Noting that contraceptive darts are currently being used against wild horses in Wales to keep their population numbers down, I did a bit of Internet searching to see whether contraceptive darts had ever been used to control feral cat populations. The answer appears to be a definitive No. There may be a number of very good reasons for this. One of the reasons is probably the cost at about £50 per dart. They would also have to be modified darts for feral cats because the darts used on horses and other large wild animals are far too large. Such darts may not be available.
However, the thought of using contraceptive darts to control feral populations would appear to have some merit. It is a very speedy efficient process. There appears to be no side effects and it is a safe process. On the face of it, it could be an alternative to TNR programs. Of course, TNR programs incorporate more than just sterilising cats because veterinarians and their assistants also treat the cats if required. In addition, a cat which has undergone the TNR process has his left ear clipped which efficiently advertises to the world that he is sterilised.
Sterilising a cat with a contraceptive dart does not allow the operator to clip the cat’s ear. That is clearly a downside but nonetheless, under certain circumstances and in certain places, it may be preferable to sterilise feral cats with a dart.
People who dislike feral cats to the point where they want them eliminated would argue that if you can get near enough to a feral cat to shoot it with a contraceptive dart then why not shoot it dead with a bullet. That suggestion is all very well and good but it is inhumane. The starting point in dealing with feral cat populations is to find a humane solution and one that works in the long run. Efficient TNR programs, widely employed, do work but they need commitment and funding.
P.S. I believe that the Porcine Zona Pellucida Vaccine (ZPV) vaccine is used for contraceptive dart use.
P.P.S. Sandy has told me about a food contraceptive that was being researched years ago.
Michelle Meister-Weisbarth, a student at the Virginia-Maryland Regional College of Veterinary Medicine developed a genetically engineered bacterium to be used as an oral contraceptive to control the unwanted cat population. It would be delivered to feral cats using a vaccine-laden bait. See page.