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Killer whales and sea otters. Daily caloric requirements:. Male killer whale: 308,000 Kcal/day or 5-7 sea otters. Killer whale and seal otter energetics. Female killer whale: 187,000 Kcal/day or 3-5 sea otters. Account for 40,000 sea otters lost over 6 years?.

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Killer whales and sea otters

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Killer whales and sea otters l.jpg

Killer whales and sea otters

  • Daily caloric requirements:

  • Male killer whale: 308,000 Kcal/day or 5-7 sea otters

  • Killer whale and seal otter energetics

  • Female killer whale: 187,000 Kcal/day or 3-5 sea otters

  • Account for 40,000 sea otters lost over 6 years?

  • 5 sea otters per day per whale x 365 days x 6 years = 10,950 sea otters!

  • 10,950 sea otters eaten x 4 whales would account for 40,000 sea otter losses

Where have all the sea otters gone?


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Killer whales and sea otters

  • Sea otters usually not main component of killer whale diet -- why the change?

  • Some fish populations have declined in recent decades

  • Shortage of certain fish caused substantial declines in harbor seals and sea lions

  • Shortage of seals and sea lions resulted in killer whales preying on smaller sea otters

Where have all the sea otters gone?


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  • Sea otters important part of coastal community; loss of sea otters results in many indirect effects

Killer whales and sea otters

  • Why should we care about sea otter declines?

Where have all the sea otters gone?


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Indirect effects on communities

  • Predation (or parasitism) can reduce competition, preventing competitive exclusion

  • Predators typically feed on several types of prey

  • Prey selected based on its relative abundance

  • Superior competitors can reach high relative abundance, but predation can control such populations

  • Example: removal of starfish (Pisaster) in rocky intertidal results in competitive exclusion by mussels

Where have all the sea otters gone?


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Indirect effects on communities

  • Predation (or parasitism) can result in many indirect effects on other species

  • Example: ant-rodent interactions

  • Both ants and rodents eat seeds in Chihuahuan Desert

  • Removal of rodents caused initial increase in ant populations, but then a decrease

Where have all the sea otters gone?


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Indirect effects on communities

  • Keystonespecies = species that have strong effect on the composition of the community

  • Removal of keystone species causes a decrease in species richness

  • Example: sea otters eat sea urchins which are superior competitors; if sea urchin populations increase, kelp reduced and species richness drops

Where have all the sea otters gone?


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Indirect effects on communities

  • Kelp ‘forest’

Where have all the sea otters gone?


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