Research Report
The Contribution of the Captive Breeding in the Mexican Grey Wolf (Canis lupus baileyi) and Red Wolf (Canis rufus) 
Author Correspondence author
International Journal of Molecular Ecology and Conservation, 2011, Vol. 1, No. 1
Received: 14 Nov., 2011 Accepted: 17 Nov., 2011 Published: 29 Nov., 2011
The availability of captive breeding makes a big contribution to wildlife conservation. The zoos become a useful and scientific place for animal protection and conservation research. Moreover, some technologies, such as noninvasive endocrine monitoring, artificial insemination (AI) and semen cryopreservation are widely implemented during the captive breeding. Reintroduction programs have been established with effective managements and monitoring to ensure the wildlife survival rate, genetic purity and original biological traits. The Mexican grey wolf (Canis lupus baileyi) and Red Wolf (Canis lupus baileyi) are two successful examples of captive breeding in order to keep genetic diversity. This article has summarized these technologies which play an important role in Mexican grey wolf (Canis lupus baileyi) and Red Wolf (Canis rufus) conservation and may be influential in other species captive breeding.
Introduction
Captive breeding is considered as an efficient and effective way in keeping the genetic diversity and against the extirpation (Frankham, 2009). The availability of captive breeding is useful in many endangered species. The IUCN (http://cmsdata.iucn.org/downloads/1987_iucn_policy_statement captive_bre eding.pdf) suggests that the captive program can be established when the number of the wild species decrease below 1000. There are many common methods that scientists are expected to utilize.
The zoos are considered to be one of the ideal places to conservation research. The zoos are able to breed the wild animals which are thought to be countless (Asa, 2010). However, more and more animals greatly decrease and face eradication from the wild, the role of the zoos has been changed in the 1970s (Ginsberg, 1993). The zoos are not only catching animals from wild populations but also protecting the large collections and attending to the conservation and reproduction for the endangered species (Asa, 2010). The benefit is obvious when the zoos take part in conservation. First of all, in addition, when replacing the wild animals to zoos, it minimizes the disturbance of the wild population (Frankham, 2009). Secondly, the scientific and excellent management provide the best methods to keep the animal healthy and easier to get the genotype. Moreover, there is enough time to explore the suitable techniques for the captive population (Frankham, 2009).
Some useful techniques, such as noninvasive endocrine monitoring, artificial insemination (AI) and semen cryopreservation played an important role in endangered species conservation in the past two decades (Wildt et al., 1997; Wildt and Wemmer, 1999).
The cryopreservation of the sperm and gametes, which is as a reservoir for maintaining the genetic diversity, is available to reduce the inbreeding in the captive population (Johnston and Lacy, 1995). This method offers the genetic resources for further research and prepares for reproducing animals via cloning (Asa, 2010). It is important that the mature animals should be preserved in the captive population, so that the embryo or tissues can be taken from the adult female and the females is capable to be inseminated (Asa, 2010).
The artificial insemination is utilized to help the animals owns valuable genes which is unable to breed naturally (Frankham et al., 2009). This approach is able to preserve the ideal animals’ genetic contribution for the future captive breeding program (Frankham et al., 2009). In addition, the artificial insemination will enhance the offspring quality by inseminating female with recommended male frozen semen rather than the natural mates (Frankham et al., 2009). Artificial insemination will be able to enhance the natality and proliferation, controlling the reproductive rates will benefit to the captive population (Asa, 2010). It prevents the captive numbers out of suitable capacity and protects the genetic health so that the appropriate resources and care can be given to the species (Asa, 2010). Another one is reproductive monitoring. This approach probably contains pregnancy diagnosis, puberty detection, mating time and quality of parental care (Asa, 2010). The monitoring needs specific requirements for different species. However, all these biotechnologies require further and more extensive study, because this is not broadly available and requirements are specific (Wildt and Wemmer, 1999).
The canid species, gray wolf (Canis lupus) used to have a huge distribution through the North America (Hedrick and Fredrickson, 2008). Due to the anthropic activity, the Mexican wolves and gray wolves (Brown, 1983) were considered to be exterminated. In 1976, only few of the Mexican wolves left and were listed as “endangered” by in 1976 (USFWS, 1998). At the same time, the red wolf became extinction from original areas and was listed as endangered species as well (Hedrick and Fredrickson 2008). Both of these remaining wild wolves started the captive breeding at the same time due to the approaching extirpation (Hedrick et al., 1997; Phillips et al., 2003).
1 Mexican grey wolf (Canis lupus baileyi)
1.1 Captive breeding techniques
The captive breeding of Mexican wolf establishes a successful example of scientific captive population management. In the late 1970s, after listed as endangered animals, four males and one pregnant female have been caught, which has been known as the certified lineage (Hedrick et al., 1997). The greatly extinction of the Mexican gray wolf happened before its biological features and history to be known (USFWS, 1998).
1.2 Reintroduction program
The wolves which have been reintroduced were expected to prey proper items, proliferate and create social communities (Hedrick and Fredrickson, 2008). The survival ability and capability were still existing on the captive population after several decades and similar as the wild wolves (Hedrick and Fredrickson, 2008). Kalinowski et al (1999) used studbook records to test the puberty survival rate and little size of the reintroduction population in the wild and found that no evidences show that it experienced the inbreeding depression, although they are highly inbred.
2 Red wolf (Canis rufus)
2.1 Captive breeding techniques
About 400 wild remnant red wolves have been captured in 1973 to establish the captive breeding program to against extirpation of this species (Phillips et al., 2003). It is estimated that a huge proportion of the remaining wild red wolves were the descendants that coyotes were mating with red wolf-coyote, merely 43 of this population was expected to be the red wolves. Finally, 14 individuals have been chosen as the initial founders of captive breeding (Phillips et al., 2003). However, the issues about the genetic purity and specialness of this population have been argued (Roy et al., 1994). The 14 founders have been examined to obtain the biological information (Miller et al., 2003) and figured out the relationship with other canids species and the ancestors of these founders (Walker et al., 2002).
Under the Species Survival Plan (SSP) management, the red wolves have become one of the most successful captive breeding species (Waddell and Henry, 1996). By 2006, the number of the red wolves in captivity has been largely increased to 200 throughout the United States. There were at least 65 red wolves replacing to the free-range site (Waddell, 2001) and a minimum of 156 individuals in captivity (Waddell et al., 2001). The mean inbreeding coefficient was 0.063 (Hedrick and Fredrickson, 2008) and 12 of the original 14 founders was considered to have the descendants.
The SSP management successfully let the 12 founders approximately make the 1/12 contribution to the offspring, but still two of them contributed to 15% respectively and more two of them contributed 2% respectively. Kalinowski et al (1999) examined the juvenile viability and there was no serious inbreeding phenomenon in this population (Kalinowski and Hedrick, 1999). Until now, the initial founders were still under strictly management in order to save the available genetic value for the future (Walker et al., 2002).
The Artificial insemination that used the frozen sperm from wolves had little effect after a large number of attempts (Walker et al., 2002). One potential problem was that the blood collection for AI has the rigorously time limitation. Given that the pressure had a negative impact in successful reproduction (Moberg, 1985; Liptrap, 1993; de Cantanzaro and MacNiven, 1992), another advanced method noninvasive monitoring was required (Walker et al., 2002).
Walker et al (2002) have made a conclusion that the fecal steroid analysis was an available means of monitoring reproductive endocrine events of female red wolves. Compare to other carnid animals, the estradiol and estrone were the predominant estrogens thing in female ones (Walker et al., 2002). Due to the time for the hormone secretion and the time for the excretion are different, it was significant to know the time period when using fecal analyses to time AI (Walker et al., 2002). Gudermuth et al (1998) figured out that the domestic dog had 24 hours’ time lag in hormone release. Hay et al (2000) indicated that the relationship between serum and progestin concentration was stronger. Through some researches, we knew that the fecal steroid concentrations of red wolves display the steroid concentrations cycle before 12-24 hours and AI was supposed to be carried out 5-6 days when the fecal progestogen concentrations increased (Walker et al., 2002).
2.1 Reintroduction program
In 1987, the first captive red wolf was reintroduced into North Carolina where has not been occupied by the coyotes (Phillips et al., 2003). However, the coyotes started to inhabit these areas and hybridized with the red wolves (Phillips et al., 2003). Therefore, the hybridization becomes the most serious threat to the pure genetic red wolves in the wild (Allendorf et al., 2001; Miller et al., 2003). A research report implicated that the hybridization and introgression of coyote events have been observed among the reintroduction animals (L. Waits, personal communication).
Some effective management was established to protect the pure genetic red wolves (Hedrick and Fredrickson, 2008). For example, people removed the animals that are likely to mate with coyotes or used the sterilization (Hedrick and Fredrickson, 2008). Later, a statistical report explained that if this cannot be controlled, the coyote introgression will have a negative impact on the red wolves population (Hedrick and Fredrickson, 2008). In a word, the management played a determinative role in the low percentage of hybridization with coyotes.
3 Discussions
There is no denying that the captive breeding brings a large number of obvious successes. Under appropriate management, no inbreeding depression has been observed in the Mexican wolves and red wolves’ population (Kalinowski et al., 1999) and the genetic variation has been maintained properly. However, only three founders are ancestry of the Mexican wolf captive group (Hedrick and Fredrickson, 2008). The other lineages Aragón and Ghost Ranch crossed with the initiate founders have provided extra genetic resources and lowered the inbreeding phenomenon (Hedrick and Fredrickson, 2008). The descendants from the crossed lineages have grown up well and the recent study demonstrates that either the reproduction or survival rate is equal to other canid species or the genetic value increases or genetic rescue (Hedrick and Fredrickson, 2008).
The applications of AI with frozen semen not only reduce the inbreeding depression but also keep the genetic diversity for future captive program (Thomassen, 2009). The exchange genetic resources of the Mexican wolves between captive and wild are consider being successful. The time limitation of the semen collection is one of the determinant components (Thomassen, 2009). In addition, AI is expected to transport the animals to new places in order to keep the stress away from individuals and greatly reduce the high cost (Andrabi and Maxwell, 2007).
In a word, the primary benefit of captive breeding is to reduce mean kinship and inbreeding depression, and to maintain genetic diversity in the captive population (Ballou and Lacy, 1995).
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