When one animal eats another, the anguish that the other feels is mainly a product of the central nervous system.  It's based in ages of trial and healing, but it's still central-nervous.  The spirit lives on, though a lot of the energy was stored within the body fat and that gets carried into the predator's, so it's a type of sharing.  If the spirit doesn't live on - I feel it depends on the type of animal - the energy just rises up and joins the sky.. and its karma is still reintegrated into the species-body, for example: deer.  (Humans live on, and cats probably do.)  

When the animal runs away from the predator, that's not necessarily out of a sense of protection of the ongoingness of one's spark of self-awareness, like it may be in humans..partially because of our deluded sense of self and other, i.e. separation..which doesn't exist (only differentiation does).  

When the animal runs away, a lot of it is instinct, and I'll tell you what instinct is later.  But the instinct in this case drives the animal to play that game we call 'survival of the fittest,' and it's not just a mechanism that randosity came up with.  In other words.. even when the lion picks a deer to kill, it picks the weakest one.  Because it's the easiest to eat?  Well, things work out that way don't they?  Karma, or nature's harmony, is efficient. there's work to be done.  But that doesn't mean it's the only reason.  Of course the lion doesn't speak so you can't ask him, and if he did, you wouldn't understand the answer because it's all beauty to him.  (That's why the fox feeds himself and God feeds the lion, so to speak.)

Instinct isn't what you may think it is, in our scientistic-paradigmatical age of thinking.. or doing something we 'call' thinking.

('The brain is the apparatus with which I think that I think.'  'The brain is the most important organ in my body.. or so it tells me.'  Now why don't you replace some of those words with 'language' and see what happens..recursively.)  

Instinct is something like, 'innate intelligence' but it's of a type that tells you what to do.

Humans have a crude form of instinct, for example sucking on nipples, yawning, sneezing, falling asleep, and some base desires related to..among other 'things'..hormones.   So as humans, we would not relate to the instinct that tells a spider to spin its web.  However, it's fucked-thinking to think that it's just a mechanism.  It goes like this..remember that I said that all things are connected, and there is no separation?  Well the spider, its body, and its consciousness are all an integral part of the spider-species, and spider and the species itself are integral parts of the intelligence of the universe..

I mention the species level of the chain of scalarity because it's a convenient razor for the same reasons the taxonomists find it so - for one, the boundaries of fertility, and for two, it's the lowest major rung on the ladder.  However, we're also talking about 'spiders' which is a name on a different rung.. and some of them spin their webs differently and some don't spin them at all.. but that notwithstanding, they all spin webs.  So we could bring up the rung in which 'spiders' applies as a genera also, as an element within the network of cosmic intelligence.

Anyway, when the spider is guided to spin its web, it's 'acting out its identity.'  It just knows what it's to do.  That's how it knows it.  It's not thinking, and it's not controlled.. because everything is life.   It may and probably would apply intelligence..because the deer when it runs away applies strategy, learned strategy, but also species-evolutionarily learned strategy.  There's not such a big divide there.  Just talk to the Deer Mother of the species and you might get it..;)  

Spiders are smaller beings than we, so we would probably not identify with its actions on our scale, I mean even being gifted with this thing called 'complex instinctual behavior.'  If I had to guess, what looks like an intelligent planning to us when the spider spins its web, to the spider carrying it out is something more like either base drives or creativity, and its being intelligently designed on the larger scale mirrors in us what we call either spontaneity, unpredictability, wish, or karma.  But those are just words, and even if there's truth to it the characteristics of the words themselves could and probably do change cross-scale.