What type of biological changes would need for animals to move earth-like on a terraformed mars?

Question

Assuming Mars was successfully terraformed. It has earth-like atmosphere composition and density. Plant life is abundant.

My question is what type of biological changes animals (and birds; not humans) would need for them to move around on the surface of the planet like animals do on earth?

I was wondering if low gravity can be dealt with in any way such that they evolved favouring more normal(earth-like) way of moving rather than hopping and jumping.

Answer 1

Walk Like a Terran:

On a fully terraformed Mars, inevitably there will be considerable pressure on organisms to move DIFFERENTLY. There would be pressure to fly, to brachiate, to glide, and to even use jets like squids to launch themselves about at breakneck speed. Moving through the air will be so much easier. So how do you create a pressure to stay on the ground?

• Arachnids and passive predators: The trees would be tall, and the vegetation thick. In this mass of growing stuff, enormous spider webs pop up everywhere, with less gravity to oppose their size and thickness (for the really big ones). All those organisms trying to move everywhere in Mars dim light will tangle in the webs strewn about. Spiders might even have nets they throw around in the air, trying to capture aerial and jumping prey. To avoid these pervasive threats, you have an incentive for animals to be slower and closer to the ground, more massive and more cautious.
• Cheap armor: Prey animals will gain a much bigger bang for their buck with heavy armor (or alternatively massive defensive structures like spikes and horns) than they could on Earth. A turtle would be jaunty. An armadillo would nimble. An ankylosaurus could grow to vast size. The soft-skinned creatures would be at a distinctive disadvantage. Predators would need to grow to increasing scale or have high-impact designs (like massive crushing jaws, now easier to carry around) to overcome such armor.
• Small legs: long stretchy limbs are vulnerable to attack. small limbs can give animals on your Mars plenty of force to move, yet be quite short. Each limb can make a smaller course correction, hold up more weight, and ultimately use fewer calories.
• Birds, birds, birds: Birds would have a lot of chances to fill a lot of ecological niches. Less energy needed to stay in the air means either birds fly farther easier OR they need smaller wings and can support more weight to get things done. Imagine a full-on deer-type bird herbivore. After all, they can still take off with a lot of undigested plant matter in their guts. Imagine a bird that can soar high over the jungles (and innumerable threats) for weeks or months at a time, eating the fruits (and spreading the seeds) of the tallest plants who rely on these birds to spread them around the world.