Berkeley: both are in the College of Letters and Science, which admits all frosh as undeclared. The math major just requires C or higher grades in the prerequisite math courses to enter (though the department recommends that only those with B- or higher grades enter). The statistics major requires a 3.2 GPA in prerequisite math courses and a B- or higher in an upper division statistics course to declare.
https://math.berkeley.edu/programs/undergraduate/majoring-mathematics
http://statistics.berkeley.edu/programs/undergrad/major
UCLA: math and statistics require a C or higher in all prerequisites; math also requires a 2.5 GPA in prerequisites.
http://www.registrar.ucla.edu/catalog/uclacatalog14-15-504.htm
http://www.registrar.ucla.edu/catalog/uclacatalog14-15-782.htm
UCSD: math and statistics are not impacted. A 2.0 GPA and no grade lower than C- in prerequisites are needed to enter the major.
https://students.ucsd.edu/academics/advising/majors-minors/undergraduate-majors.html
http://www.ucsd.edu/catalog/curric/MATH-ug.html