What term do biologist use to describe the number of individuals a species requires to reproduce successfully and prevent it from going extinct?

Minimum viable populations (MVPs) size

Explanation:

The term minimum viable populations size refers to the smallest and viable population size that will persist for a particular time period. It describes the population size that is capable to preventing itself from extinction by maintaining itself. The minimum viable population size varies for different species. It is regulated by density dependent and density independent factors that regulate the growth rate of specific population or species.

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.