When populations get very small, serious problems can be set into motion that can spiral down into an extinction vortex. An important part of small population management is to keep populations out of the vortex. The spiral can be fast unless sound genetic management is implemented.

Currently most studbook keepers manage species using the SPARKS (Single Population And Record Keeping System) software program developed by ISIS (International Species Information System). For most managed species in captivity, SPARKS is an effective tool for ensuring that enough genetic diversity is retained for the long-term stability of a small population. SPARKS does many things; including the calculation of a genetic value (mean kinship value – MKV) for each individual animal and estimating the percentage of genetic diversity (heterozygosity) in a population. The problem with SPARKS however, is that you have to make assumptions and these assumptions can be wrong, for example; if a new bird of wild origin is entered into the studbook, SPARKS makes the assumption that this bird is unrelated to any existing birds in the managed population and therefore genetically important. For species abundant in nature and especially if they have a large range, this assumption is likely to be correct, however, if the bird is from a small population it may turn out to be closely related to some and possibly all individuals managed in the studbook. SPARKS also assumes that genetic information is shared equally from parent animals to their offspring, but in reality this is not usually the case. Unfortunately what can happen, is that offspring from a particular pair may inherit significantly more characteristics from one parent and therefore the genetic material from the other parent will not be as well represented in the managed population as SPARKS predicts it should be. This could result in the loss of important genetic material if the studbook manager follows protocol and makes a recommendation to stop breeding from both parent birds once they are considered to be well or over-represented.

As the studbook manager for the Spix’s macaw Cyanopsitta spixii I am faced with the very problems mentioned above, and the species is one of the best examples of one which should not be managed solely using SPARKS. There are currently 68 (29 males, 39 females) Spix’s macaws being managed in the international studbook. Of these 68 birds, 63 are descendents from one sibling pair of founder birds which were breeders back in the 70’s and 80’s. Of the remaining 5 birds, three have successfully bred with descendants of the above mentioned sibling pair and the remaining two unrepresented founders are unlikely to ever reproduce because one is physically handicapped whilst the other is almost certainly infertile. Genetically it does not get much worse then the Spix’s macaw! To emphasize just how serious a genetic bottleneck the Spix’s macaw is in, it is worth mentioning that even the two most distantly related birds in the studbook are genetically as similar as siblings when compared to most other species. We know this because thanks to Prof. Cristina Miyaki and her colleagues at the University of Sao Paulo, we have microsatellite DNA analysis of the whole adult Spix’s macaw population and all but a handful of the juveniles. What we also know is that there are many pairs/groups of birds which are genetically as similar as identical twins, including one group of six!

The chronic inbreeding of Spix’s macaws is the most likely cause of low reproductive success which we are experiencing in the breeding program. Fertility is approximately 20% whilst hatchability is little more then 10%. Approximately 25% of the embryo’s which do not hatch die early in development, 25% mid way through development and 50% late in development – typically during the draw-down phase. The embryo’s which die late in development usually have deformities, particularly of the head and beak. The good news though, is that if embryo’s get to the point where they are breathing air, survivability in the past five years has been 100%.

In 2008 and in response the predicament of the Spix’s macaw, I developed a new system for calculating the genetic value of individual birds, as well as for the population as a whole. I did this with using the microsatellite DNA provided to me from Prof. Miyaki. For an individuals genetic value I replaced mean kinship value with a genetic similarity value (GSV) by calculating the sum of an individual’s relatedness index value(r-index) to all other individuals in the population; the lower the GSV the more genetically important the bird is. The genetic value for the population as a whole (heterozygosity) is simply the sum of each individual’s GSV. Microsatellite DNA analysis is not the complete solution to managing small captive populations, but in conjunction with programs such as SPARKS, Population Management 2000 (PM 2000) and an accurate pedigree, it provides the best method currently available for minimizing or hopefully avoiding inbreeding depression. I strongly believe that all studbook managers should look closely at the system developed by Prof. Miyaki and myself to see if it can be of benefit to the species they are managing. Currently to the best of my knowledge only the Spix’s and Lear’s macaw are managed in this way but hopefully there are others out there working on similar methods of taking advantage of the advancements and increased affordability of genetic analysis. If anyone reading this is interested to learn more about it, please do not hesitate to contact me for more details.