While browsing patents.google.com I stumbled on this invention that was patented in 2020. Its a repellent that's primarily based on the bitterant Denatonium and can be used to make certain plants unedible for pests. However this particular invention is not exactly novel because people have been aware of Denatonium's repellent properties for a long time before 2020.
Two of the main conditions for filing a patent are that the invention must be:
Novel: The idea must be new and not disclosed or publicly available before the date of filing. It should not have been previously patented, published, or in public use or on sale.
Inventive/Non-obvious: The idea should involve an inventive step or be non-obvious to a person skilled in the relevant field. This means it must not be something that would be considered obvious or easily deducible by someone knowledgeable in the field.
There are examples of people already using this substance as a pest repellent before 2020. For instance this internet article from 2018 states that Bittrex (which is the brand name for Denatonium) can be used to repel rabbits. There's even a patent filed in 2006 for a similar product that is based on asphalt and denatonium benzoate and helps prevent animals from damaging trees or other exterior surfaces.
So how is it possible that someone else was able to file another patent for a similar denatonium based animal repellent in 2020? Is it because the patent has an increased scope? I've read that it can also be used for snake and snail repellent.