observations provide a solid foundation to expand conservation efforts in this region in Qatar.
Environmental evidence for a pygmy blue whale aggregation area in the Subtropical Convergence Zone south of Australia
Maria I. Garcia‐Rojas, K. Curt S. Jenner, Peter C. Gill, Micheline‐Nicole M. Jenner, Alicia L. Sutton and Robert D. McCauley
The importance of the Subtropical Convergence zone south of Australia as a feeding area to the pygmy blue whales of the eastern Indian Ocean was investigated. A combination of satellite tagging studies and acoustic and visual surveys confirmed the presence of pygmy blue whales in the Subtropical Convergence zone and provided evidence for feeding throughout the region. Pygmy blue whales were acoustically detected in proximity to sea surface temperature fronts and high chlorophyll concentrations. Oceanographic features present throughout the Subtropical Convergence zone continue to support the world’s largest living mammals during migratory movements between the Southern Ocean and Indonesia.
Comparing depth and seabed terrain preferences of individually identified female humpback whales (Megaptera novaeangliae), with and without calf, off Maui, Hawaii
Adam A. Pack, Louis M. Herman, Alison S. Craig, Scott S. Spitz, James O. Waterman, Elia Y. K. Herman, Mark H. Deakos, Siri Hakala and Carley Lowe
We studied individual female humpback whales over 12 years in Hawaii so that we could investigate what water depth and seabed terrain type they preferred when they had a calf versus when they had no calf. At each sighting, we photographed the female’s unique tail fluke pattern and determined her water depth and whether she was associated with rugged or flat seabed terrain. We found that 35 females who were sighted with a calf and without a calf in different years preferred significantly shallower water when they had a calf, but they had no preference for particular seabed terrain.
The metabolic cost of swimming and reproduction in harbor porpoises (Phocoena phocoena) as predicted by a bioenergetic model
Cara A. Gallagher, S. Jonathan Stern and Ellen Hines
Harbor porpoises have returned to San Francisco Bay after a 65-yr hiatus. To understand the potential impact of this returning predator, we constructed an energy budget for adult male and female porpoises that estimated the costs of maintenance, swimming, thermoregulation, and reproduction. Female porpoises could be pregnant, nursing, both pregnant and nursing, or neither. We found that females that were pregnant and nursing simultaneously had the highest costs while males had the lowest. For the numbers sighted in the Bay, we found that harbor porpoises would require approximately 30.4 ± 22.0 metric tons of fish per year.
Applied zooarchaeology and Oregon Coast sea otters (Enhydra lutris)
Hannah P. Wellman
The sea otter was nearly driven to extinction on the Pacific Coast in the 19th century. Although sea otters were successfully reintroduced to parts of the Pacific Coast, the species has yet to make a return to Oregon. This study compares archaeological sea otter teeth and bones from Oregon to those from modern otters from California and Alaska, providing additional data on the distribution of sea otter sizes along the Pacific Coast. These results confirm that using archaeological animal remains has great potential and utility in examining and contributing to answering modern ecological questions and conservation biology decisions.
Association patterns of common bottlenose dolphins (Tursiops truncates) in Bahía San Antonio, Argentina
Bottlenose dolphins are often believed to have many long-lasting and stable relationships within their social structure. However, this study indicates that this is not the case for a small population of common bottlenose dolphins in Argentine Patagonia. In fact, despite some long-lasting bonds, most social bonds among individuals of this population are very flexible and vary with season, possibly related to the seasonal variation in food availability, confirming the species’ ability to adapt to changes in their environment.
Breathing synchrony in franciscana (Pontoporia blainvillei) and Guiana dolphins (Sotalia guianensis) in Southern Brazil
Pamela Soledad Actis, Daniel Danilewicz, Marta J. Cremer and Guilherme A. Bortolotto
When paired dolphins surface together to breathe, they may be doing it in synchrony. In this study we looked at the synchronization of breathing in the franciscana and Guiana dolphins that live in Babitonga Bay (southern Brazil), where many human activities may be affecting them. Using statistical methods, we found that franciscana dolphins synchronize their breathing according to the proximity to their partner. Guiana dolphins also do that, but the size of their group and the type of boat that we used to observe them, may also important. Our results help to better understand the breathing synchrony in cetaceans.
Prediction of humpback whale group densities along the Brazilian coast using spatial autoregressive models
Heloise J. Pavanato, Fernando P. Mayer, Leonardo L. Wedekin, Márcia H. Engel and Paul G. Kinas
We looked at the influence of environmental factors and autocorrelation effects on humpback whale group densities in the Southwest Atlantic Ocean. We found that humpback whale groups are mostly occupying areas relatively far from the coast (at 171 m) that are still shallow, as banks and coral reefs. We also found that groups tend to be aggregated in some areas, however, the chance of seeing a whale at any of the surveyed areas are high. These results are likely to explain the success of calving and breeding activities off the Brazilian coast.
First record of humpback whale songs in Southern Chile: Analysis of seasonal and diel variation
Sonia Español-Jiménez and Mike van der Schaar
In this study, we report results from the first continuous acoustic monitoring of a humpback whale feeding ground off southern Chile, Corcovado Gulf. We detected songs of humpback whales during summer and with a peak in autumn. Songs were detected during all light regimes studied, but most frequently during darkness.
Age estimation in bowhead whales using tympanic bulla histology and baleen isotopes
Jennifer D. Sensor, John C. George, Mark T. Clementz, Denise M. Lovano, David A. Waugh, Geof H. Givens, Robert Suydam, Raphaela Stimmelmayr and J. G. M. Thewissen
One of the ear bones of bowhead whales, the tympanic, has layers that resemble tree rings. We investigated when these layers are formed. We concluded that a thick layer is formed before the whale’s birth, and another thick layer is formed when it is nursing during the first year of life. After that, bowheads form thinner layers of bone on their tympanic, mostly at a rate of two layers per year (one dark layer, one translucent layer), although occasionally this can vary. The thickness of these layers may depend on the body condition of the whale during that year.
Description and classification of Indian Ocean humpback dolphin (Sousa plumbea) whistles recorded off the Sindhudurg coast of Maharashtra, India
Isha Bopardikar, Dipani Sutaria, Mihir Sule, Ketki Jog, Vardhan Patankar and Holger Klinck
The Indian Ocean humpback dolphin (Sousa plumbea), a common cetacean species in India, has a diverse vocal repertoire, which to date has not been described in detail. This study focused on analyzing their whistle vocalizations. Humpback dolphins were recorded off the Sindhudurg coast of Maharashtra, India and 2,260 whistles were analyzed for their acoustic characteristics. Whistles spanned a wide frequency range between 2.3 kHz and 33.0 kHz, with durations ranging from 0.01 to 1.60 s. Whistles were then classified into seven contour classes. This study provides a detailed description of acoustic features of humpback dolphin whistles from Indian waters.
Identifying critical habitat of the endangered vaquita (Phocoena sinus) with regional δ13C and δ15N isoscapes of the Upper Gulf of California, Mexico
Mónica Y. Rodríguez-Pérez, David Aurioles-Gamboa, Laura Sánchez-Velásco, Miguel F. Lavín and Seth D. Newsome
The vaquita (Phocoena sinus) is the world´s most endangered cetacean and has experienced a 60% reduction in the size of its population in the past decade. We identified vaquita foraging areas by creating a carbon (δ13C) and nitrogen (δ15N) isoscape of the Upper Gulf of California. This species is confined to the western region, characterized by relatively high δ15N, higher sea surface temperatures, higher concentrations of silt in sediments, and the highest turbidity. Our approach is an effective use of marine isoscapes over a small spatial scale to identify the environmental characteristics that define the critical habitat for marine mammals.
New diagnostic descriptions and distribution information for Shepherd’s beaked whale (Tasmacetus shepherdi) off Southern Australia and New Zealand
David M. Donnelly, Paul Ensor, Peter Gill, Rohan H. Clarke, Karen Evans, Michael C. Double, Trudi Webster, Will Rayment and Natalie T. Schmitt
Shepherd’s beaked whale is a poorly understood and rarely seen whale species. Up until 2008 there had never been a confirmed sighting of this species from vessels at sea. What was known about the species had previously been gathered from a few aerial sightings and from deceased stranded animals. Between 2008 and 2017, there have been 18 confirmed sightings of the species, which included the first detailed images of this elusive whale. This paper describes in detail the appearance of this animal as well as providing new information on the distribution and behavior of the species.
Feeding calls produced by solitary humpback whales
Michelle E. H. Fournet, Christine M. Gabriele, Fred Sharpe, Janice M. Straley and Andrew Szabo
In Southeast Alaska groups of humpback whales engaged in coordinated foraging on Pacific herring produce a long, stereotyped vocalization called a ‘feeding call’. In this study we document that solitary humpback whales throughout Southeast Alaska also produce feeding calls while herring foraging. We propose that this call serves a prey manipulation function. We did not find evidence that humpback whales use this call exclusively to coordinate group members (the observed whales were foraging alone) nor that the was used to recruit individuals into to foraging pods, though these remain possible alternative functions for feeding calls.
Assessing the abundance of Bristol Bay belugas with genetic mark-recapture methods
John J. Citta, Gregory O’Corry-Crowe, Lori T. Quakenbush, Anna L. Bryan, Tatiana Ferrer, Myra J. Olson, Roderick C. Hobbs and Brooke Potgieter
The Bristol Bay population (stock) of beluga whales (Delphinapterus leucas) is separate from other populations and resides in Bristol Bay year-round. We identified individual belugas using DNA from skin samples and statistically estimated how many belugas are in this population. We found that there were approximately 1,928 belugas in this population, not including calves, which were not sampled. Because some belugas did not enter the area we sampled while we were sampling, there are likely more belugas in the population than what we found, and our estimate is best considered a minimum population size.
Largest reported groups for the Indo-Pacific bottlenose dolphin (Tursiops aduncus) found in Algoa Bay, South Africa: Trends and potential drivers
Thibaut N. Bouveroux, Michelle Caputo, Pierre W. Froneman and Stephanie Plön
Along the Eastern Cape coastline of South Africa, the mean group size of bottlenose dolphins (Tursiops aduncus) was large with an average of 52 animals. Significantly larger groups were observed in Algoa Bay than off the Wild Coast. In Algoa Bay, the mean group size increased significantly from an average 18 animals in 2008 to 76 animals in 2016, including largest maximum group sizes ever reported worldwide (maximum group size=600). Neither season nor behavior had a significant effect on mean group size. It remains unclear which ecological drivers are leading to the large groups observed in this area.
First demographic insights on historically harvested and poorly known male sperm whale populations off the Crozet and Kerguelen Islands (Southern Ocean)
Guillemette Labadie, Paul Tixier, Christophe Barbraud, Rémi Fay, Nicolas Gasco, Guy Duhamel and Christophe Guinet
This study focused on sperm whale interacting with the Patagonian toothfish (Dissostichus eleginoides) fishery operating off the Kerguelen and Crozet Archipelagos. Demographic parameters were estimated using a 10-year long photo-identification data set. The mean annual number of interacting sperm whales and their survival were estimated in Crozet and Kerguelen. These survival and population size estimates can be used in evaluating the current conservation status of this historically harvested stock and to investigate depredation trends in both Crozet and Kerguelen Islands.
Identifying behavioral states and habitat use of acoustically tracked humpback whales in Hawaii
E. Elizabeth Henderson, Tyler A. Helble, Glenn Ierley and Steve Martin
Although humpback whales have been well-studied on their Hawaiian breeding grounds, it is difficult to track individual animals over long distances without tags. Here, singing humpback whales were tracked on the US Navy Pacific Missile Range Facility off Kauai, HI, from January 2011 through June 2014. One hundred and eight individual tracks were identified, and the behavior of these tracks was classified into four categories, described as Directed Travel, Repeated Stationary Dives, Mill, and combined behavior tracks. Some daily and seasonal patterns were identified within the tracks. These results provide new information about the movement of singing humpback whales.
Delphinid brain development from neonate to adulthood with comparisons to other cetaceans and artiodactyls
Sam H. Ridgway, Kevin P. Carlin and Kaitlin R. Van Alstyne
We explored relationships between Cetacean (whales, dolphins, and porpoises) neonatal brain size, gestation duration, maternal body mass, and body growth. Cetacean brains grow fast in the womb and longer gestation results in a larger brain. Biological scaling relationsips show that the larger the mother’s body mass, the larger the neonatal brain. After birth, dolphin bodies grow much faster than brains, and index of encephalization decreases even as brains grow beyond maturity. Dolphins’ relatively large brain growth during life at sea may be explained by differences from artiodactyls’ life on land.
Sex-related differences in the postmolt distribution of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea
Izzy Langley, Mike Fedak, Keith Nicholls and Lars Boehme
Weddell seals in the southern Weddell Sea are in a unique position on the continental shelf edge, with vast shelf waters to the south and deep ocean to the north. We describe sex-related differences in their winter distribution, from data collected by 20 satellite telemetry tags deployed in February 2011. We found that males swam less far per day and spent more time in shallower water than females. We also found that males were more resident than females, whereas females swam both on and off the continental shelf. This behavior is unlike what has been shown elsewhere in the species’ range.
Ultrasonography of mammary glands in finless porpoises (Neophocaena asiaeorientalis) at different reproductive stages
Xianyuan Zeng, Shiang-Lin Huang, Yujiang Hao, Ding Wang, Junhua Ji, Xiaojun Deng and Ghulam Nabi
Mammary glands provide energy and nutrients via milk to offspring during the beginning of their life, playing a vital role in neonatal growth and survival in mammals. We applied ultrasonography to investigate appearances and measurements of mammary glands at different reproductive stages. Our findings revealed that mammary glands develop little until the final phase of gestation, probably to reduce swimming drag, and that mammary glands increased production of milk from mid- to late lactation, likely to meet the increasing energy requirement for thermal insulation and body growth in the winter.
The potential beginning of a postwhaling recovery in New Zealand humpback whales (Megaptera novaeangliae)
Nadine J. Gibbs, Rebecca A. Dunlop, E. John Gibbs, Joseph A. Heberley and Carlos Olavarría
Humpback whales in the Southern Hemisphere were hunted to near extinction by extensive whaling in Antarctica from the 1940’s to 1970’s. Recovery has been variable with some regions reporting humpback whales now at numbers similar to those before whaling, while other regions are showing little sign of increase. This paper describes the results from 12 years of survey in Cook Strait, New Zealand. It found an increase in number of humpback whales migrating through Cook Strait, suggesting they are slowly returning to this region either through population increase or by whales coming from eastern Australia.
Occasional acoustic presence of Antarctic blue whales on a feeding ground in southern Chile
Susannah J. Buchan, Rodrigo Hucke-Gaete, Kathleen M. Stafford and Christopher W. Clark
Whales vocalize to communicate with each other, often across vast distances of ocean. By fixing underwater microphones (hydrophones) on the ocean floor, we can listen to the passage of different species and populations of whale, which allows us to monitor endangered whale populations. Antarctic blue whales were one of the most severely affected by whaling. In this study, we listen for the distinctive Antarctic blue whale song on a feeding ground in remote Chilean Patagonia. We find that Antarctic blue whales occasionally pass through this area during austral summer, straying far from their Southern Ocean summer feeding ground.
Bottlenose dolphin (Tursiops truncates) social structure in the Shannon Estuary, Ireland, is distinguished by age- and area-related associations
Isabel Baker, Joanne O’Brien, Katherine McHugh, Simon N. Ingram and Simon Berrow
This is the most thorough study so far of the social structure of a population of wild bottlenose dolphins in the Shannon Estuary, Ireland. It analyzes the dynamics of the whole population and of individuals classed by sex, age, and area. Female-male pairs had strong associations. Juveniles associated more with juveniles, and adults with adults. Within-area associations were stronger than between-area associations. Some associations lasted for over three years. Network analysis revealed a potential community division of the population by area. Socializing activity featured stronger associations than foraging activity. These results help us see how varied dolphin societies can be.
Telemetry tags increase the costs of swimming in northern fur seals, Callorhinus ursinus
David A. S. Rosen, Carling G. Gerlinsky, and Andrew W. Trites
Animal borne instruments are routinely deployed on marine mammals but few studies have examined their effects on tagged animals. We measured the effect of 2 types of small tags on the swimming speeds and costs of 4 trained female northern fur seals (Callorhinus ursinus) while swimming an underwater circuit. The placement of tags significantly increased rate of energy expenditure (8%–12%), decreased swim speed (3%-6%), and increased the total cost of swimming a set distance (12%-19%). These effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer-term impacts on the studied animals.
The influence of lipid-extraction and long-term DMSO preservation on carbon (δ13C) and nitrogen (δ15N) isotope values in cetacean skin
Seth D. Newsome, Susan J. Chivers and Michelle Berman Kowalewski
The development of projectile biopsy techniques resulted in the collection of thousands of cetacean tissue samples that were archived in a dimethyl sulfoxide (DMSO) for long-term preservation. We examined the influence of DMSO on carbon and nitrogen isotope values, which provides information about the ecology of wide-ranging and elusive marine mammals. We found that the chemical effects of DMSO preservation can be removed by treating skin with organic solvents. This method provides access to a rich archive of DMSO-preserved samples that will expand our understanding of how the ecology of cetaceans has been influenced by historical changes in environmental conditions.