Changing batch_size cause loss different

When I fine tune VGG in Stanford Dog Breed Dataset,I found different batch_size cause loss different.
for example, when I set batch_size = 1,the loss plot looks like this:

but when I set batch_size = 32, the loss plot seems normal and looks like this:

what is the reason of this phenomena?

Is it really the loss or do you mean accuracy?
If it’s the loss, both plots look fishy, since the loss should go down.