They believe the seal triggered a maternal defence mechanism in the humpbacks .
他们认为，海豚触发了座头鲸母性的防御机制。
It is estimated that when whaling stations shut in 1963 , the coastal population of humpbacks had been reduced to a little over 100 animals .
据估计，捕鲸站于1963年关闭时，驼背鲸的数量减少到大约只有100多头。
Although humpbacks face a range of threats , including climate change and pollution , there is optimism that the species will continue to rebound from the exploitation of the past .
