You will need to use original research articles as sources for your review paper assignment. If you also want to browse some of the top journals mammalogists publish in, here are some suggestions:
For your assignment, you will need to find peer reviewed original research articles. Many of the journals listed above are included in these databases. Searching a database like these casts a wide net for articles:
You might not be very familiar with your topic to start. Coming up with good keywords to use in a database can be challenging. Use reference sources like encyclopedia to investigate your topic. You can gather more keywords and form a more complete picture of your topic before diving into the journal literature.