CompLightSustenance makes an animal require light to survive. It will create a hediff called "level of sunlight" that will either increase or decrease depending on whether the tile the animal is in is lighted (more than 0.4 light) or dark. Animals with this comp can survive a night without light, but they will need artificial light during eclipses or similar events or they'll die.

It is a comp class, and it doesn't even need any parameters, so you just add it in XML in the <comps> tag. For example, this allows Needleposts in Alpha Animals to require light

<comps>		
	<li Class="AnimalBehaviours.CompProperties_LightSustenance">
	</li>
</comps>