Article

Effects of Inbreeding on Reproductive Success, Performance, Litter Size, and Survival in Captive Red Wolves (Canis rufus)

Authors:
  • Endangered Wolf Center
  • Point Defiance Zoo & Aquarium
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Abstract

Captive-breeding programs have been widely used in the conservation of imperiled species, but the effects of inbreeding, frequently expressed in traits related to fitness, are nearly unavoidable in small populations with few founders. Following its planned extirpation in the wild, the endangered red wolf (Canis rufus) was preserved in captivity with just 14 founders. In this study, we evaluated the captive red wolf population for relationships between inbreeding and reproductive performance and fitness. Over 30 years of managed breeding, the level of inbreeding in the captive population has increased, and litter size has declined. Inbreeding levels were lower in sire and dam wolves that reproduced than in those that did not reproduce. However, there was no difference in the inbreeding level of actual litters and predicted litters. Litter size was negatively affected by offspring and paternal levels of inbreeding, but the effect of inbreeding on offspring survival was restricted to a positive influence. There was no apparent relationship between inbreeding and method of rearing offspring. The observable effects of inbreeding in the captive red wolf population currently do not appear to be a limiting factor in the conservation of the red wolf population. Additional studies exploring the extent of the effects of inbreeding will be required as inbreeding levels increase in the captive population.

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... Instead of using a binary response of survival/death, the exact time to the occurrence of an event can be analysed through a statistical procedure known as survival analysis (Kleinbaum & Klein, 2005). In addition, survival analysis allows for the inclusion of data that are usually discarded, such as animal records that have been lost in the follow-up process of the studbook keeping (Boakes et al., 2007; Rabon Jr & Waddell, 2009). Likewise, random effects can be incorporated into the models, indicating animals that belong to the same litter. ...
... Neutral and even positive effects of inbreeding on survival during early life-history stages, although unexpected, are not uncommon (see Ralls et al., 1988; Rabon Jr & Waddell, 2009; Ibáñez, Moreno & Barbosa, 2013). Our results show that inbreeding has a negligible effect on survival in the early life stages, a result also found by Boakes et al. (2007) for the bush dog and other canid species. ...
... Some studies with captive wolves also found no inbreeding depression on survival using 180 or 365 days as the threshold age (e.g. Kalinowski et al., 1999; Rabon Jr & Waddell, 2009), but other studies that evaluated survival up to sexual maturity (Laikre & Ryman, 1991) and included effects other than the inbreeding coefficient (Fredrickson et al., 2007, wild animals) found evidence of inbreeding depression on the same wolf species. Ralls et al. (1988) pointed out that inbred mortality increases more rapidly than non-inbred mortality with increasing age. ...
Article
Studies evaluating inbreeding depression and purging in captive populations often focus on a single life-history stage, commonly juvenile survival, using it as a binomial response variable to model inbreeding effects. Through the use of a statistical procedure known as survival analysis, and focusing on four life stages, we examined the effects of inbreeding and other demographic and life-history variables on the survival of the bush dog Speothos venaticus captive population. Through generalized linear mixed models, we assessed the impact of these vari-ables upon litter sizes and proportional viability of pups within a litter. We found a negligible effect of inbreeding on survival in two viability periods up to weaning age. On the other two life stages, up to the age of sexual maturity, inbreeding assumed a negative effect on survival. Individual inbreeding led to decreased litter size, whereas maternal age negatively affected litter sizes and the proportional viability of pups within the litter. Partial purging could have removed some genetic load in this captive population; however, our results indicate that even in popu-lations maintained in benign conditions of captivity, deleterious effects of inbreed-ing are differentially expressed across life-history stages. Our results also underscore that investigating a single life-history stage could lead to erroneous conclusions about inbreeding and purging effects, misguiding management of captive populations.
... Under current conditions, gene diversity is expected to be maintained at or above 85% for at least 16 years (Waddell and Long 2013). However, inbreeding within the captive population has resulted in lower reproductive performance, smaller litter sizes, and reduced survivability of offspring (Rabon and Waddell 2010). Demographic projections to achieve the 5-year target population size (recently reduced to 200 individuals) require a 3% annual growth rate ( = 1.03), but current spatial limitations necessitate that the population maintain a 2% growth rate ( = 1.02) and approximately 26-35 births annually to offset the expected annual mortality rate (Waddell and Long 2013). ...
... As part of a larger study of traits that affect reproduction (e.g., Rabon and Waddell 2010), I examined longitudinal reproductive events of captive red wolves to determine whether parental age, reproductive experience (i.e., prior sexual experience and prior reproductive success), and parental rearing type were factors in the production of offspring. I also examined longitudinal reproductive events to test the relationships between the parental age and reproductive experience of adult males and females and the following measures of reproductive fitness: litter size; litter rearing type; sex ratio of the litter; viability of offspring. ...
... A previous study investigated changes in age structure in the captive red wolf population and how those changes affected the population's reproductive potential (Lockyear et al. 2009). However, the accuracy of the data set used in the previous study has been questioned (Rabon and Waddell 2010), and relatively few results of the effects of age on reproduction are similar between the two studies. For example, Lockyear et al. (2009) reported that reproductive success was negatively correlated only with female age. ...
Article
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Propagation programs contribute to the conservation of a species by preserving genetic and demographic stock that may be used to reinforce or re-establish wild populations. Identifying traits that affect reproductive success is essential to achieve this goal. Longitudinal reproductive events of the captive population of endangered red wolves (Canis rufus Audubon and Bachman, 1851) were investigated to determine whether parental age, breeding experience, and rearing type were factors in reproduction, litter size, and sex ratio, as well as viability of offspring. Younger wolves were more likely to reproduce and produce larger litters than were older individuals. The age of the female, but not the male, had a negative effect on pup survival. Wolves that had prior experience in offspring production were more likely to reproduce again than were individuals that had no prior reproductive success, but prior sexual experience alone was not a factor in offspring production. Parental breeding experience had a negative effect on pup survival, but no apparent relationships with litter size or sex ratio. Declines in reproduction, fitness, and survival with advancing age suggest the effect is due to senescence, the onset of which occurs at 8 years of age in females. The results are consistent with the breeding-experience hypothesis.
... Inbreeding Depression: Includes observed impacts on litter size, sex ratio and pup mortality for SSP and NENC In a small population with a limited founder base, mating between close relatives (inbreeding) is often unavoidable and can have potential negative impacts on population demographics and viability. Inbreeding effects were previously documented for the SSP population (Rabon and Waddell 2010), but were not detected for the NENC population (Brzeski et al. 2014). As part of this modeling effort, we re-analyzed SSP and NENC data for effects of inbreeding depression, and found statistically significant effects on offspring sex ratio, litter size, and pup mortality for both populations. ...
... Additional context on Inbreeding Analysis in comparison to other published studies: While previous analyses of red wolf inbreeding impacts have examined the SSP (Rabon and Waddell 2010) or the NENC (Brzeski et al. 2014) populations independently, no prior analyses have included both populations into a single synthethesized dataset. In addition to differences in the populations included, our treatment of the raw data differs from methods used by Rabon and Waddell (2010) and Brzeski et al. (2014). ...
... Additional context on Inbreeding Analysis in comparison to other published studies: While previous analyses of red wolf inbreeding impacts have examined the SSP (Rabon and Waddell 2010) or the NENC (Brzeski et al. 2014) populations independently, no prior analyses have included both populations into a single synthethesized dataset. In addition to differences in the populations included, our treatment of the raw data differs from methods used by Rabon and Waddell (2010) and Brzeski et al. (2014). For example, in Brzeski et al.'s analysis, they considered all "Lost to Follow-up" (LTF) animals as censored, where we treated individuals that were LTF for more than one year as dead, because they were effectively removed from the population, whether they were a "true" mortality or not. ...
... However, some metric traits like birth weight, disease conditions, life span, etc are indirectly associated with fitness and are therefore, affected by increased level of inbreeding. Close inbreeding leads to reduction in fitness (Sarre and Georges 2009, Keller and Waller 2002, Rabon and Waddell 2010. Moreover, genetic drift is another consequence of close relative mating (Sarre and Georges 2009). ...
... The association between total inbreeding coefficient in dams with mortality at days 7 (p <0.05), 30 (p <0.05) and 90 (0.10) was found to be statistically significant indicating that it would decrease the mortality risk of the litter (Quilicot 2009). Similar findings were observed with reduced litter size in wolf (Canis lupus) (Laikre 1999), Mexican wolf (Canis lupus baileyi) (Fredrickson et al. 2007) and red wolves (Canis rufus) (Lockyear et al. 2009, Rabon andWaddell 2010). The reduction of litter size in the captive tiger of Nandankanan Zoo is comparable with the brown bear (Laikre 1996). ...
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A study was carried out on the captive tigers of Nandankanan zoo, Odisha, India, to conclude any deleterious effect of inbreeding on mortality. A pedigree path analysis of 342 tigers was done to estimate the inbreeding coefficient of each tiger from the available pedigree information since the inception of zoological park in 1964. Percentage of animal with different range of inbreeding coefficient was classified based on their normal and white body coat colour. The correlation values between sex, colour and inbreeding coefficient with mortality were also estimated. The colour and inbreeding coefficient was found to be significantly (p<0.05) correlated with the mortality. The inbreeding was found to be significant (p<0.05) with white colour of tiger.
... Low genetic diversity, increased genetic drift, and inbreeding depression can be significant issues whenever low numbers of breeding animals are involved, such as captive breeding programs (Rabon and Waddell 2010) or some wild populations (Brzeski et al. 2014), which can result in reduced litter sizes (Lockyear et al. 2009;Rabon and Waddell 2010). In addition, the expansion of coyotes (Canis latrans) into the northeastern North Carolina experimental population area and the risk of hybridization represented another threat to red wolf restoration (Kelly et al. 1999;Stoskopf et al. 2005;Fredrickson and Hedrick 2006;Bohling and Waits 2015). ...
... Low genetic diversity, increased genetic drift, and inbreeding depression can be significant issues whenever low numbers of breeding animals are involved, such as captive breeding programs (Rabon and Waddell 2010) or some wild populations (Brzeski et al. 2014), which can result in reduced litter sizes (Lockyear et al. 2009;Rabon and Waddell 2010). In addition, the expansion of coyotes (Canis latrans) into the northeastern North Carolina experimental population area and the risk of hybridization represented another threat to red wolf restoration (Kelly et al. 1999;Stoskopf et al. 2005;Fredrickson and Hedrick 2006;Bohling and Waits 2015). ...
Article
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Cross-fostering offspring with nonbiological parents could prove useful to augment populations of endangered carnivores. We used cross-fostering to augment captive-born and wild-born litters for the endangered red wolf (Canis rufus). Between 1987 and 2016, 23 cross-fostering events occurred involving captive-born pups fostered into captive litters (n = 8 events) and captive-born pups fostered into wild recipient litters (n = 15 events). Percentage of pups surviving 3 and 12 months was 91.7% for captive-born pups fostered into captive recipient litters. For pups fostered into wild litters, percentage of pups surviving 5 months was > 94% among fostered pups (pups fostered into a wild red wolf litter or replaced a hybrid litter), pups in recipient litters (wild-born litters receiving fostered pups), and pups in control litters (wild-born litters not in a fostering event) when using pups with known fates. Including pups with unknown fates as deaths, percentage of pups surviving 5 months was > 54% among fostered pups, pups in recipient litters, and pups in control litters. Among wild litters, percentage of pups surviving 12 months was > 82% among fostered pups, pups in recipient litters, and pups in control litters when using pups with known fates. Including pups with unknown fates as deaths, percentage of pups surviving 12 months was > 48% among fostered pups, pups in recipient litters, and pups in control litters. Although survival to 12 months was similar among the groups, average life span was different with pups in control litters living 3.3 years, pups in recipient litters living 4.6 years, and fostered pups living 5.6 years. Of fostered pups surviving > 12 months in the wild, 9 animals whelped or sired 26 litters. Cross-fostering was successful at augmenting litter size for red wolves without any deleterious effects on recipient litters, illustrating fostering as a tool for increasing populations of endangered carnivores.
... Although heritable defects, such as progressive retinal atrophy, malocclusion, and undescended testicles, were observed in a small number of captive red wolves, early studies that examined juvenile survival and litter size reported no observable inbreeding depression in the red wolf captive program [18,86,87]. Subsequent studies found increased levels of inbreeding in the captive population were correlated with decreased litter size, but overall, inbreeding depression was minimal [19]. Rabon and Waddell [19] concluded that improvements in husbandry, veterinary care, and nutrition positively contribute to pup survival and offset the negative effects of inbreeding in the captive population. ...
... Subsequent studies found increased levels of inbreeding in the captive population were correlated with decreased litter size, but overall, inbreeding depression was minimal [19]. Rabon and Waddell [19] concluded that improvements in husbandry, veterinary care, and nutrition positively contribute to pup survival and offset the negative effects of inbreeding in the captive population. However, these services are not extended to red wolves in the wild and understanding the effects of inbreeding in the wild population requires further study. ...
Article
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Simple Summary Once widespread in the Eastern United States, early 20th century predator-control programs reduced red wolves to a remnant population by the 1970s. The U.S. Fish and Wildlife Service, through the Red Wolf Recovery Program, restored red wolves to northeastern North Carolina in 1987. After 25 years of restoration efforts, issues of hybridization with coyotes, inbreeding, and human-caused mortality continue to hamper red wolf recovery. To understand how these issues influence recovery efforts, we examine the history of red wolf restoration and its challenges. We then formulate areas of research that are of direct relevance to the restoration of red wolves. Abstract By the 1970s, government-supported eradication campaigns reduced red wolves to a remnant population of less than 100 individuals on the southern border of Texas and Louisiana. Restoration efforts in the region were deemed unpromising because of predator-control programs and hybridization with coyotes. The U.S. Fish and Wildlife Service (USFWS) removed the last remaining red wolves from the wild and placed them in a captive-breeding program. In 1980, the USFWS declared red wolves extinct in the wild. During 1987, the USFWS, through the Red Wolf Recovery Program, reintroduced red wolves into northeastern North Carolina. Although restoration efforts have established a population of approximately 70–80 red wolves in the wild, issues of hybridization with coyotes, inbreeding, and human-caused mortality continue to hamper red wolf recovery. We explore these three challenges and, within each challenge, we illustrate how research can be used to resolve problems associated with red wolf-coyote interactions, effects of inbreeding, and demographic responses to human-caused mortality. We hope this illustrates the utility of research to advance restoration of red wolves.
... In the captive red wolf population, increased levels of inbreeding are correlated with decreased litter size, but lethal equivalents are near zero suggesting minimal inbreeding depression has occurred relative to other inbred canids (Kalinowski et al. 1999;Rabon & Waddell 2010). Current management procedures include deliberately pairing captive red wolves to reduce inbreeding and maximize genetic diversity (Waddell & Long 2013), thus, the results of inbreeding depression studies from captive wolves may not reflect the potentially high levels of inbreeding found in the wild population where wolves are free to choose mates. ...
... We evaluated models with litter size as the response variable because inbreeding in the captive population was correlated with reduced litter size (Rabon & Waddell 2010). We only included litters where all pups were given transponders before becoming mobile, usually within approximately 2 weeks of parturition (n = 105; A. B. Beyer, personal communication). ...
Article
Full-text available
In natural populations, the expression and severity of inbreeding depression can vary widely across taxa. Describing processes that influence the extent of inbreeding and inbreeding depression aid in our understanding of the evolutionary history of mating systems such as cooperative breeding and nonrandom mate selection. Such findings also help shape wildlife conservation theory because inbreeding depression reduces the viability of small populations. We evaluated the extent of inbreeding and inbreeding depression in a small, reintroduced population of red wolves (Canis rufus) in North Carolina. Since red wolves were first reintroduced in 1987, pedigree inbreeding coefficients (f) increased considerably and almost every wild born wolf was inbred (average f=0.154 and max f=0.383). The large inbreeding coefficients were due to both background relatedness associated with few founders and numerous close relative matings. Inbreeding depression was most evident for adult body size and generally absent for direct fitness measures such as reproductive success and survival; no lethal equivalents (LE=0.00) were detected in juvenile survival. The lack of strong inbreeding depression in direct measures of fitness could be due to a founder effect or because there were no outbred individuals for comparison. Our results highlight the variable expression of inbreeding depression across traits and the need to measure a number of different traits when evaluating inbreeding depression in a wild population.This article is protected by copyright. All rights reserved.
... m a m m a l o g y . o r g (Roelke et al. 1993;Charpentier et al. 2008;van Coillie et al. 2008;Rabon and Waddell 2010;Cain et al. 2011). Furthermore, captive-bred animals are usually less well adapted for wild conditions because captive breeding over several generations may create unique selection pressures influencing physiological, behavioral, and evolutionary changes that compromise fitness in natural environments (Robert 2009). ...
... In conclusion, declining or endangered species most in need of emergency captive breeding programs are often similar to the CB pygmy rabbit-small populations with low genetic diversity and high genetic differentiation from possible sources for translocation (Brekke et al. 2010;Rabon and Waddell 2010;Cain et al. 2011;Karsten et al. 2011;Roberts et al. 2011). Consequently, difficult trade-offs (e.g., demographic, facility logistics, and financial expenses) often must be balanced to adaptively manage population genetics, population size, and production of enough new animals to support both a captive population and reintroduction efforts (van Heezik et al. 2005;Zeoli et al. 2008;Robert 2009). ...
... Thus, early biased removal of individuals from the data set acts to weaken estimates of inbreeding depression (Keller & Waller 2002). In addition, early mortality due to inbreeding depression may also act to reduce clutch or litter size, enabling parents to invest more in a smaller number of surviving offspring and further masking negative effects of inbreeding (Richardson et al. 2004;Rabon & Waddell 2010). If early viability selection operates to weaken estimates of inbreeding depression, this may lead to improper neglect of this process as a potential cause of reduced population productivity, and possible deprioritization of actions to ameliorate effects of inbreeding. ...
... Nevertheless, it is possible to evaluate whether early viability selection likely impacts inbreeding depression estimates in viviparous species by examining differences in litter size of related and unrelated pairs at the earliest opportunity, to infer whether early losses have occurred (e.g. Rabon & Waddell 2010). Collection of these data is straightforward and recommended in intensive conservation management contexts (Bingaman Lackey 2010) and can aid the interpretation of inbreeding effects by differentiating between different possible causes of weak effects at later stages in a given species/context: such as whether inbreeding depression simply appears weak because highly homozygous animals are removed at a young age, or whether inbreeding depression is indeed weak overall. ...
Article
Maintaining genetic diversity is a crucial goal of intensive management of threatened species, particularly for those populations that act as sources for translocation or reintroduction programmes. Most captive genetic management is based on pedigrees and a neutral theory of inheritance, an assumption that may be violated by selective forces operating in captivity. In this paper, we explore the conservation consequences of early viability selection: differential offspring survival that occurs prior to management or research observations, such as embryo deaths in utero. If early viability selection produces genotypic deviations from Mendelian predictions, it may undermine management strategies intended to minimise inbreeding and maintain genetic diversity. We use empirical examples to demonstrate that straightforward approaches, such as comparing litter sizes of inbred versus non-inbred breeding pairs, can be used to test whether early viability selection likely impacts estimates of inbreeding depression. We also show that comparing multilocus genotype data to pedigree predictions can reveal whether early viability selection drives systematic biases in genetic diversity, patterns that would not be detected using pedigree-based statistics alone. More sophisticated analysis combining genome-wide molecular data with pedigree information will enable conservation scientists to test whether early viability selection drives deviations from neutrality across wide stretches of the genome, revealing whether this form of selection biases the pedigree-based statistics and inference upon which intensive management is based. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
... Inbreeding comes with a very high price with respect to the soundness of the reproductive system. This can be manifested in sperm quality (Roldan et al., 1998; Gomendio et al., 2000; Ruiz-Lopez et al., 2010) and in the outcome in term of litter size and survival (Rabon & Waddell, 2010). Once proper sample of sufficiently good quality is in hand, there are several options for its preservation. ...
... In addition to the focus on the population's size, the genetic diversity of the red wolf population has been actively managed since the initiation of the Recovery Program (Waddell and Long 2014). Given the small size of the founding captive population and that the wolves were collected from a localized wild population, it is likely that the founders were closely related and that the population is therefore particularly prone to inbreeding (Rabon and Waddell 2010). As a result, retaining genetic diversity is crucial to the persistence of red wolves (Primack 2000) and is an explicit goal of the Recovery Program (USFWS 1990(USFWS , 2007. ...
Article
Movement connects otherwise isolated populations, influencing demographic persistence and promoting gene flow. We evaluated the effect of movement on the genetic and demographic viability of the red wolf (Canis rufus) and tested the application of metapopulation theory to management of this endangered predator. The establishment of a captive subpopulation in the 1970s allowed persistence of the species and facilitated a reintroduction program that supported 2 wild subpopulations, one of which persists today. We assessed the effect of historical and potential future movement between the wild and captive subpopulations on the genetic and demographic viability of the metapopulation. We analyzed approximately 30 years of individual-level data to quantify the effects of historical movement among subpopulations and constructed an individual-based metapopulation model to predict the effects of future potential movement (i.e., releases of captive wolves) on the species’ persistence and genetic diversity. Counter to theory, increased movement has had positive demographic effects, with higher per capita movement rates leading to increased metapopulation growth and decreased subpopulation synchrony. These counter-theoretical results are likely due to differences in reproduction and survival rates among subpopulations and the small size of the metapopulation. Furthermore, higher rates of movement did not increase retention of genetic diversity, likely because of the active pedigree-based breeding management of the species already maximizing gene retention. Our model indicates that future releases of captive wolves are necessary, but not sufficient, for the survival of the species, and must be combined with changes to demographic rates in both the captive and northeastern North Carolina subpopulations. Our results highlight the need for models and field data that more adequately describe the viability of small metapopulations.
... Finally, although the assumptions made in this study (i.e., stable population size) are not directly applicable to real situations, there are many examples where captive populations were founded by a small number of individuals , and remained small (see examples in Thévenon and Couvet 2002). Our model could also be applied to cases where even if captive populations increased in size, they remain initially small for several generations; see for instance, the ex-situ conservation of the Mauritius Kestrel (Falco punctatus) (Jones et al. 1995), the Red Wolf (Canis rufus) (Rabon and Waddell 2010) or the Puerto Rican Crested Toad (Peltophryne lemur) (Beauclerc et al. 2010). Overall, circular mating fulfils the primary goals of a captive breeding program, i.e., it maintains high levels of genetic diversity and reduces the probability of extinction of reintroduced populations. ...
Article
Full-text available
We performed computer simulations to evaluate the effectiveness of circular mating as a genetic management option for captive populations. As a benchmark, we used the method proposed by Fernández and Caballero according to which parental contributions are set to produce minimum coancestry among the offspring and matings are performed so as to minimize mean pairwise coancestry (referred to as the Gc/mc method). In contrast to other methods, fitness does not vary with population size in the case of circular mating, and can be higher than under random mating. Whether circular mating is an effective method in conserving captive populations depends on the trade-off between different considerations. On the one hand, circular mating shows the highest allelic diversity and the lowest mean pairwise coancestry for all population sizes. It also shows a relatively higher efficiency of purging deleterious alleles. More importantly, circular mating can significantly increase the success probability of populations released to the wild relative to the Gc/mc method. On the other hand, circular mating has the drawback of showing high inbreeding rates and low fitness in early generations, which can result to an increase in the extinction probability of the captive populations. However, this increase is slight unless population size and litter size are both very low. Overall, if the slight increase in extinction probability can be tolerated then circular mating fulfils the primary goals of a captive breeding program, i.e., it maintains high levels of genetic diversity and increases the success probability of reintroduced populations. KeywordsEx situ conservation-Inbreeding-Captive breeding-Genetic load-Deleterious mutation-Circular mating-Reintroduction
... Breeding may be further decreased by the sex-ratio bias that arises due to demographic or environmental stochasticity (Ripa & Lundberg 2000). Another mechanism driving the extinction vortex is inbreeding depression (Hedrick & Kalinowski 2000;Tanaka 2000), which refers to the potential negative effects of reduced genetic diversity and increased inbreeding on demographic traits, such as birth rate (Madsen et al. 1999;Rabon & Waddell 2010) and survival (Blomqvist et al. 2010;Hostetler et al. 2010; but see Bouzat 2010). Results of both simulation (Tanaka 2000) and empirical studies (Keller & Waller 2002) show that inbreeding depression affects population dynamics and extinction risk. ...
Article
Theory suggests that demographic and genetic traits deteriorate (i.e., fitness and genetic diversity decrease) when populations become small, and that such deterioration could precipitate positive feedback loops called extinction vortices. We examined whether demographic attributes and genetic traits have changed over time in one of the 2 remaining small populations of the highly endangered Iberian lynx (Lynx pardinus) in Doñana, Spain. From 1983 to 2008, we recorded nontraumatic mortality rates, litter size, offspring survival, age at territory acquisition, and sex ratio. We combined these demographic attributes with measures of inbreeding and genetic diversity at neutral loci (microsatellites) and genes subjected to selection (major histocompatibility complex). Data on demographic traits were obtained through capture and radio tracking, checking dens during breeding, track surveys, and camera trapping. For genetic analyses, we obtained blood or tissue samples from captured or necropsied individuals or from museum specimens. Over time a female-biased sex ratio developed, age of territory acquisition decreased, mean litter size decreased, and rates of nontraumatic mortality increased, but there were no significant changes in overall mortality rates, standardized individual heterozygosity declined steadily, and allelic diversity of exon 2 of class II major histocompatibility complex DRB genes remained constant (2 allelic variants present in all individuals analyzed). Changes in sex ratio and age of territory acquisition may have resulted from demographic stochasticity, whereas changes in litter size and nontraumatic mortality may be related to observed increases in inbreeding. Concomitant deterioration of both demographic attributes and genetic traits is consistent with an extinction vortex. The co-occurrence, with or without interaction, of demographic and genetic deterioration may explain the lack of success of conservation efforts with the Doñana population of Iberian lynx. Resumen: La teoría sugiere que los atributos demográficos y genéticos se deterioran (i.e., la adaptabilidad y la diversidad genética decrecen) cuando las poblaciones son pequeñas y que ese deterioro podría precipitar lazos de retroalimentación denominados vórtices. Examinamos si los atributos demográficos y las características genéticas han cambiado en 1 de 2 poblaciones remanentes del críticamente en peligro lince ibérico (Lynx pardinus), en Doñana, España. De 1983 a 2008, registramos tasas de mortalidad no traumática, tamaño de camada, supervivencia de crías, edad de adquisición de territorio y proporción de sexos. Combinamos estos atributos demográficos con medidas de endogamia y diversidad genética en loci neutrales (microsatélites) y genes sujetos a selección (complejo mayor de histocompatibilidad). Los datos de atributos demográficos fueron obtenidos mediante captura y rastreo por radio, revisión de madrigueras durante la reproducción, muestreo de huellas y cámaras trampas. Para los análisis genéticos, obtuvimos muestras de sangre o tejido de individuos capturados o muertos o especímenes de museo. A lo largo del tiempo se observó un sesgo en la proporción de sexos hacia hembras, la edad de adquisición de territorio disminuyó, el tamaño promedio de las camadas disminuyó y las tasas de mortalidad no traumática incrementaron, pero no hubo cambios significativos en las tasas de mortalidad generales, la heterocigosidad individual estandarizada declinó a ritmo constante y la diversidad alélica de los genes del exón 2 de la clase II del complejo mayor de histocompatibilidad DRB permaneció constante (2 variantes alélicas en todos los individuos analizados). Los cambios en la proporción de sexos y la edad de adquisición de territorio pudieron ser resultado de la estocasticidad demográfica, mientras que los cambios en el tamaño de la camada y la mortalidad no traumática pueden estar relacionados con los incrementos observados en la endogamia. El deterioro concomitante tanto de los atributos demográficos como en las características genéticas es consistente con un vórtice de extinción. La coocurrencia, con o sin interacción, del deterioro demográfico y genético puede explicar la falta de éxito de los esfuerzos de conservación de la población de lince ibérico en Doñana.
... Assuming longevity to be a proxy of mother quality, we would expect mortality to be lower for calves born to long-lived mothers. 4. Coefficient of inbreeding: Extensive studies of domestic and wild mammals indicate that inbreeding leads mostly to increased mortality in young animals and reduced fertility in adults (Ballou & Ralls, 1982;Swinnerton et al., 2004;Rabon & Waddell, 2010) because of what is known as inbreeding depression (Wright, 1977). Based on these findings, it has been hypothesized that, in general, quality may be lower in individuals with higher inbreeding coefficients (Charlesworth & Charlesworth, 1987). ...
... Assuming longevity to be a proxy of mother quality, we would expect mortality to be lower for calves born to long-lived mothers. 4. Coefficient of inbreeding: Extensive studies of domestic and wild mammals indicate that inbreeding leads mostly to increased mortality in young animals and reduced fertility in adults (Ballou & Ralls, 1982;Swinnerton et al., 2004;Rabon & Waddell, 2010) because of what is known as inbreeding depression (Wright, 1977). Based on these findings, it has been hypothesized that, in general, quality may be lower in individuals with higher inbreeding coefficients (Charlesworth & Charlesworth, 1987). ...
Article
Growing deterministic and stochastic threats to many wild populations of large vertebrates have focused attention on the significance of captive breeding for conservation. Nanger dama mhorr and Gazella cuvieri, two Sahelo-Saharan species, have declined dramatically since the 1950s, apparently due to excessive hunting and habitat degradation. Today, the earlier is extinct in the wild and the latter survives only in small numbers in a few isolated parts of their range, and captive breeding programmes currently provide an important tool for rearing sustained populations. In natural and captive populations, the largest percentage of mortality is among juveniles. This is most relevant, from an evolutionary perspective, as it has a profound influence on population dynamics and demography, and is pivotal to the conservation and management of captive endangered populations. This study explored the juvenile mortality curve during the first 6 months of life of the species mentioned earlier in captivity. Then, we looked at the causes of this mortality by examining potential mother-dependent as well as offspring-dependent sources of juvenile mortality. The resulting curves show that the critical period of mortality is the first 14 days of life. We also found that parity and longevity of the mother affected juvenile mortality in Mohor gazelles. Calves born to primiparous as well as those born to short-lived mothers were more prone to die than those born to either multiparous or long-lived mothers. In Cuvier's gazelles, juvenile mortality was explained by the interaction between parity and mother's age and litter composition. Neither mother nor offspring inbreeding had any effect on juvenile mortality in either population. Precise knowledge of the biological factors affecting juvenile mortality is increasingly important for the conservation of large mammals, whether they are captive, managed, reintroduced or simply fragmented, as the neonates are the population's potential recruits.
... Inbreeding depression within captive populations of Canis species ranges from low to severe (Laikre and Ryman 1991;Ellegren 1999;Kalinowski et al. 1999;Fredrickson and Hedrick 2002;Lockyear et al. 2009;Rabon and Waddell 2010). In the wild, Scandinavian gray wolves recovering from a population bottleneck exhibit signs of severe inbreeding depression (Liberg et al. 2005). ...
Article
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For cooperatively breeding groups composed of close relatives, whether and how a group avoids inbreeding are questions of key evolutionary and conservation importance. A number of strategies for inbreeding avoidance may be employed by cooperative breeders, including extrapair reproduction, reproductive suppression, and juvenile dispersal. However, population-wide information on the prevalence of different strategies is difficult to obtain. We investigated the prevalence of inbreeding and potential mechanisms for inbreeding avoidance in a reintroduced population of the red wolf. Using long-term data on individuals of known pedigree, we determined that inbreeding among first-degree relatives was rare. Potential mechanisms for inbreeding avoidance included low levels of philopatric reproduction in spite of delayed dispersal, and reproductive suppression prior to dispersal. Inbreeding avoidance among siblings may have been further facilitated by independent dispersal trajectories, as many young wolves spent time alone or in small nonbreeding packs composed of unrelated individuals. The dominant pattern of breeding-pair formation involved the union of 2 unrelated individuals in a new home range. Replacement of 1 or both members of an existing breeding pair involved new immigrants to a pack or, in a small number of cases, ascendance of either resident offspring or adopted pack members to vacant breeding positions. Extrapair reproduction was rare, suggesting that it was not a major mechanism for outbreeding. We conclude that there are several prevalent behavioral strategies within the red wolf population that may work together to minimize inbreeding and any associated fitness costs, helping make cooperative breeding an evolutionarily viable strategy.
... Therefore, older wolves have lower inbreeding coefficients. This is consistent with previous work that has demonstrated the level of inbreeding among offspring in captive red wolves has increased over time [21]. The implication this relationship has for this study is a near inability to separate any effects of these two variables on semen quality. ...
Article
Cryopreserving genetic resources is becoming increasingly important for species management. In the zoo-based red wolf (Canis rufus) population, inbreeding continues to increase in the absence of new founders. Through banking sperm, we preserve genetic diversity and create the ability to decrease inbreeding accumulation in the future. The quality and quantity of banked sperm can be affected by cryopreservation media and semen collection methods. This study's objectives were to further optimize semen extender used for red wolf sperm cryopreservation, investigate effects of post-thaw holding temperature, and to determine if urethral catheterization is an effective method for semen collection in this species. Semen collection via electroejaculation (EE) was performed on 39 adult red wolf males (ages 1 to 11) from 15 institutions. Urethral catheterization (UC) was attempted on a subset (n = 14) of those males, prior to EE. Thirteen different semen extenders were used for cryopreservation, which varied in osmolarity (HI or NORM), sugar source (glucose, fructose, or a combination), and cryoprotectant (glycerol or DMSO). Significant decreases in percent motility, forward progressive status (FPS), and acrosomal integrity were observed over time across all extenders (P < 0.0001). Among the extender components examined, post-thaw sperm motility and FPS were lower in DMSO versus glycerol based treatments (P < 0.005). Therefore, DMSO should be considered unsuitable as a cryoprotectant when freezing red wolf sperm. Effects of osmolarity and sugar source were minimal and temporally variable, however notably, a higher percentage of morphologically normal sperm were observed in the fructose-based extenders compared to glucose-based extenders post-thaw (P < 0.05). Additionally, post-thaw sperm motility and FPS declined more rapidly in samples maintained at 37 °C compared to samples held at room temperature (P < 0.05). Greater volumes of semen were collected using EE compared to UC (P = 0.041), and sperm samples collected using EE also had greater motility and FPS (P < 0.05). Additionally, though no gross morphological differences were observed, there were fewer sperm with intact acrosomes in the samples collected via UC (P = 0.0443). Thus, UC should not be considered sufficient for semen collection in red wolves when the desired fate of sperm is cryopreservation and/or AI. However, UC does provide an opportunity for a basic reproductive evaluation of a red wolf male.
... The result was supported by studying the significant association between total inbreeding coefficient in dams with mortality at days 7 (p <0.05), 30 (p <0.05) and 90 (0.10) indicating that it would decrease the mortality risk of the litter (Quilicot, 2009). Similar findings were observed with reduced litter size in wolf (Canis lupus) (Laikre, 1999), Mexican wolf (Canis lupus baileyi) (Fredrickson et al., 2007) and red wolves (Canis rufus) (Lockyear et al., 2009, Rabon andWaddell, 2010). The litter size reduction of the captive tiger in Nandankanan zoo is comparable with the brown bear (Laikre, 1999). ...
... The primary focus of an insurance population is to capture a representation of wild genetic diversity and to maintain it for as long as possible to ensure that those individuals that may be re-introduced to the wild are representative of the individuals that were originally present, as well as retaining enough genetic diversity for the species to survive ongoing evolutionary pressures (Lacy 1997). The disadvantage of any captive insurance population is the deleterious consequences of genetic adaptation to captivity (Frankham 2008), potential inbreeding depression due to small population sizes (Edmands 2007;Rabon and Waddell 2010) and loss of adaptability to future events (Lacy 1997). ...
Article
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An insurance population for the critically endangered Tasmanian devil was established in 2006. Due to successful captive breeding, the population has reached its carrying capacity of 600 devils and retains 99.95 % of founding gene diversity. Although reproduction has been quite successful, possible relatedness among founding individuals, influences of genetic provenance and pairing success on female productivity were evaluated to further refine insurance population management. Ten polymorphic microsatellite markers were used to assess the founders. Although the data were ultimately insufficient for determining specific founder relationships, a STRUCTURE analysis determined founders to be of eastern or western provenance. Western provenance animals had an observed heterozygosity of 0.38; while eastern provenance was 0.41. Allelic frequencies between the two provenances were similar. Although differences in pairing success of eastern and western provenance animals were noted, there was no difference in overall productivity (number of joeys/female). Cross-provenance pairings were not as successful as W–W but had similar productivity, and produced viable offspring. Birth origin (wild-born vs. zoo-born) had no influence on pairing success but wild-born females produce significantly more joeys/female. For zoo-born females, the number of joeys produced per female had a downward trend between respective generations in captivity. Current and future population managers should be aware of potential reductions in productivity across captive generations and adjust breeding recommendations accordingly. The ability to recruit founders from diseased females, along with a better understanding of the influence of genetic provenance and birth origin on productivity, has led to changes in acquisition of future founders for this insurance population.
... Although earlier studies did not find definitive evidence of inbreeding depression [18,45], Goodrowe et al. [18] suggested that the semen parameters of the red wolf were consistent with inbreeding effects related to the small number of founders, and Koehler et al. [19] found nonsignificant trends in their data consistent with inbreeding depression. More recent examinations of demographic data have indicated that although breeding success within the zoo-based population had not been significantly reduced at the time of analysis, litter size had been negatively affected by paternal levels of inbreeding [46], and both increasing male age and inbreeding reduce the probability of a successful mating [31,47]. Thus, it seems clear that more research focused on male reproductive capacity is warranted for this species. ...
... Perhaps inbreeding depression was implicated in this apparently low reproduction, since reproductive success in wolves is negatively affected by incest, particularly in small and isolated populations (Asa et al., 2007;Fredrickson et al., 2007;Rabon and Waddell, 2010). The East Greenland wolf population was small, but whether it was demographically isolated from the nearest source population (North Greenland) is unclear. ...
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The decline and extermination of an arctic wolf population in East Greenland between 1899 and 1939 were investigated through analysis of 40 years of archival data, which contained records of 252 sightings of wolves or their tracks. Prior to the start of exploitation by Europeans, this small, isolated wolf population probably consisted of about 38 wolves during an average year. Of 112 wolves sighted in early winter, 31.3% were lone wolves, 23.2% were in pairs, and the rest were in larger groups. Mean pack size was 3.3 wolves, and packs of more than four wolves were rare. The population was concentrated in the central part of its range, making it vulnerable to exploitation by Danish and Norwegian commercial hunters, who exterminated the population. Poison was the primary agent of destruction. There was no evidence that other proposed causes of the decline were influential. This study provided the first evidence of an arctic wolf population that was eradicated and highlights the vulnerability of small, isolated wolf populations to excessive harvest. Wolves in the High Arctic may be particularly vulnerable because of their exceptionally low densities, smaller pack sizes, lower pup production, infrequent reproduction, and insular or disjunct distributions.
... However, both of these situations would explain only an additive effect of individual's F on fitness, and would not explain the interaction with F ♀ . A linear positive effect of inbreeding on survival probability may also be explained by early mortality that reduces brood size and enables parents to invest more effort into surviving offspring (Richardson et al. 2004;Rabon and Waddell 2010). This was not the case in our dataset, as probability of breeding, clutch size, and brood size were unaffected by inbreeding. ...
Article
Inbreeding depression, the reduced fitness of offspring of related individuals, is a central theme in evolutionary biology. Inbreeding effects are influenced by the genetic makeup of a population, which is driven by any history of genetic bottlenecks and genetic drift. The Chatham Island black robin represents a case of extreme inbreeding following two severe population bottlenecks. We tested whether inbreeding measured by a 20-year pedigree predicted variation in fitness among individuals, despite the high mean level of inbreeding and low genetic diversity in this species. We found that paternal and maternal inbreeding reduced fledgling survival and individual inbreeding reduced juvenile survival, indicating that inbreeding depression affects even this highly inbred population. Close inbreeding also reduced survival for fledglings with less-inbred mothers, but unexpectedly improved survival for fledglings with highly inbred mothers. This counterintuitive interaction could not be explained by various potentially confounding variables. We propose a genetic mechanism, whereby a highly inbred chick with a highly inbred parent inherits a "proven" genotype and thus experiences a fitness advantage, which could explain the interaction. The positive and negative effects we found emphasize that continuing inbreeding can have important effects on individual fitness, even in populations that are already highly inbred. This article is protected by copyright. All rights reserved.
... The sex ratio of adult and sub-adult hirola in Tsavo did not differ significantly from the sex ratio of calves born in captivity. This is an imperfect comparison because mothers' condition and inbreeding can affect the sex ratio of captive animals but data for the sex ratio of wild calves is not available (Hintz and Foose, 1982;Rabon and Waddell, 2010;Moreno et al., 2011). ...
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The critically endangered hirola (Beatragus hunteri, Sclater, 1889) exists in two populations; a natural population on the Kenya-Somali border and a translocated population in Tsavo East National Park. The Tsavo population is becoming increasingly important for the survival of the hirola as a species yet it has been stagnant for decades, its current status is unknown and little is understood about the factors which limit its growth. This study reports the current size, distribution and demographic parameters of the Tsavo hirola population and examines whether a lack of suitable habitat could be limiting its growth. The Tsavo hirola population has not increased since the last census in 2000 but neither has it significantly decreased. Large areas of Tsavo are suitable habitat for hirola although this is relative to the environmental conditions in Tsavo rather than an absolute measure. The results of data gathered opportunistically on the behaviour, associated species, spoor, dung and awareness of hirola are also presented and the implications of the study’s findings for hirola conservation are discussed.
Conference Paper
Scientific visualization is a multidisciplinary technology, which integrates computer graphics, data mining, human-machine interface theory, and combines with the applied sciences, and provides an intuitive way to show valuable data in engineering area, and provides means to operator for exploring and studying physical phenomena. In recent year visualization techniques are used more widely in power system, more and more showing means is provided, and visual effects is also getting better, but these can't meet high demand of dispatcher in power system. How to make visualization technology more practical is a difficult problem needed to be urgently solved. This paper proposes several methods for practical research in visualization. Based on application already deployed in power system, we analysis the way how to improve practicality of scientific visualization in the power system, and introduce how to use visualization techniques for advanced application in power system. The practical research in this paper is helpful to raise the level of dispatching in power grid and provides strong technical support for changes from traditional dispatching to intelligent dispatching.
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A good reproductive performance is a central element of animal breeding. The breeders of Entlebucher Mountain dogs observed a decrease of the mean litter size and an increase of the number of unsuccessful matings in the past years. The aim of the present study was to identify factors with an influence on fertility in this breed. In total, 915 litters from 202 sires and 348 dams from 1986 to 2013 entered the analyses. The total puppy losses (7.4%) reduced the mean litter size at birth of 5.49 ± 2.13 to a mean litter size at registration of 5.08 ± 2.05. There was no deviation from the expected equal sex distribution for puppies at birth and at registration, as well as for puppy losses consisting of stillborn puppies and puppies which died or had to be euthanized before registration. The mean annual litter inbreeding coefficient increased from 0.37 in 1986 to 0.40 in 2013 and was correlated with the year of birth of the litter (Kendall's tau b = 0.46). The age of the dam and parental inbreeding were identified as significant predictors with a negative effect on litter size at birth. For the litter size at registration the age and inbreeding of the dam had a significant negative effect and a 1% increase of dam inbreeding is expected to decrease the litter size at birth and registration by 0.1 and 0.09 puppies, respectively. The occurrence of total puppy losses decreased during the years and was more frequent in larger litters. In addition, in litters of older parents the occurrence of puppy losses was more frequent than in litters from younger parents. The final generalized linear mixed-effects models for litter size at birth, litter size at registration and for total puppy losses explained 36%, 33% and 22% of the total variance, respectively. The impact of inbreeding and parental age on fertility of the Entlebucher Mountain dog was small and the influence of the dam was much bigger than the one of the sire. Other factors must be responsible for the variability of litter sizes not explained by the models. Without changes of breeding circumstances, a further increase of inbreeding must be expected. Therefore, a close monitoring and minimizing of inbreeding must be followed up by the breeding community.
Thesis
The critically endangered hirola (Beatragus hunteri, Sclater, 1889) exists in two populations; a natural population on the Kenya-Somali border and a translocated population in Tsavo East National Park. The Tsavo population is becoming increasingly important for the survival of the hirola as a species yet it has been stagnant for decades, its current status is unknown and little is understood about the factors which limit its growth. This study reports the current size, distribution and demographic parameters of the Tsavo hirola population and examines whether a lack of suitable habitat could be limiting its growth. The Tsavo hirola population has not increased since the last census in 2000 but neither has it significantly decreased. Large areas of Tsavo are suitable habitat for hirola although this is relative to the environmental conditions in Tsavo rather than an absolute measure. The results of data gathered opportunistically on the behaviour, associated species, spoor, dung and awareness of hirola are also presented and the implications of the study’s findings for hirola conservation are discussed.
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Assessment was made of all available cranial specimens of wild Canis dating since the Blancan and prior to AD 1918 in the region east of the Great Plains and south of the Prairie Peninsula, Lakes Erie and Ontario, and the St. Lawrence River. The small wolf C. priscolatrans (= C. edwardii) of the early Irvingtonian seems unrelated to the modern red wolf (C. rufus), but gave rise to a lineage including the larger C. armbrusteri and culminating in C. dirus of the late Rancholabrean. A small wolf, possibly a descendant of the Eurasian C. mosbachensis, did not reappear in the east until near the end of the Rancholabrean. At the same time, the coyote (C. latrans) disappeared from the east, not to return until the small wolf was extirpated in the 20th century. Fragmentary remains of the small wolf, dating from around 10,000 and 2,000-200 ybp, show continuity with 14 complete, mostly modern, eastern skulls. Multivariate analysis indicates those 14 represent a well-defined species, C. rufus, distinct from large series of the western gray wolf (C. lupus) and coyote. There is no evidence that the red wolf originated as a hybrid of the latter two species, though early specimens from central Texas suggest it began to interbreed with C. latrans by about 1900. Three long-recognized red wolf subspecies appear valid: C. r. floridanus, Maine to Florida; C. r. gregoryi, south-central United States; and C. r. rufus, central and coastal Texas, southern Louisiana, and probably now represented in the captive/reintroduced populations. The subspecies C. lupus lycaon of southeastern Ontario and southern Quebec is statistically intermediate to C. rufus and western C. lupus, and may have resulted from natural hybridization of those two species. Such could explain how the red and gray wolf differ so sharply where their ranges meet in the west but morphologically approach one another in the east.
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Species survival is critically dependent on reproductive performance, a complex physiological process under rigorous genetic control. Classical studies of inbreeding in laboratory animals and livestock have shown that increased homozygosity can adversely affect spermatogenesis, ovulation and perinatal mortality and morbidity1–3. For wild populations, the consequences of inbreeding depression have not been examined intensively, although our recent studies of the African cheetah revealed a striking degree of genetic uniformity4,5 combined with an extremely high incidence of structurally abnormal spermatozoa (>70%) in captive6 as well as free-ranging7 males. In this study, we report definitive evidence that the reproductive function of free-ranging mammals can be impaired as a result of demographic contraction followed by inbreeding. In an examination of three distinct lion populations (two from the Serengeti ecosystem in East Africa and a third descended from lions in the Gir Forest of western India), a direct correlation was observed between genetic variability and two physiological traits, incidence of abnormal sperm and circulating testosterone, a critical hormone for spermatogenesis.
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Assessment was made of all available cranial specimens of wild Canis dating since the Blancan and prior to AD 1918 in the region east of the Great Plains and south of the Prairie Peninsula, Lakes Erie and Ontario, and the St. Lawrence River. The small wolf C. priscolatrans(= C. edwardii) of the early Irvingtonian seems unrelated to the modern red wolf (C. rufus), but gave rise to a lineage including the larger C. armbrusteri and culminating in C. dirus of the late Rancholabrean. A small wolf, possibly a descendant of the Eurasian C. mosbachensis, did not reappear in the east until near the end of the Rancholabrean. At the same time, the coyote (C. latrans) disappeared from the east, not to return until the small wolf was extirpated in the 20th century. Fragmentary remains of the small wolf, dating from around 10,000 and 2,000-200 ybp, show continuity with 14 complete, mostly modern, eastern skulls. Multivariate analysis indicates those 14 represent a well-defined species, C. rufus, distinct from large series of the western gray wolf (C. lupus) and coyote. There is no evidence that the red wolf originated as a hybrid of the latter two species, though early specimens from central Texas suggest it began to interbreed with C. latrans by about 1900. Three long-recognized red wolf subspecies appear valid: C. r. floridanus, Maine to Florida; C. r. gregoryi, south-central United States; and C. r. rufus, central and coastal Texas, southern Louisiana, and probably now represented in the captive/reintroduced populations. The subspecies C. lupus lycaon of southeastern Ontario and southern Quebec is statistically intermediate to C. rufus and western C. lupus, and may have resulted from natural hybridization of those two species. Such could explain how the red and gray wolf differ so sharply where their ranges meet in the west but morphologically approach one another in the east.
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We tested the hypothesis that small, isolated populations would show less depression in fitness when inbred than would large, central populations. Laboratory stocks of Peromyscus leucopus and P. polionotus were established from insular, peninsular, and central populations. The isolated populations had one-third to one-half the genic diversity of central populations. Responses to inbreeding were highly varied: some populations had smaller litters, others experienced higher mortality, some showed slower growth rates, and one displayed no measurable effects when inbred. These results suggest that inbreeding depression is controlled by a small number of genes and that the size of the genetic load depends on which alleles are present in the founders of a population. The severity of fitness depression in inbred litters did not correlate with initial genic diversity of the stocks nor, therefore, with the size of the wild populations. Fitness measures appeared linearly related to the inbreeding coefficient of the liters, with no diminution of deleterious effects through subsequent generations of inbreeding. Thus overdominance of fitness traits probably contributed as much to the genetic load as did deleterious recessive alleles. The inbreeding level of the dam negatively affected the size, growth, and survival of litters only in genetically diverse populations, indicating that the load of recessive alleles negatively impacting maternal care may have been reduced by selection in the more peripheral populations during past bottlenecks.
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Although women are known to be more viable than men, the biological mechanisms for this difference are poorly understood. A relevant question is: To what extent does heterozygosity for X linked loci contribute to survival of the XX female? The advantage accruing to the XX female through having this factor can be defined as X heterosis. Practically all serious X linked disorders such as haemophilia occur in males, but the total incidence of such severe diseases is relatively small and cannot account for the observed sex differences in age specific mortality rates. It is conceivable that X heterosis is relatively insignificant in the total population, and that the bulk of the observed sex difference is attributable to physiological factors that are a consequence of sex differentiation and/or to psycho cultural factors that may pertain to diminished exposure of women to environmental hazards. Data are presented which suggest that, among the population of the Japanese island of Hirado, X heterosis contributes quite considerably to female survival during gestation. There is also a trend consistent with an X heterotic effect on postnatal survival.
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The relationship based on skull morphology of populations known as Canis latrans and C. niger in Arkansas, Louisiana, Oklahoma and Texas is con- sidered. Available evidence indicates that C. niger has become extinct except in isolated areas of Louisiana. Elsewhere, C. latrans has replaced C. niger as a primary predator. Probable previous hybridization between C. latrans and C. niger is dis- cussed. Two species of wild canines, red wolves, (Canis niger) and coyotes (C. latrans) have been reported in recent years from Arkansas (Sea- lander, 1956), Louisiana (Lowery, 1943), eastern Oklahoma (Blair, 1939; McCarley, 1952) and eastern Texas (McCarley, 1959). Both species, as presently defined, show a considerable amount of geo- graphic variation and morphological overlap of both skeletal and pelage characteristics. Considerable confusion exists in species identifi- cation in areas where both may occur. This paper is an analysis of the relationship that currently exists between coyotes and red wolves in the south central United States (Arkansas, Louisiana, Oklahoma and Texas) based largely on skull morphology. The study of variation in red wolves by Young and Goldman (1944), resulted in the naming of three subspecies of red wolves, largely on the basis of size. The largest of the subspecies, Canis n. niger (Bartram) has a geographic range in the southeastern United States east of the Mississippi River. This form is now presumed to be extinct and, because its range is beyond the confines of the present study, will not be considered further. The smallest of the red wolf populations was assigned to the subspecies C. n. rufus Audubon and Bachman with a geographic range in central Texas, central Oklahoma and northwestern Arkansas. A form described as C. n. gregoryi Gold- man has been characterized as intermediate in size between niger and rufus and has a geographic range between that of niger and rufus, i.e., the area eastward from eastern Oklahoma and Texas to, the Mississippi River and thence northward into Illinois and Indiana. Thus a west to east cline of increase in size is apparent.
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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.
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This study examined the effect of inbreeding on aggression levels and competitive ability in wild male house mice. Wild mice were bred in the laboratory to produce males of three levels of inbreeding: male offspring of unrelated parents, male offspring of first-cousin parents, and male offspring of full-sibling parents. Paired encounters were staged between males of the three offspring groups, when the males reached maturity. Less inbred males won more encounters and tended to have higher scores of aggression level than more inbred males. If competitive ability in the laboratory is related to competitive ability in nature, wild mice from this population may benefit from avoiding inbreeding and the consequent decrease in aggression levels and competitive ability.
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The costs of inbreeding in natural populations of mammals are unknown despite their theoretical importance in genetic and sociobiological models and practical applications in conservation biology. A major cost of inbreeding is the reduced survival of inbred young. We estimate this cost from the regression of juvenile survival on the inbreeding coefficient using pedigrees of 40 captive mammalian populations belonging to 38 species. The number of lethal equivalents ranged from –1.4 to 30.3, with a mean of 4.6 and a median of 3.1. There was no significant difference between populations founded with wild‐caught individuals, a mixture of wild‐caught and captive‐born individuals, and individuals of unknown origin. The average cost of a parent‐offspring or full sibling mating was 0.33, that is, mortality was 33% higher in offspring of such matings than in offspring of unrelated parents. This is likely to be an underestimate.
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Information on Alaskan wolf populations was obtained from examination of bounty records, 4,150 wolf radii and ulnae, 1,262 wolf carcasses, and from observations of wolves inhabiting an area of 20,000 square miles where wolves were protected. Pregnant adult female wolves averaged 6.5 fetuses; two-year-old females averaged 5.3 fetuses;female pups were not sexually mature. In Alaska, wolves conceive from late February through early April but most females breed in March. Multiparous females breed earlier than first breeders. Multiparous females produce an average of 7.3 ova and 6.5 implanted fetuses. The loss of ova from ovulation to implantation is significant. Multiparous females produce more ova than first breeders; the difference is highly significant. Mortality of pups rather than the lack of initial production of pups is believed to be the reason for the observed variations in the proportion of pups in wolf populations. Wolf packs include members in all categories of sex and age during the breeding season. Size of the pack is an indicator of abundance. Wolves in an area where they were protected increased at an average rate of 20–30% per year during an 11-year period.
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The Speke's gazelle captive breeding program was designed in the early 1980s to simultaneously maintain the population's genetic diversity while reducing the severity of the inbreeding depression in a situation in which inbreeding could not be avoided. Statistical analyses of the resulting data using both regression techniques and nonparametric exact contingency tests revealed that the inbreeding depression was indeed reduced, and genetic surveys revealed that high levels of nuclear genetic diversity had indeed been maintained. Hence, the twin goals of the breeding program appeared to have been achieved. Recently, several papers have been published that question the validity of the original statistical analyses and resulting biological conclusions. Specifically, these papers raise three major issues: (1) that a small sample correction factor used in the regression analysis represents a statistical “flaw,” (2) that new analyses of the data do not confirm the original conclusion of a significant reduction in the level of inbreeding depression, and (3) that the biological conclusions about the program are not justified. In this paper we show (1) that there is no “flaw” in the small sample correction, (2) that the recent permutational test given by Willis and Wiese seriously violates standard procedures and has no statistical validity, (3) that the regression procedures used by Ballou are inappropriate because the data seriously violate the underlying statistical assumptions and that the statistically valid components of Ballou's work strongly confirm the validity of the Speke's gazelle program, (4) that permutational tests done in accordance with standard statistical practice strongly confirm the results of the original analysis, and (5) that the original biological conclusions are fully justified by multiple types of statistical analyses. Zoo Biol 17:77–94, 1998. © 1998 Wiley-Liss, Inc.
Article
The Mexican gray wolf appears to be extinct in the wild and exists now only in captivity and as a reintroduced population in southeast Arizona and southwest New Mexico. A recent study did not find evidence for inbreeding depression in juvenile viability or litter size in captive animals. Here we found that captive wolves with little or no known inbreeding had lower body size than wild-caught wolves. In addition, captive wolves with higher inbreeding had lower body size than captive wolves with little or no inbreeding. The captive population was descended from three founders until two other lineages, each descended from two founders, were recently added to the population. There has been concern that the offspring from matings between these lineages may differ from the individuals in the original lineage so we examined the potential statistical power to detect differences between body size for animals from cross-lineage matings and other matings. In endangered species there are often limited opportunities to obtain sample sizes large enough to detect statistically significant differences because of the extensive resources needed to produce and maintain captive animals. In this case, however, it appears from our examination that in the next few years there will be an adequate sample size to evaluate statistically the differences in body size between these groups.
Article
In a review of the evidence for reduction in the severity of inbreeding depression in Speke's gazelle [Templeton and Read, pp. 241–261 in Genetics and Conservation: A Reference for Managing Wild Animal and Plant Populations, C.M. Schoenwald-Cox, S.M. Chambers, B. MacBryde, and L. Thomas, eds., Reading, MA, Addison-Weley, 1983; Templeton and Read, Zoo Biology 3:177–199, 1984] a flaw was found in the statistical analysis. Reanalysis of the 1983 data showed no significant reduction in the severity of inbreeding depression. An updated analysis using data from the 1992 Speke's Gazelle North American Regional Studbook [Fischer, St. Louis, St. Louis Zoological Park, 1993] also showed no significant reduction in the severity of inbreeding depression. While there is empirical evidence suggesting reduction in the severity of inbreeding depression in captive populations is possible through reduction of the founder base, maintenance of genetic variation must remain the primary goal of genetic management strategies for captive populations of exotic wildlife. Zoo Biol 16:9–16, 1997. © 1997 Wiley-Liss, Inc.
Article
Inbreeding is commonly associated with a lowering of viability and birth weights—a phenomenon known as inbreeding depression. A severe inbreeding depression was encountered in a captive breeding program for Speke's gazelle. Unfortunately, the solution of simply avoiding inbreeding could not be implemented because the entire herd was descended from one import male and three import females. Because of this founder effect, it was impossible to avoid inbreeding. However, laboratory experiments with fruit flies and basic evolutionary theory indicate that animals can rapidly adapt to inbreeding by the selective elimination of the genes responsible for inbreeding depression. These experimental and theoretical results were translated into a breeding program for the Speke's gazelle. The first goal of the breeding program is a demographic goal: increase the total population size as rapidly as possible to the carrying capacity. The other goals all deal with genetic attributes of either parents or offspring: Both parents and offspring should be inbred, and both parents and offspring should have genes from as many different founding ancestors as possible. In this paper, we document that this breeding program does eliminate the inbreeding depression very rapidly, and moreover that the genetic goals of the program aid this elimination exactly as theory predicts. Furthermore, our analysis clearly shows that the gazelles suffered from an inbreeding depression rather than an outcrossing depression. We conclude that inbreeding depressions can be rapidly and effectively reduced by an appropriate breeding program, and hence an inbreeding depression does not constitute an insurmountable barrier to the long-term maintenance of a species in which inbreeding cannot be avoided.
Article
Conservation biologists need to be able to estimate reliably the effects of inbreeding on survival, and need to be able to do so with a range of different data types. Kalinowski and Hedrick described a non-linear maximum likelihood estimation procedure for modelling relationships between survivorship and inbreeding. Although their method is useful for illustrating the concepts involved in modelling such relationships, it is only applicable to simple datasets. We illustrate that the parameter estimates generated by Kalinowski and Hedrick's method are easily obtained using generalized linear modelling procedures available in standard statistical packages, and that these offer several advantages even with simple datasets. We suggest procedures that can be used for modelling relationships between survival and inbreeding with more complex data types, including datasets with multiple and ragged encounters, uncertain detection and random effects.
Article
The current study tests the hypothesis that life-history traits (closely related to fitness) show greater inbreeding depression than morphological traits (less closely related to fitness). The mean and median slope of the standardized coefficient of inbreeding depression (the slope of the linear relationship between F and the trait value) for life-history and morphological traits were compared. Slopes for life-history traits were higher than those for morphological traits. At F = 0.25 (full-sibling mating), life-history traits experienced a median reduction of 11.8% in trait value, whereas morphological traits showed a depression in trait value of approximately 2.2%.
Article
Fitness is expected to decrease with inbreeding in proportion to the amount of deleterious genetic variation present in a population. The effect of inbreeding on survivorship is usually modeled as a negative exponential relationship, and this model has been widely used to estimate the amount of deleterious genetic varia-tion in populations. Linear regression has traditionally been used to estimate the parameters of the model, including the number of lethal equivalents. This article describes an alternative method for estimating parameters and their confidence limits: the maximum likelihood approach. The accuracy of regression and maxi-mum likelihood estimates of the number of lethal equivalents is compared through simulation. The maximum likelihood approach is found to be both median unbi-ased and capable of estimating confidence limits with nearly the stated degree of accuracy, while the linear regression approach is found to be median biased. The significance of this on previous estimates of inbreeding depression is discussed.
Article
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.
Article
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.
Article
The small group of wolves on Isle Royale has been studied for over three decades as a model of the relationship between large carnivores and their prey. During the last ten years the population declined from 50 individuals to as few as 12 individuals. The causes of this decline may be food shortages, disease, or reduced genetic variability. We address the issues of genetic variability and relationships of Isle Royale wolves using allozyme electrophoresis, mtDNA restriction-site analysis, and multilocus hypervariable minisatellite DNA analysis (genetic fingerprinting). Our results indicate that approximately 50% of the allozyme heterozygosity has been lost in the island population, a decline similar to that expected if no immigration had occurred from the mainland. The genetic fingerprinting data indicate that the seven sampled Isle Royale wolves are as similar as captive populations of siblings. Surprisingly, the Isle Royale wolves have an mtDNA genotype that is very rare on the mainland, being found in only one of 144 mainland wolves. This suggests that the remaining Isle Royale wolves are probably derived from a single female founder.
Article
A fundamental assumption underlying the application of genetics within conservation biology is that inbreeding increases the risk of extinction. However, there is no information on the shape of the relationship, the available evidence has not distinguished genetic and nongenetic effects, and the issue is controversial. Methods were devised to separate genetic and nongenetic causes of extinction in inbred populations, and they were used to analyze data from Drosophila melanogaster, D. virilis and Mus musculus. Inbreeding markedly increased rates of extinction in all cases. All showed a threshold relationship between incremental extinction and inbreeding with low initial extinction, but they showed notably increased extinction beginning at intermediate levels of inbreeding. There was no difference in extinction levels at similar inbreeding coefficients in populations inbred at different rates (full sibling versus double first cousin). Endangered species may give little warning of impending extinction crises due to inbreeding.
Article
Some of the concepts, terms, and methods used in the genetic management of captive populations have not been defined precisely in the scientific literature and consequently have been misunderstood and misused. The definitions and interrelationships among gene diversity, effective population size, founder genome equivalents, inbreeding, allelic diversity, mean kinship, and kinship value are presented here. It is important to understand what populations and generations are used as the baselines against which losses of genetic variation are measured. Gene diversity and founder genome equivalents are defined relative to a source population from which founders of the captive population were randomly sampled. Inbreeding and allelic diversity are assessed relative to the founders. The potential gene diversity that would result from an equalization of frequencies of founder alleles retained in the population can never be achieved because, among other limitations, the random process of gene transmission will prevent equalization of allele frequencies even if animals are bred optimally. The gene diversity achievable with the population can be determined by iterative production of hypothetical offspring from the pairs with lowest mean kinship. The long-term objective for offspring production from each animal is also thereby generated. Mean kinships should be recalculated with each real or hypothetical birth and death, because offspring objectives based on current mean kinships might correlate poorly with the optimal long-term offspring objectives. © 1995 Wiley-Liss, Inc.
Article
The South China tiger (Panther tigris amoyensis) is critically endangered with 73 remaining individuals living in captivity, all derived from six wild founders since 1963. The population shows a low level of juvenile survivorship and reproductive difficulties, and faces a huge conservation challenge. In this study, inbreeding depression and genetic diversity decline were examined by using pedigree data and 17 microsatellites. The constant B, which is related to the number of lethal equivalents, was estimated to be 0 for the offspring of noninbred parents, but was >0 for the offspring of inbred parents and for all offspring. Percentage of successfully breeding tigers inversely correlated with inbreeding level (r=−0.626, α=0.05). Taken together, these findings suggest the population is suffering from inbreeding depression in juvenile survivorship and fecundity. No significant correlation was detectable for the mean litter size with f of either dams (r=−0.305, α=0.46) or kittens (r=0.105, α=0.71), indicating litter size was not strongly subject to inbreeding depression. The average number of alleles per locus was 4.24±1.03 (SE), but effective number of alleles was only 2.53±0.91. Twenty-one alleles carried by early breeders at 13 loci were absent in the present breeders and potential breeders. Multilocus heterozygosity was inversely correlated with inbreeding levels (r=−0.601, α=0.004). These findings suggest rapid allelic diversity loss is occurring in this small captive population and that heterozygosity is being lost as it becomes more inbred. Our phylogenetic analysis supports past work indicating introgression from northern Indochinese tigers in the population. As no wild representatives of the South China tiger can be added to the captive population, we may consider the alternate scenario of further introgression in the interest of countering inbreeding depression and declining genetic diversity.
Article
Inbreeding is reputed to distort sex-ratios by reducing the proportion of the homogametic sex. However, many data sets do not show such an effect, and there is a known selective publication bias. To resolve the issue, we (a) developed detailed theoretical expectations for the effects of inbreeding on sex-ratios for autosomal and sex-linked loci with sex-limited effects or with equal effects in the two sexes, (b) evaluated the effects of inbreeding on sex-ratios in a new sample of 25 vertebrate taxa, and (c) evaluated the effects of inbreeding on sex-ratios for 69 replicate populations of Drosophila melanogaster. Theoretical analyses indicated that directional distortions of sex-ratios under inbreeding due to sex-linked loci with sex-limited expression are expected to be small and uncommon and that there will be no distortions in marsupials. Further, sex linked alleles expressed equally in both sexes may also distort sex-ratios following inbreeding. Autosomal sex-limited alleles should not result in directional sex-ratio distortions in large populations or across many replicates, but may lead to distortions of random direction in some small populations. There were no significant directional distortions of sex-ratio due to inbreeding in either the vertebrates or the Drosophila populations. However, there were significant random distortions of sex-ratios in both data sets, presumably from autosomal sex-limited alleles that had drifted in individual populations. Thus, directional distortions in sex-ratio are not a consistent signal of inbreeding depression.
Article
The classic study of dog behavior gathered into one volume. Based on twenty years of research at the Jackson Laboratory, this is the single most important and comprehensive reference work on the behavior of dogs ever complied. "Genetics and the Social Behavior of the Dog is one of the most important texts on canine behavior published to date. Anyone interested in breeding, training, or canine behavior must own this book."—Wayne Hunthausen, D.V.M., Director of Animal Behavior Consultations "This pioneering research on dog behavioral genetics is a timeless classic for all serious students of ethology and canine behavior."—Dr. Michael Fox, Senior Advisor to the President, The Humane Society of the United States "A major authoritative work. . . . Immensely rewarding reading for anyone concerned with dog-breeding."—Times Literary Supplement "The last comprehensive study [of dog behavior] was concluded more than thirty years ago, when John Paul Scott and John L. Fuller published their seminal work Genetics and the Social Behavior of the Dog."—Mark Derr, The Atlantic Monthly "Genetics and the Social Behavior of the Dog is essential reading for anyone involved in the breeding of dogs. No breeder can afford to ignore the principles of proper socialization first discovered and articulated in this landmark study."-The Monks of New Skete, authors of How to Be Your Dog's Best Friend and the video series Raising Your Dog with the Monks of New Skete.
Article
Barring holocausts, demographic forecasts suggest a “demographic winter” lasting 500–1,000 years and eliminating most habitat for wildlife in the tropics. About 2,000 species of large, terrestrial animals may have to be captively bred if they are to be saved from extinction by the mushrooming human population. Improvements in biotechnology may facilitate the task of protecting these species, but it probably will be decades at least before cryotechnology per se is a viable alternative to captive breeding for most species of endangered wildlife. We suggest that a principle goal of captive breeding be the maintenance of 90% of the genetic variation in the source (wild) population over a period of 200 years. Tables are provided that permit the estimation of the ultimate minimum size of the captive group, given knowledge of the exponential growth rate of the group, and the number of founders. In most cases, founder groups will have to be above 20 (effective) individuals. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/38475/1/1430050205_ftp.pdf
Article
Juvenile mortality of inbred young was higher than that of noninbred young in 15 of 16 species of captive ungulates. In 19 of 25 individual females, belonging to ten species, a larger percentage of young died when the female was mated to a related male than when she was mated to an unrelated male.
Article
ALTHOUGH the human female is known to be more viable, on the average, than the human male, the biological mechanisms for this difference are poorly understood. A relevant question is, to what extent does heterozygosity for X-linked loci contribute to survival of the XX female? The advantage accruing to the XX female because of this factor may be defined as X-heterosis1. Most instances of serious X-linked disorders such as haemophilia occur in males, but the total incidence of such severe diseases is relatively small and cannot account for the observed sex differences in age specific mortality rates. It is conceivable that X-heterosis is relatively insignificant in the total population, and that the bulk of the observed sex difference is attributable to physiological factors that are a consequence of sex differentiation (for example, the apparent oestrogen-sparing effect on coronary heart disease) and/or to psycho-cultural factors that may pertain to diminished exposure of woman to environmental hazards (for example, industrial pollutants).
Article
Analysis of 40 semen samples collected by electroejaculation from 18 cheetahs revealed no major differences in seminal traits among Transvaal, South West (Namibia) or hybrid (Transvaal X South West) males. However, mean spermatozoal concentration (14.5 X 10(6) spermatozoa/ml of ejaculate) and percent motility (54.0%) were less in cheetahs than in domestic cats (147.0 X 10(6) spermatozoa/ml of ejaculate, 77.0% motility) subjected to the same electroejaculation regimen. On the average, cheetah ejaculates contained 71.0% morphologically abnormal spermatozoa compared to 29.1% aberrant spermatozoal forms in the domestic cat. These results indicate that seminal characteristics in the cheetah are markedly inferior compared to the domestic cat, particularly with respect to the incidence of pleiomorphic spermatozoa. Because a recent parallel study demonstrates that the cheetah lacks genetic variation, it appears likely that spermatozoal abnormalities are a genetic consequence of genomic homozygosity characteristic of this endangered species.
Article
The red wolf (Canis rufus) is an endangered species with 194 individuals remaining in the wild and in various captive facilities. Breeding efforts at the Graham, WA site (Point Defiance Zoo and Aquarium) have involved artificial insemination with fresh or frozen semen in an effort to increase population and maximize the genetic potential of the stock. Electron microscopic observations were made in semen specimens obtained by electro-ejaculation from mature males prior to their use in an effort to determine semen parameters that might be useful in guiding breeding procedures. Sperm samples were either fixed immediately or treated with capacitating media and fixed after 4 to 7 hr of incubation. Many of the specimens examined were pyospermic (white cell in semen) and showed evidence of spermophagy, primarily by neutrophils. Of the six animals surveyed, only one showed little evidence of spermophagy, and three had extensive pyospermia and spermophagy but this finding was not correlated with fertility. Samples fixed immediately as well as those incubated for several hours showed evidence of spermophagy, indicating that the phagocytosis was not the result of culture. Gene pool restriction and/or captive stress may be contributing factors of reduced semen quality.
Article
Ejaculates of the red wolf (Canis rufus) were evaluated immediately after collection and freeze-thawing to initiate a reproductive database for this endangered species. Electroejaculates from 13 adult red wolves collected during the breeding season (February-March; n=25; 1-3 collections/male) had a mean volume of 4.7+/-0.7 ml, 146.5+/-25.7 x 10(6) spermatozoa/ml and 71.2% motile spermatozoa. The mean proportion of cells with normal morphology was 73.6+/-3.2% (range, 20.3-93.7%), with 64% of ejaculates (16/25) containing 70-90% normal spermatozoa. The four most predominant abnormalities were a coiled flagellum (8.1%), a bent flagellum (4.7%), a bent midpiece with no cytoplasmic droplet (3.3%;), and a detached head defect (6.4%). After cooling in glycerolated extender, semen was frozen using a pelleting method on dry ice before plunging into liquid nitrogen. Pellets were thawed in phosphate buffered saline and examined for % sperm motility, normal morphology, viability and intact acrosomes. There was a decline (P < 0.05) in sperm motility (approximately 40%) and percentage of normal sperm (11.9%) after freezing, but no change in the proportion of viable cells. After freezing, there was a marked decline (P < 0.05) in the proportion of intact acrosomes from 74.5% to 55.5% which was accompanied by an increased proportion (P < 0.05) of partial acrosomes from 11.9% to 35.8%. These data demonstrate that, although red wolf spermatozoa can survive freeze-thawing using a technique common for domestic dog sperm, the finding of significant acrosome damage reveals (1) likely species specificity in the Canis genus and (2) the need for refining sperm cryopreservation technology for the red wolf.
Article
Semen parameters were evaluated on ejaculates of a captive population of red wolves (Canis rufus) sampled over two consecutive mating seasons. A total of 31 samples from 15 animals yielded mean sperm motility of 69.6 +/- 19.4%, mean sperm density of 131 +/- 124 x 10(6) ml-1, mean total number of spermatozoa of 470 +/- 465 x 10(6) and mean percentage morphologically abnormal spermatozoa of 35 +/- 11.8%. Restricting the data to animals sampled three times or more or limiting the samples to proven breeders resulted in statistically non-significant differences in these numbers (P < 0.05). When compared with data from other canines the seminal parameters of red wolves are at the lower extremes of the range. In particular the proportion of morphologically abnormal spermatozoa (35%) is approximately twice that seen in other canine species. Light microscopic analysis of abnormal forms revealed that almost half (45%) were bent defects, another 40% were secondary defects (coiled, detached and immature) and 15% were primary defects. Electron microscopy confirmed the presence of substantial numbers of morphologically abnormal forms including double-headed and double-flagellar cells, bent or kinked forms especially in the neck region, acrosomal abnormalities and bizarre spermatids. Approximately one-third of the samples also showed the presence of white blood cells, in some cases demonstrating sperm phagocytosis (spermophagy). These results are consistent with the concept of declining sperm parameters associated with restricted gene pools in numerically limited populations. However, alternative explanations are also explored.