During evolution it is natural for some sub-species to reach a point where they become extinct. However, the extinction of more animals is becoming more prevalent due to human interactions such as habitat destruction, over-hunting of species, along with other activities that infringe upon an animal’s natural environment. A species is termed endangered when its survival in the wild is unlikely if causal factors of extinction continue to operate (Comizzoli et. al. 2000). Currently, there are approximately 67,000 species on the “Red List” of endangered species, the most heavily effected being fish and birds (Fryer,2018). Deaths that occur when endangered animals are in captivity are extremely concerning, especially when it occurs before they have contributed genetic material to the population.
The goal of many conservationists includes preservation of the habitat, increasing the population numbers of individual species in captivity and in natural environments. In recent years, there have been an increase in technological advancements in the field of biotechnology and reproduction, such as biobanking, cloning, and collective assisted reproductive techniques in an attempt to slow or reverse the number of species being lost annually. A major obstacle of reproductive conservation is the lack of information about the physiology, anatomical and behavioral factors that could influence the practicality of specific technology. Each technology has both advantages and disadvantage that prevent the wide scale use for increasing populations. A major advantage includes a decrease in generation wait-time, while a major disadvantage is the variability in success.
Biobanking is a collective term used to describe any long- or short-term storage facility of genetic material. Semen banks are used to systematically cryopreserve and store semen samples from endangered species to assist in maintaining genetic variability. Inbreeding depression is the mating of closely related animals, and control of this is necessary for the prevention of rare and problematic alleles from resurfacing. The benefits of having frozen sperm samples allows the wait time between generations to decrease, and it also protects males from the dangers of traveling from their natural habitat along with the added benefit of maintaining diversity as frozen spermatozoa. Prior to the freezing of the sperm samples, separation of X and Y spermatids is an advantageous step. This will allow researchers to control the male to female birth ratio. Increasing the number of females born per year can accelerate re-population time in endangered species. While this technology has had many successful preserved samples, unfortunately species such as the Siberian tiger, Arabian leopards and others have only been initiated.
The reasoning behind the lack of success in endangered species is due to the variability in cryopreservation procedures that have not been perfected. Similar to sperm banks, the act of applying cryopreservation techniques to endangered wildlife oocytes is more difficult than expected due to the uniqueness of the embryos of various species. Vitrification is the process of ultra-rapid freezing that could be an alternative to traditional freezing methods. Although more research would need to be conducted to determine oocyte and embryo functionality throughout the process for individual species.
Cloning, also known as nuclear transfer, has been a valuable reproductive technique since the late nineteenth century. As a technique, cloning involves the oocyte of a non-endangered species being injected with genetic material of the species of interest then cultivated into an embryo for placement into a recipient. This process creates an exact genetic match of the endangered species. This technique may allow the recovery of genetic material without dilution of DNA that occurs when hybrid animals are produced, and assist with breeding captive animals until releasement back into their natural habitat. The most notable concern is two-fold, the current success rate for nuclear transfer is less than 5% that results in a live birth, and the second concern is the presence of abnormal phenotypes and genotypes.
The increase in certain abnormal traits could hinder rather than support conservational efforts to eventually reintroduce captive endangered species back into the wild. As previously stated, the most endangered species have the least amount of information regarding any and all reproductive aspects. The lack of information prevents the establishment of reliable protocols for oocyte retrieval, embryo maturation and development for cloning application. It is possible that with further research a repeatable procedure for obtaining suitable oocytes could be determined. The next step in the reproductive process would be determining the viability, functionality and genetics of potential offspring.
In an ideal world, re-population and conservation of endangered species would include management between habitat sustainability, efficient reproductive programs and educational information about the importance of all species for proper maintenance of ecosystems. To incorporate any, if not all of these technologies, more research should be conducted on a species-specific basis.
The idea that all species genetic diversity can be preserved, should be reevaluated to allow more possible solutions for this crisis. The desire to establish captive populations and introducing variable DNA as needed to maintain diversity could play a major role in protecting the health and adaptability of whole populations long term.