GRAY WHALES (ESCHRICHTIUS ROBUSTUS) OFF SAKHALIN ISLAND,RUSSIA: SEASONAL AND ANNUAL PATTERNS OF OCCURRENCE1

The annual return, seasonal occurrence, and site fidelity of Korean-Okhotsk or western gray whales on their feeding grounds off northeastern Sakhalin Island, Russia, were assessed by boat-based photo-identification studies in 1994-1998. A total of 262 pods were observed, ranging in size from 1 to 9 whales with an overall mean of 2.0. Sixty-nine whales were individually identified, and a majority of all whales (71.0%) were observed in multiple years. Annual sighting frequencies ranged from 1 to 18 d, with a mean of 5. 4 d. The percentage of whales reidentified from previous years showed a continuous annual increase, reaching 87.0% by the end of the study. Time between first and last sighting of identified individuals within a given year was 1-85 d, with an overall mean of 40.6 d. Annual calf proportions ranged from 4.3% (1997) to 13.2% (1998), and mother-calf separations generally occurred between July and September. The seasonal site fidelity and annual return of whales to this part of the Okhotsk Sea emphasize its importance as a primary feeding ground for this endangered population.     

HEART RATE AND ELECTROCARDIOGRAM CHARACTERISTICS OF A YOUNG CALIFORNIA GRAY WHALE (ESCHRICHTIUS ROBUSTUS)1

Electrocardiogram (ECG) analyses of Holter monitor recordings from a young California gray whale were performed to determine ECG waveform characteristics, evaluate the heart rate pattern for sinus arrhythmia, obtain resting heart rates at known body masses as the whale increased in size, and compare those heart rates with predicted heart rates from allometric equations. The PR and QRS intervals (475 ± 35 msec, 208 ± 24 msec, respectively, n= 20) support the concept (Meijler et al. 1992) that atrioventricular transmission and ventricular excitation times do not increase linearly in very large mammals. A sinus arrhythmia pattern at rest (apneic heart rates of 15–25 beats per min [bpm] and eupneic heart rates of 34–40 bpm) is consistent with a relative eupneic tachycardia and apneic bradycardia during diving activity of whales. The heart rate-body mass measurements (35–24 bpm at body masses of 3,591-8,200 kg) in this study (1) extend the range of allometric heart rate and body mass data in mammals a full order of magnitude, to almost 10,000 kg, (2) support the use of allometric equations (based primarily on mammals <1,000 kg in body mass) in estimating resting heart rates in whales, and (3) demonstrate that previously reported heart rates in large whales are not representative of resting heart rate, probably secondary to circumstances during measurement.     

GROWTH IN YOUNG GRAY WHALES (ESCHRICHTIUS ROBUSTUS)

Mean body lengths of gray whale calves were found to increase linearly from 4.6 m at birth to 7 m by weaning at six mo. After weaning, rates of length increase diminish, with calves reaching 8 m by one yr of age and 9 m by two yr. Evaluations of the weights of nine gray whales as functions of their measured lengths and girths reduce the emphasis placed on fast-induced seasonal variations in girth by Rice and Wolman (1971). From birth weights of just under one metric ton, calves double their weights by three mo of age and double again by weaning at six mo.     

INTER-OBSERVER COUNT DISCREPANCIES IN A SHORE-BASED CENSUS OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS)

Estimations of gray whale abundance have generally assumed that shore-based observers record all whales migrating through the viewing area during periods uncompromised by visibility. We tested the repeatability of data collected at the standard gray whale census site at Granite Canyon Marine Laboratory in central California by using pairs of observers maintaining independent sighting records. Proximal shore sites were occupied 6 d (60 h) in January 1986 where one team counted 845 whales in 427 groups while the other team counted 990 whales in 477 groups. A comparison of the records showed that the first team missed 290 whales seen by the second team, and the second team missed 204 whales seen by the first team. The total number of whales in the viewing area was calculated for each team by the Petersen estimate, using mutually sighted whale groups as "recaptures". On average, observers recorded only 79% of the whales. More whales (68%) were missed when entire groups of whales were not seen rather than when groups were undercounted (32%). Visibility did not appear to affect observed rates of missed whales. Whales migrating at intermediate distances from the shore were less often missed than were those > 6 km or < 1 km offshore. This count discrepancy test confirms that an uncorrected calculation of population size for gray whales based on sighting records from solitary observers will be underestimated.     

MAJOR HISTOCOMPATIBILITY COMPLEX I POLYMORPHISM IN A CETACEAN: THE GRAY WHALE (ESCHRICHTIUS ROBUSTUS)

Vertebrate Major Histocompatibility Complex-I ( Mbc -I) proteins bind and display self and foreign peptides on the cell surface. Mbc -I polymorphism is considered critical for eliciting immune responses to a diversity of antigens, and thus, for the health and conservation of a species. Based on restriction fragment length polymorphism it was concluded that whales generally have low Mbc -I polymorphism. This was attributed to the weak pathogenic pressure in aquatic habitats. Since gray whales' habits might favor their encounter with diverse pathogens, resulting in selection pressures for Mbc variability, we searched for functional polymorphism of gray whale's Mbc -I exon 2 sequences that encode the α-1 protein domain of the antigen-binding region. We sequenced twelve Mbc -I exon 2 clones from each of seven gray whales. Most obtained sequences were similar to functional artiodactyl sequences, and their reconstructed phylogeny consistently showed three whale Mbc -I exon 2 sequence clusters (A, B, and C). Sequences within a given cluster and from distinct clusters, showed a greater number of non-synonymous than synonymous substitutions, that commonly shifted the physiochemical properties of the involved residue, suggesting the existence of a diverse repertoire of Mbc -I antigen recognition sites in gray whales, and that selection maintains gray whale's Mbc-I allelic diversity.     

DIET OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS) IN CLAYOQUOT SOUND, BRITISH COLUMBIA, CANADA

In Clayoquot Sound, British Columbia, gray whales ( Eschrichtius robustus ) forage for pelagic, hyperbenthic, and benthic invertebrates. Prey types were collected near feeding whales and at sites where no whales were observed to ascertain whales' diets and to describe prey populations and distributions. Characteristics of prey that are examined include species composition, density, biomass, and size. Whales foraged for mysids, Holmesimysis sculpta being the most abundant species collected. Whales foraged near concentrated patches of porcelain crab zoeal larvae, composed primarily of Pachycheles rudis , 21 –294 times the average density and biomass normally collected. Amphipod biomass, composed primarily of Ampelisca agassizi and A. careyi , was 160 ± 150 g/m² where whales foraged. Larger amphipods, rather than higher density, resulted in higher amphipod biomass between years. Whales foraged where there was a high proportion (61%) of amphipods > 6 mm in length. Whales initially foraged for amphipods along the 20-m depth contour line; amphipod biomass was best developed and least variable at depths between 16 and 20 m.     

A METHOD TO COLLECT AND PROCESS SKIN BIOPSIES FOR CELL CULTURE FROM FREE-RANGING GRAY WHALES (ESCHRICHTIUS ROBUSTUS)

For researchers studying mysticere whales few methods for determining gender or for collecting biochemical and genetic information from unrestrained animals are available. The objective of this study was to develop a reliable method for collecting viable tissue samples for establishing continuous cell cultures from skin biopsies of free-ranging whales. A method to collect and process these samples is presented. Six of seven skin biopsies from gray whales were established in cell culture. Our results suggest that the viability of the samples is improved by (1) sterile processing in the field, (2) minimizing the time between collection and delivery to the cell culture facility, (3) reducing the concentration of antifungal agent, and (4) placing tissue explants under a coverslip. While the results reported in this paper are based on a small sample size, we believe that if the procedures are followed, they will increase the probability of successfully culturing cetacean tissue. Established cell lines can supply replenishable material from identified whales still living in the wild. These cultures can then be used for determination of sex from karyotypes, and for assessing genetic relationships of cetaceans from inherited protein, chromosomal and DNA polymorphisms. These much needed analytical tools can be used to determine familial and populational relationships, leading to a better understanding of mating systems, stock identification and effective population sizes of wild cetaceans.     

CHANGES IN THE RELATIVE ABUNDANCE AND DISTRIBUTION OF GRAY WHALES (ESCHRICHTIUS ROBUSTUS) IN MAGDALENA BAY, MEXICO DURING AN EL NIÑO EVENT

The oceanographic changes during the El Niño and La Niña of 1998–1999 have provided an opportunity to document the effects of these events on the migratory patterns of gray whales ( Eschrichtius robustus ). Magdalena Bay is located at the southernmost point of the gray whale's annual breeding migration along the Baja California Peninsula in Mexico. Standardized surveys were conducted for three consecutive seasons (1997–1999) in Magdalena Bay, enabling an assessment of the changes in the relative abundance of gray whales with altered temperature. The average temperature of the bay in 1998 was 4.2°C higher than in 1997 and 5.8°C higher than in 1999. The number of whale sightings during that time period was inversely related to temperature, with nearly 15 times greater relative abundance observed in 1999 than in 1998. It is hypochesized that the decreasing temperatures associated with the La Niña event of 1999 may have induced more whales to travel farther south along their migration route. Alternative hypotheses are also expiored. Comparisons of the three years are discussed with consideration of the importance of environmental conditions versus area fidelity as determining factors in the location of gray whale calving and breeding activities.     

CHARACTERIZATION OF BEAKED WHALE (ZIPHIIDAE) AND SPERM WHALE (PHYSETER MACROCEPHALUS) SUMMER HABITAT IN SHELF-EDGE AND DEEPER WATERS OFF THE NORTHEAST U. S.

Sperm whales ( Physeter macrocephalus ) and beaked whales ( Mesoplodon spp. and Ziphius cavirostris ) are deep-diving cetaceans that frequent shelf-edge and Gulf Stream waters off the northeast U. S. coast. Sighting data collected during seven summer (1990, 1991, 1993, and 1995–1998) shipboard surveys were analyzed using a geographic information system to determine habitat use based on bathymetric and oceanographic features. Although sighting rates were lower for beaked whales, both taxa occupied similar habitats. Beaked whales were concentrated at the colder shelf edge, whereas sperm whales were associated with warmer off-shelf water. Mean sighting rates for both taxa were higher in canyon features, but only beaked whale sighting rates were significantly different between canyon and non-canyon habitat (Wilcoxon signed rank test P = 0.007). Within the shared habitat, the two taxa were separated at fine-scale based on oceanographic features.     

A KINEMATIC STUDY OF SUCTION FEEDING AND ASSOCIATED BEHAVIOR IN THE LONG-FINNED PILOT WHALE, GLOBICEPHALA MELAS (TRAILL)

Analysis of videotaped feeding sequences provides novel documentation of suction feeding in captive juvenile long-finned pilot whales ( Globicephala melas ). Swimming and stationary whales were videotaped while feeding at the surface, mid-water, and bottom. The ingestion sequence includes a preparatory phase with partial gape followed by jaw opening and rapid hyoid depression to suck in prey at a mean distance of 14 cm (duration 90 msec), although prey were taken from much greater distances. Depression and retraction of the large, piston-like tongue generate negative intraoral pressures for prey capture and ingestion. Food was normally ingested without grasping by teeth yet was manipulated with lingual, hyoid, and mandibular movement for realignment; suction was then used to transport prey into the oropharynx. Whales frequently rolled or inverted before taking prey, presumably to avoid grasping and repositioning. Prey were sucked off the bottom or sides of the pool without direct contact; lateral suction was used to ingest items from the sides of the mouth.     

VENTILATORY RATE DIFFERENCES BETWEEN SURFACE-FEEDING AND NON-SURFACE-FEEDING FIN WHALES (BALAENOPTERA PHYSALUS) IN THE WATERS OFF EASTERN LONG ISLAND, NEW YORK, U.S.A., 1981–1987

Observations of feeding and ventilatory behavior of individual fin whales ( Balaenoptera physalus )were made from various vessels during the months of May–September, 1981–1987, in the waters off eastern Long Island, N.Y., U.S.A. Intervals between blows were measured and recorded to the nearest second. Information about behavior was recorded, as were location, depth, and surface temperature at sounding dives. Animals observed feeding at the surface were noted as such, ail others were considered non-surface-feeding animals. Data were compiled by individual, month, year, and analyzed for mean interblow interval during surface activity bouts; mean dive duration; and overall mean blow interval.
Overall mean blow intervals (±SE) of 47.89 ± 0.81 set for surface-feeding ( n = 10,411), and 57.92 ±0.97 sec for non-surface-feeding animals ( n = 11,024), differed significantly (Mann-Whitney U, P < 0.001). Interblow intervals for surface activity bouts (±SE) of 12.29 ± 0.05 set for surface-feeding ( n = 7,894), and 13.58 ± 0.06 set, for non-surface-feeding animals (n = 8,187), also differed significantly (Mann-Whitney U, P < 0.001), as did mean dive duration (159.53 ± 2.16 sec, n = 2,517, for surface-feeding animals; 185.86 ± 2.53 set, n = 2,837, for non-surface-feeding animals). Yearly comparisons of blow intervals between surface-feeding and non-surface-feeding animals during surface activity bouts yielded significant differences for each year except 1981, while comparisons of dive durations yielded significant differences for all years except 1981, 1982, and 1985.