Peter J. Corkeron

The Indo-Pacific Humpback Dolphin, Sousa chinensis (Osbeck, 1765), in Australian Waters: a Summary of current knowledge

Indo-Pacific humpback dolphins (Sousa chinensis) occur in the coastal northern waters of Australia from approximately the Queensland – New South Wales border (31°27primeS, 152°55primeE) to Ningaloo Reef (22°17primeS, 113°48primeE) in Western Australia. Due to their coastal, estuarine distribution, Indo-Pacific humpback dolphins are particularly vulnerable to several human activities in and adjacent to coastal areas. At present, it is not possible to assess the population status of humpback dolphins in Australian waters because information on their biology and ecology is limited. The sparse data available for selected areas indicate that humpback dolphins occur in discrete, geographically localized populations and are susceptible to anthropogenic threats (e.g., incidental captures in gill nets). The conservation of humpback dolphins in Australias northern coastline will depend on the maintenance of high-quality habitat in areas that are already under some protection, the identification of critical habitats, the inclusion of these habitats in the rezoning initiatives of protected areas, and the reduction of conservation threats. Precautionary measures should be adopted while further work on abundance estimates, population structure, and levels of human-caused mortality are carried out on a wider scale in Australian waters.

Social structure in migrating humpback whales (Megaptera novaeangliae)

Although largely solitary, humpback whales exhibit a number of behaviours where individuals co‐operate with one another, for example during bubble net feeding. Such cases could be due to reciprocal altruism brought on by exceptional circumstances, for example the presence of abundant shoaling fish. An alternative explanation is that these behaviours have evolved through kin selection. With little restriction to either communication or movement, diffuse groups of relatives could maintain some form of social organization without the need to travel in tight‐nit units. To try to distinguish between these hypotheses, we took advantage of the fact that migrating humpback whales often swim together in small groups. If kin selection is important in humpback whale biology, these groups should be enriched for relatives. Consequently, we analysed biopsy samples from 57 groups of humpback whales migrating off Eastern Australia in 1992. A total of 142 whales were screened for eight microsatellite markers. Mitochondrial DNA sequences (371 bp) were also used to verify and assist kinship identification. Our data add support to the notion that mothers travel with their offspring for the first year of the calf’s life. However, beyond the presence of mother‐calf/yearling pairs, no obvious relatedness pattern was found among whales sampled either in the same pod or on the same day. Levels of relatedness did not vary between migratory phases (towards or away from the breeding ground), nor between the two sexes considered either overall or in the north or south migrations separately. These findings suggest that, if any social organization does exist, it is formed transiently when needed rather than being a constant feature of the population, and hence is more likely based on reciprocal altruism than kin selection.

Patterns in the vocalizations of male harbor seals

Comparative analyses of the roar vocalization of male harbor seals from ten sites throughout their distribution showed that vocal variation occurs at the oceanic, regional, population, and subpopulation level. Genetic barriers based on the physical distance between harbor seal populations present a likely explanation for some of the observed vocal variation. However, site-specific vocal variations were present between genetically mixed subpopulations in California. A tree-based classification analysis grouped Scottish populations together with eastern Pacific sites, rather than amongst Atlantic sites as would be expected if variation was based purely on genetics. Lastly, within the classification tree no individual vocal parameter was consistently responsible for consecutive splits between geographic sites. Combined, these factors suggest that site-specific variation influences the development of vocal structure in harbor seals and these factors may provide evidence for the occurrence of vocal dialects.

Accumulation and transfer of contaminants in killer whales (Orcinus orca) from Norway : indications for contaminant metabolism

Blubber tissue of one subadult and eight male adult killer whales was sampled in Northern Norway in order to assess the degree and type of contaminant exposure and transfer in the herring-killer whale link of the marine food web. A comprehensive selection of contaminants was targeted, with special attention to toxaphenes and polybrominated diphenyl ethers (PBDEs). In addition to assessing exposure and food chain transfer, selective accumulation and metabolism issues also were addressed. Average total polychlorinated biphenyl (PCB) and pesticide levels were similar, approximately 25 microg/g lipid, and PBDEs were approximately 0.5 microg/g. This makes killer whales one of the most polluted arctic animals, with levels exceeding those in polar bears. Comparing the contamination of the killer whales diet with the diet of high-arctic species such as white whales reveals six to more than 20 times higher levels in the killer whale diet. The difference in contaminant pattern between killer whales and their prey and the metabolic index calculated suggested that these cetaceans have a relatively high capacity to metabolize contaminants. Polychlorinated biphenyls, chlordanes, and dichlorodiphenyldichloro-ethylene (DDE) accumulate to some degree in killer whales, although toxaphenes and PBDEs might be partly broken down.

Vocal behaviour of Norwegian killer whales during carousel and seiner foraging on spring-spawning herring

Norwegian killer whales (Orcinus orca) use different techniques to forage on spring-spawning herring. Two of the commonly observed techniques are carousel feeding, a cooperative feeding method, and seiner feeding, a noncooperative method. During seiner foraging, large groups of whales forage on herring discards around the nets or on discarded by-catch of fishing boats. Very little is known about the acoustic behaviour during these foraging contexts. The aim of this study was to examine possible differences in killer whale acoustic behaviour during both foraging contexts using simple sound analysis techniques. Calling, echolocation, and tail-slap activities were measured and compared between foraging contexts. Of these, calling and tail-slap activities were higher during carousel feeding, whereas echolocation activity increased with the number of individuals, irrespective of foraging context. No call types were used exclusively during a particular foraging context. A difference in mean occurrence of one call type was detected; call type N21 occurred more often during seiner foraging than during carousel foraging contexts. We suggest that the sequence of call types, rather than the use of isolated call types, is of greater importance in the coordination of group movements during carousel foraging.

ONTOGENY OF VOCALISATIONS IN INFANT BLACK FLYING FOXES, PTEROPUS ALECTO

Most mega and microchiropteran bats live in large colonial roosts where potential intermingling of mother-infant pairs places immediate demands on their recognition systems. In microchiropteran bats, infants produce distinct isolation calls that appear to become less complex in structure in the latter stages of lactation. This results in a reduction in the capacity of females to locate their infants. Similar recognition pressures exist for both suborders therefore it might be expected that they would exhibit similarities in their vocal development. This study quantifies the vocal characteristics of infant black flying foxes, Pteropus alecto, to assess vocal development in this species. Recordings were made of 21 infants, nine males and twelve females, between 1 and 35 days in age. As in microchiropteran bats, infant black flying foxes produce individually distinctive calls, which persist throughout lactation. Unlike microchiropterans, calls remained stable in structure throughout lactation. Individuals produced one of three distinctive isolation call types. Whether mothers use this variation to recognise patches of infants that include their own within a camp or to locate their own infants requires further study.

Observations of blue whales feeding in Antarctic waters

Abstract There are no published accounts of blue whales (Balaenoptera musculus) feeding in Antarctic waters. This note describes the behaviour of two groups of blue whales feeding in Antarctic pelagic waters. Whales were observed during the 18th IWC/IDCR southern hemisphere minke whale assessment cruise. Feeding behaviour in both cases resembled those described previously for both northern hemisphere blue whales and fin whales (B. physalus). These observations suggest that a programme of comparative behavioural observations could be developed to test the “feeding competition” hypothesis, which suggests that recovery of populations of blue whales will be impeded by feeding competition with sympatric minke whales.

Shipboard echosounders negatively affect acoustic detection rates of beaked whales

Beaked whales are cryptic, deep-diving odontocetes that are sensitive to anthropogenic noise. While their behavioral responses to navy sonar have been the subject of extensive study, little effort has been expended to evaluate their responses to other types of acoustic signals, such as fisheries echosounders. From 1 July to 10 August 2013, the Northeast Fisheries Science Center conducted a shipboard cetacean assessment survey, combining visual observation and passive acoustic data collection. Simrad EK60 echosounders were used to collect prey field data; echosounder use was alternated on/off on a daily basis to test for an effect on beaked whale detection rates. The software package Pamguard was used to detect, classify, and localize individual beaked whales. A GLM was used to test the relationship between acoustic detections and covariates; echosounder use negatively affected beaked whale acoustic detection rates, and acoustic event durations were significantly shorter. These results suggest that beaked ...

Toward acoustically derived population estimates in marine conservation: An application of the spatially-explicit capture-recapture methodology for North Atlantic right whales

Passive acoustics provide a flexible tool for developing understanding of the ecology and behavior of vocalizing marine animals. Yet despite a robust capacity for detecting species presence, our ability to estimate population abundance from acoustics still remains poor. Critically, abundance estimates are precisely what conservation practitioners and policymakers often require. In the current study, we explored the application of acoustic data in the spatially-explicit capture-recapture (SECR) methodology, to evaluate whether acoustics can be used to infer abundance in the endangered North Atlantic right whale. We sub-sampled a year-long acoustic dataset from archival recorders deployed in Massachusetts Bay. Multichannel data were reviewed for the presence of up-calls. A total of 1659 unique up-calls were detected. Estimates of up-call density ranged from zero to 608 (± 70 SE) up-calls/hour. Estimates of daily abundance, when corrected for average calling rate, ranged from 0—69 (± 21 SE) individuals per d...

Variation in pup vocalisations and mother‐pup behaviour between harp seal whelping patches: effects of climate or geography

Harp seals breed in pack‐ice, a substrate which can vary substantially between whelping patches depending on differing environmental and oceanographic conditions. This study demonstrates clear site differences in pup vocalizations and mother pup behaviour between Northeast (Greenland Sea) and Northwest (Canadian Front) Atlantic harp seal populations. Classification trees showed a distinctive split between Front and Greenland Sea pup vocalisations. No clear sex differentiation in vocalizations was present for pups at the Front; 42% (n = 12) of male and 38% (n = 13) of female calls could be attributed to a given individual. In the Greenland Sea, 55% (n = 42) of female vocalisations were attributed to individuals compared with only 8% for males (n = 47). In addition behavioural observations of mother pup pairs were conducted (Front, n = 58; Greenland Sea, n = 78). Greenland Sea pups were found to nurse more, and were more alert than Front pups. Female attendance patterns also differed between sites: females ...