Can a mage have more than one 'Beast Friend' spell running at the same time or does he need to concentrate on spell to keep it active.
Beast Friend has a standard duration of 10 minutes and cannot be maintained after that point. As you don't have to maintain the power, this means you don't suffer the cumulative -1 penalty to rolls for using additional powers, and the power cannot be disrupted by damaging or shaking the caster.
You are able to cast multiple Beast Friends on different animals/swarms, the only cost being however many power points it costs to cast each time. The downside is that you can't extend the time each casting lasts for as you can with many other powers.
It would be treated just like any other skill with a duration. When you turn on a skill with a duration, you don't need to do anything. If there is an option to maintain a power after its duration is up (usually at a high cost, this power does not have one), then you pay the power points and also take a -1 penalty for each power you are maintaining beyond its duration.