新概念英语第三册第一课中定冠词the的使用问题

新概念英语第三册第一课中定冠词the的使用问题
新概念英语第三册第一课中"expers from the zoo felt obliged to investigate",这一句中expers前面为什么没有定冠词the ?什么情况下可以省略the ?
全句如下，However, as the evidence began to accumulate, experts from the Zoo felt obliged to investigate, for the descriptions given by people who claimed to have seen the puma were extraordinarily similar.我觉得应该是the expers from the zoo，因为既然是动物园的专家，那就应该是特指了？有没有这种说法：文中第一次出现的，都不用the，下文再提到就算特指？