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Studying Killer Whale Predation in the Field A Sound Approach to Detecting Kills

Studying Killer Whale Predation in the Field A Sound Approach to Detecting Kills. Volker B. DEECKE John K.B. FORD Peter J.B. SLATER. Introduction. Methods. Results. Conclusions.

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Studying Killer Whale Predation in the Field A Sound Approach to Detecting Kills

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  1. Studying Killer Whale Predation in the Field A Sound Approach to Detecting Kills Volker B. DEECKE John K.B. FORD Peter J.B. SLATER

  2. Introduction Methods Results Conclusions • Predation by killer whales is likely to play a crucial role in regulating marine mammal populations in the North Pacific ecosystem1,2 • Predation by killer whales is likely to play a crucial role in regulating marine mammal populations in the North Pacific ecosystem1,2 • Delineating the ecological role of mammal-eating killer whales requires precise knowledge about their abundance, dietary preferences, and the frequency of predation events • Rates of killer whale prey consump-tion are usually extrapolated from estimates of metabolic requirements. • Field data on predation rates for this area are currently limited 1 Springer, A.M. et al. 2003, Proc. Natl. Acad. Sci. U.S.A.100:12223-12228 2 Williams, T.M et al.2004, Ecology85:3373–3384 1 Springer, A.M. et al. 2003, Proc. Natl. Acad. Sci. U.S.A.100:12223-12228 2 Williams, T.M et al.2004, Ecology85:3373–3384 BACKGROUND: Killer whales in the North Pacific ecosystem • Delineating the ecological role of mammal-eating killer whales requires precise knowledge about their abundance, dietary preferences, and the frequency of predation events • Rates of killer whale prey consump-tion are usually extrapolated from estimates of metabolic requirements. • Field data on predation rates for this area are currently limited

  3. Introduction Methods Results Conclusions • Mammal-eating killer whales feed on prey that can detect killer whale vocalizations and respond with anti-predator behaviour1 • Mammal-eating killer whales feed on prey that can detect killer whale vocalizations and respond with anti-predator behaviour1 • These animals typically hunt in silence but vocalize following a successful attack2 • These animals typically hunt in silence but vocalize following a successful attack2 • Predation on some species can be very subtle and some kills may be missed using visual observations alone. This may bias data on prey preference and predation rates ►OBJECTIVE: to test whether monitoring killer whale sound production can help to detect predation events 1 Deecke V.B. et al.2002Nature, 420:171-173 1 Deecke V.B. et al.2002Nature, 420:171-173 2 Deecke V.B. et al.2005Anim. Behav.69:395-405. 2 Deecke V.B. et al.2005Anim. Behav.69:395-405. BACKGROUND: Detecting killer whale predation in the field • Predation on some species can be very subtle and some kills may be missed using visual observations alone. This may bias data on prey preference and predation rates ►OBJECTIVE: to test whether monitoring killer whale sound production can help to detect predation events

  4. Introduction Methods Results Conclusions • We recorded underwater sound production near groups of killer whales in Southeast Alaska • We documented any predatory behaviour and collected prey remains whenever possible • We measured the distance to the animals using laser rangefinders • We counted the number of sounds produced while the animals were within 500m of the boat 500m 500m The rate of sound production is: No. of sounds within 500m (No. of minutes within 500m) x (No. of animals) (Sounds per animal per minute) The rate of sound production is: No. of sounds within 500m (No. of minutes within 500m) x (No. of animals) (Sounds per animal per minute) Data Collection • We recorded underwater sound production near groups of killer whales in Southeast Alaska • We documented any predatory behaviour and collected prey remains whenever possible • We measured the distance to the animals using laser rangefinders • We counted the number of sounds produced while the animals were within 500m of the boat

  5. Introduction Methods Results Conclusions 15 15 15 10 10 10 Frequency (kHz) Frequency (kHz) Frequency (kHz) 5 5 5 0 0 0 1 1 1 2 2 2 3 3 3 4 4 4 Time (s) Time (s) Time (s) 1.5 1.5 Kruskall Wallis: p = 0.028 1.0 1.0 Calls per animal per minute Calls per animal per minute 0.5 0.5 0.0 0.0 Other behaviours (N=7) Other behaviours (N=7) After kill (N=7) After kill (N=7) See also: Deecke et al. 2005, Anim. Behav.69:395-405 Behaviour Category Behaviour Category Acoustic Detection of Kills: Pulsed Calls ►mammal-eating killer whales consistently emit pulsed calls after a kill and these are good indicators of predatory activity.

  6. Introduction Methods Results Conclusions 15 15 15 10 10 10 Frequency (kHz) Frequency (kHz) Frequency (kHz) 5 5 5 0 0 0 1 1 1 2 2 2 3 3 3 4 4 4 Time (s) Time (s) Time (s) 1.5 1.5 Kruskall-Wallis: p = 0.109 1.0 1.0 Whistles per animal per minute Whistles per animal per minute 0.5 0.5 0.0 0.0 Other behaviours (N=7) Other behaviours (N=7) After kill (N=7) After kill (N=7) Behaviour Category Behaviour Category Acoustic Detection of Kills: Whistles ►whistles are only produced rarely and are not consistently associated with predation events.

  7. Introduction Methods Results Conclusions 15 15 15 10 10 10 Frequency (kHz) Frequency (kHz) Frequency (kHz) 5 5 5 0 0 0 1 1 1 2 2 2 3 3 3 4 4 4 Time (s) Time (s) Time (s) 1.5 1.5 Kruskall-Wallis: p = 0.028 1.0 1.0 Click trains per animal per minute Click trains per animal per minute 0.5 0.5 0.0 0.0 Other behaviours (N=7) Other behaviours (N=7) After kill (N=7) After kill (N=7) Behaviour Category Behaviour Category Acoustic Detection of Kills: Echolocation Clicks ►mammal-eating killer whales typically echolocate during and after an attack and echolocation presents a useful tool to detect predation events.

  8. Introduction Methods Results Conclusions 15 15 15 10 10 10 Frequency (kHz) Frequency (kHz) Frequency (kHz) 5 5 5 0 0 0 1 1 1 2 2 2 3 3 3 4 4 4 Time (s) Time (s) Time (s) 2.5 2.5 1.0 1.0 KRaCS per animal per minute KRaCS per animal per minute 0.5 0.5 0.0 0.0 Other behaviours (N=7) Other behaviours (N=7) After kill (N=7) After kill (N=7) Behaviour Category Behaviour Category Acoustic Detection of Kills: Killing, Ramming and Crushing Sounds Kruskall-Wallis: p = 0.028 ►KRaCS are generated when killer whales handle a prey animal or carcass. They may be some of the best indicators that an attack was successful.

  9. Introduction Methods Results Conclusions • In the years 2003-2005, we followed 28 groups of transient killer whales for a total of 115 hrs while monitoring their sound production. • We documented a total of 22 successful attacks. The prey species could be identified in 12 attacks • We documented a total of 22 successful attacks. The prey species could be identified in 12 attacks • We documented a total of 22 successful attacks. The prey species could be identified in 12 attacks Harbour seal 32% Harbour seal 36% Diet of West Coast Transients Diet of West Coast Transients Dedicated acoustic follows (N=22) Diet of West Coast Transients Diet of West Coast Transients Observer Reports (N=16) Harbour porpoise 18% Steller sea lion 36% Steller sea lion 5% Harbour porpoise: 0% Dall’s porpoise: 0% Sea otter: 0% Dall’s porpoise 21% Unidentified marine mammal: 45% Sea otter: 7% • This is equivalent to a predation rate of 1.01 successful attacks per killer whale per day (when feeding on pinnipeds and small cetaceans) • This is equivalent to a predation rate of 1.01 successful attacks per killer whale per day (when feeding on pinnipeds and small cetaceans) Estimating Predation Rates: Preliminary results • In the years 2003-2005, we followed 28 groups of transient killer whales for a total of 115 hrs while monitoring their sound production.

  10. Introduction Methods Results Conclusions • Pulsed calls and KRaCS are consistently associated with kills • Acoustic monitoring presents a powerful tool to detect killer whale predation in the field • Relying on surface behaviour alone may lead to missed predations events and may bias the prey spectrum towards larger and faster prey that are more difficult to subdue Preliminary data suggest that killer whales consume the equivalent of one harbour seal per day. Killer whale predation has a significant potential impact on populations of pinnipeds and cetaceans in the North Pacific. CONCLUSIONS: acoustic detection of killer whale predation • Pulsed calls and KRaCS are consistently associated with kills • Acoustic monitoring presents a powerful tool to detect killer whale predation in the field • Relying on surface behaviour alone may lead to missed predations events and may bias the prey spectrum towards larger and faster prey that are more difficult to subdue Preliminary data suggest that killer whales consume the equivalent of one harbour seal per day. Killer whale predation has a significant potential impact on populations of pinnipeds and cetaceans in the North Pacific.

  11. How do you know that transients have made a kill? Listen to the whales – they’ll probably let you know.

  12. SUPPORT IN THE FIELD AND LAB: • Douglas Chadwick • Michael deRoos • Steve Jeffries • Vicky Livaditis • Josh London • Allyson Miscampbell • Patrick Presi • COLLABORATORS: • Lance G. Barrett-Lennard • Graeme M. Ellis • Craig O. Matkin • Dena R. Matkin • Jan M. Straley • LOGISTIC SUPPORT: • Alaska Marine Lines • Glacier Bay National Park & Preserve • The Communities of Gustavus, • Juneau, and Petersburg • FUNDING: • National Oceanic and Atmospheric Administration • Alaska Fisheries Development Foundation • North Pacific Universities Marine Mammal Research Consortium THANKS TO:

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