Biology questions???

This morning i was a bit late for DSP(digital signal processing) class. Most seats in the classroom were occupied. Finally i found an empty seat beside a pretty malay girl(my coursemate). Then, i sat down and paid attention to my DSP's lecturer who likes to smile all the time,even when he is teaching. But my lecturer's teaching style is a bit bored. Hehe......then i started to daydream in class. Suddenly, the malay girl beside me asked me a question."Lee Jun, katak itu dalam kumpulan apa,amfibia atau mamalia atau reptilia?". At first, i was a bit shocked and curious about the reason she asked such a question. I thought for quite a long while before saying out the answer "amfibia"(because i'm far far away from biology world after i took E&E engineer). Then, she told me that she is joining a sms contest which asks about general knowlegde questions. I smiled and continued sitting in the classroom with my sleepy brain. After a while, she asked me another question."Yang ikan paus itu dalam kumpulan mamalia,adakah ikan paus datang haid?" I was amazed after hearing this question. Haha....a good question that i never think before.

As we know, girls will have menstruation or period once a month. Then, my friends told me that dogs have it too. What about whales??? Just now i tried to check online but couldn't find the answer for it. Very very very curious about the answer. Can anyone who answers my question?