Advances in diet, medicine and the cleanliness of water have massively boosted human life expectancy in the last century. It is now increasing by three months per decade in the affluent west. Is the life expectancy of our pets increasing at a similar rate, proportionally speaking?

Andrew Franklin, London, UK

Some bird species, such as the great-crested grebe (pictured), hunt underwater for fish and have red eyes. The red colouring is presumably beneficial to these diving birds, but in what way? If it does provide an advantage, why have other birds with similar habits not evolved red eyes?

Ian McKechnie, Weybridge, Surrey, UK

How is it that birds which lay a large number of eggs are able to have them all hatch on approximately the same day?

As a human I do not need to go to the doctors every year and get my boosters so why do animals...is this just a  money making scheme by the drugs companies and /or vets?  Do the diseases these vaccines protect against mutate quickly more like  the human flu?

Was watching the movie 'The Informant' last night and throughout the movie Matt Damon has an inner monologue and one of those was the following...is this true or very creative writing.

When polar bears hunt, they crouch down by a hole in the ice and wait for a seal.

They keep one paw over their nose so that they blend in... ...because they've got black noses.

They'd blend in perfectly if not for the nose.

So the question is, how do they know their noses are black?

From looking at other polar bears?

Do they see their reflections in the water, and think, 'I'd be invisible if not for that.'

That seems like a lot of thinking for a bear.

My 5 year old would like to know the answer to this.  Is it the same for other birds too?  We can tell some sexes of ducks by their plumage, but do the birds do so in the same way?

I photographed this on the railing of my deck. It seems as if the trail of slime was swithcing on and off but as the animal uses the slime to enable it to move how is this possible? What else could have made this trail? I have a couple more photos.

In late winter/early spring I often come across deposits of this jelly-like substance on my farmland. It bears little resemblance to frogspawn. Apart from being egg-less, it is raised in lumps and always high and dry. Any ideas?

Is the venom that bees and wasps carry produce inside the sting, or is the sting only a delivery system of the venom? Also, is it true that bees and wasps have different ph's of their venom, as in ones acidic and ones alkaline? (simply curious as i heard a person say you could technically neutralize one with the other, which i know is probably feasible but would be highly impractical)

After a long journey, it seems to me - and I've heard other people say it - that cars are less besmattered with flies than they used to be maybe 30 years ago.

Is this the case? Has anyone measured it?

If it is true, is it because:

1. There are fewer insects?
2. There are more cars, so they get fewer flies per car?
3. Unnatural selection has favoured high-fliers?