(Princeton University) Climate change, land use and other human-driven factors could pit savannas and forests against each other by altering the elements found by Princeton University researchers to stabilize the two. Without this harmony, the habitats, or biomes, could increasingly encroach on one other to the detriment of the people and animals that rely on them.

(Academy of Natural Sciences) The Academy of Natural Sciences today announcedthe discovery of a new species of large predatory fish that prowled ancient North Americanwaterways during the Devonian Period, before backboned animals existed on land.Drs. Edward “Ted” Daeschler and Jason Downs of the Academy and colleagues fromthe University of Chicago and Harvard University describe the new denizen of the Devonianthey named Laccognathus embryi in the current issue of the Journal of Vertebrate Paleontology.

(University of California – Riverside) University of California, Riverside researchers report that the ancient deep ocean was not only devoid of oxygen but also rich in iron, a key biological nutrient, for nearly a billion years longer than previously thought–right through a key evolutionary interval that culminated in the first rise of animals. “We will need to rethink all of our models for how life-essential nutrients were distributed in the ocean through time and space,” the authors say.

(Smithsonian) Researchers from the Smithsonian Institution and the University of Florida have announced the discovery of a bone fragment, approximately 13,000 years old, in Florida with an incised image of a mammoth or mastodon. This engraving is the oldest and only known example of Ice Age art to depict a proboscidean (the order of animals with trunks) in the Americas. The team’s research is published online in the Journal of Archaeological Science.

(University of Alberta) A University of Alberta researcher has co-written an extensive study of the caribou population in the Fort McMurray oilsands region that show the animals’ survival isn’t as threatened as was perceived in the past. The study recommends efforts to manage human activity around resource development before resorting to the drastic measure of a wolf kill.

(University of British Columbia) Old trees must be protected to save the homes of more than 1,000 different bird and mammal species who nest, says a new study from the University of British Columbia. Most animals can’t carve out their own tree holes and rely on holes already formed. The study found that outside of North America, most animals nest in tree holes formed by damage and decay, a process that can take several centuries.

(Woods Hole Oceanographic Institution) Kakani Katija, a postdoctoral scholar at Woods Hole Oceanographic Institution, has been selected as one of 14 National Geographic Emerging Explorers for 2011 for her investigation into the role swimming animals might play in mixing and moving the oceans and other large bodies of water.

(University of Alberta) A University of Alberta-led research team has discovered that billions of years before life evolved in the oceans, thin layers of microbial matter in shallow water produced enough oxygen to support tiny, mobile life forms.

The ability for some animals to have live births versus eggs can normally be explained by what classification the animal belongs to.

Mammals have live births, birds have eggs, Echidnas (a relative of mammals, think platypus) have eggs (like birds) but also have some characteristics only seen in mammals (fur and milk for their young).

There are some classification of animals that can have either live birth or eggs, such as sharks, fish and some reptiles.

The difference between the whether there are live births versus eggs is usually determined by the environment.