How do animals know when to hibernate?

Question

How do animals know when to hibernate?

Answer 1

they start to feel cold because they hibernate only during winters

Answer 2

It's actually a variety of things.  The temperature does play a big part in it, but it's also the length of the days and other environmental cues they get.

Also, very few animals actually "Hibernate."  Animals like bears and squirrels go into what is called a torpor, which is similar to hibernation, but is more like a deep sleep.  Many wake up at odd points throughout the winter when it's warmer or if they need more food.

Answer 3

The length of daylight and the cooling temperatures are usually the triggers that instigate hibernation, along with the increased maximum body weight the animal has attained to allow it to go without food for a long period.

Answer 4

i assumed the weather- this is why they are stuggling here- in england- these days as our seasons have merged and dont show much change anymore with no clear warm summer or cold winter...pretty much just spring & autumn, so the animals arent sure if the should be hibernating or not...

Answer 5

It appears that photoperiod is the determining factor under controlled conditions, at least for jumping mice.  You might want to peruse this abstract.  I learned a few things.

http://www.jstor.org/pss/1933855