WALRUS IN THE MIXING BOWL University of Alaska, October 2012 G. Carleton Ray, Resesarch Professor University of Virginia Charlottesville, Virginia

Transcription

1 WALRUS IN THE MIXING BOWL University of Alaska, October 2012 G. Carleton Ray, Resesarch Professor University of Virginia Charlottesville, Virginia Photograph G. C. Ray

2 Theme: NATURAL HISTORY First Principle Indifference to a phenomenon s natural context can result in a paralyzing mismatch between the problem and the questions put to it. G.A. Bartholomew (1986). The role of natural history in contemporary biology. BioScience 36: Second Principle We miss the signal by focusing intently on what is all too commonly statistical noise. J.C.B. Jackson and Karen E. Alexander (2011) Shifting Baselines

3 Pacific Walrus Odobenus rosmarus divergens Females with juveniles and young-of-year in annual ice of the Chukchi Sea (north of Bering Strait). Photograph G. C. Ray

4 Atlantic Ocean The basics 1. Range 4 2 A cline of global populations: O.r. rosmarus & O.r. divergens laptevi 5 3 Arctic Ocean 6 1 Modified from Fay (1982) Pacific Ocean

5 The basics 2. Migration Pacific walrus migration patterns Modified from Fay (1982)

6 The basics 3. Very large groups possible Visual count NASA Convair 990 flight: ca. 10,000 animals in ~ 400 nmi 2

7 The Basics 4. Getting a feel for the environment Photograph G.C.Ray

8 Yu pik Captain Winfred Aningayou Gambell, St.Lawrence Is. Alaska Photograph G.C.Ray

9 Extending observations to regional scales Cruises: Burton Island Glacier, Polar Star, and Healy Photograph G.C. Ray

10 Helicopter assist, 50 nmi radius from ship Photograph J.McCormick-Ray

11 Observation 1 Thigmotaxis Photograph G.C. Ray

12 Observation 2 Thermoregulation Ray and Fay (1968)

13 Observation 3 Differential migration behavior of Walrus bulls Photograph G.C. Ray

14 Observation 4 Differential behavior of females with young-of-year Photograph G.C. Ray

15 Observation 5 A Water Ice Reproductive behavior The LEK Scale (m) Approximate scale (A) males on ice o males in water (B) Sonogram of males song 4 B From Fay et al. (1984) Frequency (khz) Whistle Dive Underwater Emerge Surface Time (s)

16 Observation 6 Annual Reproductive Cycle ~3 months delayed implantation, months pregnancy Modified from Fay 1982

17 Observation 7 An energetically-efficient food: Soft Clam (Mya truncata) Photograph J.McCormick-Ray

18 Observation 8 A central place forager Energetic trade-offs: distance traveled, prey size. The central place moves!

19 The walrus other half of life PC 8B 2-person submersible Photograph G.C. Ray

20 Observation 9 Walruses feeding underwater (Painting by Robert Hynes, National Geographic: from Ray and Curtsinger, 1979)

21 The extent ot feeding bioturbation! Atlantic Walrus (O. r. rosmarus) Northeast Greenland, 5 August 2005 Photograph Gören Ehlmé

22 Observation 10 Nitrogen release from sediments by walrus feeding accompanied by changed benthic communities and sediment structure Depth (cm) Sediment NH 4 + ( µ M) Water Column Nitrogen release (mmol m -2 day -1 ) Ratio ~ Natural release Walruses feeding Data from Rysgaard et al. (1998)

23 A widespread phenomenon - relative bioturbations Size of walrus disturbance is for 1 feeding trough. For whole population for 1 year size is ~10 6 Hall et al (1994)

24 Counting walruses MSY s counterpart Survey of 2006: 129,000 (50, ,000) estimated Number of animals (thousands) Pre-assessment period Russian expansion Assumed equilibrium (K) Assessment period What s wrong with this picture : First Year commercial exploitation What do these -- or any other -- numbers signify NOTE: populations for most other pinnipeds are even more uncertain.

25 What has been learned Lots of biology Only a bit of environmental relationships So what of HABITAT!

26 Hierarchies in Landscape REGION Ecology > 100 kms Months < 100 kms SEASCAPE Weeks < 10 kms PATCH Hours to Days

27 Sea-ice associations over the years: consistent floe configuration Central Bering Sea Winter 1973 Chirikov spring migration 2006

28 150 E 170 E 170 W 150 W 130 W 150 E 170 E 170 W 150 W 130 W 150 E 170 E 170 W 150 W 130 W JAN. FEB. MARCH SIBERIA ALASKA SIBERIA ALASKA SIBERIA ALASKA Search for a pattern: Two subpopulations &winter avoidance of eastern Bering Sea APRIL JULY MAY SIBERIA ALASKA SIBERIA ALASKA AUGUST JUNE SEPT. SIBERIA ALASKA SIBERIA ALASKA SIBERIA ALASKA SIBERIA ALASKA All observations (Fay, 1982) OCTOBER SIBERIA ALASKA NOVEMBER SIBERIA ALASKA DECEMBER SIBERIA ALASKA Number of Animals Miles

29 Search for a pattern: Centers of abundance of ice-associated pinnipeds, based on numbers sighted per minute during NMFS, ADF&G, and TINRO aerial surveys, 6-26 April Note: walrus as in Fay (1982). No surveys Nunivak to Norton Sound Braham et al. (1984)

30 Putting 2 & 2 together (1988) 1. Pack ice with leads 2. broken pack 3. rounded pack 4. loose pack 5. polynya 6. continuous ice

31 Beringian walruses in broken pack West-central Bering Sea 20 April 2007 Photograph G.C. Ray

32 The rounded pack Inimical to marine mammals and birds. Highly convergent in winter. Here divergent in spring. Formed by opposing northerly Winds and north-flowing Eastern Bering Sea coastal baroclinic current.

33 A principal components analysis of broken versus rounded pack 10 years March Shades of blue differ statistically A B Siberia Alaska Siberia Alaska Major winter concentrations Broken pack ice Rounded pack ice

34 Walrus habitat Where from How old

35 Placing pinnipeds in the seascape Simultaneous satellite and ship observations Pacific walrus and ringed seal (Phoca hispida) within broken pack. (Ray et al., 2010) RUSSIA 5 ALASKA GA CN 3 1 SL 2 SM 4 NU

36 Placing pinnipeds in the seascape Simultaneous satellite and ship observations Spotted seal (Phoce largha) in loose pack. (Ray et al 2010) Spotted Spotted seals typicaly seal: occur in family Simultaneous groups (male, satellite female, newborn and in ship mid-april observations to mid- May. Adults mate following pup weaning.

37 Placing pinnipeds in the seascape Simultaneous satellite and ship observations. Ribbon seal on remnant loose pack (Ray et al 2010) ibbon Remnant seal: ice ( last ice ) Simultaneous comes from the satellite Kamchatka Area, reaching St. Lawrence and ship observations Island late May to early June, and occasion ally Bringing large numbers of Ribbon seals.

38 USCGC Healy tracks 8 May 2 June April- 7 May March March -4 May 2008

39 A 8 May-5 June ribbon seals on remnant loose pack ~5,000 walruses on migration B 14 April-10 June ribbon seals on loose pack 1545 walruses on broken pack and on migration C 15 March-4 May ribbon seals on loose pack 805 walruses in 2 waves of migration

40 2006 March ice less than climatological norm March ice at climatological norm March ice exceeded climatological norm. All years Numerous melting and freezing events resulted in large expanses of young ice. No statistical differences in weather. Red chevrons = Bering Strait White line = ice climatological norm Arrows, Bering Sea = floes tracked Arrows, Chukchi Sea = position of ice front

41 2006 Sea ice retreated to near the 100 m isobath Sea ice retreated to north of the 100 m isobath, setting record conditions. Entire area south of the 100m isobath ice-free Ice north of the 100 m isobath. Scattered floes barely visible under clouds near Wrangel Island White line = 100m isobath Yellow line =minimum ice climatological norm Arrows = southerly ice limits

42 THE MIXING BOWL Floes generally moved km day -1 S of 64 N and picked up speed to 92 km day -1 N of 64 N. Exceptional floes moved from the Gulf of Anadyr: 2006, 674 km in 33 days 2006 A 2007 B 64 N 64 N 62 N 62 N 60 N 58 N Floe 1 Floe 7 Floe 2 Floe 8 Floe 3 Floe 9 Floe 4 Floe 10 Floe 5 Floe 11 Floe 6 Floe 12 Floe RBS 60 N 58 N Floe 1 Floe 2 Floe 3 Floe 4 Floe 5 Floe 6 Floe 7 Floe 8 Floe 9 Floe 10 Floe 11 Floe SL W 170 W 165 W W 170 W 165 W 64 N 62 N 2008 Floe 1 Floe 2 Floe 3 Floe 4 Floe 5 Floe 6 Floe 7 Floe 8 C 64 N 62 N 2009 D 60 N 58 N 60 N 58 N Floe 1 Floe 2 Floe 3 Floe 4 Floe 5 Floe 6 Floe 7 Floe 8 Floe W 170 W 165 W W 170 W 165 W

43 Not all floes travel at the same speed: A ratio of keel to sail

44 Bottom line: effect of matrix quality on the population Loss and structural change of habitat increases the proportion of time that the population spends in the portion of the habitat where reproduction may not be possible and where mortality is higher, thereby leading to a downward spiral to extinction (Fahrig Emigration Dispersal mortality = Immigration Landscape matrix

45 The importance of Seascape Ecology As studies in landscape ecology have demonstrated, significant errors can accrue if spatially-explicit, environmentally-scaled natural history is not included as a fundamental basis for conservation (Wu, 2003). " Questions Is the Pacific walrus a keystone and/or foundation species" If walruses are in a mixing bowl, how to assess the population" Is ecosystem-based management possible" Will this require a new research agenda" And, if so, what would that be" The End