Marine Mammal Ecology Ecology : An attempt to describe and explain the patterns of distribution and abundance of organisms. These patterns reflect the history of complex interactions with other organisms as well as the environment. Marine mammal ecology is had to get data on. Marine mammals live in the ocean, which makes everything harder Marine Mammal Protection Act prohibits many techniques typically used to study animals Distribution Ecology attempts to explain the restricted and generally patchy distribution of species Marine mammals inhabit almost all marine environments, including estuarine and even freshwater Factors affecting the distribution of marine mammals Habitat including the type of substrate Biology: including productivity (food) the distribution of predators Demography of population Size Sex ratios Age Reproduction Species Adaptations Morpholigical Physiological Behavioral Human effects Disturbances Pollution Methods used to study Marine Mammal distributions Surveys Counting who is where when Shore based, especially with pinnipeds Ship based, more common with cetaceans Telemetry Radio tags Use VHF radio waves to keep track of the animals Also link the tags to satellites, which only works when the animal is at the surface Seasonal Movements Migratory
Many marine mammals move seasonally in order to take advantage of seasonally abundant food sources Non Migratory Dispersal: movement of an individual from its birth place to subsequent breeding ground Pinnipeds Must periodically leave the sea in order to breed, birth or molt Either land on shore or ice Changes in the ice pack will definitely alter their distribution Great variability in seasonal distribution among the families. It seems that phocids tend to be more migratory than otariids Remember phocids are more 'adapted' for a strictly marine lifestyle Phocids which breed on ice are obviously more migratory, because their substrate is very seasonal in nature Ex: Harp Seal Give birth, rear offspring and molt on pack ice, whose distributin varies greatly Gather in large concentrations in Newfoundland Jan Mayen island White Sea The size, location and distribution of the whelping patch (colony) is known to vary due to surface currents and wind Cetacea Mysticetes 9 of the 11 baleen whales undertake long seasonal migrations Tend to migrate from the tropics to high latitudes This allows them to feed during the summer in the highly productive high latitude areas and give birth in the winter in the warm tropics, where the offspring don't need all that blubber Ex. Humpback Whales In the Atlantic they migrate from breeding grounds in the Caribbean to summer feeding grounds around Iceland In the Pacific, there are two winter breeding areas Hawaii and Mexico Summer feeding grounds include California to the Gulf of Alaska Ex. Gray Whales Migrate annually between calving areas in the lagoons in Baja and feeding grounds in the Arctic. They tend to remain coastal as they migrate < 10km from shore. This may help with navigation Odontocetes The pelagic species tend to migrate more than coastal species
Pilot whales move from Cape Hatteras to Newfoundland and George's Bank following their favorite prey, squid Many, such as the harbor porpoise, stay in coastal regions year round, but may migrate from the Bay of Fundy (Nova Scotia) to the Gulf of Maine The sperm whale does migrate over long distances Move toward equator in fall and toward the subtropics in the spring, averaging around 1550km for males and 680 km for females. Sirenians The Florida Manatee Winters consistently in Florida, but may move as far north as Rhode Island and as far west as Texas during the summer Population biology Abundance Very hard to get estimates because they're always in the water. Methods Census: count everything Very accurate, not very practical Subsample Most common, easier, not as accurate Measure and Index of population size Ex. # of whales counted moving up the coast Also not as accurate, and you need to find a good index Mark and recapture Used frequently in pinniped studies Population Structure Want to know the distribution of genetically isolated groups. Use mark and recapture Also use enzyme and DNA techniques now Population dynamics How the population varies in abundance over time Populations increase by Births New Recruits Populations decrease by Natural Mortality Emigration Predation What the age structure is like The age structure tells you about the fertility of the organisms Hard to measure Use bone samples, with definite growth patterns, like a tree Marine mammals tend to be long lived, with little reproductive output, but high success of the offspring
Known as k selected organisms K refers to the "carrying capacity" or how much of an organism the environment can support K selected organisms are particularly vulnerable to overharvesting Populations increase slowly Sometimes there is rapid population growth Gray Seal data Foraging Ecology What an organism eats, where it eats it and how much it eats Can be very difficult to determine in marine mammals Some Methods Analyze what wasn't digested, ie hard parts Stomach contents Can be hard to get Feces Easier to get Get different results from stomach content, though Serology: analysis of serums and enzymes Certain enzymes will react with certain foods, thus telling you what the organism was eating Fatty acids Fatty acid composition of the prey influences the fatty acid composition of the predator. By analyzing the chemical make up of the acids, you can determine where they came from Diet: what they eat Pinnipeds Not very specific Fish, squid, crustaceans Remember, they're like a dog Strong preferences though Often most of the food is <5 species of prey Also strong seasonality to prey choice Mostly eat fish and squid Some eat krill The crab eater seal Cetaceans Very hard to determine diet Fecal pellets are rarely available Most stomach content data comes from commercial whaling or stranded animals Can't pump their stomachs Mysticetes
Those with coarse baleen feed on swarming zooplankton or fish Blue whales, humpback whales Benthic feeders filter out mud and invertebrates Gray whales Skimmers have log plates of baleen and feed on zooplankton such as copepods Right whale, bowhead whale Odontocetes Feed mostly on squid, fish and other large animals Teeth designed for holding onto fast moving prey Sirenians Feed mostly on sea grass In Shallow areas Factors affecting diets Age Young feed more than adults Sex Pregnant females eat a lot, particularly fatty food Seasonal and Geographic factors Where the food is and what time of year affect its abundance Role of Marine mammals in Marine ecosystems Little is known They do eat a lot though Sperm whales eat >400million tons of squid/year Antarctic Our killing off of many whales the feed in the Antarctic has made more krill available for other animals Consequently penguin and seal numbers have increased over the last 100 yrs