What causes the protein digestion there?

Enzymes and Amino Acids

Mechanical digestion of protein begins in the mouth. There are two enzymes in our saliva called amylase and lipase. They mostly break down carbohydrates and fats. Then they are transferred to the stomach and at last go to small intestine. Once a protein source reaches our stomach, hydrochloric acid and enzymes called proteases break it down into smaller chains of amino acids. In this way chemical digestion of protein begins in the stomach and ends in the small intestine.

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.

c. live where it’s cold and icy