What do Kooikerhondjes and Cheetahs (Acinonyx jubatus) have in common? Not much on the surface, but as it turns out, they share aspects of their history, genetics and population dynamics that may be illuminating in the pursuit of breed preservation – the domestic cousin of conservation.
After seeing a post about the Otterhound breed being rarer than the iconic giant panda (so recognizable as the public face of international conservation that it is the logo of the World Wildlife Fund) it occurred to me that many other breeds must have similar populations to endangered wild animals. When I started casually researching wild population numbers, which are of course imprecise estimates, a few numbers stuck out to me and I noticed a trend – estimates for cheetah populations tended to align very closely with population estimates of Kooikerhondjes.
While it’s very difficult to estimate true population sizes of both domestic and wild animals, both Kooikers and cheetahs are relatively well-studied. As discussed here previously, Kooikers have a comprehensive population database in the form of the VHNK’s Clubregister, and its subsequent digitizations. It is reliant on owner- and breeder-reported data, however, so its statistical weakness lies in the very real possibility of under- or mis-reported information. However, breeders internationally are usually quite competent at reporting litters born. Using these numbers, factoring in an approximately 14 year lifespan, and adjusting numbers for some litters born to the minority of breeders that do not report data to the Register, breed experts have come up with a worldwide population figure of 7000 – 9000 Kooikers (thanks to Diana Striegel for these numbers). The functional population, those individuals who are available for breeding, is both much lower and harder to calculate.
This seven- to nine-thousand number aligns curiously with the most recent scientific estimate for the population of the cheetah, estimated by Durant et. al in 2017 in “The global decline of cheetah Acinonyx jubatus and what it means for conservation” as 7,100. While population genetics, especially of wild species, is a field far more nuanced than two estimated numbers of individuals, the similarities between cheetahs and Kooikers go further.
Both Kooiker and cheetah populations are both relatively genetically-distinct groups that experienced a population bottleneck in recent history that irretrievably reduced their genetic diversity. A bottleneck is an event during which reproductive populations are reduced drastically over a short period of time, so that all later individuals descend only from a small subset of the original population. In cheetahs, this bottleneck has been timed to approximately 10,000 – 12,000 years ago at the end of the Pleistocene, when many large animals went extinct (Menotti-Raymond and O’Brien 1993). In Kooikers, following a gradual population decline over a few hundred years after their original eendenkooi work became mostly obsolete, they experienced a bottleneck in the early to mid 20th century. Like many European breeds, the pressures and rationing of World Wars I and II meant that very few dogs were bred. By the time the Baroness von Hardenbroek van Ammerstol began efforts to reconstitute the breed during WWII, there were so few Kooikers left in the Netherlands that today’s entire breed descends from only 13 “founder” individuals. From those 13 individuals comes ALL of the genetic diversity we have in the breed today, which is – briefly – not much. Using pedigrees to calculate, the average breed-wide coefficient of inbreeding is 34.5%, and the founder genome equivalent – how many statistically completely unrelated dogs exist in the population – is 1.45. (Data from Oliehoek 2017.) In Cheetahs such precise pedigree data is not possible to achieve for comparison, but advances in DNA technology may in the future allow us to compare our two animal populations with much greater accuracy.
While Kooikers’ population bottleneck happened far more recently than that of the cheetah’s, we see similar outcomes. The few cheetahs that remained after their near-extinction were so closely related that the species has been experiencing problems related to this lack of genetic diversity since. Most famously, cheetahs were found to be so closely related that individuals can accept skin grafts from each other without their immune systems recognizing the foreign graft as coming from a separate individual: “The cheetah’s MHC, which mediates graft rejection in most species was so similar that their immune system failed to recognize ‘nonself,’ as if the cheetahs tested were immunological clones or identical twins.” (From O’Brien et al. “Conservation Genetics of the Cheetah: Lessons Learned and New Opportunities.”) Both cheetahs and Kooikers have abnormally widespread fertility problems, especially in males – although this may be because they are easier studied. Males with few, low quality sperm are less likely to leave any offspring at all, and any male offspring they have are also more likely to have similar subfertility. To add insult to injury, cheetahs experience very high cub mortality. Furthermore, their lack of genetic diversity offered them no protection when a captive population was exposed at a breeding facility in 1983 to a feline coronavirus (FeCV) which decimated the cats, infecting every individual housed there and ultimately causing a mortality rate of 60%. (O’Brien et al. 2017) Unfortunately, as all these issues contribute to further curtail the population of breeding individuals, they cause an “extinction vortex” from which there is minimal hope of escape.
“The lessons for conservation from the cheetahs’ experience were chilling and clear. When a threatened population drops to very small numbers and survives, it can lose its endowment of genetic diversity, which otherwise provides an innate protection against rare recessive genetic abnormalities as well as a hedge against deadly infectious agents. With the example of the cheetah, the conservation community began to pay attention to genetic loss in small threatened populations.”Conservation Genetics of the Cheetah: Lessons Learned and New Opportunities
Stephen J O’Brien, Warren E Johnson, Carlos A Driscoll, Pavel Dobrynin, Laurie Marker
Cheetahs are a tragic but perfect example for study by all those who steward and breed domestic animals of any kind, but it so happens that their population similarities allows Kooiker fanciers a window into a possible future. Our breed already struggles with fertility and autoimmune problems – should we not do everything in our power to avoid adding to these problems, so in a few years we are not also dealing with increased puppy deaths and deaths due to infectious disease? Many dog breeders will argue the merits of linebreeding to solidify “type” or any given aspect of phenotype or temperament, but – as all things in breeding – care must be taken to maintain the balance between these goals and the longer-term robustness of our breeding population. Cheetahs illustrate a version of the future when conscious efforts to maintain genetic diversity are abandoned, and we should be both honored and unsettled to witness the example set by these beautiful cats.
Thank you to the aforementioned researchers, authors, and judges whose work informed this blog post.
(Please note, my original intention was to include a section in this article comparing MHC haplotype studies, but I found I couldn’t adequately extrapolate and summarize the comparison data, so I chose for the first draft to leave it out entirely. If any readers would like to take a stab at writing this paragraph using cheetah data and the now-abandoned Finnish DLA haplotype studies, please shoot me an email!)