"Blind as a bat" is a cute but zoologically inaccurate simile. All bats have some vision, and some can even perceive ultraviolet light. A new study investigated whether "blind" bats could still find their way back home.
Bats have visual, magnetic, and olfactory senses in addition to echolocation. Scientists made blindfolds from pieces of adhesive tape, used a chemical to induce temporary anosmia, and affixed magnets to interfere with the magnetic compasses to limit bats to using only echolocation. The bats were transported away from their roost and released.
The researchers found that 95% percent of the bats could return to their roost using echolocation alone. They were surprised to find that even the species of bats used in the study, which had very limited visual acuity, still use vision to some extent, and they performed better when using both vision and echolocation.
Side note: I was concerned that the bats in this experiment would have blindfolds stuck to them indefinitely. Thankfully, I found this in the study's supplementary material.
To avoid the possibility of bats removing their eye cover, we examined their
behavior with eye covers in the lab and found that they cannot remove their eye cover while flying
but can do so within a few minutes of rest.
There was no mention of the bats with neodymium magnets superglued to their heads, but I am hoping the bats could also remove them in time.