The chemical castration: part 1

Dalcash Dvinsky
The Bunny Years
Published in
5 min readNov 26, 2023


Chemical castration is actually a thing. The dog gets an implant in the neck, which releases a chemical, which makes the dog infertile, but only temporarily, for half a year or a full year, depending on dose. The chemical is deslorelin, sold as suprelorin, which suppresses the production of testosteron, as a result the libidos is reduced. By a lot.

Suprelorin wasn’t developed for this purpose, it was more an accidental side effect. It has been tested and studied on male dogs, but the sample sizes are quite small. Therefore it is still a bit experimental. It seemed like a good option for my dog. He was humping everything that moved since autumn 2022, and at some point interactions with dogs became essentially impossible. Permanent neutering was difficult to think about because it involves surgery and the outcome was uncertain for my complicated dog. So, investing three hundred pounds in a transient castration seemed like a good idea.

The implant was put in place in late August 2023. During the first couple of weeks his libido was, if anything, slightly enhanced, which seems to be a normal consequence of this process. The actual effects started to take place after four to six weeks, as promised, in late September. Now it is late November and his behaviour seems to be stable enough to document what exactly has changed with the implant. There is of course always the risk that other factors have caused the changes, but I think for anything related to sexual prowess it seems at least plausible to attribute it to the hormone killer.

Let’s start with the obvious one. No humping, at all. Not a single time since mid September. Not with dogs, not with me, not with anyone. It’s a relief, and it opens up a lot of space for dog meetups.

The second one is also obvious: Less marking. Bunny used to pee only in tiny little spurts, but then distributed his urine all over the village. All over, as an attempt to signal to absolutely everybody that this is his space. Hello, Bunny was here. Since September the walk starts with an extended pee break right behind the house. He had never peed there before, except in emergencies. Now we stand there for a minute before going for a walk. He just pees to pee, not to signal something. This also means that some walks are just that, pee breaks, nothing else. We went from about 10 km per day, every day, to maybe 7. It’s also a bit of a relief.

This brings us to the third point: As his dog walker put it, he is less single minded. It turns out that his relentless need to walk and sniff and walk and sniff, several hours a day, was in turn caused by his libido. Now that this is gone, it opens up the possibility to have other interests. He plays more, he is more interested in training, and he is even more interested in hunting. The last one is an undesirable side effect. I imagine that this also takes a lot of frustration away.

He is also again absolutely obsessed with food. Over most of winter and spring 2023, he ate really poorly. He skipped breakfast, didn’t take treats on walks, and had to be encouraged to eat. As a result he also had stomach issues. This makes life really difficult, not just that he is uncomfortable, but also harder to train and to communicate with. Food is such an essential part of our work together that I had to devise entirely new ways to connect — probably a useful exercise. I’m still glad we have the old food motivation back.

Overall, and a bit harder to see, there is a general problem with confidence. This dog was so incredibly confident in all his interactions with the world that I didn’t mind taking a bit of that away. Mostly it manifests itself just as a tiny bit of insecurity, a bit more wobbling in moments when he doesn’t know what to do, a few more looks back at me. It is overall positive, but I need to be aware of this and react accordingly. Instead of throwing him off his game, I need to make him feel more secure, at times. It makes sense of course that a dog whose self-esteem was derived to a great deal from his sexual prowess feels completely different about the world once we take that away. And we need to recognise that.

This also leads to a completely unexpected outcome: He refuses to walk with the dog walker who has walked him for over a year. Or with anyone, for that matter, except me. He walks away with them hesitantly, and after a hundred metres he stops and refuses to go any further, visibly stressed. Nobody told me THAT.

Overall I have the feeling he is a bit more stable and balanced. His extreme mood swings have evened out a bit. He still has grumpy days, and very happy days, but he doesn’t seem to fall into deep holes anymore, and he is not completely out of his mind anymore. That’s also a bit of a relief. Overall the sum of all the changes enable us to do more things, which is very positive.

What didn’t change at all, by the way, is the aggression towards large unneutered males. It was a long shot, but since that seems to be tied to competition with other males, I had some remote hopes that a castration would at least remove some of the urgency. But it didn’t. These reactions do happen less often, and when they happen they are often milder, or better managed, but that’s a long-term trend that started long before the implant. And they have as much to do with me than with him.

I don’t know yet what we are going to do once the drug wears off. I want to wait until I see the old behaviours coming back, if they come back. Maybe this year of forming new habits will be enough to break some of the obsessive behaviours. Maybe not. But before I know that, we won’t do anything. And at that point he will be almost seven, and perhaps develops other priorities.

One final change: He is going through a very unusual, poorly timed shedding phase, and lost half of his hair this month, just as it is getting cold. Not that this bothers him, at all.

Update January 2023: Almost all of that has gone back to normal. Marking, relentless walking, confidence, all back. First attempts of humping as well. The implant, supposedly covering a year or so, seems to have lasted only four months.