Animal shelters are dealing with a huge problem. There are too many pets, and too little homes for them.
Over 176,185 cats were admitted in Canada 1993 to SPCA's, and 60% of those cats killed. And over 
dogs 102,132 are admitted in 1993 Canada and 30% were killed. Just like the cats just a different species.

People drop off pets at animal shelters because: lost pets, death of owner, moving, divorce, and allergies.
Shelters should be the last choice for options, try at least three other options before shelters. Try training your pet, or finding a loving home if you have to.
Overpopulation is the biggest problem. Theoretically a female cat and her offspring can produce 420,000
cats in 7 years.
Always keep your pets until they die, and remember to get your pet fixed.

The reason pets get killed in shelters is because there is not enough room for all of them (if you didn't know),
or sometimes the animal is too sick.
Things are getting a little better, in 2008 the number dropped with admissions and killing of pets to about
120,952  were admitted and approximately 36.5% killed. (84,301 cats and 54% put down & 36,651 dogs and 19% put down).

Pet tips:
-fix your pets
-if you have a cat don't let it wander off
-adopt instead of buy