Variation in δ13C and δ15N values of mothers and their calves across southern right whale nursery grounds: The effects of nutritional stress?
Emma L. Carroll, Glenn Dunshea, Paulo H. Ott, Luciano O. Valenzuela, C. Scott Baker, Simon J. Childerhouse, Oscar E. Gaggiotti, Paulo A. C. Flores, Karina Groch, Darren R. Gröcke, Mark A. Hindell, David Lundquist, Larissa R. Oliveira, Victoria Rowntree, Mariano Sironi, Seth D. Newsome
Southern right whales (SRW) are capital breeders that use stored energy reserves to sustain themselves and their calves on nursery areas. With successful calving events declining in some SRW populations, it has been hypothesized that nutritional stress in adult females causes reproductive failure or death of calves shortly after birth. Here we compared offsets in carbon and nitrogen isotope values of mothers and their offspring (∆13Ccalf-cow and ∆15Ncalf-cow) among three SRW populations. SRW from Aotearoa New Zealand, with high population growth rates and body conditions scores, have negative ∆13Ccalf-cow suggesting calves are utilizing 13C-depleted lipid carbon in milk to fuel the synthesis of nonessential amino acids used to build new tissues and rapidly grow. In contrast, a significantly positive ∆13Ccalf-cow offset previously reported for SRW from Argentina during a mass die-off event was hypothesized to be due to calves consuming milk with low lipid content. Patterns in ∆15Ncalf-cow were more difficult to interpret and highlight the complexity in nitrogen transfer between mother and offspring. When combined with similar data collected from Brazil and during a low mortality year in Argentina, we hypothesize this approach provides a way to retrospectively compare nutritional condition of breeding adult female SRW across nursery areas.
Las ballenas francas australes (BFA) tienen una estrategia de reproducción de “acumulación de capital”, es decir que utilizan las reservas de energía almacenadas para mantenerse a sí mismas y a sus crías en las áreas de cría. Con la disminución de los eventos de partos exitosos en algunas poblaciones de BFA, se ha planteado la hipótesis que el estrés nutricional en las hembras adultas causa fallas reproductivas o la muerte de los ballenatos poco después del nacimiento. En este trabajo comparamos las diferencias en los valores de isótopos de carbono y nitrógeno de las madres y sus crías (∆13Ccría-madre y ∆15Ncría-madre) entre tres poblaciones de BFA. Las BFA de Aotearoa Nueva Zelanda, con altas tasas de crecimiento de la población y altos puntajes de condiciones corporales, tiene ∆13Ccría-madre negativo, lo que sugiere que las crías están utilizando carbono lipídico empobrecido en 13C en la leche para impulsar la síntesis de aminoácidos no esenciales utilizados para construir nuevos tejidos y crecer rápidamente. En contraste, diferencias significativamente positivas de ∆13Ccría-madre reportadas previamente para BFA de Argentina durante un evento de muerte masiva han sido hipotetizadas como debido al consumo de leche con bajo contenido de lípidos. Los patrones de ∆15Ncría-madre fueron más difíciles de interpretar y resaltan la complejidad en la transferencia de nitrógeno entre las madres y sus crías. Al combinar los datos de este estudio con datos similares recopilados en Brasil y durante un año de baja mortalidad en Argentina, podemos plantear la hipótesis de que este enfoque proporciona una forma de comparar retrospectivamente la condición nutricional de las hembras adultas de BFW en distintas áreas de cría.
A baleia-franca-austral (BFA) possui a estratégia de acumular energia para manter a si mesma e aos seus filhotes nas áreas reprodutivas. Devido a diminuição do número de partos bem sucedidos em algumas populações de BFA, foi sugerida a hipótese de que o estresse nutricional nas fêmeas adultas causaria falhas reprodutivas ou a morte dos filhotes logo após o nascimento. Neste estudo comparamos as diferenças nos valores dos isótopos de carbono e nitrogênio das fêmeas e seus filhotes (∆13Cfilhote-mãe e ∆15Nfilhote-mãe) entre três populações de BFA. As BFA de Aotearoa Nova Zelândia, com altas taxas de crescimento da população e altos valores de condição corporal, têm ∆13Cfilhote-mãe negativo, resultado que sugere que os filhotes estão utilizando carbono lipídico empobrecido em 13C do leite para estimular a síntese de aminoácidos não essenciais utilizados para construir novos tecidos e crescer rapidamente. Por outro lado, as diferenças significativas positivas de ∆13Cfilhote-mãe reportadas previamente para BFA de Argentina, durante um evento de mortalidade em massa, foram atribuídas ao consumo de leite de baixo conteúdo de lipídios. Os padrões de ∆15Nfilhote-mãe foram mais difíceis de se interpretar e demonstraram a complexidade na transferência de nitrogênio entre as mães e seus filhotes. Ao combinar os dados deste estudo com dados similares coletados no Brasil e durante um ano de baixa mortalidade na Argentina, sugere-se que os estudos isotópicos seriam uma forma de comparar retrospectivamente a condição nutricional das fêmeas de BFA em distintas áreas reprodutivas.
Population structure of North Pacific gray whales in light of trans-Pacific movements
Aimée R. Lang, David W. Weller, Alexander M. Burdin, Kelly Robertson, Olga Sychenko, Jorge Urbán R., Sergio Martínez-Aguilar, Victoria L. Pease, Richard G. LeDuc, Dennis I. Litovka, Vladimir N. Burkanov, Robert L. Brownell Jr.
A small number (~200) of gray whales feed in the western North Pacific (WNP). Many of these whales migrate to the Mexican wintering ground, which is also used by whales that feed in the eastern North Pacific (ENP). Despite this shared wintering area, we identified genetic differentiation between whales sampled on the WNP and ENP feeding grounds, suggesting that WNP whales overwintering in the ENP may interbreed largely with each other early on the migration. However, the lack of samples known to represent whales remaining in the WNP year-round limits understanding of the basin-wide structure of gray whales.
Passive acoustic monitoring reveals feeding attempts at close range from soaking demersal longlines by two killer whale ecotypes
Gaëtan Richard, Julien Bonnel, Julie Beesau, Eva Calvo, Fabio Cassiano, Maéva Dramet, Aziliz Glaziou, Kinga Korycka, Christophe Guinet, Flore Samaran,
This study focused on killer whales feeding on fish caught on longlines, named depredation behavior, around Crozet Archipelago. To observe what can’t be seen, we used hydrophones fixed on longlines to record killer whale sounds. Recordings revealed that killer whales were present and probably looking for food (production of echolocation clicks) around soaking longline when no boat were around. Since food is available on longline, killer whales were likely depredating whereas depredation was thought to only occur when longlines are hauled by fishermen. These results suggest then that depredation at Crozet may have been underestimated until now.
Observations of parturition in humpback whales (Megaptera novaeangliae) and occurrence of escorting and competitive behavior around birthing females
Nicola Ransome, Lars Bejder, Micheline Jenner, Gavin Penfold, Violeta J. Brosig, Craig Kitson, Rebecca Skjothaug, Emma Neilson, Neil R. Loneragan, Joshua N. Smith,
Documented cases of whale births in the wild are rare. While there are currently no direct observations of a complete humpback whale birth, they are one of the few species where observers have been present during a birthing event. We compiled eye-witnessed accounts of all known humpback whale birthing events and found nine well-documented cases globally. In two-thirds of accounts another ‘escort’ whale was present and in close association with the birthing female, and of these, most cases involved multiple escorts. We describe details of birthing events, including whale behavior, calf appearance, and discuss reasons for escort presence during births.
Site fidelity, spatial use, and behavior of dwarf sperm whales in Hawaiian waters: using small-boat surveys, photo-identification, and unmanned aerial systems to study a difficult-to-study species
Robin W. Baird, Sabre D. Mahaffy, Jordan K. Lerma
Dwarf sperm whales are notoriously difficult-to-study. We combined sightings and drone observations from directed research with citizen science photo contributions to reveal new details into their lives in Hawaiian waters. Re-sightings of distinctive individuals up to 15 years suggests a small resident population off Hawaiʻi Island, primarily living in island slope waters. This slope-dwelling population appears to overlap with an offshore population primarily found in deeper waters. Evidence of unsuccessful attacks by large sharks, and injuries caused by fishery interactions, were documented. Drone observations revealed details on social behavior and vigilance for predators not previously documented for this species.
Killer whale predatory scarring on mysticetes: A comparison of rake marks among blue, humpback, and gray whales in the eastern North Pacific
Enrico Corsi, John Calambokidis, Kiirsten R. Flynn, Gretchen H. Steiger
Killer whale predation on baleen whales is challenging to observe in the wild. We quantified the killer whale scars on the flukes of three large whale species. We compared scarring location, severity and incidence in humpback, gray, and blue whales in the eastern North Pacific. Gray whales showed the highest incidence of scars and they and humpback whales bore most scars on the trailing portion of their tail flukes, while blue whales bore most scars on the leading edge. This reflects that killer whales adapt their hunting strategy to different species based on the particulars of their distribution and response.
Humpback whale call repertoire on a northeastern Newfoundland foraging ground
Mikala V. Epp, Michelle E. H. Fournet, Gail K. Davoren
Throughout their range, humpback whales produce non-song vocalizations known as ‘calls’. To describe the calling repertoire of humpback whales on a coastal Newfoundland, Canada foraging ground, we recorded humpback whales from July-August 2015 and 2016 using a bottom-mounted hydrophone. Through combining human and statistical classification techniques, we identified a repertoire of 13 call types. Some call types were distinct, while others were graded. This acoustic variability matched previous studies suggesting that humpback whale calls fall along a continuum, rather than into discrete call types.
Against all odds: Harbor porpoises intensively use an anthropogenically modified estuary
In this work, the occurrence of harbor porpoises (small whales) at two stations in the River Ems (Germany, Netherlands) was examined using an 8-year data set. Harbor porpoises were present year-round at both stations. Their detection was mainly explained by season, tide, and noise level, with the highest detection probabilities in spring, at high tide, and at low noise levels. The seasonal and tide-dependent occurrence of harbor porpoises coincided with prey (fish) availability. The results of this study can help to improve estuarine management through measures that include conducting dredging and disposal activities when harbor porpoise occurrence is less likely.
Humpback whale abundance in Hawai‘i: Temporal trends and response to climatic drivers
Adam S. Frankel, Christine M. Gabriele, Suzanne Yin, Susan H. Rickards
Consistent shore-based visual counts of humpback whales were conducted from Hawai‘i Island in winter 2001 to 2019. These whales migrate to feed in summer off Alaska and British Columbia. Hawai‘i whale numbers generally increased from 2001 to 2015 but dropped suddenly in 2016 by 60% during a severe marine heatwave. Calving rate fell by 83%, and both of these indicators have been slow to recover. We found that cool productive waters in the summer feeding grounds strongly correlated with higher numbers of adults and calves in winter the following year. Climate change affects ocean temperatures, which affects this whale population.
Body condition index in beluga whale (Delphinapterus leucas) carcasses derived from morphometric measurements
Sylvain Larrat, Stéphane Lair
A body condition index was derived from the weight and length taken of beluga whale carcasses. This scaled mass index was well correlated with subjective visual evaluation of body condition in beluga whales >290 cm, but not in whales <290 cm. The alternative indices that were best correlated with the scaled mass index were those calculated using the sacral circumference and the ventral adipose thickness in individuals <290 cm and the back-muscle mass and maximum circumference in individuals >290 cm. These scaled indices could provide objective tools to evaluate body condition of stranded beluga whales.
Climate anomalies influence tooth growth patterns of South American sea lion
Federico M. Heredia, Ailin Sosa Drouville, Ana M. Srur, Enrique A. Crespo, M. Florencia Grandi
Climate anomalies indirectly affect tooth growth of marine mammals through changes in diet. This is reflected as variation in the dentine deposition, which determines the formation of annual layers. The aim of this work was to study potential effects of El Niño-Southern Oscillation (ENSO) and Southern Annular Mode (SAM) on South American sea lion of Patagonia, by examining width variation of dentine layers. Our results did not indicate any ENSO effects on this species, while positive SAM events could affect the nutritional status of females, generating thinner dentine layers during the next year.
Glycopatterns of the foregut in the striped dolphin Stenella coeruleoalba, Meyen 1833 from the Mediterranean Sea
Roberto Carlucci, Giulia Cipriano, Carmelo Fanizza, Tommaso Gerussi, Rosalia Maglietta, Antonio Petrella, Guido Pietroluongo, Pasquale Ricci, Daniela Semeraro, Marco Vito Guglielmi, Giovanni Scillitani, Donatella Mentino
We studied by histochemical and lectin-histochemical methods the carbohydrate composition of the mucus secreted by the stomach and the first tract of the duodenum of the striped dolphin, Stenella coeruleoalba. The stomach can be divided into four compartments: main stomach, two connecting chambers and a pylorus, followed by the duodenal ampulla. Mucus is secreted by both surface cells and intramucosal glands specific for each compartment. Carbohydrate complexity and sulphation is highest in the connecting chambers, probably as a defense against pathogens. The results are compared with those available in literature.
finFindR: Automated recognition and identification of marine mammal dorsal fins using residual convolutional neural networks
Jaime W. Thompson, Victoria H. Zero, Lori H. Schwacke, Todd R. Speakman, Brian M. Quigley, Jeanine S. Morey, Trent L. McDonald
Photographic identification is an essential research and management tool for marine mammal scientists. However, manual identification of individuals is time-consuming. To shorten processing times we developed finFindR, an open-source application that uses a series of neural networks to autonomously locate dorsal fins in unedited field images, quantify an individual’s unique fin characteristics, and match them to an existing photo catalog. FinFindR allows users to build a catalog of known individuals either in conjunction with, or independent from existing systems. Given training data, finFindR’s architecture can be modified to identify members of other species with various types of distinctive markings.
Behavioral responses of humpback whales to biopsy sampling on a breeding ground: the influence of age-class, reproductive status, social context, and repeated sampling
Claire Garrigue and Solène Derville
Acquiring biological samples is essential to understand and protect marine mammals, yet it is important to evaluate the disturbance that it may cause to individuals. Using over 20 years of data, we assessed the short-term response of humpback whales to remote biopsy and boat approach in a breeding ground to inform management. Among the many factors tested, our study provided new insights into the effect of age-class as we found no significant difference between the response of calves (young of the year) and that of adults, whereas juveniles responded significantly more strenuously to being biopsied.
A decade of photo-identification reveals contrasting abundance and trends of Type B killer whales in the coastal waters of the Antarctic Peninsula
Holly Fearnbach, John W. Durban, David K. Ellifrit, Alyssa Paredes, Leigh S. Hickmott, Robert L. Pitman
We assessed abundance trends of Type B1 and B2 killer whales around the Antarctic Peninsula. By identifying individuals in photographs collected during austral summers from 2008/2009 to 2017/2018, we documented site fidelity across years for both types and fit mark-recapture models to estimate the size of their wide-ranging populations. The results revealed contrasting status: a smaller (~102) and declining population of B1s had reduced survival in recent years compared to a larger (~740) and stable population of B2s. We hypothesize that B1s may be responding to declining sea-ice and resulting changes in the availability of their primary ice-seal prey.
Use of satellite imagery to identify southern right whales (Eubalaena australis) on a Southwest Atlantic Ocean breeding ground
Audrey A. Corrêa, João H. Quoos, André S. Barreto, Karina R. Groch, Patricia P. B. Eichler
Satellite imagery has been used to improve scientific research worldwide. The southern right whale was chosen to test the use of medium, high, and very high resolution (VHR) satellite images, on the Brazilian breeding ground. These images were used to identify the whales and compare to aerial survey data collected in the same area. The VHR satellite images from the Pleiades-1A, available on Google Earth, displayed the best results when compared to that of Sentinel2, Landsat8, Rapid Eye, and Planet Scope. This technique may represent an important tool for detecting right whales, especially in countries where research funding is scarce.
Age-related changes to the speckle patterns on wild Indo-Pacific bottlenose dolphins
Genfu Yagi, Mai Sakai, Kazunobu Kogi
We studied age-related changes in the speckle density and shape of Indo-Pacific bottlenose dolphins. Speckles tended to increase from the genital to the throat area along the caudal-cranial axis, and from the ventral to the lateral area along the dorsal-ventral axis. The speckles continued to increase with age and may increase throughout their lifespan. We also found no speckle area around the genital slit which differed in shape between the sexes. Our study suggests speckle can be used for visual signals of age and sexual maturity among dolphins. We also suggest the speckle can be used for noninvasive age estimation.
Bony labyrinths of the Blackfish (Delphinidae: Globicephalinae)
Rachel A. Racicot and V. Eve Preucil
The inner ear contains key information about hearing sensitivity and ecology. We investigated inner ear variation in melon-headed dolphins by digitally extracting ‘virtual’ inner ears using X-ray imaging technology. Analysis of measurements from melon-headed dolphin inner ears alongside a broad sampling of whales, dolphins, and their relatives, generated a visualization of hearing ‘morphospace’. In this morphospace, melon-headed whales appear in two distinct clusters, reflecting differences in environmental influences on echolocation abilities. The shape of the inner ear thus sheds light on hearing abilities related to specializations in echolocation related to habitat.
Southern right whales generally appear not to react to transiting research vessels
María Belén Argüelles, Mariano Coscarella, Carla Fiorito, Marcelo Bertellotti
Reactions of southern right whales related to whale-watching boats have been reported but there are no quantitative data showing how these whales react to boats not preforming whale-watching trips. The objective of this study was to investigate the reaction of southern right whales to transiting vessels in Puerto Madryn city, Argentina. We found that the response differed depending on the number of whales present. The lack of reaction of whales suggests that they would not consider transiting research vessel as a threat. This study represents an important piece of information for the conservation of southern right whales.
Examining shark bite scars on dolphins off Bimini, The Bahamas: Comparisons between bottlenose and Atlantic spotted dolphins
Kelly Melillo-Sweeting, Maria Maust-Mohl, Matthew J. Smukal
Since direct predation is rarely observed, researchers look for injuries on living dolphins to understand the impact of shark predation risk. Off Bimini, The Bahamas, at least 29% of bottlenose and 15% of Atlantic spotted dolphins survived a bite. For both species, bites were predominantly on the dorsal (back) side; this isn’t surprising since bites to their bellies (ventral side) may be more likely to be fatal. We did not determine the shark species responsible, but these dolphins overlap with tiger and bull sharks. This study builds on long-term research in this region, providing insight into factors influencing predation risk.
Spatiotemporal variation in harbor porpoise distribution and foraging across a landscape of fear
Laura D. Williamson, Beth E. Scott, Megan R. Laxton, Fabian E. Bachl, Janine B. Illian, Kate L. Brookes, Paul M. Thompson
Increased understanding of porpoises’ seasonal distribution, key foraging areas, and their relationship with competitors can shed light on management options and potential interactions with offshore industries. Data from an array of echolocation-click detectors were analyzed to investigate spatial and temporal variation in occurrence and foraging activity of harbor porpoises. The porpoises’ overall distribution shifted throughout the summer and autumn, likely influenced by seasonal prey availability. Probability of porpoise occurrence was lowest in areas close to the coast, where dolphin detections were highest and declined prior to dolphin detection, leading potentially to avoidance of spatiotemporal overlap between porpoises and dolphins.