[Dilettante_Pro]

К нему надо подобраться по другому. Как?

Например, так

Animal.prototype.moveAnimal = function(i) {
	var stepTop, stepLeft, unitTop, unitLeft, noFree, unitPos = {};
//	for (var i = 0; i < animals.length; i++) {
		noFree = true;
		do {
			stepTop = Math.round(Math.random() * 2 - 1) * 20;
			stepLeft = Math.round(Math.random() * 2 - 1) * 20;
			unitTop = +animals[i].top.replace(/\D/g,"") + stepTop;
			unitLeft = +animals[i].left.replace(/\D/g,"") + stepLeft;
			if (unitTop < 0 || unitLeft < 0 || unitTop >  380 || unitLeft > 380) {
				noFree = true; 
			} else {
				unitTop = unitTop + 'px';
				unitLeft = unitLeft + 'px';
				noFree = false;
				
				for(var j = 0; j< units.length; j++) {
					if(units[j].top == unitTop && units[j].left == unitLeft) {
						noFree = true;
					}
				}
			}

		} while (noFree);
		units[i].top = unitTop;
		units[i].left = unitLeft;
		animals[i].top = unitTop;
		animals[i].left = unitLeft;
		var elem = document.querySelector('#a' + i);
		elem.style.top = unitTop;
		elem.style.left = unitLeft;
//	}
}

setInterval(function() {
		newAnimals.forEach(function(animal, index) {
			console.log(animal);
			animal.moveAnimal(index);
		});
	}, 1000);