How to tell what age your Pig is?( And Other questions)

Question
I've been seeking a way to tell how old my boar,Henry is.
My memory is fuzzy and i do not remember what year i bought him. I heard something about wrinkles in ears but never found an explanation.


Also what is the life expectancy of guinea pigs?

I know my guinea pig is old ( Maybe about 5 years) and lately he's been grinding his teeth at me. From my exsprince with smaller rodents, this is a warning sign/ anger sign.
Why is he doing this all of a sudden?
For exsample, i have him sitting on a pillow next to me as i'm typing, and i hear him chatting his teeth at me, but i've done nothing to provoke him.

Thanks` Paige

Answer
cut a leg off and count the rings... nah it is difficult to tell if you did not know from the begiinning. sometimes there ears are a little more "crinkly" with age, any age you could make would be an estimate that tends to be based on their weight which changes as they get older and wont be useful after an certain point, some people can sometimes know when a girl is past the age of being able to deliver a litter but an exact age is nearly impossible.

the teeth chattering is a warning, put two males next to each other and they'd fill a concert theatre with that noise. it is possible that he want to be left in his cage and doesnt want to be fussed by you anymore, it is also possibe that for some reason he has just decided he does not like you. it could even be that because he is older now he has more aches and pains and the prospect of you picking him up means he is likely to expect pain. if you give him nice treats then he might ease off a little but at his age there is not much you could do to change it short of just chekcing with the vets that he isn't in pain.

as for age they tend to live between 5-7 years, though I know of one that lived for 13