The Contribution of the Captive Breeding in Mexican Grey Wolf ( Canis lupus baileyi ) and Red Wolf ( Canis rufus )

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Rates of hybridization and introgression are increasing dramatically worldwide because of translocations of organisms and habitat modifications by humans. Hybridization has contributed to the extinction of many species through direct and indirect means. However, recent studies have found that natural hybridization has played an important role in the evolution of many plant and animal taxa. Determining whether hybridization is natural or anthropogenic is crucial for conservation, but is often difficult to achieve. Controversy has surrounded the setting of appropriate conservation policies to deal with hybridization and introgression. Any policy that deals with hybrids must be flexible and must recognize that nearly every situation involving hybridization is different enough that general rules are not likely to be effective. We provide a categorization of hybridization to help guide management decisions
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This study was initiated to determine the relationship between canine ovarian steroids detected in serum and feces during the periovulatory interval in domestic dogs, and to examine the feasibility of a non-invasive method to estimate the time of ovulation in canid species. When bitches (n = 14) were observed to enter proestrus (based on vulvar enlargement or serosanguineous vaginal discharge), paired daily serum and fecal samples were collected for a 15- to 20-day period and stored at -20 degrees C. After extraction, progestin concentrations in both substrates were measured using an established enzyme immunoassay procedure. All samples were aligned to Day 0, the first day in which fecal progestins reached a sustained rise above 100 ng/g feces. Mean fecal progestin concentrations increased in parallel with mean serum progesterone values (r = 0.78), rising from 44.6+/-2.6 ng/g feces to 409.6+/-90.9 ng/g feces, and 5.4+/-0.9 nmol/L to 81.2+/-18.5 nmol/L, on Day -5 and Day 5, respectively. Individual fecal progestin concentrations varied markedly, but plotted against serum progesterone concentrations demonstrated correlation coefficients ranging from 0.41 to 0.97 (P<0.05). These results demonstrate that sequential changes in domestic dog serum ovarian steroid concentrations are paralleled in the feces, and that it is feasible to non-invasively monitor individual progestin changes in the periovulatory interval using fecal hormone analysis.
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Stopping further global losses of amphibian populations and species requires an unprecedented conservation response.
"WOLFERS" IN NORTHEASTERN North Carolina were busy on February 5, 1768. Records from the Tyrrell County courthouse read: “Giles Long and Thomas Wllkinson awarded one pound for a certified wolf scalp; Jeremiah Norman awarded two pounds for certified wolf and wild-cat scalps; Davenport Smithwick awarded one pound for a certified wolf-scalp. Such was the nature of the war on the wolf: people killed them for money. The belief of the time held that the war was necessary because it was humankind's manifest destiny to tame the wilderness. And for the wilderness to be tame, the wolf had to be exterminated. The wolf was resourceful and hardy, but the wolfers persisted with increasingly sophisticated methods of killing. The war lasted 200 years, and the wolf lost.”
Reproduction can serve as a barometer of animal well-being. Whenever a group of animals stops reproducing, researchers begin to examine various aspects of their well-being. Do they have sufficient food? Are they too crowded? Is housing adequate? Are the animals being stressed? Scientists feel justified in making this correlation between well-being and successful reproduction, because reproduction is one of the most basic drives for all animals. When an animal fails to reproduce, not only is its genetic potential lost, but survival of an entire group may be jeopardized. To prevent such a consequence, an animal will make considerable physiological sacrifices to ensure reproductive success; only the most severe threats to its well-being will prevent the animal from reproducing.
Inbreeding depression is expected to affect populations of outbreeding mammals in inverse propor- tion to their population size and can affect whether small populations persist or go extinct. We used studbook records to examine the effect of inbreeding upon juvenile viability and litter size in two endangered species that have recently been reintroduced to the wild: the Mexican wolf ( Canis lupus baileyi ) and the red wolf ( C. rufus ). We found that neither juvenile viability nor litter size was lowered by inbreeding in either taxon. In fact, both captive breeding programs appear to have less lethal equivalents than the median estimate for mammals. We did find that year of birth was correlated with increasing viability in both taxa. We conclude that there is no evidence that inbreeding depression will prove a major obstacle to the success of either recovery effort.
The Mexican gray wolf appears to be extinct in the wild and exists now only in captivity. There are three captive putative Mexican wolf lineages: Certified, Ghost Ranch, and Aragón lineages. From pedigree analysis, the Certified lineage has the lowest level of inbreeding and has retained the most founder alleles. In contrast, the Ghost Ranch has a high level of inbreeding and fewest founder alleles. From molecular genetics data, particularly from microsatellite loci, it appears that all of the lineages consist of Mexican wolves, and none of them appear to have ancestry from dogs or coyotes. Further, the molecular data are consistent with the Certified lineage having three founders instead of the four previously assumed. From these findings, we recommend that the three lineages be combined to increase the number of founders and to postpone any inbreeding depression. The combination of pedigree analysis and molecular genetic data allowed us to resolve several long-standing concerns in Mexican wolves. Zoo Biol 16:47–69, 1997. © 1997 Wiley-Liss, Inc.
Reproductive steroid profiles in female (n=13) and male (n=5) red wolves (Canis rufus) were characterized in fecal samples collected during the breeding season (December—May) and over a 1 year period, respectively. Blood samples from females (n=12) also were collected during the periovulatory period for luteinizing hormone (LH) and steroid analysis. High performance liquid chromatography (HPLC) of fecal extracts determined that estradiol and estrone constituted the major and minor forms, respectively, of fecal estrogen metabolites. Although native progesterone was present, pregnane metabolites predominated as the major forms of fecal progestins. HPLC analysis of fecal extracts from males revealed no native testosterone, but rather the predominance of more polar androgen metabolites. Based on hormone profiles and/or pup production, females were classified as pregnant (n=3), ovulatory-nonpregnant (n=9), or acyclic (n=3). Longitudinal monitoring of females indicated no pregnancy-specific differences in concentrations of either fecal progestagen or estrogen metabolites compared to ovulatory-nonpregnant individuals; however, baseline progestagen concentrations were consistently elevated in acyclic females. There was good correspondence between serum and fecal steroid concentration during the periovulatory period. A rise in serum estrogens preceded the ovulatory LH surge which was then followed by a significant progesterone rise during the luteal phase. In males, changes in fecal androgen metabolite concentrations coincided with photoperiod fluctuations, increasing in late autumn and reaching peak concentrations during mid- to late winter just before the start of the breeding season. Collectively, these results serve as a database of ovarian and testicular endocrine events in this species, which can be utilized in population management and application of assisted reproductive technologies. Zoo Biol 21:321–335, 2002. © 2002 Wiley-Liss, Inc.
The importance of captive breeding has evolved as zoos themselves have evolved. Beyond allowing captive populations to be self-sustaining, zoos can contribute to species recovery and reintroduction by improving reproductive rates and developing monitoring techniques that provide data critical to understanding reproductive processes. Several threatened canid species have recently been saved through captive-breeding efforts in partnership with reintroduction programmes. Two of those, the Mexican grey wolf Canis lupus baileyi and the Island fox Urocyon littoralis, provide case studies. For both species, data generated during monitoring revealed important basic features of their biology and also provided critical information to managers that could be used to enhance reproductive rates. Both species are also part of reintroduction programmes that exemplify successful partnerships between the United States Fish and Wildlife Service and North American zoos.
Uncertainty currently exists regarding the extent to which mammalian carnivores suffer from inbreeding depression. In particular, it has been proposed that wolves and species with a similar social structure are adapted to close inbreeding. Empirical data, however, are scarce. This paper provides strong evidence against the contention that natural populations of wolves are resistant to inbreeding depression. We analyzed studbook data of a captive wolf population bred in Scandinavian zoos and found negative effects of inbreeding expressed as reductions in juvenile weight, reproduction, and longevity. The occurrence of an apparently bereditary form of blindness is also associated with inbreeding. Different effects of inbreeding can be attributed to genes originating from different founder pairs, thus indicating that alleles that are deleterious in the homozygous state are fairly common in natural wolf populations.
During the past two decades, pedigree analysis has documented inbreeding depression in many captive populations. This and subsequent research has led to a recognition that inbreeding depression is a potentially important determinate of small population fitness, in both captivity and the wild. Modern captive-breeding programmes now universally avoid inbreeding. We use simulation to investigate how much traditional pedigree analysis will reveal about the effect of inbreeding in such populations. We find that pedigrees typical of breeding programmes designed to avoid inbreeding have low statistical power to detect inbreeding depression.
The ultimate goal of the Mexican gray wolf Canis lupus baileyi captive management program is reintroduction of healthy individuals into wild habitats. To this end, zoo population managers work to provide not only for the physical well-being but also for the genetic health of these animals. However, the very limited genetic founder base, exacerbated by breeding within three distinct lineages, resulted in very high coefficients of inbreeding. Because support for measurable levels of inbreeding depression in the captive wolf population, as defined by reductions in common fitness measures such as juvenile survival or reproductive success, has been weak, we investigated the potential effects on male reproductive capacity. We analyzed semen samples from wolves from all three lineages and compared them with samples from subsequent lineage crosses and from generic gray wolves. We not only found a significant effect of inbreeding on sperm quality but we related both inbreeding and sperm quality to reproductive success. Samples from male offspring of lineage crosses, with inbreeding coefficients of zero were similar in quality to those from generic gray wolves. However, samples from a limited number of offspring from back-crosses were of extremely poor quality. Although it is reassuring that sperm quality was so much improved in male offspring of lineage crosses, the concomitant reduction in inbreeding coefficient does not eliminate the potentially deleterious alleles. Our results demonstrate that sperm quality is an important indicator of fertility and reproductive success in Mexican wolves. In addition, our data lend further support to the presence of inbreeding depression in this taxon.
The Mexican wolf (Canis lupus baileyi), an endangered subspecies of gray wolf, was native to parts of Mexico and the southwestern United States. Currently, only a few individuals, if any, exist in the wild, so planned reintroduction programs must use captive-raised wolves. In only one captive population, however, designated the certified lineage, are all the founders (n = 4) known to be obtained from a wild population of Mexican wolves. Two captive populations were founded from individuals of uncertain ancestry and have not been included in the species survival plan. To preserve genetic diversity and reduce inbreeding so that fitness will be maintained, it would be desirable to include these two captive populations in the breeding program if it could be shown that they were derived from a wild population similar to the certified lineage. We compared allele frequencies of 10 hypervariable microsatellite loci in Mexican gray wolves with those found in a sample of 42 domestic dogs, 151 northern gray wolves, and 142 coyotes to determine if uncertified Mexican wolves had specific markers from these animals. We analyzed pairwise genetic distance measures to demonstrate that the three captive populations of Mexican gray wolves were closely related to each other and distinct from dogs and northern gray wolves. The three captive populations are genetically more similar to each other than to any other population of dog or wolf-like canid, and they shared alleles that were rare in other canids. The genetic distance between them is similar to that between closely spaced populations of northern gray wolves. As a group, moreover, they are the most genetically distinct population of North American gray wolf. Therefore, the three captive populations could potentially be interbred to augment the genetic diversity of the certified lineage. Source individuals for reintroduction should be derived from the captive Mexican wolf population rather than populations of captive or wild northern gray wolves. El lobo Mexicano (Canis lupus baileyi) nativo de algunas partes de México y el suroeste de los Estados Unidos, es una subespecie del lobo gris que se encuentra en peligro de extinción. En la actualidad solo unos cuantos organismos (y posiblemente ninguno) viven en estado salvaje, de tal forma que los programas de reintroducción tienen que hacerse con lobos mantenidos en cautiverio. Sin embargo, en una sola población cautiva de linaje certificado se encuentran todos los organismos fundadores (n = 4) conocidos por haber sido obtenidos de una población silvestre de lobos mexicanos. Dos poblaciones cautivas fueron fundadas con individuos de incierta procedencia y no han sido incluidas en el plan de supervivencia de especies. Para preservar la diversidad genética y reducir la consanguinidad de tal forma que la buena condición de la población se mantenga, sería deseable incluir estas dos poblaciones cautivas en el programa de reproducción siempre y cuando se demuestre que los organismos provienen de una población silvestre similar a la línea certificada. Con la finalidad de determinar si los lobos mexicanos sin certificar presentaban marcadores específicos comparamos las frecuencias alélicas de 10 loci microsatélites hipervariables en lobos grises mexicanos con aquellos obtenidos de una muestra de 42 perros domésticos, 151 lobos grises del norte y 142 coyotes. Se empleó el análisis de comparaciones pareadas de las medidas cde distancia genética, para demostrar que las tres poblaciones cautivas de lobos mexicanos se encuentran estrechamente relacionadas entre sí y distanciadas de cualquier otra población de perros o cánidos relacionados con lobos, así como para demostrar que comparten alelos raros en otros cánidos. La distancia genética entre ellos es similar a las encontradas para poblaciones cercanas de lobo gris del norte. Como grupo, estos animales además conforman la población de lobos grises genéticamente más distintiva de norteamérica. Por lo tanto, las tres poblaciones cautivas pueden ser potencialmente apareadas entre sí para aumentar la diversidad genética del linaje certificado. Los individuos empleados para la reintroducción deberán provenir de las poblaciones cautivas de lobos mexicanos, en lugar de aquellas cautivas o silvetres de lobos grises del norte.
This essay explains the role of reproductive science, including what are termed reproductive technologies (i.e. artificial insemination, in vitro fertilization, embryo transfer, cloning), in conservation biology. Reproductive techniques (high- and low-tech) find their greatest application in understanding species uniqueness, adaptations and physiological mechanisms, not in the large-scale assisted breeding and the production of offspring. Models of how to use these tools to study reproductive fitness are emerging to help insure gene diversity and even propagate endangered species, but only after fundamental databases have been developed. Examples are provided of how non-invasive hormone metabolite monitoring, artificial insemination and genome resource banking are being used ex situ and in situ to understand wildlife biology. We predict that as the fundamental, multi-species database grows, so will the applied benefits for: (1) developing genome banks for insuring extant genetic diversity; (2) assessing the relationship of physiology, behaviour and environmental perturbations; (3) managing small populations; and (4) dealing with dilemmas ranging from contraception to skewed sex ratios to animal welfare. Most progress will be made in using these tools in systematic studies to solve the mystery of how thousands of unstudied species reproduce. Carried out appropriately, financial costs will be consistent with any approach for generating sound scientific knowledge.
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Artificial insemination (AI) and semen freezing have become services available to dog owners worldwide, and the demand for services to freeze semen is increasing. In other canids such as the fox, the fur industry utilizes fresh or frozen semen to artificially inseminate vixens to produce pelts. Clearly, AI facilitates the use of a male to sire several females by diluting the ejaculate, increases breeding hygiene, and allows crossing between species with slightly different breeding seasons. The African wild dog (Lycaon pictus) is currently considered by the World Conservation Union (IUCN) as one of most endangered canids. In captive populations of African wild dogs, semen has been frozen with encouraging results, using a standard cryopreservation protocol for domestic dogs, but successful AI has not been reported. In wolves, there is one report regarding the live birth of an offspring after intravaginal AI of a deslorelin-induced estrous female. In 2005, three Mexican gray wolf females were artificially bred by intrauterine insemination with freshly collected semen from unrelated males, and all females whelped. Artificial insemination may be vaginal, intrauterine or intratubal, and the semen may be fresh, fresh and chilled (diluted), or frozen-thawed, and the source of semen may be epididymal or ejaculated. In the domestic dog, the results are good to excellent for AI with all three types of processed semen when the source is ejaculated semen, whereas epididymal sperm still yields poorer results. Species differences in female physiology, as well as differences in the cryotolerance of the sperm from various canid species, warrant further research and development.
Evidence scattered over the literatures of zoology, psychology, agricultural science, and medicine indicates that diverse stressors will interfere with pregnancy in its early stages. It is probable that the most sensitive period is around the point of intrauterine implantation of fertilized ova. Although there is some indication that conventional "stress" hormones of the pituitary-adrenal axis can inhibit implantation, this evidence is too weak and inconsistent to suggest that these hormones are primary mediators of early pregnancy disruptions. Increasingly, evidence indicates that the balance of ovarian steroids is most important for pregnancy maintenance. It is well known that minute amounts of exogenous estrogens can completely disrupt pregnancy, and some new evidence suggests that endogenous estrogens may be released from the adrenals and/or ovaries during psychological stress.
The systematic banking of genome resources using cryopreserved germ plasm offers the opportunity to further conservation strategies of endangered species by assisting in the effective genetic management of captive populations. Cryopreserved germ plasm will allow indefinite preservation of the presently available gene diversity represented in either captive or wild populations. If properly utilized, genome resource banks have the potential to decelerate the loss of gene and allelic diversity in captive populations through reintroducing "original" genetic material through time to counter genetic drift. However, in order for any genome resource bank to be effective, strategies need to be developed to identify genetically valuable individuals to bank which will represent optimal gene diversity of the specific population. Four selection strategies were evaluated to identify individual donors from four North American captive populations representing differently structured pedigrees. The strategies consisted of selecting: (1) all males in the population ("All Male Bank"); (2) only living founders and early generation descendents ("Founder Method Bank," FMB); (3) males remaining after culling to minimize mean kinship ("Culled Male Bank 1"); and (4) males remaining after culling to minimize mean kinship, with the males reduced to the number in the FMB ("Culled Male Bank 2"). The effectiveness of each strategy was based on the comparison of genetic variation metrics in each bank with the genetic variation in the present living managed population. Although maximal retention of allelic diversity was achieved by banking genes from all living animals, nearly optimal retention of allelic and gene diversity was obtained by utilizing the selection strategy based on minimizing mean kinships. As a consequence, properly designed and utilized, genome resource banks can become effective tools for preserving gene diversity in future generations of living populations.
Estradiol (E2), testosterone (T) and progesterone (P4) concentrations were determined by enzyme-immunoassay in aqueous extracts of fecal samples obtained during anestrus, proestrus, estrus and metestrus of 11 nonpregnant and 11 pregnant bitches. Fecal hormone concentrations (ng/g) changed in relation to stage of cycle. Mean fecal steroid concentrations in 22 anestrous bitches and 3 ovariectomized bitches were low and similar for E2 (53 +/- 5 and 27 +/- 2), T (60 +/- 7 and 36 +/- 6), and P4 (62 +/- 6 and 86 +/- 15). Within 0 to 3 d of the ovulatory LH surge fecal E2 reached peak concentrations (301 +/- 38). The T peaks (281 +/- 41) were coincident or 1 to 3 d later. Fecal P4 was then elevated for approximately 2 m.o. Between Days 26 and 45 after ovulation, mean fecal P4 concentrations were higher (P < 0.05) in pregnant (401 +/- 60) than in nonpregnant bitches (164 +/- 23) and peak fecal P4 concentrations in individual animals were higher (P < 0.01) in pregnant (812 +/- 121) than in nonpregnant bitches (425 +/- 97). In the same period mean concentrations of E2 (117 +/- 13 vs 61 +/- 5) and T (102 +/- 10 vs 70 +/- 6) were also higher (P < or = 0.05) in pregnant than in nonpregnant bitches. Serum E2, T and P4 concentration were positively correlated (P = 0.1) with concentration in fecal samples obtained one day after serum collection. Although serial fecal ovarian steroid concentrations demonstrate the time course of ovulatory cycles, the diagnostic value of individual fecal samples appears limited. The ratios of peak to basal values were approximately 6, 5 and 7 for E2, T and P4, respectively, and were considerably lower than ratios of 12 to 50 previously reported for serum or plasma concentrations. The results demonstrate that there are pregnancy-specific increases in P4, E2 and T production reflected in fecal concentrations. While such increases are reflected in fecal samples, they are generally not evident in serum or plasma concentrations because of increased hemodilution, metabolism and clearance in pregnant bitches. The physiological stimulus for these increases, presumably ovarian in origin, or the potential role of prolactin is not known.
The principal threat to the persistence of the endangered red wolf (Canis rufus) in the wild is hybridization with the coyote (Canis latrans). To facilitate idengification and removal of hybrids, assignment tests are developed which use genotype data to estimate identity as coyote, 1/4, 1/2, 3/4 or full red wolf. The tests use genotypes from the red wolves that founded the surviving population and the resulting pedigree, rather than a contemporary red wolf sample. The tests are evaluated by analysing both captive red wolves at 18 microsatellite loci, and data simulated under a highly parameterized, biologically reasonable model. The accuracy of assignment rates are generally high, with over 95% of known red wolves idengified correctly. There are, however, tradeoffs between ambiguous assignments and misassignments, and between misidengifying red wolves as hybrids and hybrids as red wolves. These result in a compromise between limiting introgression and avoiding demographic losses. The management priorities and level of introgression determine the combination of test and removal strategy that best balances these tradeoffs. Ultimately, we conclude that the use of the assignment tests has the capacity to arrest and reverse introgression. To our knowledge, the presented approach is novel in that it accounts for genetic drift when the genotypes under analysis are temporally separated from the reference populations to which they are being assigned. These methods may be valuable in cases where reference databases for small populations have aged substantially, pedigree information is available or data are generated from historical samples.
This review describes the use of modern reproductive biotechnologies or assisted reproductive techniques (ART) including artificial insemination, embryo transfer/sexing, in vitro fertilization, gamete/embryo micromanipulation, semen sexing, genome resource banking, and somatic cell nuclear transfer (cloning) in conservation programs for endangered mammalian species. Such biotechnologies allow more offspring to be obtained from selected parents to ensure genetic diversity and may reduce the interval between generations. However, the application of reproductive biotechnologies for endangered free-living mammals is rarer than for endangered domestic breeds. Progress in ART for non-domestic species will continue at a slow pace due to limited resources, but also because the management and conservation of endangered species is biologically quite complex. In practice, current reproductive biotechnologies are species-specific or inefficient for many endangered animals because of insufficient knowledge on basic reproduction like estrous cycle, seasonality, structural anatomy, gamete physiology and site for semen deposition or embryo transfer of non-domestic species.
Mexican and red wolves were both faced with extinction in the wild until captive populations were established more than two decades ago. These captive populations have been successfully managed genetically to minimize mean kinship and retain genetic variation. Descendants of these animals were subsequently used to start reintroduced populations, which now number about 40-50 Mexican wolves in Arizona and New Mexico and about 100 red wolves in North Carolina. The original captive Mexican wolf population was descended from three founders. Merging this lineage with two other captive lineages, each with two founders, has been successfully carried out in the captive population and is in progress in the reintroduced population. This effort has resulted in increased fitness of cross-lineage wolves, or genetic rescue, in both the captive and reintroduced populations. A number of coyote-red wolf hybrid litters were observed in the late 1990s in the reintroduced red wolf population. Intensive identification and management efforts appear to have resulted in the elimination of this threat. However, population reintroductions of both Mexican and red wolves appear to have reached numbers well below the generally recommended number for recovery and there is no current effort to re-establish other populations.
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