Distribution, abundance and biology of Group V humpback whales ...

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During the northern migration there is a distinct peak in abundance during late June and early July observed off North Stradbroke Island (Paterson 1984) but no such peak is observed during the southern migration that occurs in late August off the Whitsunday Islands (Malcom and Duggan 1997). In Hervey Bay, the Pacifi c Whale Foundation (1997) reported humpbacks appearing at earlier dates in successive years. The peak abundance of humpbacks in Hervey Bay varies from days to weeks (Corkeron et al.1994). Dawbin (1956) observed a variation in the peak abundance of migrating humpbacks past New Zealand to be as much as fi ve-and-a-half weeks. The structure of pods was identifi ed by a genetic study by Brown et al.(1995). They noted the northward migrating pods were signifi cantly smaller than southward migrating pods and that more male humpback whales were found in the larger pods than females. The most common pod type observed during the study was the male-female pair, which is suggestive of either mating on migration and/or mate guarding. There is growing support for the hypothesis that not all females migrate annually to winter grounds but remain on the feeding grounds during rest years, or produce offspring in the higher latitudes of Antarctica (Chittleborough 1958a; Brown et al.1995; Craig and Herman 1997; Mikhalev 2000). Chittleborough (1965) and Brown et al.(1995) documented the ratio of migrating Group V males to females, sampled in south-east Queensland, and is approximately 2:1. This is a similar ratio for other humpback stocks in the North Pacifi c (Medrano et al.1994; Calambokidis 2000; Craig and Herman 2000). However, researchers from the North Atlantic argue that there is no evidence for a male-biased sex ratio in wintering humpbacks in the North Atlantic. The migration southward may be delayed by some individuals due to their mating drive being stronger than hunger as individuals and groups of humpback whales have been observed to continue to seek mates, at least in the early stage of the southern migration (Paterson 1984). 5.3 Site fi delity and habitat preference Humpback whales exhibit a high degree of site fi delity both towards feeding and wintering grounds (Clapham et al.1993). Urban et al.(2000) determined that the migratory movements of eastern Pacifi c humpbacks were clearly non-random. Photographic comparisons between areas showed clear evidence for preferred migratory destinations. Kaufmann (1990) describes the movements of an adult humpback whale sighted in Antarctic Area V that was resighted 19 months later in Platypus Bay, Queensland, Australia. The re-sightings were verifi ed using both tail-fl uke and lateral body markings. The resighting of this animal is the fi rst photographic documentation of movement between the described areas, and provides support for the assumption, based upon discovery tags, that whales found along the east cost of Australia migrate from Antarctic Area V. Genetic studies demonstrate that, despite the nearly unlimited migratory potential of the species, there is a striking degree of genetic structure both within and between oceanic populations of humpback whales (Baker et al.1994). Several authors have concluded that site fi delity in humpbacks is a maternally driven trait (Baker et al.1994; Palsbøll et al.1995; Urban et al.2000). Photo-identifi cation studies are not consistent in their fi ndings in relation to sex biases in site fi delity. Garrigue et al.(2000) and Sladen et al.(1999) concur in their conclusions of male exhibiting less fi delity than females. In New Caledonia Garrigue et al.(2000) found that there is an interchange of males between winter grounds. In Hawaii males are more likely to wander between wintering grounds than females (Sladen et al.1999). However, a photoidentifi cation study by Craig and Herman (1997) suggests males show greater site fi delity than females in Hawaiian wintering grounds. Baker et al.(1994) concluded from their genetic data that there was no obvious evidence of sex biases in site fi delity and that humpbacks used a strategy that is a combination of imprinting and genetic traits to return to the winter grounds. Craig and Herman (2000) used photographic techniques to investigate sex differences in site fi delity and migration. They concluded that the wintering areas utilised by breeding females is dependent upon their reproductive status. Gregr and Trites (2000) used positional information and oceanographic data (bathymetry, temperature, and salinity) to predict critical habitat off the coast of British Columbia for fi ve whale species including humpback whales. Using six predictor variables (month, depth, slope, depth class, and sea surface temperature and salinity) the model developed identifi ed critical habitat for sei, fi n, and male sperm whales. However, due to the small sample size, the model was relatively insensitive to the predictor variables for humpback whales. However, the habitat predictions did identify humpback whale habitat in sheltered bays and straits throughout the coast. The application of this model could be considered for identifying humpback whale habitat in Queensland. The high degree of site fi delity exhibited by humpbacks, especially females, is an important consideration for the management and planning of marine protected areas. The high degree of site fi delity exhibited by humpbacks is likely to have implications for breeding success. It has been suggested site fi delity is maternally driven and that females with calves favour habitats that provide protection from predators and rough sea conditions. If this is the case, there are only limited areas breeding females can utilise. If females have already expended huge energy budgets during migration, the energy required to search for other suitable breeding habitat may be enough to cause a decline in breeding success over a long period. 10 • Distribution, abundance and biology of Group V humpback whales Megaptera novaeangliae: A review • August 2002
6 Individual identifi cation The ability to recognise individual animals has substantially increased our knowledge of the biology and behaviour of many taxa (Palsbøll et al.1997). A wide-ranging transient species such as humpbacks can be tracked using a number of techniques. The techniques can be divided into non-manipulative and manipulative. Photo-identifi cation, sloughed skin sampling and acoustic tracking are nonmanipulative techniques, whereas conventional tagging and biopsy sampling are manipulative techniques. Each technique has its cost and benefi t; the advantages and disadvantages of photo-identifi cation versus genetics were debated in depth at the Humpback Whale Research and Conservation Seminar, Brisbane 1998 (Department of Environment and Heritage Proceedings 1999). Some of the conclusions from the seminar were that genetic techniques are technically superior to photo-identifi cation as a tool. However, its practical constraints limit its exclusive use. The photo-identifi cation and genetic techniques should be integrated to target specifi c issues such as: long-term tag changes; survivorship (especially with calves); discreteness of stocks; relatedness of individuals; gender determination of individuals; abundance; determining the sex composition of a population and standardising genetic markers to facilitate the comparison of data across jurisdictions. Genetic tagging is an effective method for individual identifi cation even in a large population of wide-ranging and inaccessible mammals such as cetaceans. The data obtained from genetic tags can be used to address evolutionary, demographic and behavioural questions to which traditional tagging methods are unsuited. All living organisms possess genetic material that in principle enables individuals within any taxon to be identifi ed reliably from minute quantities of tissue. Such tissue is commonly derived from biopsies, but can also come from sloughed skin, shed hair or faecal material, thus potentially allowing genotyping and individual recognition even of unobserved animals (Palsbøll et al.1997). Contemporary genetic techniques are capable of extracting DNA from samples that have been preserved for 10 years unless they have been fi xed in formalin. As large numbers of samples exist from commercial whaling operations for a number of species including humpbacks, genetic typing of these samples would provide an invaluable context in which to study extant populations (Valsecchi et al.1997). Stevick et al.(2001) undertook a double-marking experiment that compared photographic and genetic techniques for identifying individuals. His study concluded that photographic techniques are a reliable method of identifying humpback whales on a large scale. The study is the fi rst large-scale test of errors in individual identifi cation by natural markings for any species. 6.1 Non-manipulative sampling techniques Non-manipulative techniques have the advantage of minimal disturbance to an individual as samples are collected remotely. The two non-manipulative techniques provide very different types of information; photo-identifi cation relies upon the repeated recognition of physical features to identify an individual. Sloughed skin sampling is a genetic technique that examines the genetic make-up of an individual that does not vary over time. The disadvantages of non-manipulative techniques include high costs in time and data collection and analysis, diffi culties in using appropriate mathematical analytical techniques, weather dependence and the certainty of which individual the sample originated from. 6.1.1 Photo-identifi cation Photo-identifi cation relies on the ability to identify an individual based upon the level of pigmentation (black and white markings and patterns) and the shape of the dorsal fi n. The photo-identifi cation technique is validated and its success is reliant upon the quality and content of each photograph (Hammond 1986). A series of photographs may be required to clearly identify an individual. Several authors describe protocols and standards for the taking of photographs and the evaluation of photographs for identifi cation purposes (Hammond et al.1990; Mizroch et al.1990; Friday et al. 2000). Hammond (1986) reviews the method of estimating population size from the capture and recapture of animals with respect to population of naturally marked whales. The paper is divided into three main sections dealing with (i) using natural markings to “mark” an animal, (ii) the basic models, and (iii) the effect on population estimates of variation in the characteristics of individual animals. Suggestions are made concerning the sampling of naturally marked whale populations and the analysis of data from such experiments. Traditionally, photo-identifi cation techniques have relied upon an individual humpback revealing the underside of its the tail or fl uke, long enough for a good quality photograph to be taken of the unique pattern of pigmentation on the underside of its fl uke. However, pigmentation is variable with age and calves have the greatest variation in pigmentation during their fi rst two years (Clapham 1993). It is unlikely that a calf can be identifi ed at a young age using photoidentifi cation techniques and tracked to maturity. Research programs using photo-identifi cation have provided substantial information about the life histories of individuals on the feeding grounds in Maine, Norway and Antarctica, and the wintering grounds of Hawaii, Bahamas/West Indies. Research groups that have developed photo-identifi cation catalogues of individual humpbacks for the Group V population include Pacifi c Whale Foundation (1987–2000), The Oceania Project (1992–2001), The University of Sydney (Corkeron 1992), Bryden et al.(1996) and Garrigue (1995–2001). A recent study by Blackmer et al.(2000) demonstrated that dorsal fi n shape and the confi guration of the peduncle knobs, found just behind the dorsal fi n, are highly stable over time and are easy to capture on fi lm each time a whale is sighted. They suggest that a protocol should be adopted of taking photographs based upon an existing protocol used by fi n whale researchers, which involves taking identifying photographs from the right side of humpbacks. Australia has yet to develop a common protocol that encourages that sharing of photo-identifying data between researchers and management agencies. Queensland Parks and Wildlife Service, in a pilot project, investigated the viability of an existing electronic catalogue that is a sightings database, a storage facility for data and photography used to identify individuals; and that assisted in the matching of photographs to identify individual humpback that return to locations over long periods. The project has not been developed beyond the pilot stage but identifi ed the need for the implementing standard methodologies for data collection for photo-identifi cation and the resources required for developing an electronic catalogue. 11 • Distribution, abundance and biology of Group V humpback whales Megaptera novaeangliae: A review • August 2002
Page 1 and 2: Distribution, abundance and biology
Page 3 and 4: Contents 1 Introduction............
Page 5: Figure 1. Queensland marine parks a
Page 8 and 9: Figure 4. Group IV and V distributi
Page 10 and 11: The main calving ground of the east
Page 14 and 15: 6.1.2 Sloughed skin sampling Slough
Page 16 and 17: Variations in the abundance of prey
Page 18 and 19: Appendix 1. Summary of population e
Page 20 and 21: Craig, A.S. & Herman, L.M. 1997. Se
Page 22: 20 • Distribution, abundance and

Distribution, abundance and biology of Group V humpback whales ...

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