Chronicle of a death re-told:Chronicle of a death re-told:quantifying predation on juvenile quantifying predation on juvenile

Steller sea lions in the Gulf of AlaskaSteller sea lions in the Gulf of Alaska

Markus HorningMarkus HorningDept. Fisheries & WildlifeDept. Fisheries & Wildlife

Marine Mammal InstituteMarine Mammal Institute

Oregon State UniversityOregon State University

Jo-Ann MellishJo-Ann MellishUniversity of Alaska FairbanksUniversity of Alaska Fairbanks

Alaska Sea Life CenterAlaska Sea Life Center

• The Life History Transmitter The Life History Transmitter (LHX tag)(LHX tag)– Horning & Hill Horning & Hill IEEE J. Oceanic Engineering 2005IEEE J. Oceanic Engineering 2005 (with Wildlife Computers, Redmond, WA) (with Wildlife Computers, Redmond, WA)

• WantedWanted for Steller sea lions: for Steller sea lions:life-long, spatially & temporally explicit data on:life-long, spatially & temporally explicit data on:– forage (dive) effortforage (dive) effort– survivalsurvival– emigrationemigration– causes of mortality causes of mortality in individualsin individuals

• Impact of predation on near apex Impact of predation on near apex mesopredators is ‘empirically intractable’ mesopredators is ‘empirically intractable’

– Williams et al. “Killer Appetites” Williams et al. “Killer Appetites” Ecology 2004Ecology 2004

TheLifeHistoryTransmitter

TheLifeHistoryTransmitter

implanted

records data through entire life of animal

Dual tagging:Dual tagging:

- to determine failure rate- to determine failure rate

- derive correction factor- derive correction factor

Host has died,Host has died,

where, when, why,where, when, why,

cumulative weeklycumulative weekly

dive effortdive effort

25 sea lions released with LHX tags since 200425 sea lions released with LHX tags since 2004 - 4 - 4 Z. californianusZ. californianus (TMMC, California) (TMMC, California) - 21 - 21 E. jubatus E. jubatus (ASLC, Alaska)(ASLC, Alaska) Horning et al. Horning et al. BMC Vet. Res. 2008BMC Vet. Res. 2008

Captive period clinical responses: Captive period clinical responses: ↑ lympho- & monocytes, globulins, haptoglobins ↑ lympho- & monocytes, globulins, haptoglobins ↓ baseline by ≤ 45 days ↓ baseline by ≤ 45 days Mellish et al. Mellish et al. JEMBE 2007JEMBE 2007

Post-release external tracking 2-6 months:Post-release external tracking 2-6 months: - No differences in diving, ranging behavior - No differences in diving, ranging behavior - Min. confirmed post-procedure survival for - Min. confirmed post-procedure survival for 264 264dd (72 - 932 (72 - 932 n=15 E.j, sem 72.3n=15 E.j, sem 72.3)) Thomton et al. Thomton et al. End. Spec. Res. 2008End. Spec. Res. 2008

Results of control & validation Results of control & validation studiesstudies

• 21 juvenile Steller sea lions in PWS / KF – 8492 days21 juvenile Steller sea lions in PWS / KF – 8492 days

• n=12 male juveniles n=12 male juveniles →→ 6 tags from 4 animals in 4898 days6 tags from 4 animals in 4898 days

• 1 1 xmitxmit from each event + 2 beach recoveries: from each event + 2 beach recoveries: 0.25 0.25 ≤ P≤ Pff ≥ ≥ 0.50.5 1 undetected mortality for 4 detected events 1 undetected mortality for 4 detected events → → 5 deaths5 deaths

• Estimated MSR Yr 1-3: Estimated MSR Yr 1-3: 35.7%35.7% (0.15-0.86) (0.15-0.86) Yr 1-4: Yr 1-4: 31.1%31.1% (0.12-0.84) (0.12-0.84) (Mayfield (Mayfield Wilson Bull. 1961Wilson Bull. 1961 - Johnson - Johnson Auk 1979)Auk 1979)

• Brand re-sight based MSR for Seal Rocks – PWSBrand re-sight based MSR for Seal Rocks – PWS NMML data (L. Fritz, R. Towell) 143 males x 4 yrs (2001-05) NMML data (L. Fritz, R. Towell) 143 males x 4 yrs (2001-05) Yr 1-3: Yr 1-3: 36.5%36.5% (0.25 - 0.49)(0.25 - 0.49) Yr 1-4: Yr 1-4: 29.0%29.0% (0.17 - 0.43)(0.17 - 0.43)

• Within limits of n, d:Within limits of n, d: no mortalities missed; no mortalities causedno mortalities missed; no mortalities caused

Preliminary Preliminary ResultsResults

LHX tag LHX tag DATADATA from 4 events from 4 events

• one event with incomplete dataone event with incomplete data

Preliminary Preliminary ResultsResults

Preliminary Preliminary ResultsResults

Preliminary Preliminary ResultsResults

(calc.: Henssge 1988 Forensic Sci. Int.)

LHX tag LHX tag DATADATA from 4 events from 4 events

• one event with incomplete dataone event with incomplete data

• three events likely acute / traumatic death:three events likely acute / traumatic death: - temperature profiles - temperature profiles - onset of transmissions - onset of transmissions at next opportunityat next opportunity - two data sets: - two data sets: ‘normal’ diving‘normal’ diving until date of deathuntil date of death - one animal - one animal ‘normal’ appearance, movement (remote video)‘normal’ appearance, movement (remote video)

• at least 3 of 4 detected mortalities: at least 3 of 4 detected mortalities: Predation – likely by killer whalesPredation – likely by killer whales is single greatest cause of mortality for juvenile is single greatest cause of mortality for juvenile Stellers in PWS-KF Stellers in PWS-KF

• 51.5% of females (42.7–59.6) consumed before 51.5% of females (42.7–59.6) consumed before primiparityprimiparity (predation of 3/4 @ age 2 -20% p.a. & NMML ASR data)(predation of 3/4 @ age 2 -20% p.a. & NMML ASR data)

Preliminary Preliminary ResultsResults

Impact of killer whale predation Impact of killer whale predation on Steller sea lion population trajectories? on Steller sea lion population trajectories?

Dependent on prevalence of predationDependent on prevalence of predationin relation to productivity!in relation to productivity!

The predator pit conceptual frameworkThe predator pit conceptual framework- based on density dependent type III functional response- based on density dependent type III functional response- assumes prey shifting- assumes prey shifting– C. S. Holling C. S. Holling Can. Entomol. 1959Can. Entomol. 1959

– A. Bakun A. Bakun Progr. Oceanog. 2006Progr. Oceanog. 2006

– Horning & MellishHorning & Mellish Frontiers in Ecology & Environment - in Review Frontiers in Ecology & Environment - in Review

Consummate and consumed Consummate and consumed predatorspredators

Consummate and consumed Consummate and consumed predatorspredators

Consummate and consumed Consummate and consumed predatorspredators

How applicable is the predator pit conceptual frameworkHow applicable is the predator pit conceptual framework? ?

Has substantial qualitative explanatory power! Has substantial qualitative explanatory power! ↔ ↕↔ ↕

Suggests that western SSL are in refuge of predator pit:Suggests that western SSL are in refuge of predator pit:

• 20% of peak abundance20% of peak abundance

• Neutral population trajectoryNeutral population trajectory

• Recent increases in juvenile survivalRecent increases in juvenile survival

• Predation rates may have been higher, may re-occurPredation rates may have been higher, may re-occur

• Recent decrease in natality may relate to:Recent decrease in natality may relate to:

1) High 1) High formerformer juvenile predation juvenile predation → 2) → 2) reduced recruitmentreduced recruitment→ 3) → 3) shift in age structure to older femalesshift in age structure to older femalesReproductive senescence?Reproductive senescence?Natality from pup / non-pup ratios could be due to 1) & 3)Natality from pup / non-pup ratios could be due to 1) & 3)– Lunn et al. Lunn et al. J. Anim. Ecol. 1994; J. Anim. Ecol. 1994; Beauplet et al. Beauplet et al. OIKOS 2006OIKOS 2006

– Holmes et al.Holmes et al. Ecol. Applications 2007 Ecol. Applications 2007

Consummate and consumed Consummate and consumed predatorspredators

Future directions:Future directions:

Needs - Needs - spatially explicitspatially explicit data for multiple data for multiple speciesspecies on: on:

1.1. Mortality & predationMortality & predation

2.2. ProductivityProductivity

3.3. Predator prey habitsPredator prey habits

LHX tags are LHX tags are spatially explicityspatially explicity viable tool for 1 (2) viable tool for 1 (2)

AcknowledgementsAcknowledgements

Roger Hill (Wildlife Computers)Roger Hill (Wildlife Computers)Marty Haulena (TMMC, Vanc Aq), Pam Tuomi (ASLC)Marty Haulena (TMMC, Vanc Aq), Pam Tuomi (ASLC)Lowell Fritz, Rod Towell (NMML)Lowell Fritz, Rod Towell (NMML)

Funding through:Funding through:

• North Pacific Marine Research ProgramNorth Pacific Marine Research Program

• Pollock Conservation Cooperative Research ProgramPollock Conservation Cooperative Research Program

• Steller Sea Lion Research Initiative (NOAA)Steller Sea Lion Research Initiative (NOAA)

• Alaska Sea Life CenterAlaska Sea Life Center

• North Pacific Universities Marine Mammal ResearchNorth Pacific Universities Marine Mammal Research Consortium Consortium

NMFS Permits # 1034-1685 & #881-1668/1890NMFS Permits # 1034-1685 & #881-1668/1890