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The Persian Fallow Deer (Dama dama mesopotamica) is a rare ruminant mammal belonging to the family Cervidae. Its taxonomic status is disputed, with some maintaining it as a subspecies of the Fallow Deer, while other treat it as a separate species, Dama mesopotamica.

Description
Persian fallow deer are physically larger than Fallow Deer, their antlers bigger and less palmated. They are nearly extinct today, inhabiting only a small habitat in Khuzestan, southern Iran, two rather small protected areas in Mazandaran (northern Iran), an area of northern Israel and an island in Lake Urmia in north-western Iran and in some parts of Iraq. They were formerly found from Mesopotamia and Egypt to the Cyrenaica and Cyprus. Their preferred habitat is open woodland. They are bred in zoos and parks in Iran, Israel and Germany today. Since 1996 they have been gradually and successfully reintroduced from a breeding center in the Carmel, into the wild in northern Israel, and more than 650 of them now live in the Galilee, Mount Carmel areas and the Brook of Sorek. Due to the rarity of this species, little information exists on their behavior and social structure in the wild; therefore, most biological information comes from captive-bred or reintroduced deer, which may not present an accurate representation of the natural population.

Early History
Persian Fallow Deer were introduced to Cyprus in the pre-pottery Neolithic (Cypro-PPNB), if not earlier. They occurred in significant numbers at the aceramic Neolithic sites of Khirokitia, Kalavasos-Tenta, Cap Andreas Kastros, and Ais Yiorkis, and were important through the Cypriot Bronze Age. A Greek legend, related by Aelianus ca 200 AD, recounts how the deer of the Lebanon and Mount Carmel reached Cyprus by swimming the Mediterranean, the head of each animal placed on the back of the deer in front of it.

Deer from Epirus in Greece are said to have reached Corfu in the same manner. While Red Deer are known to cross open water in their seasonal migrations, for example on the Scottish islands, this behaviour is unknown in Fallow Deer.



History of Population Decline
Persian fallow deer were formerly found in Iran, Iraq, Israel, Jordan, Lebanon, Palestine, Syria, and eastern Turkey. By 1875, the range of the Persian fallow deer was restricted to southwestern and western Iran, having disappeared from the rest of its range. The species, thought to be extinct by the 1940s, was subsequently rediscovered as a population of approximately 25 individuals in the Khuzestan Province in Iran in 1956. Today, the only surviving indigenous populations are in the Des Lacs National Wildlife Refuge and Karkeh Wildlife Refuge in southwestern Iran.

Factors Leading to Endangerment
Habitat destruction of tamarisk, oak, and pistachio woodlands, in which the deer is found, have contributed to its population decline. Approximately 10% of their former range still exists for habitation in the present day. The Persian fallow deer is a grazing herbivore, with grass comprising 60% of its diet along with leaves and nuts. Since the Persian fallow deer is a primary consumer in its ecosystem, it is negatively affected by the destruction of the habitat that supports the primary producers on which it feeds. The decline of the Persian fallow deer’s habitat is also likely to have contributed to increased pressure from predators due to the loss of dense areas that can be used as a refuge from predators; this phenomenon has been noted in a similar deer species.

Natural predators of the Persian fallow deer include the Golden jackal, the Arabian wolf, the Caracal, the Striped hyena, and the Syrian brown bear ; however, the primary predation pressure on the Persian fallow deer is human poaching. Hunted for sport and for food since the early Neolithic era, the range of the deer was restricted from areas in northern Africa, eastern Europe, and western Asia to only including small regions of western Iran by 1875. The spread of firearms caused a further increase in deer poaching, dropping the population size to what was regarded as the deer’s extinction in the 1940’s.

Interspecific competition with domestic livestock, including cattle, has also further reduced the amount of food available to the deer. A study performed in Africa found that densities of the zebra, another herbivore with a diet similar to cattle and to the Persian fallow deer, increased by 46% on average when cattle were removed from a region, which indicates that cattle are strong competitors for food and may be able to exert competitive pressure on the Persian fallow deer.

Concerns of Population Decline
Due to these factors, the overall population of the Persian fallow deer lingered at approximately 250 individuals in 2005, and suffers from the effects of small population size, notably inbreeding. Genetic variation is a major concern in small populations because inbreeding can cause further loss of genetic variation, an effect known as inbreeding depression. For Persian fallow deer, there is little genetic variation for the entire species because all the animals that currently exist were bred from a relatively small surviving group that was found living in the wild; genetic studies have shown that the individuals alive today are similar in 95% of their genes.

History of Conservation
The first actions taken to help conserve the Persian fallow deer were the designation of the Dez Wildlife Refuge and Karkeh Wildlife Refuge around the site of this animal’s rediscovery by the Iranian Game and Fish Department. The reintroduction of Persian fallow deer is of religious importance to Israel because of the initiative by the Israel Nature and Parks Authority to restore Biblically-named mammals that had been lost. Due to the lack of ecological data available regarding the Persian fallow deer (see above), planning for the species’ reintroduction without this vital background information has proven difficult.



Capture and Captive Breeding
In 1957-1958, a wild pair of pureblood fawns were captured and brought to the Von Opel Zoo in Germany, where the wild female gave birth to its first pureblood captive female in 1960; however, the wild male partner did not survive long enough to produce a second fawn. From 1964 to 1967, the Iranian Game and Fish Department sent three expeditions to the Kareheh area near the rediscovery site, during which three males and three females were captured to initiate the species’ conservation at the Dasht-e-Naz and Kareheh Wildlife Refuges. Israel initiated a reintroduction program with three pureblood Persian fallow deer from the Von Opel Zoo in Germany and an additional four deer translocated from Dasht-e-Naz, which were taken to a breeding enclosure in the Carmel Hai-Bar Nature Reserve.

Reintroduction
Planning for the Persian fallow deer’s successful reintroduction has proven difficult because not much information regarding the species’ behavior and population dynamics is available. While it is hoped that as much as possible can be done to help ensure the success of the reintroduced population, most of the measures that could help the probability of success are costly. Because of the extensive financial investment involved in a fruitful reintroduction, many biologists believe the money could be better spent towards other conservation efforts.

There are a variety of factors that contribute to the success of reintroductions, several of which involve alleviating the concerns of small population size. For Persian fallow deer, some additional factors include fecundity and reproduction, survivorship, dispersal and movement patterns, population composition, and genetic variation within the population.

Population Composition
The Allee effect may lead to a higher extinction probability by causing a crash in the population if the population is subject to unstable fluctuations in size. Because the Allee effect can arise from variability in the numbers of males versus females, sex ratio plays an important role in extinction probability in the Persian fallow deer’s population. Having more females than males increases the chances of species survival due to the fact that one male can fertilize multiple females and thus fewer males are needed. However, having too many female deer may lead to more intense polygynous mating behaviors. Because males in a polygynous mating system are each responsible for fertilizing multiple females, the loss of a single reproducing male would reduce the reproductive output of several females in a given breeding season; in a comparable monogamous system, loss of a single male only impacts the reproductive capacity of one female. For this reason, the population growth rate of a polygynous system is subject to more fluctuations from year to year than in a monogamous system, and such variation in growth rate could lead to higher chances of extinction. Therefore, an optimal balance in sex ratio is an important component of the reintroduction of the Persian fallow deer.

The reintroduction process also depends on the availability of breeding sources, which are captive populations that are permitted to breed in a safe environment, and the number of animals that can be periodically removed from these sources for reintroduction. Because poor sex ratios and low proportions of breeding individuals are a major cause of extinction in very small populations, the size of each group removed should be large enough to maintain a low extinction probability but small enough to maintain the core breeding population. Monte Carlo Leslie matrix growth models were used to determine the maximum sustainable yield, the greatest number of individuals that can be removed from the breeding pool to maximize the reintroduced population’s size while allowing the breeding core to recover between each reintroduction event, and the projected population growth after reintroduction. The removal of 28% of female deer from the breeding source in the first year of reintroduction and then the removal of approximately 12 females during each subsequent year is sufficient to lower the extinction probability due to demographic stochasticity in each release to less than 1% over 100 years while maintaining a breeding source size of 250 deer.

Dispersal, Movement Patterns, and Home Range
Size of the home range can also impact the chances of extinction, since a species is more likely to go extinct when it’s habitat is smaller. While it is necessary for deer to disperse and establish themselves in a habitat, having a range that is too broad can also be detrimental because the population can become thinned out and more vulnerable to threats, such as fragmentation. Fragmentation, which can lead to lower genetic variation through inbreeding in small subpopulations, is of particular importance in the Persian fallow deer because their genetic variability is already low.

Persian fallow deer home range sizes vary based on gender and age. Older male deer are more territorial than younger males ; however, older females stay closer to the site (within an average of 0.9 kilometers) where they were reintroduced, while younger females migrate farther away (an average of 2.3 kilometers from release site). Because of these migration behaviors, introducing younger Persian fallow deer along with adults is critical to rebuilding the wild population so that they can expand the range of the population, thereby reducing overcrowding and intraspecific competition. Together, increased migration and dispersal and a larger home range size can contribute to higher chances of reintroduction success.

Anti-Predator Behavior
The behavioral balance between timidity and boldness in Persian fallow deer is vital in establishing a long-lasting species reintroduction. Timidity describes the anti-predator behavior exhibited in the deer that have been exposed to perceived threats from predators and have adopted a more careful and hesitant disposition when navigating their surroundings. Though the increased hesitance of deer raised in the wild often reduces dispersal rates, this timidity can have a positive effect on a Persian fallow deer’s ability to survive in the wild by limiting a deer's risk of being poached or preyed upon. Boldness refers to the risk-taking attitude shown by deer that are willing to capitalize on perceived opportunities and have a reduced concern for the consequences of such actions. The deer that are more daring generally manifest a greater degree of population dispersal in the wild. In Persian fallow deer reintroductions, securing a balance between these two factors can prove difficult, especially when information on population dynamics and individual and group behavior is limited.

The reintroduction of Persian fallow deer relies on individuals that have been raised in captivity that do not possess the timidity and anti-predator precautions that their wild counterparts exhibit. Direct human intervention in captive animals greatly reduces the difficulties and threats that would otherwise be present in the wild. This commonly results in a dulled wariness of potential predators and thus an increase in risk-taking behavior and dispersal rate. When comparing reintroduced deer from breeding facilities that were subjected to substantial human interaction and from facilities that had significantly less human interaction, deer that experienced less human interaction had an 80% higher survival rate than those exposed to more human interaction. Therefore, if Persian fallow deer populations are to later function in reintroduction programs, exposure to humans should be kept at a minimum to increase the deer’s probability of survival.

Multiple Release Sites
While the use of multiple release sites for reintroducing captive-bred deer into the wild could improve the outlook of reintroduction by reducing competition among the individuals of the reintroduced species, there are several risks associated with multiple sites of release. Some of these risks include the increased monetary cost of the reintroduction project, the reduced genetic diversity of the subpopulations, and the Allee effect (see previous), which involves a reduced proliferation rate in small populations. Data from the Persian fallow deer’s reintroduction, including the reproduction rates, survival rates, and movement patterns of released individuals, were used for simulations that compared whether the use of multiple release sites would have an effect on the survivorship and growth of a reintroduced population. The results of computer simulations comparing the use of one to nine release sites suggested that, while two sites were significantly better than one with regards to the survivorship of the reintroduced species, any additional sites did not greatly improve the outlook of the species. The optimal distance between release sites was determined to be approximately 11 kilometers, allowing the sites to be separated enough to reduce intraspecific competition immediately after release yet close enough to allow the subpopulations to merge once they had begun to proliferate.

Repeated Releases
Repeated releases in the same area have affected reintroduction success. The first group of Persian fallow deer released into the wild displayed a slow, gradual movement away from the release site over relatively short distances and the establishment of regular movement patterns and a home range within 8 to 10 months. Subsequent releases indicated an establishment of a home range in less than one month. Overall recruitment success after 3 years appears to be at least 30%. Moreover, with an exception of a small number of females killed by domestic dogs, the survival of the reintroduced deer was high, having an 85% survival rate after reintroduction. These results indicate that repeated releases from a single enclosure have no detrimental effects and actually may enhance the establishment of females released in later reintroduction events.

Time Since Release
Trends in survival rates of the reintroduced deer were compared to several different models predicting survival patterns of the reintroduced population: one model assumed constant survivorship, another assumed that survival would vary with age, a third predicted that survival would depend on an individual deer’s time since release, and the last combined the predictions that age and time since release would have an impact on survival. The reintroduced population’s survivorship best matched the model that accounted only for changes in survival based on the time since the release of the individuals in that population, which was statistically about three times more probable, on average, than the other models that were tested. There are several possible causes of this reduction in survivorship soon after an individual is released into the wild. Some of these causes include the stress induced by releasing captive individuals into the wild and the reduced success of inexperienced mothers attempting to raise their first young in an unfamiliar habitat. Because time since release into the wild has a significant impact on the survival of this species, this effect needs to be considered when planning for any further releases of captive Persian fallow deer.

Current Status
Currently, there are two populations of Persian fallow deer born native to the wild which are located in the Karkeh and Dez wildlife refuges in Iran; additionally, there are several reintroduced populations in Iran and Israel. As a result of conservation efforts thus far, the current world population of the Persian fallow deer is estimated to be approximately 365 individuals. Due to the most pressing concerns affecting the current populations of Persian fallow deer, future conservation efforts should focus on genetic studies, protecting the habitat of the deer, and releasing more deer into the reintroduction areas.