Runner's Companion lists quite a few metavariants and infected character types that have the Increased Senses ability. I'm not sure what this means in game terms. The description in the critter powers section (SR4 p.288) says ... covers any improved or augmented senses beyond the normal human range of awareness. For example, a dog shapeshifter would gain the ability to hear ultrasound.

But what about the dog's sense of smell? This ought to grant him a bonus on a test such as perception, memory or tracking. Olfactory-based cyber and bioware give a bonus equal to their ratings. What should the bonus be for this ability?

My first guess was that the bonus should be equal to the Magic attribute, but it's not really a critter power. Aside from that, the book says If an Infected character’s Magic attribute is reduced to 0 (temporarily or permanently), it loses the use of all its powers except Natural Weapon and Enhanced Senses, if any. So if increased senses was tied to Magic, the creature would lose its ability if it lost its magic, which contradicts that sentence.

What's your suggestion? Do we get a bonus? If so, how much?

We talked about that in our group and came to the conclusion that this power doesn't really add any dice or stuff but simply that the hits the character rolls are more potent than the hits generated without ES.

In prior editions, if an adept power duplicated a piece of sense-enhancing cyberware, the adept power defaulted to the maximum. So there's precedence for that.

Though I personally like the magic rating = level.

I like the thought behind a magical sense being at least as good as any that technology can provide. I'll run that by my GM. If he thinks that's too much, we'll probably go with the Magic thing. I'm sure that most of the time, though, he'll just play it loose, and give me extra information.