7. SHORT NOTES FROM MEMBERS

Cooper, J., Ross, G. J. B. &; Shaughnessy, P. D. 1978. Seasonal and spatial distribution of Rockhopper Penguins ashore in South Africa. Ostrich 49:40-44. There are 30 records of Rockhopper Penguins Eudyptes chrysocome ashore in South Africa. Both the southern subspecies E.c. chrysocome, and the northern subspecies E.c. moseleyi have been recorded. The northern subspecies has occurred more frequently. Most records are of moulting juveniles in January and February. Records of adult birds are more scattered throughout the year. Rockhopper Penguins in South Africa have been recorded only south of 30S. Birds of the northern subspecies probably originate from South Atlantic islands (Tristan da Cunha group and Gough). Birds of the southern subspecies are probably from the Prince Edward Islands.     

Age structure of strandings and growth of Lahille's bottlenose dolphin (Tursiops truncatus gephyreus)

This study describes the age structure and sex-specific growth patterns of Lahille's bottlenose dolphins (Tursiops truncatus gephyreus), a subspecies endemic to the Southwest Atlantic Ocean (SWAO). The ages of 120 animals collected in southern Brazil between 1976 and 2017 were determined. We found high frequencies of young animals, mostly males, with no sex bias among adults. A temporal change in the age structure of strandings was observed, and we conclude it is a consequence of increased bycatch rates of young dolphins after 2000. The oldest male and female were 27 and 44 years old, respectively, suggesting that females live longer than males in southern Brazil. Growth curve analysis using Gompertz and Laird-Gompertz growth models estimated asymptotic lengths of 316.5 cm for females and 351.6 cm for males, (reached around 13 and 18 years old, respectively), supporting sexual size dimorphism for the subspecies. A second growth pulse was identified for males. Our work highlights the benefit of long-term studies and contributes valuable information toward understanding the life history of Lahille's bottlenose dolphin. It will serve as baseline for future studies that seek to understand mortality patterns of bottlenose dolphins elsewhere and the effects of anthropogenic actions on the survival of these animals.     

Remarkably low genetic diversity and strong population structure in common bottlenose dolphins (Tursiops truncatus) from coastal waters of the Southwestern Atlantic Ocean

Knowledge about the ecology of bottlenose dolphins in the Southwestern Atlantic Ocean is scarce. Increased by-catch rates over the last decade in coastal waters of southern Brazil have raised concerns about the decline in abundance of local dolphin communities. Lack of relevant data, including information on population structure and connectivity, have hampered an assessment of the conservation status of bottlenose dolphin communities in this region. Here we combined analyses of 16 microsatellite loci and mitochondrial DNA (mtDNA) control region sequences to investigate genetic diversity, structure and connectivity in 124 biopsy samples collected over six communities of photographically identified coastal bottlenose dolphins in southern Brazil, Uruguay and central Argentina. Levels of nuclear genetic diversity were remarkably low (mean values of allelic diversity and heterozygosity across all loci were 3.6 and 0.21, respectively), a result that possibly reflects the small size of local dolphin communities. On a broad geographical scale, strong and significant genetic differentiation was found between bottlenose dolphins from southern Brazil–Uruguay (SB–U) and Bahía San Antonio (BSA), Argentina (AMOVA mtDNA Φ_ST = 0.43; nuclear F_ST = 0.46), with negligible contemporary gene flow detected based on Bayesian estimates. On a finer scale, moderate but significant differentiation (AMOVA mtDNA Φ_ST = 0.29; nuclear F_ST = 0.13) and asymmetric gene flow was detected between five neighbouring communities in SB–U. Based on the results we propose that BSA and SB–U represent two distinct evolutionarily significant units, and that communities from SB–U comprise five distinct Management Units (MUs). Under this scenario, conservation efforts should prioritize the areas in southern Brazil where dolphins from three MUs overlap in their home ranges and where by-catch rates are reportedly higher.     

Site fidelity,residency, and abundance of bottlenose dolphins (Tursiops sp.) in Adelaide's coastal waters,South Australia

Little is known about the ecology and behavior of southern Australian bottlenose dolphins (Tursiops sp.). This hinders assessment of their conservation status and informed decision‐making concerning their management. We used boat‐based surveys and photo‐identification data to investigate site fidelity, residency patterns, and the abundance of southern Australian bottlenose dolphins in Adelaide's coastal waters. Sighting rates and site fidelity varied amongst individuals, and agglomerative hierarchical cluster analysis led to the categorization of individuals into one of three groups: occasional visitors, seasonal residents, or year‐round residents. Lagged identification rates indicated that these dolphins used the study area regularly from year to year following a model of emigration and reimmigration. Abundance estimates obtained from multisample closed capture‐recapture models ranged from 95 individuals (SE ± 45.20) in winter 2013 to 239 (SE ± 54.91) in summer 2014. The varying levels of site fidelity and residency, and the relatively high number of dolphins found throughout the study area highlights the Adelaide metropolitan coast as an important habitat for bottlenose dolphins. As these dolphins also appear to spend considerable time outside the study area, future research, conservation, and management efforts on this population must take into account anthropogenic activities within Adelaide's coastal waters and their adjacencies.     

Ecological divergence and speciation in common bottlenose dolphins in the western South Atlantic

Coastal and offshore ecotypes of common bottlenose dolphins have been recognized in the western South Atlantic, and it is possible that trophic niche divergence associated with social interactions is leading them to genetic and phenotypic differentiation. The significant morphological differentiation observed between these ecotypes suggests they represent two different subspecies. However, there is still a need to investigate whether there is congruence between morphological and genetic data to rule out the possibility of ecophenotypic variation accompanied by gene flow. Mitochondrial DNA (mtDNA) control region sequence data and 10 microsatellite loci collected from stranded and biopsied dolphins sampled in coastal and offshore waters of Brazil as well as 106 skulls for morphological analyses were used to determine whether the morphological differentiation was supported by genetic differentiation. There was congruence among the data sets, reinforcing the presence of two distinct ecotypes. The divergence may be relatively recent, however, given the moderate values of mtDNA nucleotide divergence (dA = 0.008), presence of one shared mtDNA haplotype and possibly low levels of gene flow (around 1% of migrants per generation). Results suggest the ecotypes may be in the process of speciation and reinforce they are best described as two different subspecies until the degree of nuclear genetic divergence is thoroughly evaluated: Tursiops truncatus gephyreus (coastal ecotype) and T. t. truncatus (offshore ecotype). The endemic distribution of T. t. gephyreus in the western South Atlantic and number of anthropogenic threats in the area reinforces the importance of protecting this ecotype and its habitat.     

Evoked potential audiometry of 13 Pacific bottlenose dolphins (Tursiops truncatus gilli)

Evoked potential audiograms were measured in 13 Pacific bottlenose dolphins (Tursiops truncatus gilli) to determine the variability in hearing sensitivity and range of hearing. The auditory evoked potential system used a transducer embedded in a suction cup to deliver sinusoidal amplitude modulated tones to each dolphin through the pan region of the lower right jaw. Evoked potentials were recorded noninvasively using surface electrodes, and hearing thresholds were estimated by tracking the amplitude of the envelope following response, an evoked potential that is phase‐locked to the stimulus modulation rate. Frequencies tested ranged from 10 to 180 kHz in each animal. Variability in the range of hearing and age‐related reductions in hearing sensitivity and range of hearing were consistent with those observed in Atlantic bottlenose dolphins. Comparison of audiograms to a captive population of Atlantic bottlenose dolphins demonstrated that the Pacific bottlenose dolphins tested in this study had significantly lower thresholds at frequencies of 40 and 60–115 kHz. Differences in thresholds between the groups are unlikely to be due to methodological factors.     

Skull morphology of bottlenose dolphins from different ocean populations with emphasis on South America

The bottlenose dolphin, genus Tursiops, is cosmopolitan occurring in tropical and temperate regions, with morphological variation between and within different oceans. Since the genus' taxonomy has been under discussion for a long time, this work aimed at analyzing the cranial variability of T. truncatus from different regions of the world. Geometric Morphometrics analyses were performed in 201 skulls of adult specimens, on dorsal, ventral, and lateral views, from the Eastern North Pacific, Eastern North Atlantic, Eastern South Atlantic, and Western South Atlantic oceans. The results indicate differences between individuals that inhabit the Atlantic and Pacific oceans. Within the Atlantic Ocean, there is an evident longitudinal differentiation of specimens from the eastern and western regions. A latitudinal separation was also observed, considering specimens from the North and South Atlantic Ocean. In the Western South Atlantic statistical differences were found between two morphological groups, identified as T. gephyreus (sensu Lahille, 1908) and T. truncatus, and the cross-validation presented 98% as minimum confidence for correct classification of these two groups. The present study provides strong morphological support to consider these two lineages as separate species.     

Mitochondrial DNA analysis of sympatric morphotypes of bottlenose dolphins (genus: Tursiops) in Chinese waters

The classification within the bottlenose dolphin (genus Tursiops) is controversial. Although many morphological variants exist, most authors have concluded that the genus is composed of a single species, Tursiops truncatus (Montagu 1821). Two distinct morphotypes of bottlenose dolphins, which have been referred to as T. truncatus and T. aduncus, exist in sympatry in Chinese waters. Comparisons of a 386-bp fragment of the mitochondrial DNA (mtDNA) control region (n = 47) indicated that the two sympatric morphotypes were genetically distinct, with seven fixed site differences and a sequence divergence of approximately 4.4%. Phylogenetic analyses using maximum likelihood, neighbour-joining and maximum parsimony approaches showed that the truncatus-type dolphins from Chinese waters were more closely related to Atlantic Ocean truncatus-type than to the sympatric aduncus-type dolphins. The Atlantic truncatus-type dolphins also shared the same diagnostic sites that separated Chinese truncatus-type from aduncus-type dolphins. The molecular data agreed completely with the morphological classifications of the specimens. This congruence is strong evidence that the sympatric morphotypes in Chinese waters are reproductively isolated and comprise two distinct species. These findings have important implications for the conservation of bottlenose dolphins in Chinese waters.     

Defining bottlenose dolphin (Tursiops truncatus) stocks based on environmental,physical, and behavioral characteristics

The population structure of bottlenose dolphins, Tursiops truncatus, along the U.S. Atlantic coast has recently been redefined from one homogenous population into five coastal stocks. Local studies indicate even finer structure, primarily based on isolation of dolphins inhabiting estuaries. We identified population structuring of non‐estuarine coastal bottlenose dolphins during a study in New Jersey, the northern range along the Atlantic Coast. Using photo‐identification and distribution survey results, an analysis identified two major clusters of individuals significantly separated by five variables (distance from shoreline, group size, occurrence of the barnacle Xenobalanus globicipitis, avoidance behavior, and individual coloration). Sightings assigned to cluster 1 occurred in nearshore shallow waters (0–1.9 km, x?= 3.5 m), and those assigned to cluster 2 occurred further offshore in deeper waters (1.9–6 km, x?= 9.5 m). Only eight of 194 individuals (4%) were identified in both regions. Collectively, this suggests an occurrence of two stocks that are spatially, physically, and behaviorally distinguishable over a small distance. These results indicate that complexity in Tursiops population structure is not limited to latitudinal gradients or barriers created by estuarine habitats, but also by partitioning of habitat as a function of distance from shore and depth over small distances.     

Distributional patterns of the species of <Emphasis Type="Italic">Valeriana</Emphasis> (Valerianaceae) in southern South America

Distributional patterns of Valeriana species from southern South America were analyzed. We prepared a database with the records of 40 species from Argentina and Chile south of 33°S, obtained from herbarium specimens, published taxonomic studies and field trips. We undertook a track analysis and a parsimony analysis of endemicity (PAE), the latter with 134 grid cells of 1.5° latitude by 1.5° longitude. Three generalized tracks and one node were obtained, and three areas of endemism were identified. These general patterns of distribution in Valeriana were used to infer possible vicariance and dispersal events that might have shaped them. We identified a center of diversification in Central Chile and the Argentinean province of Neuquén. It represents a complex area that is related to both the Central Chilean and Subantarctic subregions.     

Patterns of seasonal occurrence,distribution, and site fidelity of coastal bottlenose dolphins (Tursiops truncatus) in southern New Jersey,U.S.A.

Coastal bottlenose dolphins (Tursiops truncatus) form a mosaic of resident and seasonal migratory populations along the United States Atlantic seaboard. Seasonal, poorly known migrants (identified as a separate stock) move as far north as New Jersey. During 2003–2005, 73 boat‐based photo‐identification surveys were conducted in southern New Jersey to discern seasonal occurrence, distribution, and patterns of movement and site fidelity. Neonates, young‐of‐year, and adults occurred in the study area from late May through late September, corresponding to water temperatures of 14.0–16.3°C. Of 205 individuals identified, 44% (n= 90) were sighted multiple times within or among years, including 10% (n= 20) of individuals identified in all 3 yr. Almost half (47%) of the multiple sightings were observed along a core area encompassed by the southern part of the Jacques Cousteau National Estuarine Research Reserve. In contrast to stocks studied in southern coastal areas of the U.S. Atlantic and Gulf of Mexico, estuaries were used significantly less than open‐beach habitat, which is consistent with the relative prey abundance in these habitats. Research at additional sites will help confirm whether bottlenose dolphins at the northern end of their migratory range exhibit local site fidelity and habitat preferences similar to those found in this study.     

Rectal temperatures before and after parturition in bottlenose dolphins

In five parturitions of four bottlenose dolphins (Tursiops truncatus gilli), rectal temperatures (Rts) were determined at least once a day during the late period of pregnancy. Four of the five pregnancies showed a drop in RT ranging from 0.7 to 1.3°C (an average decrease of 0.9°C) from 24 to 12 hr pre‐partum. In these four cases, RT was significantly lower than their averages from 10 days to 1 day pre‐partum (P < 0.05). In two dolphins, the first RT post‐partum was higher than the average RT from 10 days to 1 day pre‐partum. Seasonal changes in RT were observed in six non‐pregnant dolphins. Average RT in June through August was significantly higher and in December through February was significantly lower than the rest of the year (P < 0.01). Zoo Biol 18:153–156, 1999. © 1999 Wiley‐Liss, Inc.     

Biogeography of common dolphins (genus Delphinus) in the Southwestern Atlantic Ocean

• 1 The common dolphins (genus Delphinus) have one of most problematic taxonomies and complex distribution patterns of all cetaceans. Although the taxonomy and the distribution seem to have been clarified somewhat in the eastern North Pacific and Indo‐Pacific Oceans, many questions remain in the Southwestern Atlantic Ocean (SWA). We review the biogeography of Delphinus in the SWA.
• 2 We reviewed data from strandings, incidental catches and sightings since 1922. Systematic surveys were conducted in five major areas. Twenty‐one natural history collections were examined, and 135 skulls were measured.
• 3 A total of 184 records of common dolphins were compiled. Delphinus apparently occurs in three stocks in the SWA: one located in northern Brazil and two from southeastern Brazil (～22°S) to central Argentina (～42°S). Two distinct patterns in habitat use were observed by depth: in southeastern Brazil, sightings were restricted to coastal waters with water depths ranging from 18m to 70m. On the other hand, in the area that extends from southern Brazil to Central Argentina (from 28°S to 42°S), sightings were recorded in deeper waters, ranging from 71m to 1435m, with the exception of occasional coastal sightings. The cranial analyses demonstrated that both short‐beaked common dolphins Delphinus delphis and long‐beaked common dolphins Dephinus capensis occur in the SWA.
• 4 In the SWA, Delphinus seems to occur near areas of high productivity. One stock is associated with the productive waters discharged by the Amazon River and possibily with the coastal upwelling system off the coast of Venezuela, while the other stocks are associated with the Cabo Frio upwelling system and the Subtropical Convergence. Our results indicate that the current taxonomy does not adequately reflect the amount of variation within the genus in the world.

     

Phylogenetic placement and population structure of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) off Zanzibar,Tanzania, based on mtDNA sequences

Phylogenetic placement of bottlenose dolphins from Zanzibar, East Africa and putative population differentiation between animals found off southern and northern Zanzibar were examined using variation in mtDNA control region sequences. Samples (n= 45) from animals bycaught in fishing gear and skin biopsies collected during boat surveys were compared to published sequences (n= 173) of Indo‐Pacific bottlenose dolphin, Tursiops aduncus, from southeast Australian waters, Chinese/Indonesian waters, and South African waters (which recently was proposed as a new species) and to published sequences of common bottlenose dolphin, Tursiops truncatus. Bayesian and maximum parsimony analyses indicated a close relationship between Zanzibar and South African haplotypes, which are differentiated from both Chinese/Indonesian and Australian T. aduncus haplotypes. Our results suggest that the dolphins found off Zanzibar should be classified as T. aduncus alongside the South African animals. Further, analyses of genetic differentiation showed significant separation between the T. aduncus found off northern and southern Zanzibar despite the relatively short distance (approximately 80 km) between these areas. Much less differentiation was found between southern Zanzibar and South Africa, suggesting a more recent common evolutionary history for these populations than for the northern and southern Zanzibar populations.     

Niche overlap and diet composition of three sympatric coastal dolphin species in the southwest Atlantic Ocean

Sympatric species are expected to differ in ecological requirements to minimize niche overlap and avoid competition. Here we assess the trophic interactions among three coexisting dolphin species from southern Brazil: the franciscana dolphin (Pontoporia blainvillei), the Guiana dolphin (Sotalia guianensis), and the Lahille's bottlenose dolphin (Tursiops truncatus gephyreus). We evaluated temporal variation in carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values of bone collagen to examine potential dietary shifts resulting from increased fishing activity over the past three decades. We estimated the degree of niche overlap among these species and the contribution of potential prey sources to their diet. δ¹⁵N values were consistent among species and across years, while δ¹³C values increased for Guiana dolphins and decreased for bottlenose dolphins, suggesting changes in diet and/or foraging habitats through time. The similar δ¹³C and δ¹⁵N values and the high niche overlap between Guiana and bottlenose dolphins indicate that these species are primarily feeding on demersal prey. The franciscana diet is primarily composed of pelagic prey, resulting in a lower niche overlap in comparison with the other dolphin species. Our study provides further information about the foraging ecology of this unique dolphin community in southern Brazil with implications for its management and conservation.     

Detection of specific antibodies to morbilliviruses, Brucella and Toxoplasma in the Black Sea dolphin Tursiops truncatus ponticus and the beluga whale Delphinapterus leucas from the Sea of Okhotsk in 2002–2007

The prevalence of antibodies to morbilliviruses, Brucella and Toxoplasma was studied in the Black Sea bottlenose dolphin Tursiops truncatus ponticus and the beluga whale Delphinapterus leucas from the Sea of Okhotsk. The blood serum of 74 dolphins and 147 beluga whales was tested in 2002–2007. Antibodies to morbilliviruses were detected in 15 (20.3%) bottlenose dolphins and 20 (13.6%) beluga whales. Antibodies to Brucella were detected in 17 (23.0%) bottlenose dolphins and 10 (6.8%) beluga whales. Toxoplasma-specific antibodies were detected in 39 (52.7%) bottlenose dolphins and 7 (4.8%) beluga whales. Some animals had antibodies to two, or even three, of the pathogens. A high level of incidence of the pathogens in the sea animals was found in the densely populated coastal areas with high economic development.     

Feeding aggregation and aggressive interaction between bottlenose (Tursiops truncatus) and Commerson’s dolphins (Cephalorhynchus commersonii) in Patagonia,Argentina

We report the first recorded interactions between bottlenose dolphin (Tursiops truncatus) and Commerson’s dolphins (Cephalorhynchus commersonii). The diurnal behavioral patterns of bottlenose dolphins in Bahía Engaño, Argentina, were similar to those described for other coastal populations around the world. The majority of the feeding bouts were recorded near the mouth the Chubut River. When not feeding near the river, bottlenose dolphins generally swam along the coast, and interactions with Commerson’s dolphins were recorded very close to the shore on two occasions during a 3-year period. In the first event, both species were feeding on a fish school. The second interaction was aggressive in nature, involving one juvenile and three adult bottlenose dolphins with several Commerson’s dolphins. Two of the adult bottlenose dolphins attacked the Commerson’s dolphins. We propose that the observed behavior represented defense of the juvenile bottlenose dolphin.

     

Offshore and coastal common bottlenose dolphins of the western South Atlantic face‐to‐face: What the skull and the spine can tell us

The taxonomy of Tursiops truncatus in the western South Atlantic is not resolved. Two different hypotheses have been proposed: (1) offshore and coastal ecotypes with a parapatric distribution, and (2) two species, T. truncatus and T. gephyreus, living in sympatry. To test these hypotheses, we examined a total of 100 physically mature skulls and 35 vertebral columns from the suggested overlap zone in southern Brazil. In all skulls, 24 measurements, four alveoli counts and two categorical variables were analyzed. Vertebral formula was determined and five measurements were taken from selected vertebrae. Multivariate analyses were conducted for skull and vertebral data. Results revealed the presence of two well‐separated groups. Specimens of Group1 had smaller skulls and shorter body lengths, but more vertebrae, than Group2. The morphological characteristics of each group corresponded well with two ecotypes of common bottlenose dolphins reported in other ocean basins. Therefore, we assigned the specimens of Group1 to the offshore ecotype, and Group2 to the coastal ecotype. Differences in the geographic locations and ratio of strandings supported the parapatric hypothesis. The significant morphological differentiation observed suggests the presence of different subspecies, but an additional independent line of evidence is needed to hypothesize whether they represent different species.     

Age and growth in Peale's dolphin (Lagenorhynchus australis) in subantarctic waters off southern South America

The Peale's dolphin, Lagenorhynchus australis, is a mainly coastal and one of the most often seen species off southernmost South America from 33°S off Chile and 38°S off Argentina to south of Cape Horn. Although a common species, its IUCN status is “Data Defficient”, so any information on this species is relevant. Age, growth and physical maturity were examined in skeletons of 57 specimens of this species, mostly from the coasts of Tierra del Fuego, Argentina; this represents most of the known specimens of this species available in museum and private collections. Most specimens were by-catch in shore-set gillnets or had been harpooned for crab bait. Age was determined for 23 specimens, all from Tierra del Fuego. The maximum age was 13 years for a 199 cm female. The largest female in this survey was 210 cm, the largest male 205 cm in total length (12 years), but this probably does not represent the maximum length for this species. Only two animals, of 12 and 13 years, were physically mature. Animals reach asymptotic length (188 cm) with less than the 30% of the vertebral epiphyses fused. The animals in this study were mainly subadults, as has been found for other southern by-caught dolphins. Growth was studied for total length using 18 osteological characters with the Gompertz model. We propose that zygomatic width can be used to estimate total length for incomplete beach-cast specimens.     

Cranial variation in bottlenose dolphins<Emphasis Type="Italic">Tursiops spp.</Emphasis> from the Indian andwestern Pacific Oceans: additional evidence for two species

We examined the skulls of 72 bottlenose dolphins from the Indian and western Pacific Oceans to clarify the systematics in genusTursiops. We also examined type skulls ofTursiops aduncus (Ehrenberg, 1832),T. eurynome (Gray, 1846),T. catalania (Gray, 1862),Delphinus (Steno) gadamu Owen 1866,T. dawsoni Lydekker 1908, andT. truncatus (Montagu, 1821). The specimens were divided into two groups, A and B, based on rostrum length and characters of the basal part of the rostrum. The rostrum of group A was longer and tapered abruptly near the base, whereas that of group B was shorter and tapered more gradually throughout its length. Group A contained specimens from western, central, and eastern Asia, Africa, and Australasia. Group B contained specimens from central and eastern Asia and Australasia. The six type skulls were also clearly divided into two groups; the type skulls ofT. aduncus, T. catalania, andDelphinus (Steno) gadamu were included in group A, whereas the type skulls ofT. truncatus, T. eurynome, andT. dawsoni were included in group B. This grouping was consistent with the genetic status. Therefore, we identified group A specimens asT. aduncus and group B specimensT. truncatus, the oldest scientific names related to the two groups.