David K. Mattila

Genetic tagging of humpback whales

The ability to recognize individual animals has substantially increased our knowledge of the biology and behaviour of many taxa. However, not all species lend themselves to this approach, either because of insufficient phenotypic variation or because tag attachment is not feasible. The use of genetic markers (‘tags’) represents a viable alternative to traditional methods of individual recognition, as they are permanent and exist in all individuals. We tested the use of genetic markers as the primary means of identifying individuals in a study of humpback whales in the North Atlantic Ocean. Analysis of six microsatellite loci, among 3,060 skin samples collected throughout this ocean allowed the unequivocal identification of individuals. Analysis of 692 ‘recaptures’, identified by their genotype, revealed individual local and migratory movements of up to 10,000 km, limited exchange among summer feeding grounds, and mixing in winter breeding areas, and also allowed the first estimates of animal abundance based solely on genotypic data. Our study demonstrates that genetic tagging is not only feasible, but generates data (for example, on sex) that can be valuable when interpreting the results of tagging experiments.

Segregation of migration by feeding ground origin in North Atlantic humpback whales (Megaptera novaeangliae)

Results from a large-scale, capture–recapture study of humpback whales Megaptera novaeangliae in the North Atlantic show that migration timing is influenced by feeding ground origin. No significant differences were observed in the number of individuals from any feeding area that were re-sighted in the common breeding area in the West Indies. However, there was a relationship between the proportion (logit transformed) of West Indies sightings and longitude (r 2 = 0.97,F1,3 = 98.27,P = 0.0022) suggesting that individuals feeding farther to the east are less likely to winter in the West Indies. A relationship was also detected between sighting date in the West Indies and feeding area. Mean sighting dates in the West Indies for individuals identified in the Gulf of Maine and eastern Canada were significantly earlier than those for animals identified in Greenland, Iceland and Norway (9.97 days, t179 = 3.53, P = 0.00054). There was also evidence for sexual segregation in migration; males were seen earlier on the breeding ground than were females (6.63 days, t105 = 1.98, P = 0.050). This pattern was consistently observed for animals from all feeding areas; a combined model showed a significant effect for both sex (F1 = 5.942, P = 0.017) and feeding area (F3 = 4.756,P = 0.0038). The temporal difference in occupancy of the West Indies between individuals from different feeding areas, coupled with sexual differences in migratory patterns, presents the possibility that there are reduced mating opportunities between individuals from different high latitude areas.

Do humpback whales exhibit lateralized behaviour

Lateralized behaviour has been documented in non-human species, although many observers believe that it occurs at the individual rather than the population level. Its occurrence in humpback whales,Megaptera novaeangliae, in Massachusetts Bay was investigated by examining active behaviour types in which preference could be given to one direction or side. These included head breaching (direction of spin), flippering (right or left) and tail breaching (direction of movement). In addition, persistent abrasions on the right or left jaw resulting from turns to one side during bottom feeding were noted. Of 75 individuals with jaw abrasions, 60 (80%) showed abrasions on only the right jaw, while 15 (20%) had abrasions on only the left. No whales had abrasions on both jaws. Location of abrasions was consistent in all resighted individuals for up to 12 years. Two of the three active behaviour types were not strongly lateralized: directional bias was seen in only five of 21 bouts (23·8%) of breaching, and in three of 11 bouts (27·3%) of tail breaching. However, 22 of 34 bouts (64·7%) of flippering showed a bias towards one direction (generally the right). Furthermore, direction of bias in all behaviour types was individually consistent between bouts and was strongly correlated with abrasions on the corresponding jaw (P=0·0032). The sex ratio of individuals with jaw abrasions, and of those showing directional bias in active behaviour, did not differ significantly from that of the overall population. Overall, these data suggest that humpback whales exhibit some behavioural asymmetries, at least one of which is at the population level. This result suggests assymmetry of function in motor or somatosensory representations, although too little is known about the brain of this species to permit definitive conclusions.

Humpback Whale Populations Share a Core Skin Bacterial Community: Towards a Health Index for Marine Mammals?

Microbes are now well regarded for their important role in mammalian health. The microbiology of skin – a unique interface between the host and environment - is a major research focus in human health and skin disorders, but is less explored in other mammals. Here, we report on a cross-population study of the skin-associated bacterial community of humpback whales (Megaptera novaeangliae), and examine the potential for a core bacterial community and its variability with host (endogenous) or geographic/environmental (exogenous) specific factors. Skin biopsies or freshly sloughed skin from 56 individuals were sampled from populations in the North Atlantic, North Pacific and South Pacific oceans and bacteria were characterized using 454 pyrosequencing of SSU rRNA genes. Phylogenetic and statistical analyses revealed the ubiquity and abundance of bacteria belonging to the Flavobacteria genus Tenacibaculum and the Gammaproteobacteria genus Psychrobacter across the whale populations. Scanning electron microscopy of skin indicated that microbial cells colonize the skin surface. Despite the ubiquity of Tenacibaculum and Psychrobater spp., the relative composition of the skin-bacterial community differed significantly by geographic area as well as metabolic state of the animals (feeding versus starving during migration and breeding), suggesting that both exogenous and endogenous factors may play a role in influencing the skin-bacteria. Further, characteristics of the skin bacterial community from these free-swimming individuals were assembled and compared to two entangled and three dead individuals, revealing a decrease in the central or core bacterial community members (Tenacibaculum and Psychrobater spp.), as well as the emergence of potential pathogens in the latter cases. This is the first discovery of a cross-population, shared skin bacterial community. This research suggests that the skin bacteria may be connected to humpback health and immunity and could possibly serve as a useful index for health and skin disorder monitoring of threatened and endangered marine mammals.

Nuclear and Mitochondrial Patterns of Population Structure in North Pacific False Killer Whales (Pseudorca crassidens)

False killer whales (Pseudorca crassidens) are large delphinids typically found in deep water far offshore. However, in the Hawaiian Archipelago, there are 2 resident island-associated populations of false killer whales, one in the waters around the main Hawaiian Islands (MHI) and one in the waters around the Northwestern Hawaiian Islands (NWHI). We use mitochondrial DNA (mtDNA) control region sequences and genotypes from 16 nuclear DNA (nucDNA) microsatellite loci from 206 individuals to examine levels of differentiation among the 2 island-associated populations and offshore animals from the central and eastern North Pacific. Both mtDNA and nucDNA exhibit highly significant differentiation between populations, confirming limited gene flow in both sexes. The mtDNA haplotypes exhibit a strong pattern of phylogeographic concordance, with island-associated populations sharing 3 closely related haplotypes not found elsewhere in the Pacific. However, nucDNA data suggest that NWHI animals are at least as differentiated from MHI animals as they are from offshore animals. The patterns of differentiation revealed by the 2 marker types suggest that the island-associated false killer whale populations likely share a common colonization history, but have limited contemporary gene flow.

Sedation at Sea of Entangled North Atlantic Right Whales (Eubalaena glacialis) to Enhance Disentanglement

Background The objective of this study was to enhance removal of fishing gear from right whales (Eubalaena glacialis) at sea that evade disentanglement boat approaches. Titrated intra muscular injections to achieve sedation were undertaken on two free swimming right whales. Methodology/Principal Findings Following initial trials with beached whales, a sedation protocol was developed for right whales. Mass was estimated from sighting and necropsy data from comparable right whales. Midazolam (0.01 to 0.025 mg/kg) was first given alone or with meperidine (0.17 to 0.25 mg/kg) either once or four times over two hours to whale #1102 by cantilevered pole syringe. In the last attempt on whale #1102 there appeared to be a mild effect in 20–30 minutes, with duration of less than 2 hours that included exhalation before the blowhole fully cleared the water. Boat avoidance, used as a measure of sedation depth, was not reduced. A second severely entangled animal in 2009, whale #3311, received midazolam (0.03 mg/kg) followed by butorphanol (0.03 mg/kg) an hour later, delivered ballistically. Two months later it was then given midazolam (0.07 mg/kg) and butorphanol (0.07 mg/kg) simultaneously. The next day both drugs at 0.1 mg/kg were given as a mixture in two darts 10 minutes apart. The first attempt on whale #3311 showed increased swimming speed and boat avoidance was observed after a further 20 minutes. The second attempt on whale #3311 showed respiration increasing mildly in frequency and decreasing in strength. The third attempt on whale #3311 gave a statistically significant increase in respiratory frequency an hour after injection, with increased swimming speed and marked reduction of boat evasion that enabled decisive cuts to entangling gear. Conclusions/Significance We conclude that butorphanol and midazolam delivered ballistically in appropriate dosages and combinations may have merit in future refractory free swimming entangled right whale cases until other entanglement solutions are developed.

The Usefulness of Parallel Analysis of Uni- and Bi-Parental Markers: The North Atlantic Humpback Whale

The majority of studies of the evolution and structure of animal populations are based upon analysis of either mitochondrial (mt) or nuclear DNA. Although each genome provides unique information, the combined results from parallel analyses of the two genomes can uncover additional facts that would otherwise have escaped detection.

Don’t assume it’s ghost gear : accurate gear characterization is critical for entanglement mitigation [poster]

Presented at the Society for Marine Mammology 22nd Biennial Marine Mammal Conference, Halifax, Nova Scotia, October 23-27, 2017