Estimated calf and perinatal mortality in western North Atlantic right whales (Eubalaena glacialis)

Reduced reproductive success has contributed to lack of recovery of the endangered western North Atlantic right whale (Eubalaena glacialis). Here we examined the specific life history period from just before birth through the first year to estimate calf and perinatal losses between 1989 and 2003. The lower bound estimate (17 mortalities from 208 calving events) included documented calf mortalities and presumed deaths from serious injury or disappearance from the sighting record. The upper bound estimated potential calf losses from females with delayed first parturition (>10 yr) and shortened (2 yr) or lengthened (≥4 yr) calving intervals, if the female migrated to the calving ground during these intervals. Because cows were sighted in the calving ground predominantly in years when they were available to calve, adult females sighted there in a possible calving year without a calf were assumed to have experienced a perinatal loss. Twenty-eight potential perinatal losses were detected, bringing the upper bound of calf and perinatal mortality to 45 (3.0 calves/yr). The high frequency of lengthened calving intervals in E. glacialis suggests that abortion and neonatal losses are contributing to lower reproductive success compared to Southern Hemisphere right whales (Eubalaena australis).     

Historic and current habitat use by North Pacific right whales Eubalaena japonica in the Bering Sea and Gulf of Alaska

1. To help define areas and ecological parameters critical to the survival and recovery of the remnant population of North Pacific right whales, habitat use was investigated by examining all available sighting and catch records in the south-eastern Bering Sea (SEBS) and Gulf of Alaska (GOA) over the past two centuries. 2. Based on re-analyses of commercial whaling records, search effort, and resultant catches and sightings, waters of the: (i) SEBS slope and shelf, (ii) eastern Aleutian Islands and (iii) GOA slope and abyssal plain were important habitat for North Pacific right whales through the late 1960s. 3. Since 1980, the only area where right whales have been seen consistently is on the SEBS middle shelf. However, acoustic detections and single sightings have been reported in all other regions except the SEBS slope and oceanic GOA (areas where little, if any, acoustic and visual effort has occurred). 4. Sightings since 1979 were in waters < 200 m deep which may simply reflect the paucity of search effort elsewhere. From the commercial whaling era to the late 1960s, right whales were commonly seen in waters > 2000 m deep, indicating that their distribution is not restricted to shallow continental shelves. 5. North Pacific right whale sightings through the centuries have been associated with a variety of oceanic features, and there is little in common in the bathymetry of these regions. These whales appear to have a greater pelagic distribution than that observed in the North Atlantic, which may be related to the availability of larger copepods across the SEBS and GOA.     

Body growth of North Atlantic right whales (Eubalaena glacialis) revisited

Knowing size-at-age is important for determining food requirements and making inferences about the nutritional status of individuals and their populations. Accurate growth curves are also needed to quantify drug dosages to treat wounded or entangled animals. However, body sizes are often based on small numbers of measured animals that must be improved as new data become available. We updated an existing body growth model for North Atlantic right whales (NARWs) using new data from dead animals and from older individuals. Our models indicate that NARWs attain mean lengths and weights of 4.3 m and 1.0 mt at birth, and 13.1 m and 31.7 mt when sexually mature. Calves more than double their length and attain nearly three-quarters of their asymptotic adult size during their first year of life. Overall, our length estimates agreed well with previous estimates, but our mass-at-age values were considerably higher. These differences revealed that necropsy data used alone in allometric models underestimate mass due possibly to several of the stranded animals in the database having been chronically entangled and in poor body condition. Augmenting the database with healthier individuals, such as harvested North Pacific right whales, yielded mass predictions that reflect both healthy and unhealthy individuals.     

Molecular identification of individual North Atlantic right whales (Eubalaena glacialis) using free-floating feces

During the 1990s, North Atlantic right whales had significantly decreased reproduction and showed signs of compromised health, prompting the initiation of noninvasive fecal-based studies to investigate potential causal factors. The interpretation of these studies is enhanced when the defecator is identified, as data can then be linked to individual life history information. Fecal samples (n= 118) were either collected from single photoidentified whales, associated with several individuals by photoidentification of whales in the vicinity upon sample collection, or were collected when no whales were in the vicinity. Genetic profiles from fecal DNA comprising sex, mitochondrial haplotype, and five microsatellite loci helped assign specific samples to individual right whales based on existing genetic profiles. Profiles were informative in assigning 61 fecal samples to known individuals, 24 of which were collected when no whales were in the vicinity. Whales identified genetically were typically photographed in the same habitat area and on the same day of sample collection (n= 35/48). Twelve profiles new to the genetic database were identified, suggesting fecal sampling provides a means to obtain genetic profiles from previously unsampled individuals, which may help refine estimates of population size and habitat use patterns if annual fecal sampling continues.     

North Atlantic right whales (Eubalaena glacialis) ignore ships but respond to alerting stimuli

North Atlantic right whales were extensively hunted during the whaling era and have not recovered. One of the primary factors inhibiting their recovery is anthropogenic mortality caused by ship strikes. To assess risk factors involved in ship strikes, we used a multi-sensor acoustic recording tag to measure the responses of whales to passing ships and experimentally tested their responses to controlled sound exposures, which included recordings of ship noise, the social sounds of conspecifics and a signal designed to alert the whales. The whales reacted strongly to the alert signal, they reacted mildly to the social sounds of conspecifics, but they showed no such responses to the sounds of approaching vessels as well as actual vessels. Whales responded to the alert by swimming strongly to the surface, a response likely to increase rather than decrease the risk of collision.     

Past and present distributions of southern right whales(Eubalaena australis)

Abstract

During the 19th century, sail whalers hunted right whales throughout the southern oceans north of 50 degrees. This review seeks to document the recovery of southern right whales by comparing the northernmost recent sightings with older sightings that survive “fossilised” in historical records of the sail whaling era. Despite a steady expansion northwards in recent years, the present distribution of right whales is still far short of that recorded by sail whalers over a century ago.     

Critically endangered western gray whales migrate to the eastern North Pacific

Western North Pacific gray whales (WGWs), once considered extinct, are critically endangered with unknown migratory routes and reproductive areas. We attached satellite-monitored tags to seven WGWs on their primary feeding ground off Sakhalin Island, Russia, three of which subsequently migrated to regions occupied by non-endangered eastern gray whales (EGWs). A female with the longest-lasting tag visited all three major EGW reproductive areas off Baja California, Mexico, before returning to Sakhalin Island the following spring. Her 22 511 km round-trip is the longest documented mammal migration and strongly suggests that some presumed WGWs are actually EGWs foraging in areas historically attributed to WGWs. The observed migration routes provide evidence of navigational skills across open water that break the near-shore north–south migratory paradigm of EGWs. Despite evidence of genetic differentiation, these tagging data indicate that the population identity of whales off Sakhalin Island needs further evaluation.     

Mitochondrial DNA diversity and population structure among southern right whales (Eubalaena australis)

The population structure and mitochondrial (mt) DNA diversity of southern right whales (Eubalaena australis) are described from 146 individuals sampled on 4 winter calving grounds (Argentina, South Africa, Western Australia, and the New Zealand sub-Antarctic) and 2 summer feeding grounds (South Georgia and south of Western Australia). Based on a consensus region of 275 base pairs of the mtDNA control region, 37 variable sites defined 37 unique haplotypes, of which only one was shared between regional samples of the Indo-Pacific and South Atlantic Oceans. Phylogenetic reconstruction of the southern right whale haplotypes revealed 2 distinct clades that differed significantly in frequencies between oceans. An analysis of molecular variance confirmed significant overall differentiation among the 4 calving grounds at both the haplotype and the nucleotype levels (F(ST) = 0.159; Phi(ST) = 0.238; P < 0.001). Haplotype diversity was significantly lower in the Indo-Pacific (h = 0.701 +/- 0.037) compared with the South Atlantic (h = 0.948 +/- 0.013), despite a longer history of exploitation and larger catches in the South Atlantic. In fact, the haplotype diversity in the Indo-Pacific basin was similar to that of the North Atlantic right whale that currently numbers about 300 animals. Multidimensional scaling of genetic differentiation suggests that gene flow occurred primarily between adjacent calving grounds within an ocean basin, with mixing of lineages from different calving grounds occurring on feeding grounds.     

Respiration cycle duration and seawater flux through open blowholes of humpback (Megaptera novaeangliae) and North Atlantic right (Eubalaena glacialis) whales

Little is known about the dynamics of baleen whale respiratory cycles, especially the mechanics and activity of the blowholes and their interaction with seawater. In this study, the duration of complete respiration cycles (expiration/inhalation events) were quantified for the first time in two species: North Atlantic right whale (NARW) and humpback whale (HW) using high resolution, detailed imagery from an unoccupied aerial system (UAS). The mean duration of complete respiration cycles (expiration/inhalation event) in the NARW and HW were 3.07 s (SD = 0.503, n = 15) and 2.85 s (SD = 0.581, n = 21), respectively. Furthermore, we saw no significant differences in respiration cycle duration between age and sex classes in the NARW, but significant differences were observed between age classes in the HW. The observation of seawater covering an open blowhole was also quantified, with NARW having 20% of all breaths with seawater presence versus 90% in HW. Seawater incursion has not been described previously and challenges the general consensus that water does not enter the respiratory tract in baleen whales. Prevalent seawater has implications for the analysis and interpretation of exhaled respiratory vapor/mucosa samples, as well as for the potential inhalation of oil in spills.     

Seasonality of reproduction and the length of gestation in southern right whales Eubalaena australis

From the seasonal occurrence of 11 stranded nconates, the earliest and latest observations of possible calving behaviour, and the seasonal incidence of calves in shore-based counts, the extent of the calving season for southern right whales off South Africa can be characterized as from late June to late October, with a peak in August. The occurrence of 89 'new' calves located during monthly photogrammetric flights between July or August and November indicated that 50% were born by 1 September in 1988 and by 15 August in 1989, and that the effective calving season (in which 95.5% of calves are estimated to have been born) lasted 118 days in each year. From regression analysis of the lengths of 221 foetuses and their dates of death, and assuming a mean date of birth of 24 August, the duration of the linear phase of foetal growth is estimated to be 325 days, and the mean size at birth 6-1 m. Uncertainty over the duration of the initial, non-linear phase of foetal growth results in alternative estimates of 357 or 396 days for the total length of gestation. Foetuses of smaller females seem to be conceived later (or experience a longer initial, non-linear phase of foetal growth) than those of larger females. The apparent rarity of adult females in coastal waters in the year in which they are presumed to conceive is attributed to either a brief residence time or the possibility that conceptions may occur well outside coastal waters.     

G-banded karyotype and ideogram for the North Atlantic right whale (Eubalaena glacialis)

Published cytogenetic data for extant cetacean species remain incomplete. In a review of the literature, we found karyotypic information for 6 of the 13 tentatively recognized species of the suborder Mysticeti (baleen whales). Among those yet to be described is the critically endangered North Atlantic right whale (Eubalaena glacialis). Herein, we describe and propose a first-generation G-banded karyotype and ideogram for this species (2n = 42), obtained from peripheral blood chromosome preparations from a stranded male calf. This information may prove useful for future genetic mapping projects and for interspecific and intraspecific genomic comparisons by techniques such as zoo-FISH.     

North Pacific right whale (Eubalaena japonica) seasonal and diel calling patterns from long‐term acoustic recordings in the southeastern Bering Sea, 2000–2006

We assessed North Pacific right whale (Eubalaena japonica) seasonal and daily calling patterns in the southeastern Bering Sea (SEBS) using long‐term hydrophone recordings from October 2000 through January 2006. We detected right whale calls on the SEBS middle shelf (<100 m depth) as early as May, intermittently throughout summer and fall, and as late as December. Calls also were detected on one day in June 2005 on the SEBS slope (>1,000 m), but were not detected near Kodiak Island from April to August 2003. In months with calls, detections occurred on more days in July–October (≥6 d/mo), than from May to June or November to December (≤3 d/mo). Calls were clustered in time and were usually detected on 1–3 consecutive days with a median interval of 6.5 d for calls >1 d apart. Hourly calling rates were significantly higher at night than during the day. These data indicate that right whales occur in the SEBS later in the year than previously known, intermittently pass through the middle‐shelf study region, and usually remain there no longer than a few days. Right whale habitat use in the SEBS may intensify in mid‐summer through early fall based on higher monthly and daily call detection rates.