This site provides information on a range of marine mammals. It includes explanations of habitat, range, diet, reproduction and endangered status. To find your species, type it into the search box at the top right. You get many results. You want the one that describes your species, towards the top of the results.
Click on the species fact sheet for your animal for information on habitat, range, reproduction, and endangered status.
Type in a species on the search bar on the lower left. Look for an entry that appears to be a general description--usually the first one. This site provides information on habitat, range, diet, reproduction, threats, and conservation efforts.
This site has information on endangered species in the North Atlantic. Click on the PDF link (the little red square) on the bottom of each short description for the full article.