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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
- Reproduction, Pinniped, males, socially mature males