Reintroduced Population Research Articles

Progeny sex ratio variation in ungulates: maternal age meets environmental perturbation of demograpgy

Many adaptive theories have been proposed for explaining variation in progeny sex ratio (PSR) of vertebrates (Hardy 1997). Of these, two opposing hypotheses are commonly used for ungulates: the Trivers and Willard hypothesis (TWH, Trivers and Willard 1973) and the local resource competition hypothesis (LRC, Silk 1983, Caley and Nudds 1987). Trivers and Willard (1973) proposed that when adaptive variance in reproductive success differs between the sexes, mothers should invest more in the sex with the higher variance and, therefore, opt to produce this sex when conditions enable the extra investment. Because most ungulates are polygynous with reproductive success varying considerably between males, this hypothesis is invoked if a male-biased PSR is associated with favorable conditions (e.g. Clutton-Brock et al. 1988 and others mentioned in Table 1). LRC predicts that the gender less apt to disperse imposes overall greater competition on the mother. To minimize this competition, mothers should produce the non-dispersing gender when conditions are favorable. Because in ungulates sons tend to disperse earlier than daughters, the LRC hypothesis is invoked if favorable conditions are associated with a female biased PSR (e.g. Hewison and Gaillard 1996 and others mentioned in Table 1). A separate adaptive theory for each of two opposing situations makes any results explainable on an ad hoc basis. This has caused several critics to question the findings (Williams 1979, Festa-Bianchet 1996, and others) and attribute them to random occurrences. However, as long as the pattern remains consistent within a species, the findings cannot be challenged and could be explained by differences in the biology of the various species (Kojola 1998). Nonetheless, I documented nine cases where the pattern was inconsistent within a species (Table 1). As pointed out by Hewison and Gaillard (1999), the abundance of intraspecific inconsistencies requires some explanation. While Type-I-error (Festa-Bianchet 1996) or heterogeneity within species (Hewison et al. 1999) are possible explanations for these inconsistencies, they appear improbable to me. It is my opinion that in many cases PSR is determined by the age of the mother and if the age of the mother is unaccounted for spurious correlations may be produced between PSR and other factors that have an age-dependent impact on the population. I demonstrate this effect using a Leslie matrix model (Appendix I) based on the dynamics of a reintroduced population of Asiatic wild ass exhibiting PSR that is dependent on maternal age (Saltz and Rubenstein 1995).

Population structure in the endangered Mauna Loa silversword, Argyroxiphium kauense (Asteraceae), and its bearing on reintroduction.

Reintroduction of populations of endangered species is a challenging task, involving a number of environmental, demographic and genetic factors. Genetic parameters of interest include historical patterns of genetic structure and gene flow. Care must be taken during reintroduction to balance the contrasting risks of inbreeding and outbreeding depression. The Mauna Loa silversword, Argyroxiphium kauense, has experienced a severe decline in population size and distribution in the recent past. Currently, three populations with a total of fewer than 1000 individuals remain. We measured genetic variation within and among the remnant populations using seven microsatellite loci. We found significant genetic variation remaining within all populations, probably related to the recent nature of the population impact, the longevity of the plants, and their apparent self-incompatibility. We also found significant genetic differentiation among the populations, reinforcing previous observations of ecological and morphological differentiation. With respect to reintroduction, the results suggest that, in the absence of additional data to the contrary, inbreeding depression may not be a substantial risk as long as propagules for the founding of new populations are adequately sampled from within each source population before additional inbreeding takes place. The results further suggest that if mixing of propagules from different source populations is not required to increase within-population genetic variation in the reintroduced populations, it may best be avoided.

Status of a reintroduced population of mountain gazelles Gazella gazella in central Arabia: management lessons from an aridland reintroduction

AbstractMountain gazelles were reintroduced to central Arabia during 1991–95. Hawtah reserve was searched for gazelles during the 1998–99 winter. Gazelles were seen in one wadi system and their signs were found in several others and on the plateau. Sightings were used to calculate the minimum number of gazelles in the Matham wadi system, which previously held most of the population. During October–November 1998, the minimum number was 64 per cent less than 4 years earlier. Frequent observation of recent signs in areas where no gazelles were seen suggested that daytime sightings alone were no longer adequate for monitoring this population. The decline in the number of gazelles seen, an increase in their flight distance and an apparent change in their activity patterns were consistent with the rangers' claim that poaching had commonly occurred. Poaching started after reserve management built, without adequate consultation, a new fence that was intended to bar local people from part of the reserve. Management lessons include the need for the following: continued monitoring of reintroduced populations after the initial postrelease phase; long-term dialogue with local people; effective law enforcement; and the management of aridland domestic livestock in ways that prevent inter specific competition for food causing the elimination of wild ungulates.

Status of a reintroduced population of mountain gazelles Gazella gazella in central Arabia: management lessons from an aridland reintroduction

Mountain gazelles were reintroduced to central Arabia during 1991–95. Hawtah reserve was searched for gazelles during the 1998–99 winter. Gazelles were seen in one wadi system and their signs were found in several others and on the plateau. Sightings were used to calculate the minimum number of gazelles in the Matham wadi system, which previously held most of the population. During October–November 1998, the minimum number was 64 per cent less than 4 years earlier. Frequent observation of recent signs in areas where no gazelles were seen suggested that daytime sightings alone were no longer adequate for monitoring this population. The decline in the number of gazelles seen, an increase in their flight distance and an apparent change in their activity patterns were consistent with the rangers' claim that poaching had commonly occurred. Poaching started after reserve management built, without adequate consultation, a new fence that was intended to bar local people from part of the reserve. Management lessons include the need for the following: continued monitoring of reintroduced populations after the initial postrelease phase; long-term dialogue with local people; effective law enforcement; and the management of aridland domestic livestock in ways that prevent inter specific competition for food causing the elimination of wild ungulates.

ASSESSMENT OF GENETIC VARIANCE AMONG SOURCE AND REINTRODUCED FISHER POPULATIONS

Abstract A series of reintroduction programs have reestablished fisher (Martes pennanti) populations to a large part of their former range. Horizontal starch-gel electrophoresis of 20 presumptive gene loci was used from 1996 to 1998 to investigate gene dynamics in 4 remnant fisher populations (sources) and 4 reintroduced fisher populations from the northeastern and Great Lakes regions of the United States. Mean multilocus heterozygosities, mean number of alleles per locus, and percentage polymorphic loci were 0.027–0.090, 1.2–1.6, and 10.0–30.0, respectively, in the 8 populations surveyed. Significant allelic frequency differentiation was detected among the 4 source populations and among the 4 reintroduced populations, but a significant proportion of the genetic variance was partitioned only among the 4 reintroduced populations. Pairwise comparisons between each source and its associated reintroduced population indicated that only older reintroductions have attained significant differentiation of allelic ...

Genetic Diversity and the Reintroduction of Meadow Species

Abstract: Restoration of formerly nutrient‐poor and species‐rich grasslands generally leads to an increase in species diversity. However, species without a persistent seed bank and with poor dispersal ability often do not re‐establish spontaneously. Here, reintroduction is an option. If existing populations are comparable in their genetic composition, any population will do. This is not the case if populations have local adaptations. Unfortunately, whether populations are adapted locally is not easily determined, in contrast to assessing differentiation using neutral genetic markers. We used AFLP to study genetic diversity of Cirsium dissectum and Succisa pratensis within and among several Junco‐Molinion plant communities in the Netherlands (up to 200 km apart) that were potential source populations, and followed the reintroduction using seeds from these populations. Also, vegetative growth phase characteristics of three populations of C. dissectum were analyzed under controlled conditions. Most of the genetic variation in these cross‐fertilizing species was found within populations. Small but significant genetic differences in band frequencies were found among populations (Fst 0.100 ‐ 0.135). The first generation of reintroduced plants contained less polymorphic bands than the source populations. The genetic differences caused by reintroduction using a limited number of seeds (founder effects) were significant in all except one case (Fst 0.012 ‐ 0.101 between source and corresponding reintroduced population), but the magnitude was smaller than the source population differentiation. In assignment tests, reintroduced populations resembled their source population more than any other population, but all populations contained sizeable proportions of plants that were assigned to most similar plants from other populations, indicating that the populations are only marginally distinct. Calculations show that reintroduction from more than one source population introduces significantly more polymorphic bands into the new population, capitalizing on the existence of band frequency differences among populations.

The influence of rainfall on range in a female desert ungulate: the Arabian oryx (Oryx leucoryx) in the Sultanate of Oman

AbstractIn this study we investigated the effect of rainfall on the home range (calculated over 90 days) of adult female Arabian oryx (Oryx leucoryx) in a reintroduced population in central Oman. We looked at response to rainfall for six rain events in the period June 1986 to January 1992; rainfall was localized on five occasions and on one occasion covered the study area. Response, in terms of range and core area, showed considerable variation between rainfall events, perhaps as a result of variation in ranging behaviour between individual oryx. However, in the first 90 days after localized rainfall the home range and core area of oryx outside rain areas increased before decreasing significantly 91–180 days after rain. In comparison, range and core area of oryx inside areas of localized rainfall either did not change or decreased after rainfall as animals took advantage of improved conditions locally rather than investigating grazing elsewhere. When rain fell over the whole study area, range size did not change, but there was an immediate increase in core area and a reduction in range overlap indicating movement to new areas. During extended drought very localized rainfall caused oryx to move quickly to areas of new rain and by 28 days 70% of all adult females had found fresh grazing. Thereafter numbers declined to around 30% by 225 days, before oryx again moved back into the new rain areas. We attributed this pattern of movement to changes in the nutritional quality, measured as crude protein, of available forage. Data for single animals revealed considerable individual variation in response to rainfall; some animals moved quickly to rain whilst others failed to reach it. This variation had consequences for reproductive success and survival and illustrated that, for the oryx, response to rainfall is a key to desert success.

Landscape-Scale Foraging Decisions by Reintroduced Arabian Oryx

We evaluated landscape-level movements of reintroduced Arabian oryx (Oryx leucoryx) in relation to rainfall for 8 years (1982-89). For the first 4 years (1982-85), captive-bred oryx released into habitat devoid of conspecifics demonstrated a distinct shift in movement patterns as foraging conditions deteriorated. Based on mean monthly estimates, during the first 2 months after rain, oryx used large areas (297-724 km 2 ), exhibited low site fidelity (15-32%) overlap between consecutive months), high range expansion (45-62%) new area used each month), and undertook more long distance journeys than expected (P < 0.01). From 2 to 3 months after rainfall, oryx reduced the amount of area used by 86%, increased site fidelity by 72%, reduced range expansion by 29%, and gradually suspended long distance forays. We related this shift to the low nutritive quality of the oryx's primary forage species (Stipagrostis spp.). Once Stipagrostis declined to extremely low levels of crude protein, copper, and phosphorus, the oryx apparently suspended their nutritionally costly searching activities, and instead remained in areas where Stipagrostis was most palatable. In contrast, in years 6 through 8 following their release, the oryx responded to rain with no apparent shift in foraging patterns. Instead, they exhibited less variable and reduced levels of range expansion (10-42%) and area use (180-211 km 2 ). In addition, site fidelity was more consistent on a monthly basis (46-65% overlap),. and long distance movements were more random regardless of the influence of rainfall on the nutritive value or palatability of Stipagrostis. The changes in movement patterns over time were attributed to: (1) a reduction in the oryx's threshold of acceptance for low-quality Stipagrostis; (2) decreased consumption of Stipagrostis and a concomitant increase in browse consumption, and (3) greater knowledge of the landscape. Captive-bred oryx released in years 7 and 8 into the existing reintroduced population reacted to changes in forage nutritive quality caused by rain with a similar shift in foraging patterns as exhibited by the first releases during their first 4 years in the desert. This result emphasizes the relative importance of learned foraging behavior in explaining changes over time in the movement patterns of the oryx. Results of this study indicate that reintroductions of social herbivores should be implemented in ways that enhance the transfer of knowledge from experienced to naive individuals.

Long-Term Viability of the Re-Introduced Population of the White-Tailed Eagle Haliaeetus albicilla in Scotland

The white-tailed eagle became extinct in Scotland early in the twentieth century after persecution by humans. A population has been re-established in western Scotland by the release, mainly as juveniles, of 82 wild-bred birds imported from Norway between 1975 and 1985. Some released immatures wandered widely, but birds settled on fixed home ranges within 100 km of the release site on Rum, usually at 3-4 years old. In 1992 there were c. 19 individuals, including eight pairs, occupying fixed home ranges. There was also an unknown number of immature birds. Annual survival rates were estimated at 73% for young birds prior to settlement and 94% thereafter from the observed numbers of released and established birds. However, estimates were imprecise because of the small size of the population and the lack of reliable individual marks. By 1992 a total of 29 young had been fledged in the wild from five home ranges. None of these young have yet bred. The mean breeding success of released birds increased with age up to 0.465 fledged young/pair/year at about 6 years old. There was significant variation in breeding success among individuals and/or home ranges. 13% of bird-years of occupation of fixed home ranges involved either unmated birds or supernumeraries in the home ranges of pairs, creating trios. A simulation model indicated that the observed proportion of unmated birds was similar to that expected from differences in the numbers of males and females arising by chance. It was estimated from the available demographic data that the population would be more likely to grow slowly than decrease if stochastic effects due to small population size did not operate. However, the 95% confidence interval for the estimated population multiplication rate encompassed decline at 11% per year and growth at 11% per year. Simulation models indicated that, with realistic assumptions about variation among individual birds or ranges and demographic parameters set at their maximum-likelihood values, there was a probability of about 0.6 that the present population would become extinct within 100 years. Only conditions which would permit population growth at 2-3% per year in the absence of stochastic, small-population effects would reduce the probability of extinction within 100 years to less than 0.1. Simulation of supplementary releases of imported juveniles indicated a substantial reduction in extinction risk from the release of a further 60 juveniles. Variation in the rate of release, within a range considered feasible (10 birds per year -1 or 20 birds year -1 ), had little effect on this result.

Breeding biology during establishment of a reintroduced Griffon Vulture Gyps fulvus population

We studied the breeding parameters of a reintroduced population of individually marked Griffon Vultures Gyps fulvus in the Grand Causses region of southern France from the time of first reintroduction in 1982 to 1992. Among nesters, 65% of the birds released as immatures or born in the wild recruited into the breeding population when 4 years old, i.e. 1 year earlier than previously described. The proportion of birds nesting each year was relatively high and increased with time, suggesting that conspecific attraction favoured recruitment. We detected a permanent adverse effect of long‐term captivity on the nesting success of birds released when more than 2 years old: compared to the natural population, birds which had been kept in captivity showed a reduced breeding success during the whole study period. The breeding success of released immatures and wild‐born birds was similar to the highest values observed in a natural population in the Spanish and French Pyrenees. Breeding failures did not usually result in mate change but affected nest‐site fidelity. Birds not born in the wild were more likely to recruit to the largest subcolonies available, which highlights the role of social attraction. The observed philopatry of wild‐born birds probably resulted from such a social attraction since most of them were born in the largest subcolony. Conspecific attraction maintained the spatial aggregation of nests, whereas nest changes after a breeding failure favoured the spatial expansion of the colony.

Effects of pH on embryo tolerance and adult behavior in the tiger salamander, Ambystoma tigrinum tigrinum

We examined adult discrimination ability and embryo performance under different pH conditions in the eastern tiger salamander, Ambystoma tigrinum tigrinum. We collected individuals from three populations in habitats that differed naturally in pH, thus allowing interpretation of population-specific responses in embryos and adults. We conducted pool-choice experiments in the field using two pH treatments to determine adult pH discrimination ability and controlled laboratory toxicity tests using eight pH treatments to evaluate embryo performance. Adult discrimination ability differed among source populations. Male salamanders from the locality with the highest pH were more likely to stay in neutral-pH pools and more likely to leave acidic ones. Males from the locality with the lowest pH were also more likely to remain within neutral pools, but their rates of staying and leaving acidic ones did not differ. These results suggest that the pH of the source-population habitat may influence breeding-habitat discrimination by adults. Decreasing pH produced similar patterns of lethal (survival) and sublethal (date and size at hatching) effects on embryos from the three populations, with reduced performance at low pH. Survival of embryos was more than 70% at pH 4.5 and above, but decreased dramatically at lower pH levels. The pH at which 50% mortality occurs (LC50) was estimated as 4.2, suggesting that tiger salamanders from our populations were relatively acid tolerant compared with congeners. However, significant sublethal effects could reduce the subsequent success of surviving hatchlings. Our results are consistent with the hypothesis that adult discrimination ability depends on pH levels in the breeding habitat. This suggests that adult behavior patterns could influence the success of population reintroductions to previously acidified areas. Thus, data on pH responses at all stages in the amphibian life cycle should contribute to management decisions.

Patterns of Predation by Reintroduced European Lynx in the Swiss Alps

We monitored European lynx (Lynx lynx) in a reintroduced population in the Swiss Alps from 1983 to 1988. We predicted that recolonizing lynx initially would reach a higher population density (and would kill more ungulates) than they would sustain once the population was established. We compared the home ranges and distribution of kills of 8 lynx in the established center of the population with those of 6 lynx at the expanding front of the population. Home ranges overlapped between males and females and were exclusive within the sexes in both areas, but at the front, home-range sizes were 3 times smaller. The distributions of kills were more concentrated, and distances between consecutive kills were shorter at the front

Management Options for Preserving Genetic Diversity: Reintroduction of Guam Rails to the Wild

Abstract: Population management programs recognize the importance of managing genetic diversity in species that are candidates for eventual reintroduction to natural habitats. The planned 1989 release of captive‐born Guam rails (Rallus owstoni), extinct in the wild since 1986, to the Northern Mariana island of Rota provides an opportunity to evaluate various management options for selecting breeders to produce young rails for release. Six options were compared to determine which one best replicated genetic diversity in the original captive founder population. Heterozygosity, allelic dimity, founder contribution, and founder genome equivalents were used as indicators of genetic diversity. Option 1: Randomly choose adults for breeding. Option 2: Choose the most fecund captive breeders. Option 3: Use allozyme data to choose parents that will produce the most genetically diverse chicks. Option 4: Choose pairs to equalize founder contribution in the population. Option 5: Choose pairs to maximize allelic diversity. Option 6: Choose pairs to maximize founder genome equivalents. Genetic management options based on pedigree analysis (#4, 5, 6) produced the most genetically diverse release populations for Rota. Managing founder genome equivalents produced a balance between equalizing founder contribution and maximizing allelic diversity, and provided the most genetically diverse population. Randomly selecting breeding pain, choosing the best captive breeding stock, or managing by allozyme data resulted in substantially reduced genetic diversity. Results illustrate that some of the most common approaches to population management or population reintroduction may produce significant loss of genetic diversity, whereas certain genetic management options may actually increase genetic diversity over current population levels.

An Analysis of Composition, Distribution, and Habitat Use of Reintroduced Desert Bighorn Sheep in Arches National Park, Utah

The ecology of a reintroduced population of desert bighorn sheep (Ovis canadensis nelsoni} is being investigated in Arches National Park. National Park Service objectives are: (1) determine general ecological parameters, including population and social dynamics, seasonal distribution and habitat use patterns, and general health characteristics; and (2) develop a comprehensive program of habitat analysis and evaluation that can be used to determine habitat suitability and identify transplant sites in other National Park Service units.

Cardiac Telemetry, Natality, and Food Habits of Bighorn Sheep at Bighorn Canyon National Recreation Area

Data were collected from May 1988 to May 1989 to aid in the development of a management program for Rocky Mountain bighorn sheep (Ovis canadensis canadensis) at Bighorn Canyon National Recreation Area (BICA). A principle goal of the management program at BICA is to promote the continued expansion of a reintroduced population of bighorn sheep throughout its ancestral habitat (BICA 1984). In previous research at BICA (Coates and Schemnitz 1988) we identified 3 factors as potentially limiting to herd expansion: visitor and/or vehicular disturbance of bighorns (especially reproductive ewes), competition with horses for a limited supply of grasses, and possible genetic constraints on recruitment (i.e., inbreeding depression) resulting from small founder group size.