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Unformatted text preview: Migrations o Why do this? Food, reproduction, climate/temps. o Typically a compromise between driving needs Commonly between food and reproduction What is needed is not found in same place at same time o Right whales: Go south to breed and calf but there is little food Go north for food but is cooler and is harder on calves o Grey whales: Feed on Bering Sea Shelf in the summer Migrate along west coast to Baja and Gulf of CA in winter to calf There is a smaller pop in west pacific Whalers would harpoon calf to bring in mom and others o Humpback whale: Calf in caribbean in winter and feed in the north in the summer o Not all species fit this pattern Bowheads: circumpolar all year along with belugas and narwhals Not all have thick blubber layers Fill different niches Migrate to avoid orca predation? o Some fit better as "range expansion" Elephant seals Breed along CA coast Expand into Pacific for food Males will go farther Will return to CA to molt After molt, will again go to Pacific Reproduction o Goal is to have successful offspring o Strategies may be different for males and females o Why sexual reproduction? Genetic diversity increases survival Long term strategy for survival of the species o Why is there death? Make room in population Genetic variation to deal with varying conditions and catastrophic events o Why two sexes? Theories point to 2 opposing best strategies: Have a lot of offspring- attributed to males because they can produce a lot of sperm with low energy cost Have fewer offspring with lots of parental care- attributed to females; egg takes more energy so have fewer of them and take care of the few young they have Dictated by biological and environmental factors o Behavioral strategies: Females- be choosy about mate and environmental conditions Males- mate as much as possible Dictated by biological and environmental factors Determines which genes are passed on Behavioral dispositions for strategies are both inherited and shaped by environment o Pinniped mating strategies: Dictated by environmental considerations (seasons, food, stability) These determine the distribution if females Land Breeders : Temperate climate (experience seasonality) Otariids, elephant seals, some phocids (harbor and grey) Seasonal= temporal predictability of female distribution Site selection for rookeries Protected beaches by cliffs, rocky environs, deserted islands, difficult access for predators= spatial predictability for females **female distribution is predictable in both time and space***...
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- Spring '08