Inbreeding and inbreeding depression in endangered red wolves (Canis rufus)

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, re‐introduced population of red wolves (Canis rufus) in North Carolina. Since red wolves were first re‐introduced 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.     

Using faecal DNA sampling and GIS to monitor hybridization between red wolves (Canis rufus) and coyotes (Canis latrans)

The US Fish and Wildlife Service's (USFWS) Red Wolf Recovery Program recognizes hybridization with coyotes as the primary threat to red wolf recovery. Efforts to curb or stop hybridization are hampered in two ways. First, hybrid individuals are difficult to identify based solely on morphology. Second, managers need to effectively search 6000 km(2) for the presence of coyotes and hybrids. We develop a noninvasive method to screen large geographical areas for coyotes and hybrids with maternal coyote ancestry by combining mitochondrial DNA sequence analysis of faeces (scat) and geographic information system (GIS) technology. This method was implemented on the Alligator River National Wildlife Refuge (1000 km(2)) in northeastern North Carolina. A total of 956 scats were collected in the spring of 2000 and 2001 and global positioning system (GPS) coordinates were recorded. Seventy-five percent of the scats were assigned to species and five coyote/hybrid scats were detected. Placement of scat location coordinates on a map of the experimental population area revealed that four of the coyote/hybrid scats were detected within the home ranges of sterilized hybrids. The other coyote/hybrid scat indicated the presence of a previously unknown individual. We suggest this method be expanded to include more of the experimental population area and be optimized for use with nuclear markers to improve detection of hybrid and back-crossed individuals.     

Reproductive endocrine patterns in captive female and male red wolves (Canis rufus) assessed by fecal and serum hormone analysis

Reproductive steroid profiles in female (n=13) and male (n=5) red wolves (Canis rufus) were characterized in fecal samples collected during the breeding season (December—May) and over a 1 year period, respectively. Blood samples from females (n=12) also were collected during the periovulatory period for luteinizing hormone (LH) and steroid analysis. High performance liquid chromatography (HPLC) of fecal extracts determined that estradiol and estrone constituted the major and minor forms, respectively, of fecal estrogen metabolites. Although native progesterone was present, pregnane metabolites predominated as the major forms of fecal progestins. HPLC analysis of fecal extracts from males revealed no native testosterone, but rather the predominance of more polar androgen metabolites. Based on hormone profiles and/or pup production, females were classified as pregnant (n=3), ovulatory‐nonpregnant (n=9), or acyclic (n=3). Longitudinal monitoring of females indicated no pregnancy‐specific differences in concentrations of either fecal progestagen or estrogen metabolites compared to ovulatory‐nonpregnant individuals; however, baseline progestagen concentrations were consistently elevated in acyclic females. There was good correspondence between serum and fecal steroid concentration during the periovulatory period. A rise in serum estrogens preceded the ovulatory LH surge which was then followed by a significant progesterone rise during the luteal phase. In males, changes in fecal androgen metabolite concentrations coincided with photoperiod fluctuations, increasing in late autumn and reaching peak concentrations during mid‐ to late winter just before the start of the breeding season. Collectively, these results serve as a database of ovarian and testicular endocrine events in this species, which can be utilized in population management and application of assisted reproductive technologies. Zoo Biol 21:321–335, 2002. © 2002 Wiley‐Liss, Inc.     

Captive breeding and the reintroduction of Mexican and red wolves

Mexican and red wolves were both faced with extinction in the wild until captive populations were established more than two decades ago. These captive populations have been successfully managed genetically to minimize mean kinship and retain genetic variation. Descendants of these animals were subsequently used to start reintroduced populations, which now number about 40-50 Mexican wolves in Arizona and New Mexico and about 100 red wolves in North Carolina. The original captive Mexican wolf population was descended from three founders. Merging this lineage with two other captive lineages, each with two founders, has been successfully carried out in the captive population and is in progress in the reintroduced population. This effort has resulted in increased fitness of cross-lineage wolves, or genetic rescue, in both the captive and reintroduced populations. A number of coyote-red wolf hybrid litters were observed in the late 1990s in the reintroduced red wolf population. Intensive identification and management efforts appear to have resulted in the elimination of this threat. However, population reintroductions of both Mexican and red wolves appear to have reached numbers well below the generally recommended number for recovery and there is no current effort to re-establish other populations.     

Estrous cyclicity and reproductive success are unaffected by translocation for the formation of new reproductive pairs in captive red wolves (Canis rufus)

This study investigated possible female-related causes for inconsistent success among reproductive pairs in the zoo-based red wolf (Canis rufus) population. Females (n = 13) at seven institutions were assessed for evidence of ovulation and normal reproductive cycles through the measurement of estradiol and progesterone metabolite excretion in feces. Fecal cortisol metabolites (FCM) were also measured. Factors potentially affecting FCM and/or estrous cyclicity were recorded, including exhibit status (on vs. off), reproductive history (proven vs. unproven), copulatory behaviors (ties observed: yes or no), pregnancy/parturition (pups or no pups produced), and translocation before the observed breeding season (yes or no). No differences were observed in baseline FCM between females housed on versus off-exhibit (p = .46) or between females producing pups and those who did not (p = .19). Baseline FCM were significantly lower among females observed in copulatory ties compared to females never observed in a tie (p = .04), and tended to be higher in females translocated before the breeding season compared to females in existing reproductive pairs (p = .11), and among historically unproven females compared to proven females (p = .11). All females evaluated had an endocrine profile indicative of ovulation and among the four females translocated to be paired with a new male before the breeding season, two had successful pregnancies, producing litters. Therefore, despite observed differences in baseline FCM among factors, estrous cyclicity and reproductive success are unaffected by translocation for the formation of new reproductive pairs in the zoo-based red wolf population.     

Size‐assortative choice and mate availability influences hybridization between red wolves (Canis rufus) and coyotes (Canis latrans)

Anthropogenic hybridization of historically isolated taxa has become a primary conservation challenge for many imperiled species. Indeed, hybridization between red wolves (Canis rufus) and coyotes (Canis latrans) poses a significant challenge to red wolf recovery. We considered seven hypotheses to assess factors influencing hybridization between red wolves and coyotes via pair‐bonding between the two species. Because long‐term monogamy and defense of all‐purpose territories are core characteristics of both species, mate choice has long‐term consequences. Therefore, red wolves may choose similar‐sized mates to acquire partners that behave similarly to themselves in the use of space and diet. We observed multiple factors influencing breeding pair formation by red wolves and found that most wolves paired with similar‐sized conspecifics and wolves that formed congeneric pairs with nonwolves (coyotes and hybrids) were mostly female wolves, the smaller of the two sexes. Additionally, we observed that lower red wolf abundance relative to nonwolves and the absence of helpers increased the probability that wolves consorted with nonwolves. However, successful pairings between red wolves and nonwolves were associated with wolves that maintained small home ranges. Behaviors associated with territoriality are energetically demanding and behaviors (e.g., aggressive interactions, foraging, and space use) involved in maintaining territories are influenced by body size. Consequently, we propose the hypothesis that size disparities between consorting red wolves and coyotes influence positive assortative mating and may represent a reproductive barrier between the two species. We offer that it may be possible to maintain wild populations of red wolves in the presence of coyotes if management strategies increase red wolf abundance on the landscape by mitigating key threats, such as human‐caused mortality and hybridization with coyotes. Increasing red wolf abundance would likely restore selection pressures that increase mean body and home‐range sizes of red wolves and decrease hybridization rates via reduced occurrence of congeneric pairs.     

黑龙江省圈养狼交配行为的初步观察

2005 年10 月至2006 年4 月,采用焦点动物取样法和全事件扫描取样法,对黑龙江省哈尔滨北方森林动园4 对圈养狼交配活动进行了观察,以期了解无人干扰下圈养狼的交配过程及其交配模式。观察时间共计25 d, 225 h,实际录像时间为126 h,记录到爬跨741 次,成功交配46 次,成功爬跨交配占总爬跨次数的6. 2% 。狼在交配过程中有锁结现象,雄狼通常在一次爬跨、多次抽动后出现射精。交配行为一般发生在8∶ 00 ～10∶ 00和14∶00 ～ 16∶ 00。雌性具有明显的邀配模式,一旦邀配成功,雌狼站立不动,尾巴偏向一侧,腰部微下躬,配合雄狼爬跨。对交配参数进行单因素方差分析,4 只雄狼的抽插时间没有差异(P = 0. 827),而其锁结行为的时间差异极其显著(F = 71.43,P <0.001),交配期持续5 ～ 14 d,交配平均持续时间为534 ± 402 s,最长达1 588 s,
最短只有28 s。     

Locating hybrid individuals in the red wolf (Canis rufus) experimental population area using a spatially targeted sampling strategy and faecal DNA genotyping

Hybridization with coyotes (Canis latrans) continues to threaten the recovery of endangered red wolves (Canis rufus) in North Carolina and requires the development of new strategies to detect and remove coyotes and hybrids. Here, we combine a spatially targeted faecal collection strategy with a previously published reference genotype data filtering method and a genetic test for coyote ancestry to screen portions of the red wolf experimental population area for the presence of nonred wolf canids. We also test the accuracy of our maximum-likelihood assignment test for identifying hybrid individuals using eight microsatellite loci instead of the original 18 loci and compare its performance to the Bayesian approach implemented in newhybrids. We obtained faecal DNA genotypes for 89 samples, 73 of which were matched to 23 known individuals. The performance of two sampling strategies - comprehensive sweep and opportunistic spot-check was evaluated. The opportunistic spot-check sampling strategy required less effort than the comprehensive sweep sampling strategy but identified fewer individuals. Six hybrids or coyotes were detected and five of these individuals were subsequently captured and removed from the population. The accuracy and power of the genetic test for coyote ancestry is decreased when using eight loci; however, nonred wolf canids are identified with high frequency. This combination of molecular and traditional field-based approaches has great potential for addressing the challenge of hybridization in other species and ecosystems.     

The effects of inbreeding, genetic dissimilarity and phenotype on male reproductive success in a dioecious plant

Pollen fate can strongly affect the genetic structure of populations with restricted gene flow and significant inbreeding risk. We established an experimental population of inbred and outbred Silene latifolia plants to evaluate the effects of (i) inbreeding depression, (ii) phenotypic variation and (iii) relatedness between mates on male fitness under natural pollination. Paternity analysis revealed that outbred males sired significantly more offspring than inbred males. Independently of the effects of inbreeding, male fitness depended on several male traits, including a sexually dimorphic (flower number) and a gametophytic trait (in vitro pollen germination rate). In addition, full-sib matings were less frequent than randomly expected. Thus, inbreeding, phenotype and genetic dissimilarity simultaneously affect male fitness in this animal-pollinated plant. While inbreeding depression might threaten population persistence, the deficiency of effective matings between sibs and the higher fitness of outbred males will reduce its occurrence and counter genetic erosion.     

Factors influencing reproductive success and litter size in captive island foxes

A severe decline of island foxes (Urocyon littoralis) on the northern Channel Islands in the 1990s prompted the National Park Service to begin a captive breeding program to increase their numbers. Using detailed records of all the fox pairs (N = 267) that were part of the program on San Miguel, Santa Rosa, and Santa Cruz Islands from its inception in 2000 through 2007, we identified factors influencing the breeding success of pairs in captivity in the interest of formulating strategies that could increase captive productivity. We compiled a database of variables including litter size, reproductive success, distance to nearest occupied pen during the breeding season, subspecies, exposure, female age, male age, age difference, female and male origin (wild vs. captive born), same versus different origin, years paired, previous reproductive success by the pair, previous reproductive success by the female, mate aggression-related injuries, male previous involvement in a pair with mate aggression, and female previous involvement in a pair with mate aggression. We used multiple linear regression to identify factors predictive of litter size, and logistic regression to predict the probability of reproductive success. A larger inter-pen distance, older male age, less exposure, and a smaller intra-pair age difference positively affected litter size. The probabilities of reproductive success increased with fewer years paired and less exposure. Comparatively, pairs with wild born females (vs. captive born females), and previously successful pairs (vs. previously unsuccessful and new pairs) were most likely to be successful. These results indicate that the optimal situation was to pair wild-caught females with older males in sheltered pens that were as far from other pens as possible, to maintain successful pairs and repair unsuccessful ones. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

Group size,composition, and reproductive success in wild common marmosets (Callithrix jacchus)

Data from published sources about size and composition of wild common marmoset groups (Callithrix jacchus) were analyzed to see if the number of juveniles in a group is closely related to the number of other group members. Mean group size was 8.7 members including 4.4 adults (1.8 females, 2.5 males), 2.9 subadults, and 1.4 juveniles. The number of juveniles was significantly positively correlated to the number of adult males. Groups with one or two adult males had significantly fewer juveniles (mean: 1:1 juveniles) than groups containing more than two adult males (mean: 2.0 juveniles). Apart from a different number of subadults, results showed obvious similarities between common marmosets and tamarins of the genus Saguinus in size and composition of subgroups of adults as well as the key role of adult males in mediating the reproductive success of a breeding female. Common marmoset females seem to gain direct fitness benefits in increased reproductive success from the presence of a larger number of adult males. Whether or not other group members get fitness benefits depends on the reproductive strategy of adult males (monogamy vs. polyandry), their kinship, and on the genetic relationship of nonbreeders to the offspring of the breeding female. © 1995 Wiley-Liss, Inc.     

Retrospective investigation of captive red wolf reproductive success in relation to age and inbreeding

The critically endangered red wolf (Canis rufus) has been subject to a strictly managed captive breeding program for three decades. A retrospective demographic analysis of the captive population was performed based on data from the red wolf studbook. Data analyses revealed a decrease in the effective population size relative to the total population size, and changes in age structure and inbreeding coefficients over time. To varying degrees, the probability of successful breeding and litter sizes declined in association with increasing dam age and sire inbreeding coefficients. Neonate survival also declined with increasing dam age. Recent changes in strategies regarding breed-pair recommendations have resulted in moderate increases in reproductive success. Zoo Biol 28:214–229, 2009. © 2009 Wiley-Liss, Inc.     

The effect of fast created inbreeding on litter size and body weights in mice

This study was designed to reveal any differences in effects of fast created versus total inbreeding on reproduction and body weights in mice. A line selected for large litter size for 124 generations (H) and a control line (K) maintained without selection for the same number of generations were crossed (HK) and used as a basis for the experiment. Within the HK cross, full sib, cousin or random mating were practised for two generations in order to create new inbreeding (IB_F) at a fast rate. In the first generation of systematic mating, old inbreeding was regenerated in addition to creation of new inbreeding from the mating design giving total inbreeding (IB_T). The number of pups born alive (NBA) and body weights of the animals were then analysed by a model including both IB_T and IB_F. The IB_T of the dam was in the present study found to reduce the mean NBA with -0.48 (± 0.22) (p < 0.05) pups per 10% increase in the inbreeding coefficient, while the additional effect of IB_F was -0.42 (± 0.27). For the trait NBA per female mated, the effect of IB_T was estimated to be -0.45 (± 0.29) per 10% increase in the inbreeding coefficient and the effect of IB_F was -0.90 (± 0.37) (p < 0.05) pups. In the present study, only small or non-significant effects of IB_F of the dam could be found on sex-ratio and body weights at three and six weeks of age in a population already adjusted for IB_T.     

Effects of inbreeding on infant mortality in captive primates

Breeding records for 16 primate colonies representing six families and both suborders were obtained from 10 institutions breeding primates in captivity and from the international studbook on one endangered species. Inbreeding coefficients relative to the founding population were calculated for each individual born. Individuals with an inbreeding coefficient of zero were classified as “noninbred” those with inbreeding coefficients greater than zero, as “inbred.” Infant mortality was defined as all deaths prior to the age of 6 months. Infant mortality of inbred young was higher than that of noninbred young in 15 of the 16 colonies surveyed (P =0.0003, one-tailed sign test). The higher mortality rate of the inbred young was significant by a Fisher’s exact test with a probability less than or equal to 0.05 in five of the individual colonies: Lemur fulvus, Saguinus fuscicollis illigeri, Saguinus fuscicollis, Leontopithecus rosalia,and Mandrillus sphinx.     

Helper effects on pup lifetime fitness in the cooperatively breeding red wolf (Canis rufus)

The evolutionary maintenance of cooperative breeding systems is thought to be a function of relative costs and benefits to breeders, helpers and juveniles. Beneficial effects of helpers on early-life survivorship and performance have been established in several species, but lifetime fitness benefits and/or costs of being helped remain unclear, particularly for long-lived species. We tested for effects of helpers on early- and late-life traits in a population of reintroduced red wolves (Canis rufus), while controlling for ecological variables such as home-range size and population density. We found that the presence of helpers in family groups was positively correlated with pup mass and survival at low population density, but negatively correlated with mass/size at high density, with no relation to survival. Interestingly, mass/size differences persisted into adulthood for both sexes. While the presence of helpers did not advance age at first reproduction for pups of either sex, females appeared to garner long-term fitness benefits from helpers through later age at last reproduction, longer reproductive lifespan and a greater number of lifetime reproductive events, which translated to higher lifetime reproductive success. In contrast, males with helpers exhibited diminished lifetime reproductive performance. Our findings suggest that while helper presence may have beneficial short-term effects in some ecological contexts, it may also incur long-term sex-dependent costs with critical ramifications for lifetime fitness.     

Experimental manipulation of breeding density and litter size: effects on reproductive success in the bank vole

1. Reproductive success of individual females may be determined by density-dependent effects, especially in species where territory provides the resources for a reproducing female and territory size is inversely density-dependent.
2. We manipulated simultaneously the reproductive effort (litter size manipulation: ± 0 and + 2 pups) and breeding density (low and high) of nursing female bank voles Clethrionomys glareolus in outdoor enclosures. We studied whether the reproductive success (number and quality of offspring) of individual females is density-dependent, and whether females can compensate for increased reproductive effort when not limited by saturated breeding density.
3. The females nursing their young in the low density weaned significantly more offspring than females in the high density, independent of litter manipulation.
4. Litter enlargements did not increase the number of weanlings per female, but offspring from enlarged litters had lower weight than control litters.
5. In the reduced density females increased the size of their home range, but litter manipulation had no significant effect on spacing behaviour of females. Increased home range size did not result in heavier weanlings.
6. Mother's failure to successfully wean any offspring was more common in the high density treatment, whereas litter manipulation or mother's weight did not affect weaning success.
7. We conclude that reproductive success of bank vole females is negatively density-dependent in terms of number, but not in the quality of weanlings.
8. The nursing effort of females (i.e. the ability to provide enough food for pups) seems not to be limited by density-dependent factors.