Your Wild shape and polymorphs work differently. Instead of choosing the animal, the target turns into, it is rolled on a d100.

1-10 > Use the spell as normal

11- 20 > Crab 

21 - 25 > Giant Crab

26 - 29> Permenantly shrink a foot

30 - 35 > Permenantly Grow a foot

36 - 50 > Rat

51 - 60 > Cat

61 - 68 > Boar

69 >  Giant Elk

70 - 79 > Baboon

80 >  Giant Centipede

81 - 90 > The Closest beast to you

91 > The Closest Party Member to you

92 - 98 > Giant Spider

99 > Giant Ape

100 > DM Suprise