Castration of male rats
Nuts, torpedoes, balls... If any male animal can be said to think with its testicles,
it would seem obvious that rats are ruled by sexual hormones.
Rat testicles have twice the volume of the rat brain! When people see those goolies for the first time
they can hardly believe their own eyes.
Is it a tumor,
or is it really... (blush, blush)?
Some rat owners never get used to their outsized outgrowths, but others, like me, are fascinated by
them. By how they work when in place, and what happens when male rats are deprived of their family
jewels by castration. Guessing all the effects of the sexual hormones from their pouch is a tall order.
There was a quiet interlude where I could concentrate on Frodo's behaviour. He was up to no good at all, see Frodo's story. At the same time I could see Birk slowly but relentlessly rising in the rat ranks. As he grew he took on the other rats one by one and taught them that he was not a pup anymore. It all happened quietly - I only got to see Birk powergrooming an increasing number of his cage mates behind the ears and in the neck. I realised he was the new Omega rat. As he still weighed 50 g less than my Alpha, I was not worried about the coming dispute just yet. But for some reason or other all my rats started acting strange! All of a sudden every one of them became master groomers. They would clean my nails for me, lick me, come up for a cuddle - and each of them would leave a wet, yellow stripe across my hand. Preferably across where someone else had just left his. Labben, the Alpha, prefered to watch it all from a vantage point on my shoulder. When he had left a few drops of himself on my hand going up, that is...
Birk is a sweater rat, he loves to crawl inside my clothes. I usually wear a T-shirt beneath my sweater because of his claws. One warmish day I was without the T-shirt, I dug him out from Valley High and deposited him on my right shoulder. Labben was occupying my left. This was when Birk got it into his head that he would challenge the boss! The sound of two rats making warning signals while balancing on their hind legs behind my left ear and boxing was a hair rising experience for me too! My name is Lorrain, Alsace Lorrain, and it was me they were fighting about! I enforced an armistice without having any fallen rats, and no blood was spilled. But the next day, poor walk-all-over-me Ulf had a long, fresh cut on his flank behind the shoulder. He was in pain and I rushed him to the vet. It was the third shoulder flank wound in a month, but the first serious one. Even if Birk was a prime suspect, Frodo's candidature was equally strong. However, as all of them had started pee marking I felt that by rights no one should be excluded from the list of possible perpetrators. Ulf could not very well have made the wounds himself (he had been a victim twice), but had he snapped at Labben and pushed him over the ledge? The other rat with a scratch was Mimer. He could still have made Ulf's wounds. Had Mimer become mean, or was Yggdrasil egging towards a battle?
Weeks passed. In the daytime all was quiet in the cage. At night I heard the rattling of rats hurtling down the sides of the cage and hitting the bottom drawer. No wounds, until I found a tiny one on Birk's shoulder. All right, this one was acquitted. Frodo was going through a difficult phase, and I could not believe I had two rats with the same fighting style. I intensified my work with Frodo. Even so it seemed to me there were dark undercurrents in these seemingly quiet wasters. The Rat gang - now called the Venetians after their new Essegi Venezia cage - were fine as long as I stayed close by. If I left the room I risked mutiny. They knew when I was near and ready to break up a fight. And the wounds continued to trickle in, about one each fortnight. They were steering towards a major battle. One in which they wanted no interference! In the middle of all this Frodo developed food aggression and had to be put down. I was hoping for a new calm. I got the calm before a storm. One day I was returning after driving the children to school I heard the ruckus the moment I walked in. It had been a long time since I climbed the stairs as speedily. I barely caught the sight of Birk pushing Yggdrasil - the new Alpha after the death of his brother - off a hammock. Birk himself vas unscathed. Yggdrasil had a long slit in his side... New telephone call to the vet, but thanks to the re-generating superpowers of rat skin the wound closed overnight before I had the appointment.
Ulfs wound before the edges started to gape. I cannot be a 100% sure Birk made it, but it was identical to the one he gave Yggdrasil a couple of months later.
I could not let Birk share a cage with other rats. Even if he had only made that wound it was definitely one
to many. I am sure Frodo was jointly responsible, but the casualty list from the latest four months
After much debating and research I got an appointment for castrating him with the vet. I did not do so lightly. Birk was just turning a year old, and he had perfectionated his fighting technique. Most people who have written about castration of bucks are very clear about the advantages of an early castration. They also write that surgery should take place before the buck has formed a habit of hurting other rats. On top of this I had just heard several stories of rats that did not make it through the operation. On the other hand I had run out of options. I did not want him to die a lonely and premature death of mycoplasma. My vet had castrated rats before without killing them in the process. She knew what kind of medication my rats could (normally) take, and how much. I finally made up my mind when I was offered another castrate for company in case he needed a companion. Castrated rats cannot always live with their former mates again, even if they become docile and friendly. Sometimes the other males seem to think that they have a girl in their group. This can get rather tiresome to a rat who must suddenly watch his back side all the time...
Birk was castrated on his 1 year birthday. Birthday gift: a new chance. Towards the end of this page you can read a full description of Operation Balls end. (No pictures!) Birk recovered quickly, had no wound abscess, and after a week I could let him join a pre-pubertal male during free-range time. Before two weeks had passed he tolerated all of them. After three weeks he was back in the Venetia cage. He has not caused any trouble since. I have never regretted the decision I made for him.
Enter Birk's brothers Jonathan and Skorpan. I rescued them from their second rescue home with the knowledge that both were sweet with humans and had a reputation of beating up other rats. After a start which seemed to belie their reputation I learned that it was not totally unfounded. They were not all out aggressive, but they were no safe with other bucks, and both did bite seemingly without provocation. Having had such great results with Birk, I was eager to see if castration would solve this problem too. Skorpan, the smaller of the two by 200g totally dominated his huge brother. At the time I decided to castrate him, Jonathan still had not attacked any of my other rats. Hence Skorpan underwent the operation alone. After only two days I began to see the changes. Skorpan had been an adventurous guy, leaping from the large table where my other males are content to stroll about, in order to explore the rest of the house. His escapes came to an end. He now preferred to stay inside a cardboard house on the table top. Jonathan took advantage of his brother’s changed state and became the new Alpha of the two. He behaved as ruthlessly to Skorpan as Skorpan had behaved towards him, but there were no wounds from their dominance displays over eachother. Unfortunately, Skorpan proved to be a real whimp without his testicular hormones. I tried him with a pre-pubertal male, which he ignored until the "baby" reached puberty. Skorpan was terrified of the tiny buck. Then I tried him with two young females who were visiting. Skorpan tolerated the shy one at a distance, but made no overtures to her what so ever even when, presumably, she was in heat. The more sprightly one was more than he could handle, even if she were 200g lighter and just being curious.
I did not wish to castrate Jonathan. Some rats become less fearful after castration, but if Jonathan resembled his smaller brother he would grow more fearful than he ever was. The thought of a panicky, almost 900g buck with a habit of biting did not make me inclined towards a surgical solution. I did not think it would help him integrate with other rats. Most of the time the two of them behaved like great friends. Still, each day Jonathan would have at least one major display of dominance. And then I found a bite mark on Jonathan. I called the vet right away, but before Jonathan could lose his balls he managed to inflict a second bite wound on Skorpan. It was a great relief to me than Jonathan both survived the operation and seemed to adjust well to his new hormonal status.
The net result did not seem too bad: the two of them co-habited without quarreling, and Skorpan was much more calm when he was not being bullied anymore. Maybe, just maybe the castration of both could get them to the point where they could be re-introduced to other rats. After one months of intensive work I did see progress with Skorpan. He was able to spend time in a playground with my most gentle buck. It was a fragile peace. It did not hold if Jonathan could smell the other males on their play things. With Jonathan the introduction to other rats took months, even after the castration...
Summing up: my limited experience with castration tells me that this step is not always advisable. I wish I knew in advance which rats would respond favourably, and which would not. I do not. Skorpan at least would have been better off with his balls on. As I cannot predict if the operation will be for the best, it will remain a second-to-last solution for any problem rats in this house. Although it does make chemical castration as a 3 month test trial seem more interesting... I may be writing of Tardak in the future.
Laws and ethicsIn spite of the narcosis and pain medication, the aftermath of castration remains a painful experience for the awakening rat. Nor is narcosis in itself a risk free process. Some never wake up, or wake up only to drift into the final sleep. Add that castration has a permanent effect on health and the mental state of the animal. The tendency to overeat and gain weight is increased. Fat rats are more prone to heart- and circulatory diseases as well as diabetes. Their spatial memory suffers. So how can one defend the removal of the testicles from an ethical point of view?
In 2001 the Norwegian Rådet for dyreetikk - an independent, advisory board on ethics, appointed by Landbruksdepartementet (the Department of Agriculture) - delivered a paper on castration which, among others stated:
As examples of when castration could be in the best interests of the animal, the statement mentioned aggression and the ability to move among its own species.
Anatomy of the rat testiclesRat testicles (testes) are lung, tubular organs connected with the urethra by first the epidydermis and the vas ductus (seminal ducts). The epidydermis are two lumps hanging by the testicles. The semen must pass through them to ripen. If not they are not capable of aiding propagation. Parts of the surface of both the testicles and the epidydermis are covered by a beautiful meandering pattern of fine seminal ducts. Unfortunately I do not have any close-ups. My vet wondered if I wanted to bring home a trophy to display in formalin. I was tempted but knew that the pharmacy would have to order the formalin and that the sample would rot in the meantime. Besides, I suspected my husband and the boys might be made to feel a bit Freudian angst if I had displayed my trophy on the mantelpiece. To make amends I've added a link to Kenyon College which has a photo of an opened rat showing the anatomy. Unfortunately the details are not good enough to catch the beauty of the seminal duct pattern.
The testicles are located under the anal orifice and behind the penis of the male rat. As with the human testicles they depend on a fairly narrow temperature range to produce high quality semen. The rat can regulate their temperature by pulling the testicles into the body. In a fight the testicles can be retracted for protection. The muscle which facilitates the withdrawal reacts to noradrenalin (norepinephrine). Noradrenalin is a stress hormone which the rat produces when preparing for fight or flight. The testicles are also protected by a thick layer of fat all around them.
The testicles not only produce semen. They also produce the hormones testosterone, oestradiol, androstendione, and dehydroepiandrosterone (DHEA). These hormones have such a vast number of different effects on the body that listing them all is not possible. Especially since scientists are still finding new effects. It has been shown beyond doubt that a serious fall in the level of these hormones have a positive influence on certain forms of aggression and anxiety in rats. There are other beneficial effects from lowering the level of gonad hormones in the male rat. There are harmful effects too.
After a surgical castration the testosterone stores in the body fat is gone after only a few hours. The behavioral changes, on the other hand, may take two to three weeks. This is partially because of a storage pool of testosterone esters. This storage pool takes about two weeks to deplete. Secondly, the regulation of the receptors in the brain and other body parts takes time. Another quick drop in hormone level is seen in dihydrotestosterone (gone from blood serum in 6 hour but remains longer in the bladder which contains the semen.)
Some effects of castration
The timing of a castration influences the effect of castrating a rat buck. Rats castrated before puberty and before their bone growth is complete will behave differently and have a more "female" shape than if the operation had been delayed. These changes happen no matter at what age the rat is castrated:
When Birk no longer reacted to having his ears touched, nor the closing of his eyelids he was ready. I put him
on his back on a special pillow, with his tail against the veterinary. First he was shaved around the operation area
and the field of operation was drenched in spirits.
Birk had Simplex eye ointment (a vaseline oil based product) to prevent his eyes from drying up.
The vet cut a hole in a small paper operating towel so that she could fasten it around his balls.
The paper was fastened with clips to the skin of his belly. Then the vet put one hand on his abdomen to push the
testicles downwards into his pouch. slik at hun kunne tre det rundt ballene til Birk.
Papiret ble festet med klemmer til mageskinnet hans. With the other hand she cut a small incision
in the skin over each testicle before she anchored it with a kind of forceps that could be locked in place.
With one testicle fixated she could concentrate on the other: pulling it out by the opening while she
was loosening the thin membranes around it. Next came tying catgut above the place to cut. The organ was so much
longer than I had ever imagined!
After the operation
It is not unusual for a rat to start "snoring" when in narcosis. This has to do with an increase in the secretion of mucus. None of my rats have been greatly troubled by it, but I do watch over them, and change their sleeping position if they become noisy. Usually a new sleeping position is all that it takes to quiet them. I do not know how rats behave if they have been awakened by an injection. All my rats have slept solid for about eight hours (give or take a couple of hours) before the first signs of awakening. It usually starts with small movements around their nose or eyes. Quite often these movements can be seen on and off for a couple of hours before they start crawling around, totally disoriented.
The next stage is when the rat finds out that he can walk again. Birk staggered around with a drunkard's balance and Dutch courage. Having been through this before I did not put him in an ordinary bar cage. He would have tried to climb the bars, definitely lost his balance and probably got a limb stuck in the bars when falling. That is why I use a traveller's cage for a cat or small dog - a plastic shell - for rats who are in the process of waking up. Soft food is still a good idea. I usually do not use painkillers until I have seen the rat swallow anything. After the castration Birk was not interested in dry food pellets for 1 1/2 day, but he lapped up a great deal of yoghurt and porridge. His weight loss was about 45 g during the reconvalescent period. That is more than the weight of the testicles. They are on an average 4,26% of its body weight, that is 21,3g for a 500 gram rat. The weight difference is partly due to the fact that the layer of fat around the testicles, which is removed with them, is not part of the testicle weight. When Birk weighed around 650 g before the castration and ate less than normal for two days, the weight loss seems pretty normal.
Birk did go home with a course of antibiotics. I chose not to give it to him. This was partly because he managed to spit out his entire first dosage. But the fact remains that the testicles and the pouch have an excellent blood supply. Infections are rare. Abscesses are a fairly common complication of the procedure, but reaching an abscess with oral antibiotics is a problem anyway. Had it been a different kind of operation, or a rat in poor health I would not have hesitated to give the medication. As it was, Birk was a model patient. He kept his wound clean, took it easy, and extracted the stitches himself when he felt the wound had knit. He looks a bit odd with those shrivelled, raisin sized appendixes that remain. On the other hand he as stopped using his balls like a dish rag to wipe his urine all over my hands...
ReferencesStatement, Norwegian from Rådet for dyreetikk 2001 about castration
Fulltext Human epididymal proteins and sperm function during fertilization: an update
ANDREA LASSERRE et al.
Abstract Long-lived testosterone esters in the rat
W Borg, C H Shackleton, S L Pahuja, and R B Hochberg
Abstract Changes in Testosterone and Dihydrotestosterone Levels in Male Rat Accessory Sex Organs, Serum, and Seminal Fluid After Castration: Establishment of a New Highly Sensitive Simultaneous Androgen Measurement Method
BUNZO KASHIWAGI et al.
Abstract Testosterone deprivation by castration impairs expression of voltage-dependent potassium channels in rat aorta.
P Zhou et al.
Abstract Effects of Dehydroepiandrosterone (DHEA) on Pituitary Prolactin and Arcuate Nucleus Neuron Tyrosine Hydroxylase mRNA Levels in the Rat
Ester Garcia De Yebenes et al.
Abstract Territorial aggression of the rat to males castrated at various ages
Kevin J. Flannellya og Donald H. Thor
Fulltext Gender related differences in antinociceptive properties of morphine after gonadectomy in male and female rats
Manzumeh-Shamsi Meimandi et al.
Abstract Castration decreases amylase release associated with muscarinic acetylcholine receptor downregulation in rat parotid gland
Lucila Busch1 og Enri Borda
Abstract Sex differences in hepatic uptake of long chain fatty acids in single-pass perfused rat liver
Michael C. Kushlan et al.
Abstract Hormonal influence on the secretory immune system of the eye: androgen regulation of secretory component levels in rat tears
D.A. Sullivan et al.
Abstract SEX-DEPENDENT DIFFERENCES IN DRUG METABOLISM IN THE RAT II. Qualitative Changes Produced by Castration and the Administration of Steroid Hormones and Phenobarbital
S. EL DEFRAWY EL MASRY og G. J. MANNERING
Abstract Experimental studies on the effects in helminthic infection, with special reference to the gonadectomy of the host.