The ratio of the mass of an object to its volume

Density is the mass of an object divided by its volume. Density often has units of grams per cubic centimeter (g/cm3). Remember, grams is a mass and cubic centimeters is a volume (the same volume as 1 milliliter).

Explanation:

Ok,for some animals to survive,then ww should first look at the kind of ecosystem they ate exposed to.

So first for some animals to survive,some of them will have to migrate,and so migration in a given set up of an ecosystem,the other animals may lack food as in they depend on the migrating animals as their prey hence their food.

Secondly,hibernation some animals may hibernate due to intensive weather or climate change which is inevitable,and this might affect other animals in such a way that may lead to decrease of their counterparts hence dying due to an imbalance as the other animals may become prey to the predators available.