4. Flying insects can't do this; there's no direct way to mark a trail
in the air. So bees, as is well known, have evolved a form of symbolic
communication: the "waggle dance". By dancing in a certain fashion, a
worker can "tell" other workers the direction and distance to a food
source. The dance indicates direction relative to the sun - bees can
see the polarisation of light and thus see the sun even when it is
covered by clouds - and distance, and it does so independent of the
orientation of that bee while it is dancing relative to the sun.

In other words, bees have symbolic communication. Their signals are
not direct, one-to-one, follow this to the food; they are abstract and
require interpretation. Obviously, this is innate, it is not learned
behaviour, but individual insects learn the way to food and
communicate this symbolically to other individuals.

5. Small mammals can be taught complex behaviours in the lab. Rats can
be taught to press levers to obtain treats; mice can be taught to run
mazes; "experiments" with wild squirrels have shown that the animals
will perform an amazing array of actions to obtain a food reward. Many
of these patterns of behaviour show that the animal is able to learn
that unrelated actions can elicit a reward, showing some kind of
understanding of cause and effect.

6. Non-mammalian vertebrates perform all sorts of ritualistic behaviour
that is not directly related to finding food, a mate, predator
avoidance and so on. Many birds have mating rituals; male bower birds
construct huge and elaborate structures to tempt females into mating,
which are presumably derived from nest-building behaviour, but
actually the structures serve no purpose other than to be on some
level "pleasing" to the females. Many migratory birds such as
albatrosses and swans form long-term pairs which persist over years,
sometimes lifelong. They can recognise their mate and when they
rendezvous at breeding time indulge in long rituals which appear to
stimulate and reinforce the pair bond. Obviously mate recognition does
not involve some simple biochemical cue of kinship which might be used
in a mother finding her offspring in a large, mobile breeding colony
independent of environmental cues, such as penguins. Maybe penguins
can "smell" or "taste" their own offspring by some form of genetic
resemblance; I'm not aware of any research into this. However, even if
they can, and don't somehow just learn what their offspring look or
sound like, the same cannot apply to individuals recognising their
mates, who are, by choice, usually not directly related.

In other words, these birds "know" their non-related partners, can
recognise them and distinguish them from strangers, and behave in
entirely different manners around their partners to around other
individuals. When encountering their partners for the first time after
a protracted absence, they indulge in displays and other complex
behaviours which are not directly survival-related. It is hard to
watch such a pair being reunited without thinking that they "feel
happy" to see one another. It is also a reasonably common experience
to see one which is isolated and has lost its partner, witness its
lack of animation, listless behaviour and so on, and the human
reaction is to interpret this as the animal "feeling sad".