Captive Breeding of Mauritius Pink Pigeon
Introduction
Biodiversity is much more in peril than it was half a century ago. Biodiversity is threatened so much by human population and its activities that tend to destroy and overexploit resources. The extent of the effect of human activity to the lives of other organisms is reflected in the reports of the World Conservation Union or the IUCN. They report that there are over 5000 species all over the world that are threatened to very low population numbers, even to the point of extinction, and it is highly possible that this number is a mere estimate.
Many of the species found in the IUCN Red List of Threatened Species are endemic meaning that if lost, the whole world loses them forever.
This paper is a report on the conservation efforts done to save the Mauritius Pink Pigeons from extinction. It will include information about the species, the conservation program and the limitations challenges that the program faces. A set of recommendations to answer the limitations and challenges will also be included by the author.
Conservation Status of the Mauritius Pink Pigeon
The Mauritius Pink Pigeon (Columba mayeri) is a member of the family Columbidae, the dove and pigeon family. This species is endemic to Mauritius and used to be widely distributed among its islands. Today, it is only found in Mascarene Island having been extinct from its neighboring islands. The Mauritius Pink Pigeon, which gets its name from the color of the feathers that cover its belly, wing tips and head, is known to feed on the flowers, leaves, fruits and seeds of the native vegetation on the island.
The pink pigeon species was once considered very rare and was put in the IUCN Red List as critically endangered as its estimated numbers in the wild were very low. In the 1950s, scientists estimated the number of individuals of the population found in the wild to be only 40-60, and it continued to dwindle to an alarming number of just 10-20 individuals in the 1970s. The dwindling populations of many species in the Mauritius are caused by threats that go beyond than just habitat fragmentation and destruction. For example, natural pressures such as frequent typhoons that threatened the number of the pigeons combined with the presence of invasive species like black rats and crab-eating macaques that feeding on the pigeons, raiding their nests and competing with them for fruits and food made it difficult for the birds to recover.
Sadly, the ecosystem cannot be fully restored anymore because of the extent of damages caused by such threats. Conservation biologists, therefore, only have to rely on certain strategies that will allow them to create the maximum effect on the survival and propagation of the threatened species.
The first program that aimed to save this species was started by Durell Wildlife Trust in 1977. The foundation decided that the species would be bred in captivity. Captive breeding is a strategy employed by conservation biologists to rehabilitate species that are threatened. This strategy is an ex situ (out of site) approach, wherein members of the population are taken from their native habitat and bred in another facility under supervision of a team of scientists, veterinarians and wildlife experts. The goal of captive breeding is to be able to produce fit and healthy individuals to sustainably grow the species population to be later released into the wild. Threatened species are captive bred following a consideration of various factors and conditions. Species that are critically endangered and are living in an environment where threats to their survival are difficult to be controlled are perfect candidates for captive breeding. Imbalanced predator activity, disease, unnatural competition and large scale damage brought about by human activity, among others, are examples of these threats.
Pink pigeons were first bred in captivity in the Jersey Zoo and at the Black River aviaries in Mauritius. Today, the efforts of the Durell Wildlife Trust have managed to lower the status of the pink pigeon species from critically endangered to endangered in 2000, and as of 2003, the number of living individuals was raised to 355.
Inasmuch as captive breeding has produced such good improvement on the state of the species, there are several considerations that many conservation biologists have seen regarding the said strategy. There are several limitations and problems that this method faces that if left unchecked could defeat the purpose of the conservation efforts through captive breeding.
Problems encountered by the captive breeding program
Several set-backs of captive breeding of species have been outlined over the years of observation and research on the facilities, system and the reintroduced species themselves. Several of the most common charted problems include concerns with high costs and efficiency of the facility to produce fit individuals for reintroduction into the wild.
Costs
Cost problems are considered intrinsic to any captive breeding program because the facility is quite difficult to maintain. The efforts to control factors in the facility that may be detrimental to the survival of the species while in captivity need significant amounts of money to be continued. Considerations for space and land area, maintenance costs like electricity, lighting, food, medical attention for the animals and staff compensation are some factors that can cause the rise in the cost of maintaining the facility.
These costs pushed several conservation programs to turn zoos into captive breeding facilities. The revenues gained by zoos in their operation can help answer the costs for maintaining the species. The problem, however, is the fact that most endangered species in need of conservation are not profitable in the sense that they lack the visual display quality that most zoo animals have. Another option chosen by programs is to put animals in the care of a private breeder. The problem encountered in this set-up is the fact that several conflicts in interest and ownership will ensue. The animal is compromised as the private breeder is most often unwilling to allow a special group of biologists to monitor the animal and lax in monitoring the genetic welfare of the animals.
Disease
Several studies have described how individuals of a species in a captive breeding facility and even free-living populations can be affected by pathogens. Captive-bred individuals risk obtaining exotic diseases from being captive bred and transmitting them to other individuals in the wild when they are finally reintroduced. Wild populations possess no immunological mechanism to overcome a new disease, and the species risk dying out because of this threat. One such case involves Hawaiian endemic bird species wherein their numbers declined significantly and some were totally lost because of avian malaria.
In the case of the pink pigeon, one specific pathogen that limits its recovery is Trichomonas gallinae. The source of this pathogen is unknown, as this particular bacterial strain is only observed in wild populations of the birds and the individuals bred in captivity did not exhibit any signs of the disease prior to reintroduction. Other birds of the islands of Mauritius were also found to carry this pathogen and could be the source of this pathogen.
Genetic problems
The fact that individuals of the species are isolated in a captive breeding facility presents several implications in their genetic fitness and this is a potential threat to the species recovery. Inbreeding is the mating of two very closely related individuals allows the appearance of recessive characteristics that have the potential to reduce the genetic fitness of the offspring. If this occurs for numerous generations, a decreased genetic fitness of the whole population is observed, an effect called inbreeding depression. This effect is not only observed in captive bred birds, but more so in wild populations. The very small population size of the birds in the wild leaves individuals with little mate choice, which leads to inbreeding. Inbreeding compromises the survival of individuals because detrimental characteristics are fixed in the gene pool of the species if this effect is allowed to continue. Another factor that could compromise the species recovery is the fact that inbred individuals displayed a decrease in their reproductive capabilities and fertility.
Behavioral deviance
Captive bred individuals could have decreased survivorship in the wild because of certain problems that center on changes in behavior of the animal. A study conducted by McPhee (2003) highlighted the changes in the behaviors of captive bred animals in relation to the presence of a predator. The study shows that the longer an individual is held under captivity, the higher its tendency to not hide from a predator. With protection-seeking behavior dramatically reduced among captive bred individuals their potential to survive in the wild is also significantly decreased.
Proposed Solutions
The problems highlighted in the studies discussed in the previous section were reasons that moved scientists to question the effectivity and the actual benefit of captive breeding programs in saving endangered species from extinction. In this section, the author will present his recommendations based on these studies that would hopefully solve and reduce the risks that these problems pose on the species.
Very important prerequisites in captive breeding
Some of the problems have even caused biologists to recommend that captive breeding should be the last resort, and is not supposed to be viewed as a long-term solution for the problem.
Captive breeding requires a specific set of knowledge about the species that is to be saved. Lack in knowledge has lead to the failure and aggravation of the state of many species that are endangered. Therefore, it is important that before a species is decided to be taken in for captive breeding, an excellent base of the causes of its dwindling number, characteristics, life cycle, feeding patterns and other ecological considerations like their niche and relationships exists. It is very risky for bold moves to be done on the species as they might be lost forever because of hasty decisions.
Potential facilities must be carefully considered and designed so as to create the best possible environment for the rehabilitation of the species. It is important that the needed technology and equipment are available in the facility. Furthermore, those that will work with the animals need to be trained and experienced when it comes to working with such species. Their knowledge of and care for the species are some of the key concepts that will determine the effectivity of the program as a whole.
Lastly, it is also important that the program be continuously updated and improved through research. There might be new considerations that were not present in the early years of the program which might be detrimental to the species. Constant investigation, monitoring and observation will lead to new knowledge that will ultimately benefit the program.
Cost reduction
It is natural for such a program to incur high costs therefore, the problems of cost will always be present. Expenses that involve transportation, food, medical attention and expert fees are the most common factors that heighten the costs. It is important for such programs to get a sure source of funding that will continue to support the program to ensure its success but it is important to put the welfare of the animals first in considering such offers. Terms and conditions of a deal should be sealed under the condition that the survivorship of the animals and integrity of the program is not compromised. Therefore, species can be allowed to be captive bred in zoos and in private breeders facilities provided that should be regularly monitored by a team of experts and should be protected from behavioral and genetic aberrations that the species might incur in such facilities.
To further reduce the costs of protecting these species via captive breeding, it is highly encouraged that a captive breeding facility be built in an area very near the native habitat of the species. This allows the facility to reduce the cost of transportation and food as the proximity of the native habitat allows the breeders to procure food naturally occurring in the area. In the case of the pink pigeons, aviaries owned by the Mauritian government provide such a convenience to the breeders.
Controlling Disease
Isolated and small populations have the most tendencies to die out due to an outbreak. Immunologically nave populations will die out even before genetic adaptations occur that can save the species from extinction. This risk is heightened if captive bred individuals are exposed to a pathogen from the outside, get infected and are released in the wild.
Therefore measures to know the epidemiology and control measures of the disease is very essential to control disease from further jeopardizing the survival and recovery of endangered species. In pink pigeons, regular and routine testing of individuals living both in captivity and in the wild for the highly pathogenic T. gallinae have been performed in the effort to understand the dynamics of the disease and how to prevent it from spreading. A method that can be employed is by monitoring the deaths and their causes that occur in both the wild and captive bred population. The risk of bringing an infected individual in a captive breeding facility or releasing an infected individual in the wild could be prevented by first testing for the presence of a potential pathogen before further action is performed. Sophisticated techniques that include DNA-based pathogen presence kits can hasten the process.
Avoiding genetic anomalies
Genetic anomalies due to a small founder population produce deleterious effects on the species overtime. Genetic aberrations that exist in recessive alleles will appear in greater frequency causing serious set-backs on the goals of the conservation methods. The best way to avoid such genetic aberrations to occur within populations is to perform genetic testing and examinations to the individuals of the population.
This recommendation would require the cooperation of molecular biologists, conservation biologists and the breeders in the facility. Education and training of staff members in this respect is emphasized with utmost importance.
Genetic analysis would reveal which individuals are fit to be mated and which are not because of relatedness. These tests, if performed correctly would allow the breeders to gauge which individuals would produce the best offspring that are fit for release into the wild. Several measures to control breeding like separating males and females during mating season and monitoring can be performed to prevent captive bred birds from randomly mating with each other.
Correcting behavior
Captive bred individuals receive more human contact compared to their wild counterparts. This produces both positive and negative effects with regards to the welfare of the birds in the facility.
Captive breeding requires utmost human guidance and attention for it to be successful but set-backs observed in the reintroduced individuals behaviors in the wild is a negative effect of frequent human exposure. The individuals get used in such a sheltered and protected environment that they tend to lose their natural instincts and behaviors developed in the wild.
It is important, therefore, to make sure that the facility holding the animals would mimic their natural surroundings as much as possible. Setting up the facility quite near their native surroundings lessens the risk of them being too acclimatized to a foreign surrounding. Minimizing human contact is very necessary. Scientists and staff members working with the birds should not expose themselves too much to the animals, most especially juvenile ones. It is also possible that exposing the animals to training sessions that involve a pseudo-predator (like a rat) could help them develop protective behaviors.
Conclusion
The program to save the Mauritius Pink Pigeon from extinction have adapted captive breeding as its strategy for conservation due to various considerations and so far it has achieved to remove the bird from the IUCNs critically endangered list. The program is still ongoing, and over the years problems and limitations that involve costs and concerns about factors that affect the welfare of the animal have emerged that could potentially jeopardize conservation efforts.
To address these problems, a wide knowledge base about the animal, continuous support, and monitoring are essential. Constant research and improvements in the methods that are utilized to take care of the animals must be done. In captive breeding programs, the welfare and the high survivorship of the animals must come first.
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