VOA慢速英语:野生动物专家担心露脊鲸的出生率

endangered - adj. used to describe a type of animal or plant that has become very rare and that could die out completely

pivotal - adj. very important

figure (something) out - phrasal verb. to understand or find (something, such as a reason or a solution) by thinking

mortality - n. the quality or state of being a person or thing that is alive and therefore certain to die : the quality or state of being mortal

sustain - v. to provide what is needed for (something or someone) to exist, continue, etc.

trajectory - n. used to describe a process of change or development that leads toward a particular result

migrate – v. to move from one place to live or work in another

straggler - n. : a person or animal that moves slower than others and becomes separated from them

calf - n. the young of various other large animals (such as the elephant or whale)

baby boom – expression. a time when there is a great increase in the number of babies born

all hands on deck – idiom. used to say that everyone is needed to help in a given situation