Handing food to a wild animal produces an immediate, memorable result for the person doing it. The lasting effect falls on the animal, and it is more severe than the interaction suggests.
Foraging is a calculation animals keep updating
Wild animals continually weigh the energy a food source returns against the effort and risk of obtaining it. Natural foraging is uncertain, seasonal and physically demanding, so the return per hour is modest and variable.
Food from a person inverts that balance completely. It is dense, reliable and obtained with almost no expenditure, which makes it the best option available by a wide margin.
Animals do not need many repetitions to learn this. Some species change their movement patterns after a single successful encounter, and primates and corvids after even less.
Learned association spreads to all humans
The animal does not associate food with one generous individual. It generalises to the category of people, and often to vehicles, bags, tents and buildings as well.
That generalisation is what turns a charming encounter into a problem. The next visitor is approached, and an approach by a large animal is frightening whether or not it is aggressive.
Where food is not forthcoming the animal may escalate: pulling at bags, entering vehicles, or defending a person it now treats as a resource. Behaviour read as aggression is usually persistence.
Nutrition and disease follow
Human food is calorie-dense and poorly matched to most wild diets. Sustained access produces dental damage, digestive disorders and animals in visibly poor condition despite appearing well fed.
Concentration around feeding points raises transmission of parasites and disease, because animals that would normally forage apart gather in numbers at the same spot.
Primates share enough physiology with people that pathogens move in both directions, which is why sites with habituated monkeys enforce distance rules more strictly than elsewhere.
The outcome usually falls on the animal
A fed animal that raids crops, enters property or injures a visitor becomes a management problem, and the responses available to managers are limited.
Relocation frequently fails, because the animal either returns or arrives in occupied territory it cannot hold. Habituated individuals are often destroyed instead.
None of that traces back to the animal's behaviour. It traces back to a sequence of small human decisions, each of which seemed harmless at the time.
Indirect feeding counts too
Most feeding is unintentional: food waste left at a picnic site, an unsecured bin, scraps thrown from a vehicle, or a bag left unattended at a viewpoint.
The animal cannot distinguish deliberate from careless, so the learning is identical. This is why parks invest heavily in animal-resistant bins and food storage rules.
The practical rule is that food and waste stay contained and no encounter is rewarded, including by putting a bag down to take a photograph.