Note: Two questions combined. Q: "Please enlighten this person of very little brain. Just WHAT is a "Founders Effect?" "Ok, exactly how can a founders effect show how ferrets can't go feral?" A: I know the flounder's effect can leave you feeling a bit flat, but the idea is just a bit fishy. "Founder's effect" is a term that comes from population genetics where there is a noticeable loss of genetic variation within the descendents of a new colony because of a limited number of breeding individuals. This could mean that there were a limited number of breeding individuals, or that there were a large number of individuals, but most did not breed. In either case, there are fewer genetic differences within the descendants (offspring) compared to the founders (ancestors). Sometimes a founder's effect is called a bottleneck (they are sometimes used interchangeably), although a bottleneck is generally defined as being caused by a large die off of animals (at least 50%), such as with the black-footed ferret, while the founder's effect is usually applied to colonization events, such as with feral animals in New Zealand. Black-footed ferrets, cheetahs, golden hamsters, American bison, and northern elephant seals all display the effects of a bottleneck. While the reason for the loss of genetic information is different between the two, the results are similar. However, the loss of genes in a bottleneck can be permanent, while the loss from a founder's effect can be reversed by the introduction of breeding individuals from the unaffected population. This loss of genetic information can occur with line breeding, in-breeding, the breeding of endangered species, or a small number of animals establishing a feral population. There are some genetics studies that have concluded all modern polecats descended from a single small founding population between 250,000 and 100,000 years ago. This would imply that the founding population of modern polecats suffered a bottleneck as ancestral polecats survived, but the other polecats went extinct. After surviving polecats repopulated Europe and Asia, the steppe polecats crossed into North America. As their offspring became landlocked, they underwent a founder's effect, resulting in the black-footed ferret. Later, black-footed ferrets suffered a bottleneck when the population crashed. Got all that? Well, the end result is that polecats are very closely related. Yep, all of 'em. So closely related that there is some argument that -- based on genetic studies -- all polecats are a single species (including the black-footed ferret). The other implication is that the animal domesticated from these closely related polecats -- our domesticated ferret -- would also be closely related. I am sure you can intuitively understand why it is so difficult to identify the ancestor (or progenitor) of the domesticated ferret; it is easier to, um, ferret out genetic relationships when there is more genetic variation present. Ok, but what about the feral ferrets in New Zealand? The history of the introductions of ferrets in New Zealand has two separate histories: the official government history, and the unofficial actual history. Understanding both is very important. In the official story, ferrets were bred and released by acclimation societies and government agencies beginning in the 1870s. New Zealand law protected ferrets until the 1920s. The introduction was to control the rabbits that had been released earlier, and it failed to such an extent that weasels and stoats were later released to accomplish what ferrets couldn't do. There are now sizable populations of feral ferrets on both North and South Islands. Estimates of the number of ferrets released during the initial introduction vary, and some government agencies seem to be purposely disingenuous in reporting the numbers. For example, some reports like to say something along the lines of "five ferrets were released in 1879 and now New Zealand has the largest wild ferret population in the world." This implies that a small number of ferrets can populate a large geographic area, when in fact, the introduction took decades, large numbers were initially released, the ferrets were protected, and current populations are due to a century of breeding, as well as additional releases. The unofficial story, much harder to document, is that not just government agencies and acclimation societies were involved in the ferret releases, but also scores of private individuals. I have several sources that say cattle and sheep ranches would breed ferrets purposely to release them in an effort to control rabbits. I have documents in hand that prove American ferrets were being shipped to New Zealand during the introduction period. Obviously, more ferrets were being released than the government suggests, but I don't think a realistic estimate of additional numbers can be made. Both histories are true (well, not the disingenuous part), but it shows how difficult it can be to document the numbers of ferrets initially released. When you add to the mix the numbers of ferrets accidentally and purposely released by fur farms, it is probably not possible to determine ANY number with accuracy. Nonetheless, the numbers must have exceeded 20,000 breeding animals released during the introduction years (1880-1900), and it could have reached to as many as 100,000. Even if the number released were only 20,000 ferrets capable of breeding, how does that fit with a founder's effect? Conservationists are not in agreement with a minimum number of breeding individuals that would prevent a founder's effect, but conservatively, that number could be as small as 25 to 400 breeding individuals. Obviously, the numbers of ferrets released in New Zealand significantly exceeds that number, so a founder's effect should not be a factor. Of course, there is the question of genetic drift, which suggests the genetic composition of a population can randomly shift for no apparent reason (assuming the shift is not under selective pressure). However, with the decades-long release of ferrets, as well as the large number of ferrets released from fur farms, there would have to be a lot of corroborative evidence before genetic drift could be accepted. So, why is this important in the California feral ferret issue? There are three major attributes of ferrets that have been historically used to maintain their illegal status (or in attempts to make them illegal). The danger of ferrets biting young children is one, another is the risk of rabies, and the last is the danger of feral ferrets. Since ferrets have been shown to be as safe or safer than cats or dogs, the first argument is void. An effective rabies vaccine and virus shedding studies have voided the second argument. The remaining argument is the feral ferret issue. There are two types of feral ferret reports: those that can actually document ferrets living in the wild (such as the feral ferrets in New Zealand), and those that cannot document feral ferrets but suggest they are there (such as "reports" of ferrets in New Mexico). The vast majority of feral ferret reports are of the second type, where uncorroborated reports are offered as evidence, and any found ferret (even a lost pet) is defined as feral. Except for those biologists with a clear anti-ferret bias, these reports can't fool a single biologist. But, you still have the feral ferrets that live on some British islands, and -- of course -- the New Zealand feral ferrets. Thus, the New Zealand feral ferrets have become quite important to the California Fish & Game; for them it is clear evidence that ferrets could actually become feral. This is the remaining evidence; the cornerstone of their existing argument at ferrets should be kept illegal in that state. To strengthen the argument, the CF&G tries to make California as "New Zealand-Like" as possible. So, how does finding a founder's effect/bottleneck in the remains of 88 New Zealand feral ferrets fit into the equation? Simple. Remember that the genetic variation in a species is conserved if the number of breeding individuals is between 25-400? Well, if only 20,000 ferrets were released in New Zealand between 1880 and 1900, that means an average of 1000 breeding ferrets were released each year. Even if ALL ferrets died between the yearly releases, the number of ferrets released still well exceeds the number required to maintain genetic variation. In short, there shouldn't be a founder's effect. When you add in all the private releases, fur farm releases, and survivors and offspring, there clearly should not be a founder's effect. Are you beginning to see the implication? Why would I find clear evidence of a founder's effect in the New Zealand feral ferret population if such an event should not have occurred? The possible explanations are that only a few ferrets were able to breed, most of the ferrets died, or a combination of the two. These explanations suggest that despite the efforts of the New Zealand government, acclimation societies, and private individuals to stack the deck and insure the initial survival of the released ferrets, the ferrets did very poorly. This undermines the CF&G position that pet ferrets are a danger for being able to go feral. If a founder's effect/bottleneck exists in the New Zealand feral ferret population, it means most of the released ferrets never reproduced or did not survive to reproduce. Ready for the curve ball? It could also mean the initial releases of ferrets were successful, but something later caused a huge population crash. So, the two (most likely) possible scenarios are that the initial releases were a failure, or that something later caused a huge decline in feral ferret numbers (or some degree of both, I suppose). What could have caused such a crash? It is hypothesized that rabbit control measures caused a huge ferret crash in New Zealand. This is actually a very attractive hypothesis because in every place where ferrets once were or are feral, there are also feral European rabbits. Recent studies in New Zealand suggest feral ferret numbers are directly tied to feral rabbit numbers. Luckily for us, both scenarios are really cool. For example, if it is discovered that ferrets have a hard time going feral, then it shows pet ferrets are low risk animals for going feral. However, if it discovered that ferrets could only go feral where there are large numbers of feral rabbits, well, the risk is likewise as low if there are no large feral European rabbit populations. In either case, the CF&G argument is undermined. There is one last piece of the puzzle. In Europe, the American mink was released, mostly accidentally, starting in the late 1950s. Barely 50 years later, American mink are naturalized throughout Europe. Compare that to the ferret in North American, where I can first document them being here between the 1780s (indirect evidence) to 1820s (direct evidence). They were most likely here before then, but there is a difference between thinking they were here and proving they were here. In 200 years, there are no feral ferret populations in North America (and I can document both intentional and accidental releases during that time). Mink? 50 years to spread over Europe. Ferrets? 200 years to hide under a china cabinet. My working hypothesis is that ferrets have not been able to go feral in North America because 1) there are no large populations of feral European rabbits, and 2) they cannot out-compete the American mink. Part of the trip is to get supportive evidence that ferrets in New Zealand had a founder's effect/bottleneck, and part is to document the ability of the American mink to out-compete the local polecats. If I can get the empirical evidence, then it can go a long way to undermine the last argument of the CF&G for outlawing ferrets. I think that could be a good thing. I could discuss this for hours and I am creating a Powerpoint presentation on the subject. While important to California ferret owners, it deserves national exposure because the feral issue can crop up at any time. Like my dental findings, it will also get published in appropriate publications and presented at zoological meetings. I could even have a preliminary report ready for the ferret symposium if invited. The point is that this is an important issue and it needs to be discussed in as many formats as possible. It takes a lot of shot-gunning to get some people to listen, so if that is what it takes, then that is what I will do. Bob C [log in to unmask] [Posted in FML 5855]