Outline. North Pacific Cetaceans - Biogeographic Distributions - Migrations and Breeding Cycle

Transcription

1 Hawaiian Cetaceans

2 Outline North Pacific Cetaceans - Biogeographic Distributions - Migrations and Breeding Cycle Hawaiian Cetaceans - Seasonal Visitors: Humpback Whale - Year-around Residents: Melon-headed Whale

3 North Pacific Oceanography Water mass: Body of water with a common formation history, which has physical properties distinct from other such water masses. (e.g., Temperature & Salinity) Ocean Domains: Distinct regions of the ocean, defined using physical, chemical and biological metrics (e.g., Depth, Thermocline, Seasonality, Productivity) North Pacific Transition Frontal Zone (Polovina et al. 2011)

4 North Pacific Cetacean Distributions COSMOPOLITAN REGIONAL / LOCAL PANTROPICAL AMPHITROPICAL TROPICAL TROPICAL- TEMPERATE TEMPERATE Jefferson, T.A., S. Leatherwood, and M.A. Webber FAO species identification guide. Marine mammals of the world. Rome, FAO p. 587 figs.

5 I. Cosmopolitan Distribution In theory a large and contiguous distribution In practice its more complicated: - Different overlapping stocks / species (e.g., Bottlenose dolphin) - Non-overlapping stocks / species (e.g., Bottlenose dolphin: coastal / pelagic) Frequently, evidence of disjunct distributions - Biases (low connectivity, low density) - Island-associated stocks

6 Distribution Patterns: Cosmopolitan Tursiops truncatus (Bottlenose Dolphin)

7 Distribution Patterns: Regional (Ocean Basin) Tursiops aduncus (Indian Bottlenose Dolphin)

8 Distribution Patterns: Cosmopolitan Grampus griseus (Risso s Dolphin)

9 Distribution Patterns: Local (Disjunct) Delphinus tropicalis (Arabian Common Dolphin) Delphinus capensis (Long-beaked Common Dolphin)

10 II. Distribution Patterns: Pantropical Lagenodelphis hosei (Fraser's dolphin)

11 III. Distribution Patterns: Amphitropical Orcinus orca (Killer Whale)

12 Distribution Patterns: Amphitropical Lissodelphis peronii (So. Right Whale Dolphin) Lissodelphis borealis (No. Right Whale Dolphin)

13 IV. Distribution Patterns: Tropical-Temperate Delphinus delphis (Common Dolphin)

14 V. Distribution Patterns: Temperate Lagenorhynchus obliquidens (Pacific White-sided Dolphin)

15 Distributions Throughout Breeding Cycle Physeter catodon (Sperm Whale) Length: Males, ft. Females, ft. Weight: Males, 80,000 lb. Females, 44,000 lb. Females: schools ~ 12 adults / calves Males: leave "nursery schools" at 4-21 years of age and join "bachelor school" with other males of similar age / size Whitehead, H Sperm whales: social evolution in the ocean. Chicago, IL: Univ. of Chicago Press

16 Hawaiian Cetacens Balaenopterid Rorquals Balaenopterid Rorquals Odontocetes Mysticetes

17 Visiting Cetaceans - Mysticetes Other occasional visitors rorquals: - Fin whale (Balaenoptera physalus) - Minke Whale (Balaenoptera acutorostrata) Fin whales observed feeding south of Hawai i in spring and during winter Some researchers suggest that whales migrate into Hawaiian waters primarily in the autumn and winter - Sei Whale (Balaenoptera borealis) - Bryde s Whale (Balaenoptera edeni) (Mobley et al. 2006)

18 Humpback Whale Distribution Cosmopolitan distribution But they have a seasonal changing distribution Megaptera novaeangliae (Big-winged New Englander) Humpback whales born in tropical waters in winter; mean = 4.3m long at birth Peak birth months: - So hemisphere (August) - No hemisphere (February) Mating during winter At winter s end, calves and mothers migrate to highlatitude feeding grounds

19 Large-scale Oceanographic Context Summering Grounds: - High productivity Wintering Grounds: - Warm water - Less predators Mean Annual Chlorophyll-a concentration from MODIS satellites (2002 present)

20 Studying Humpback Migrations Photographs of individually identified humpback whales collected in central and eastern North Pacific during the years 1977 to 1983 Photographs revealed extensive movement between seasonal habitats Whales wintering in Hawaii traveled to feeding regions throughout the coastal waters of Alaska Whales wintering off Mexico went to Alaskan feeding regions and to the Farallon Islands off central California

21 2 Winter / 5 Summer Grounds Fidelity to a given feeding region demonstrated by high proportion of return Fidelity to a given wintering ground less conclusive Humpbacks in eastern and central North Pacific form a single 'structured stock' consisting of several geographically-isolated 'feeding herds' which intermingle on one or more wintering grounds (Baker et al. 1986)

22 Humpback Whale Life Cycle Gestation lasts one year Calves nurse for 6 12 months before becoming independent; at 8-10 m long At a minimum, they live for 50 years, perhaps up to 90 Data on life expectancy came from animals killed by whaling or stranded Disagreement regarding age determination method, by examining ear "plug" with annual growth layers (Gabriele et al. 2009)

23 Humpback Whale Breeding Season During winter breeding season, males sing, to attract females and to mediate interactions with other males Males also engage in aggressive competition for access to mates Such "competitive groups" feature ramming, tail-slashing and other aggressive behaviors as other males attempt to displace the male closest to the central female

24 Singing During the Breeding Season Singing is virtually ubiquitous in the species' breeding range in winter Humpback whale songs consist of several themes sung in the same order, the entire song lasting from a few minutes to half an hour Singers, who are always male and are usually alone, will sometimes sing continuously for hours or even days All of the whales in a given population sing the same song. The song changes progressively, yet all singers keep up with the changes What drives the change in the songs is unknown, but researchers assume sexual selection plays a key role

25 Abundance in the Wintering Grounds Partenavia Observer (P68) Aerial surveys from planes Need to account for visibility (wind) and for group size Widely distributed across MHI Mostly shelf-slope (e.g., Penguin Banks) Use this information to develop corrected abundance estimates

26 Corrected Abundance Abundance in the Wintering Grounds Significant linear increase (p < 0.05) Average increase of 7% per year Reason of 2003 decrease unclear Humpback Whale Abundance ( ) 6,000 5,000 4,000 3,000 2,000 1,000 Mean +/- SD of humpback whale abundance over 11- year period

27 SPLASH project results (May 2008) Humpback whale population rebounds A new study shows the number of humpback whales in the Northern Pacific has grown dramatically to more than 18000, a finding likely to spark new debate about the whales' status as an endangered species, according to Hawai'i whale experts

28 SPLASH project results (May 2008) Connections of wintering / summering grounds by migrating whales

29 SPLASH project results (May 2008) Hawaiian whales spend summer from BC to Russia

30 SPLASH project results (May 2008) Canadian, Alaskan and California-OregonWhales winter in Hawaii

31 Acoustic Monitoring ( ) Over past 3 decades, population recovery from whaling-era losses resulted in steady increase in whales wintering in Hawaiian waters and an expansion of their distribution in the MHI Until recently, no evidence that this expansion included the islands, atolls, and banks of the NWHI (Lammers et al. 2011) Singing Season: Dates First / Last Recording: Number days detected in Singing Season (%)

32 Acoustic Monitoring ( ) Songs prevalent at Maro Reef, Lisianski Island, and French Frigate Shoals; also recorded Kure Atoll, Midway Atoll, and Pearl and Hermes Atoll Timing and abundance of songs followed trends observed on Oahu Suggests humpbacks use NWHI as wintering area NWHI could be unknown wintering area (photo-id) (Lammers et al. 2011)

33 Resident Cetaceans - Odontocetes

34 Melon-headed Whale Distribution Grow up to 3 meters (9.8 ft) long and weigh over 200 kilograms (440 lb) The lifespan is at least 20 years and probably up to 30 years Forms large pods, sometimes up to 1000 strong (Taylor et al. 2008)

35 Resident Melon-Headed Whales To assess population structure in Hawai i, dedicated surveys from 2000 to 2009 Figure 1. Survey effort trackline and sightings of melon-headed whales around the main Hawaiian Islands: (Aschettino et al. 2011)

36 Resident Melon-Headed Whales Using good quality photographs, there were 1,433 unique photo-identified whales 1,046 were distinctive Of these, 31.5% were seen more than once (Aschettino et al. 2011)

37 Resident Melon-Headed Whales Resighting data combined with social network analyses showed evidence of two populations: - a smaller ( ) resident population, seen exclusively off northwest of the island of Hawai i - a larger population ( ), throughout MHI Resightings of individuals up to 22 yr apart for the Hawai i-island resident population and up to 13 yr apart for the MHI population, suggesting long-term residency (Aschettino et al. 2011)

38 Resident Melon-Headed Whales Depth of encounters for Hawai i-island resident population was significantly shallower (median = 381 m) than those for the MHI population (median = 1,662 m) Filled triangles show encounter locations with Hawai i Island resident population, unfilled triangles show encounter locations with MHI population, and the unfilled diamond represents encounter with group that did not link to either population (Aschettino et al. 2011)

39 Cetaceans Associated with Eddies Study of the MHI population (n = 10 melon-headed whales) Tagged off Kona and Kauai in 2008 Tracks in offshore habitat (depth > 3,000 meters) (Woodworth et al. 2011)

40 Island Lee Eddies Propagate Westward friction & eddy decay with time Island Cyclonic eddies drift northward as they propagate and anticyclonic eddies drift southward as they propagate

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42 Island Lee Eddies Propagate Westward Melon-headed whale track, superimposed on satellite altimetry. Average buoy drifter data shows an average pattern of cyclonic circulation north of 20ºN and anticyclonic circulation south of 20ºN in lee of high Hawaiian Islands This area corresponds to the general location/paths of mesoscale eddies generated in the lee of the high islands

43 Whales Associated with Eddy Edges (Woodworth et al. 2011)

44 References Cetacean ranges from: Jefferson, T.A., S. Leatherwood, and M.A. Webber FAO species identification guide. Marine mammals of the world. Rome, FAO p. 587 figs. Figures / Images / Reports from Cascadia Research Collective and Marine Mammal Consulting Group

45 References Baker, C.S., Herman, L. M., Perry, A., Lawton, W.L., Straley, J.M., Wolman, A.A., KaufmanWinn, H.E.,Hall, J.D., Reinke, J.M., Ostman, J. (1986). Migratory movement and population structure of humpback whales (Megaptera novaeangliae) in the central and eastern North Pacific. Marine Ecology Progress Series 423: Lammers, M.O., Fisher-Pool, P.I., Au, W.W.L., Meyer, C.G., Wong, K.B., Brainard, R.E. (2011). Humpback whale Megaptera novaeangliae song reveals wintering activity in the Northwestern Hawaiian Islands. Marine Ecology Progress Series 423: Aschettino, J.M., Baird, R.W., McSweeney, D.J., et al Population structure of melon-headed whales (Peponocephala electra) in the Hawaiian Archipelago: Evidence of multiple populations based on photoidentification. Marine Mammal Science. DOI: /j x Woodworth PA, Schorr GS, Baird RW, et al. (2011). Eddies as offshore foraging grounds for melon-headed whales. Marine Mammal Science DOI: /j x

46 Additional References Range and primary habitats of Hawaiian insular false killer whales: informing determination of critical habitat Baird RW, Hanson MB, Schorr GS, Webster DL, McSweeney DJ, Gorgone AM, Mahaffy SD, Holzer DM, Oleson EM, Andrews RD [2012] Endangered Species Research 18(1): DOI: /esr00435 Temporal patterns in the acoustic signals of beaked whales at Cross Seamount Johnston DW, McDonald M, Polovina J, Domokos R, Wiggins S, Hildebrand J [2008] Biology Letters 4(2): Identification of humpback whale Megaptera novaeangliae wintering habitat in the Northwestern Hawaiian Islands using spatial habitat modeling Johnston DW, Chapla ME, Williams LE, Mattila DK [2007] Endangered Species Research 3(3):