If you're not very good at maths and science then mammalogy isn't for you.
See here:
http://upl.co/uploads/Mammalogy1528839769.jpg
That summary of what you need to become a mammalogist is taken from the website of the American Society of Mammalogists.
(Full source:
https://www.mammalogy.org/uploads/scienceofmammalogy.pdf )
Any biological science, taken at degree level, is likely to involve quite a lot of mathematics (especially statistics). When I was studying for my mathematics degree, I got fed up of all the time that I had to spend helping the biology students to understand statistics. (The chemistry students got fed up of helping them with organic chemistry too!) That was despite the fact that the biology students needed good school qualifications in both mathematics and chemistry to get onto their courses in the first place.
If you require further advice on possible study and career options which might be open to you, it would help us to know:
(a) which country you're in. (Your use of 'math', rather than 'maths', suggests that you might be outside the UK, where this website is based - possibly in the USA?) ;
(b) how old you are ;
(c) what level of qualifications you already have or might reasonably expect to get in the future (as appropriate).