If an animal goes to sleep during cold periods it is called hibernation. If an animal goes to sleep during hot periods it is called estivation. Because climate and geography influence language there is often not a word for both of them in everyday language. So for example Swedish has a word for hibernation (ide) but not estivation.
On a (slightly) related note nocturnal means active at night and diurnal means active during the day. Crepuscular means active at dusk and dawn. Anyone who has cats who get the ‘cat crazies’ at dusk and dawn will know this phenomenon!
Another word that people who do not live in a very animal-rich country do not know is extirpation. Extirpation means local extinction, where a species that is extinct in the area of study still exists elsewhere. So a subspecies of giraffe which is extinct in its region of origin may exist in a game park or zoo or another area entirely. So you can talk about local extinction and global extinction.
Below is an example of how the word is used:
For example, Giraffes have been extirpated from much of their historic range including Eritrea, Guinea, Mauritania and Senegal. They may also have disappeared from Angola, Mali, and Nigeria, but have been introduced to Rwanda and Swaziland. (Wikipedia)
Interestingly, I think the giraffe that is the most common in zoos is the reticulated giraffe, but there are so many different kinds, each slightly different. My favourite is the Masai giraffe
And this is the South African giraffe
I come from game farm country in South Africa so you often see these on either side of the road as you drive from place to place. Here are some bad photos I took of a Rhodesian giraffe from the car as I was on the way home one day the last time I was there. They are enormous. You don’t actually realise how big until you get close to one – about 6m/20ft tall.