People often consider themselves to be vulnerable like domesticated chicken when lost in the wild... they say that if he's faced with a wild animal, he will not survive... he does not have the natural 'defenses'... that is physically he's defenseless... however I don't think so and here are my opinions.
You would have noticed, that I'm talking a 'he' here... that's cause there's nothing a women can do in the wild, but a man can.
I say humans can mostly handle creatures roughly equal to their own size alone... that is I'm removing some big cats from the list, but not all like cheetah, a small lepord etc... and of course if you encounter a bear, buffalo, wildebeest etc... there's no way you can fight um back. Even the biggest are afraid of poisonous frogs and snakes.
First, we underestimate our physical strength, apart from being one of the largest land animals, we're also one of the strongest, if you did not fear to death or tried running away from a 80KG anaconda, instead decided to fight it aways, most probably you will win.
So let's start with the anaconda... most men are strong enough to lift it up and if we think we're vulnerable... it wont make sense. If the anaconda grabs one arm, we got the other, if it grabs the head and tries to suffocate, we can still move our arms and all for a while, but what if we get a grab of it's neck tight and to top that, what if we twist it bad?... there's absolutely nothing an anaconda can do, death will come at an instant; the creature might not be able to tell but it will realize humans are pretty powerful creatures physically.
A very powerful thing that we can do is kick, ever realized the amount of muscle around your legs... the thickness of your thies and how fat your ass is? And ever realize how high we can jump with it?... if that impulse (of the order of tons) is applied to your rival, you will know the consequence, what if you just dropkick and it hits your competitor straight?... it might fracture a few bones and after that the wild animal will never face a human... it'll be surely shot afraid. Currently we don't keep any nails on our toes, but you would have noticed it grows pretty thick and will actually work like a small dagger if you do have them.
Next comes the weight. So what if you just fall down on the animal... what will it be able to do?... that's right, nothing. So we got the weight advantage. Instead something like this happens to us, we can at least grab um by our hands by at least a small angle, our limbs have enough flexibility to reach our backs, and we can at least attempt!
Then comes the hands. Something that most land animals miss and our unique weapon. Our hands can slide to the animal's throat, then we can grab some of it's vital organs and cause some serious damage after which the animal won't forget till death (which will be soon). Our hands have fingers which are 'sort of' blunt, but what if you combine with all your force and push it into the animal's eyes or ears?, sure that might hurt you, but it'll hurt your opponent harder. Let's see other things that our hands can do – pull it's ears, pock into it's ears, grab the tongue, and best of all... pull his balls, or private organs... or punch the lower back side which's usually uncovered and very vulnerable.
So next time you see a wild animal or even something crazy like a bear or tiger attacking you (and it's too late to run away), instead of trying to run, stand helpless praying for god, or searching for a weapon which you know is not around; think about these few things that you were born with and use them to your best struggle to survival.
Of course prevention is better than cure, even the animals know that, so should you.