Somehow i think If another predator had intervened it would be with it's jaws and would have stolen the fisher's meal
The predator : prey index of ecology argues that a predator only expends energy on prey it nearly assuredly gets, or at least the gamble of trying will be a net sume game -- I agree with SAR MT ; the disservice to the fisher was an unfair userpt of it's precious energy.
Nature isn't fair...disservices abound. It's the way of the wild.
Examples of "unfair" scenarios:
Something comes along that's interested in eating the fisher...the fisher runs off and, as a consequence, the fawn escapes.
A potential mate appears and distracts the fisher (that kind of thing can happen during mating season/estrous).
Echoing your sentiment, something bigger than the fisher comes along and steals the fawn from the fisher.
Again, nature isn't fair...what happens is what happens. The fisher has probably had food stolen before, from larger prey or from a mother protecting its young. Those other animals certainly didn't stop to think, "wait, the fisher worked hard for this, we should just leave everything be." No -- animals take what they need.
The hikers saved the fawn because they felt the need to save the baby animal...a "need" I emotionally understand, though I don't always agree with it. If these hikers had come across a baby fisher being attacked by a larger predator, they may have acted in the exact same fashion. Save the baby, it's a natural instinct.
Is it fair to the fisher? No. Is getting eaten fair to the fawn -- or the fawn's mother? Maybe, maybe not...the doe would argue that it isn't fair for the fisher to reduce her reproductive success, not after all that energy spent gestating, lactating, and otherwise caring for her young.
Food gets stolen. Someone's RS is reduced by a predator. And so it goes.
Should the hikers have saved the deer? My initial, knee-jerk response was no, for the reasons Sabrina typed above. However, after deeper thought, I don't think there is one right answer. The hikers were probably acting on their own natural instincts, just as the fisher was acting on his. Which instinct is "more correct?" I get the energy expenditure argument. However, that's just one way to look at it...there are others.
ETA: I also totally agree with the sentiment that the hikers saved the fawn only for it to be killed and eaten later. However, perhaps "later" would be enough time for that fawn to have its own young, thus increasing its (and its mother's) RS (reproductive success).
NONE of what I write should be taken as advocacy of rescuing prey from predators. Everything needs to eat. I just don't buy the "it's not fair" argument. Nature itself isn't fair, there's nothing fair about natural selection or hawks/doves or life in general (outside of what we humans try to make of it).
