Q: "When at [a ferret show] I saw some male ferrets that had not been neutered...they had really large [scrotums]. Is this normal? Do they all have such large [testes] and where do they go when they are no longer in season?" A: They head south to play ball in Mexico. The following answer contains graphic descriptions of ferret sex and is not recommended for young children, members of S&M Anonymous, or fans of Ann Coulter. Rush Limbaugh and Bill O'Reilly declined comment, but are reported to have giggled and asked for a phone and privacy. There is a general rule among mammals that in promiscuous species, males have larger testes than males that are of the same body mass that are from monogamous species. A hypothesis to explain this general observation suggests, in part, that if the goal is to insure successful breeding, then promiscuous males need more ammunition for their cannon. This is why the hypothesis is sometimes called "Sperm Wars." Among other things, it suggests that he who deposits the most sperm has the highest chance of making babies in the reproduction lottery. Assuming most mammals have similar sperm production rates (not a great assumption), an easy way to make more sperm is to increase the size of the little sperm factories. It's true; size matters if your goal is to make more spermatozoa than your competitor. Polecats, the progenitor of our domesticated ferrets, have a kind of promiscuous reproductive strategy in which a jill could theoretically mate with all hobs that overlap her territory. Certainly, a polecat hob could mate with several jills in a single reproductive season. However, in a practical sense, most polecat jills probably only successfully mate with a single male per reproductive event. The reason is because a polecat hob captures the jill in heat, overpowers and pins her down, drags her around, chews her neck until it is bloody, and has prolonged sexual congress that is designed to cause ovulation and fertilization. Only after the male is satisfied that the jill has ovulated -- presumably by scent if some studies are correct -- will he willingly let her escape from his powerful canines and hooked baculla. Generally, this brings the female out of heat, although the process is not instantaneous. It is possible the jill could mate with another male, get wrestled to the ground, neck chewed, and mounted for another indeterminable time, and ovulate again. This has been widely reported anecdotally in the ferret literature, but the possibility of occurrence in polecats is poorly studied. So, what about the size of a hob's testes; are they larger than to be expected? Probably not. Although polecats are promiscuous by nature, other aspects of their reproductive strategy (the sex until ovulation thing) generally overpower the need to grow big 'uns. To answer this question, I consulted "Mammalian Body Masses," "Asdell's Patterns of Mammalian Reproduction," and about two-dozen body composition papers. The size of ferret testes is just about what should be expected for their body size. I suspect the startling observation of a pair of dangling fur-de-spheres is unusual enough to spur this question. Normally, males carry those cute little baby makers hidden away until needed, just before they go into rut. Then they drop down to swing gently in the breeze, which isn't a joke. For the best sperm production, the testicles need to be about 2-9 degrees Centigrade cooler than core body temperatures. Not only is sperm produced better at cooler temperatures, but the numbers of mutated or malformed sperm are reduced. The swinging in the breeze isn't the only way those reproductive nuggets keep from overheating; they also use a countercurrent-heat-exchange mechanism, where the cooled venous blood from the testes chills the warm arterial blood from the abdomen. Now you know what is meant by "chill out." There is an aspect of this phenomenon that has direct bearing on current ferret breeding. For most of 2500 years, ferrets have been housed outdoors. Only in the last 30 years or so have ferrets been brought inside the house. Recently, I've been asked to investigate the strange phenomenon that ferret reproductive success -- at a national level with hobby breeders -- has suffered the last few years. Litters are reportedly smaller, more birth defects are noted, and an increase in false pregnancies is being seen. END OF PART 1, PART 2 TO FOLLOW PART 2 I've come up with a few hypotheses about these problems: 1. Deteriorated plastics (water bottles, plastic food storage containers and bags, food dishes, cage wire coatings, etc.) may be producing enough pseudohormones to cause problems. These pseudohormones have been strongly linked to birth defects and resorbed embryos in numerous species. Pseudohormones are not really hormones. They are just molecular fragments that -- by coincidence -- contain a binding site that attaches to a hormone receptor site. This prevents the real hormone from attaching and regulating proper development. 2. Phytochemicals, including phytoestrogens and other endocrine disrupters (ED). These are natural chemicals that are produced by plants that could wind up in ferret kibbles. There are two main types of phytoestrogens of importance to ferrets. The first is Lignans, found in minor amounts in plant cell walls, and in high concentrations in oil seeds, such as flaxseed. They are also found in whole grains, cereal brans, legumes and other vegetables. The other phytoestrogens of importance to ferrets are the Isoflavonoids. These are found in a lot of plants, but are particularly common in soy products. Grains used to construct kibble may contain enough trace amounts of endocrine disrupters to impact reproductive success from either the male or female side. 3. Diet may partially to blame. It could be that some unknown trace element is acting like a limiting factor. It is also possible that the chicken meal used in some kibbles contains trace amounts of residual hormones (not plant based -- see above) that can impact the outcomes of pregnancy. 4. Both jills and hobs, being housed indoors, are being kept too warm, and because they are caged, they cannot use natural behaviors to better thermoregulate themselves, such as going underground, sprawling on a cool floor, splashing in water, etc. When jills are too warm during specific periods of time during embryonic development, it can throw off the development of the young. Many of the resulting changes can mimic other genetic problems, including neural crest disorders, cleft palates, and far worse. In males, the extra heat can reduce sperm quality and quantity. Ferrets are very sensitive to overheating, and while the degree of hyperthermia is not enough to harm adult ferrets, it could be enough to screw with reproduction. 5. Breeding practices have introduced too many random or mutative errors into some ferret lines, which are depressing reproductive success. This is a problem in many species, but currently no evidence exists that suggests it is one with the majority of ferret breeders. If the problem is as widespread as some have suggested, it is probably not genetics, but something in the environment. Personally, I think the problem is multifactorial, but I am leaning to a combination of overheating, and exposure to deteriorated plastics and phytochemicals. There may be other factors I have yet to consider (I'm still studying the problem). A great deal of applicable work has been done on mink and fox by the fur industry. The mink investigations in particular hold great promise for understanding what is going on. I am currently in the process of testing some of these hypotheses. For those of you that know Scarlett from Ohio, she has donated two whole jills from her fine stock. I have housed them in a cool (68 degrees), natural light, plastics-free environment (only metal and wood), and have only fed them mice and naturally grown chicken for most of the last year. When they come into season in the spring, Scarlett has agreed to breed them to healthy hobs and we will see if the different environment and diet has an impact on litter size and success. Yes, a tested population of 2 is very small, so don't consider it a test, but rather a preliminary result. If it works out, the results can be retested with a larger population that would have statistical significance. The tests don't end there. The kits will be randomly divided into two groups. One group will only be given an evolutionary diet and the other group will eat commercially available kibbles. Among other things, I will make periodic evaluations of their activity cycles, growth rates and adult size, kibble damage to teeth, weight, and health problems. This population can be small. With the statistical data I already possess, this test is simply to show the damage is not due to genetic problems, but biomechanical forces. Not that I really need the additional data. The populations I have now are large enough, composed of so many different ferrets from so many different areas, that the genetic question has been resolved. This is just to dispel the last tiny doubt. The last part of this post has drifted away from the testicle question a bit, but it relates if you realize the courage Scarlett displays in assisting my efforts to, um, ferret out some understanding to current problems in ferret reproduction. Need I say it? The lady has hurones cahones. Bob C [log in to unmask] [Posted in FML issue 5341]