maybe we could soak the dart tip with grease from some American restaurant's deep fryer. atta kill the animal in a few minutes.

I was really hoping that nobody would mention Ricin on this thread. This is a public forum and certain words cause alarms to sound in certain governmental agencies best know by their initials. Law enforcement takes a particularly dim view of ricin. You have been warned.

It's my impression that hunting with poisons is generally illegal.   However, it may interest you to know that there was a campaign of sorts some years back to allow a certain type of "poison".
This would have been for archery hunting.  Instead of a regular broadhead, the arrow would have been fitted with a device very much like a tranquilizer dart.

The substance used would have been (guessing at the spelling) succilinine hydrochloride, which is quite deadly in a large enough dose.   
The idea behind this was the large number of lost/wounded deer.  Deer wandering around with an arrow stuck somewhere, suffering.....That sort of thing.
With the "poison dart" arrow, any good hit would be fatal....No wounding.

I saw this promoted in outdoor magazines years ago, but it didn't go anywhere.