Uncaught TypeError: Cannot read property 'frame' of undefined

[P@M@K]

I am trying to load a sprite sheet into the game and animate, but I keep getting the Error: "Uncaught TypeError: Cannot read property 'frame' of undefined". 

        this.anims.create({

        key: "animate"+faculty[f],

        frames: this.anims.generateFrameNumbers("animal" , {starts:0, ends:5}),

        frameRate: 10,

        repeat: -1})

I see that it has something to do with the "frames" key. 

Looked up online but the only thing I can find is someone who accidently put the "this.anims.create()" in his preload function instead of the create function. 

That is not my issue. 

Please some HELP! (been stuck on this for hours)

this is the preload for the spritesheet: (it has a total of 5 frames. dimensions: height= 16, width=80)

this.load.spritesheet("animal", "animal_image.png", { frameWidth: 16, frameHeight: 16 });