Successful assisted rearing and reintegration of a blue wildebeest calf into a managed herd prior to weaning.

The blue wildebeest (Connochaetes taurinus; Burchell, 1823) is an African ungulate that is notoriously difficult to hand-rear and reintegrate into managed herds. The following case report is of a female wildebeest neonate that was orphaned, bottle-reared, and successfully reintroduced into a herd at a zoological facility. Since blue wildebeests are a highly precocial and herd-oriented species that calve synchronously in the wild as a reproductive strategy to maximize survival, early release of assist-reared neonates into managed herds before weaning may be an effective strategy for increasing the chance of acceptance. Wildebeest calves can also be easily trained for bottle-feedings in the field to facilitate early release. Due to a lack of literature on the assisted rearing and reintegration of wildebeest calves into managed herds, this case report provides useful techniques for the feeding, training, and releasing of bottle-reared wildebeests that may also be applicable to other assist-reared herd species at zoological facilities.

Comparison of divergent breeding management strategies in two species of semi-captive eland in Senegal.

Breeding management of small populations may have a critical influence on the development of population characteristics in terms of levels of genetic diversity and inbreeding. Two populations of antelope sister species - Critically Endangered Western Derby eland (Tauroragus derbianus derbianus) and non-native Least Concern Cape eland (Taurotragus oryx oryx) bred under different management strategies were studied in Senegal, Western Africa. The aims of the study were to compare the population genetic parameters of the two species and to test for the presence of interspecific hybrids. In total, blood and tissue samples from 76 Western Derby elands and 26 Cape elands were investigated, using 12 microsatellite markers. No hybrid individuals were detected in the sampled animals within the multispecies enclosure in Bandia Reserve, Senegal. The parameters of genetic polymorphism indicated much lower genetic diversity in Western Derby elands compared to Cape elands. On the other hand, the coefficient of inbreeding was low in both species. It is hypothesized that this could be a positive effect of strict population management of Western Derby elands, which, despite the loss of genetic diversity, minimizes inbreeding.

Individual variation of isotopic niches in grazing and browsing desert ungulates.

Ungulates often adjust their diet when food availability varies over time. However, it is poorly understood when and to what extent individuals change their diet and, if they do so, if all individuals of a population occupy distinct or similar dietary niches. In the arid Namibian Kunene Region, we studied temporal variations of individual niches in grazing gemsbok (Oryx gazella gazella) and predominantly browsing springbok (Antidorcas marsupialis). We used variation in stable C and N isotope ratios of tail hair increments as proxies to estimate individual isotopic dietary niches and their temporal plasticity. Isotopic dietary niches of populations of the two species were mutually exclusive, but similar in breadth. Isotopic niche breadth of gemsbok was better explained by within-individual variation than by between-individual variation of stable isotope ratios, indicating that gemsbok individuals were facultative specialists in using isotopically distinct local food resources. In contrast, inter- and intra-individual variations contributed similarly to the isotopic niche breadth of the springbok population, suggesting a higher degree of individual isotopic segregation in a more generalist ungulate. In both species, between-individual variation was neither explained by changes in plant primary productivity, sex, geographical position nor by group size. Within species, individual dietary niches overlapped partially, suggesting that both populations included individuals with distinct isotopic dietary niches. Our study provides the first evidence for isotopic dietary niche segregation in individuals of two distinct desert ungulates. Similar, yet isotopically distinct dietary niches of individuals may facilitate partitioning of food resources and thus individual survival in desert ecosystems.

Craniometrical studies on the skull of Tibetan gazelle (Procapra Picticaudata) / Estudios craneométricos en el cráneo de la gacela del Tibet (Procapra Picticaudata)

A total of 10 skulls of Tibetan gazelle were utilized in this study. Craniometric measurements for 22 different parts of the skull were made. Skull indices and ratios were calculated. A skull index of 43.22+/-0.44, a cranial index of 58.37+/-0.80 and a facial index of 116.37+/-1.24 were obtained.

Un total de 10 cráneos de gacela tibetana se utilizaron en este estudio. Mediciones craniométricos para 22 diferentes partes de los cráneos fueron realizadas. Los índices craneales y sus razones fueron calculadas. Un índice de cráneo de 43,22 +/- 0,44, un índice craneal de 58,37 +/- 0,80 y un índice facial de 116,37 +/- 1,24 se obtuvieron.

Developmental changes of nasal and oral calls in the goitred gazelle Gazella subgutturosa, a nonhuman mammal with a sexually dimorphic and descended larynx.

In goitred gazelles (Gazella subgutturosa), sexual dimorphism of larynx size and position is reminiscent of the case in humans, suggesting shared features of vocal ontogenesis in both species. This study investigates the ontogeny of nasal and oral calls in 23 (10 male and 13 female) individually identified goitred gazelles from shortly after birth up to adolescence. The fundamental frequency (f0) and formants were measured as the acoustic correlates of the developing sexual dimorphism. Settings for LPC analysis of formants were based on anatomical dissections of 5 specimens. Along ontogenesis, compared to females, male f0 was consistently lower both in oral and nasal calls and male formants were lower in oral calls, whereas the first two formants of nasal calls did not differ between sexes. In goitred gazelles, significant sex differences in f0 and formants appeared as early as the second week of life, while in humans they emerge only before puberty. This result suggests different pathways of vocal ontogenesis in the goitred gazelles and in humans.

Indirect effects and traditional trophic cascades: a test involving wolves, coyotes, and pronghorn.

The traditional trophic cascades model is based on consumer resource interactions at each link in a food chain. However, trophic-level interactions, such as mesocarnivore release resulting from intraguild predation, may also be important mediators of cascades. From September 2001 to August 2004, we used spatial and seasonal heterogeneity in wolf distribution and abundance in the southern Greater Yellowstone Ecosystem to evaluate whether mesopredator release of coyotes (Canis latrans), resulting from the extirpation of wolves (Canis lupus), accounts for high rates of coyote predation on pronghorn (Antilocapra americana) fawns observed in some areas. Results of this ecological perturbation in wolf densities, coyote densities, and pronghorn neonatal survival at wolf-free and wolf-abundant sites support the existence of a species-level trophic cascade. That wolves precipitated a trophic cascade was evidenced by fawn survival rates that were four-fold higher at sites used by wolves. A negative correlation between coyote and wolf densities supports the hypothesis that interspecific interactions between the two species facilitated the difference in fawn survival. Whereas densities of resident coyotes were similar between wolf-free and wolf-abundant sites, the abundance of transient coyotes was significantly lower in areas used by wolves. Thus, differential effects of wolves on solitary coyotes may be an important mechanism by which wolves limit coyote densities. Our results support the hypothesis that mesopredator release of coyotes contributes to high rates of coyote predation on pronghorn fawns, and demonstrate the importance of alternative food web pathways in structuring the dynamics of terrestrial systems.

Irruptive population dynamics in Yellowstone pronghorn.

Irruptive population dynamics appear to be widespread in large herbivore populations, but there are few empirical examples from long time series with small measurement error and minimal harvests. We analyzed an 89-year time series of counts and known removals for pronghorn (Antilocapra americana) in Yellowstone National Park of the western United States during 1918-2006 using a suite of density-dependent, density-independent, and irruptive models to determine if the population exhibited irruptive dynamics. Information-theoretic model comparison techniques strongly supported irruptive population dynamics (Leopold model) and density dependence during 1918-1946, with the growth rate slowing after counts exceeded 600 animals. Concerns about sagebrush (Artemisia spp.) degradation led to removals of >1100 pronghorn during 1947-1966, and counts decreased from approximately 700 to 150. The best models for this period (Gompertz, Ricker) suggested that culls replaced intrinsic density-dependent mechanisms. Contrary to expectations, the population did not exhibit enhanced demographic vigor soon after the termination of the harvest program, with counts remaining between 100 and 190 animals during 1967 1981. However, the population irrupted (Caughley model with a one-year lag) to a peak abundance of approximately 600 pronghorn during 1982-1991, with a slowing in growth rate as counts exceeded 500. Numbers crashed to 235 pronghorn during 1992-1995, perhaps because important food resources (e.g., sagebrush) on the winter range were severely diminished by high densities of browsing elk, mule deer, and pronghorn. Pronghorn numbers remained relatively constant during 1996-2006, at a level (196-235) lower than peak abundance, but higher than numbers following the release from culling. The dynamics of this population supported the paradigm that irruption is a fundamental pattern of growth in many populations of large herbivores with high fecundity and delayed density-dependent effects on recruitment when forage and weather conditions become favorable after range expansion or release from harvesting. Incorporating known removals into population models that can describe a wide range of dynamics can greatly improve our interpretation of observed dynamics in intensively managed populations.

An exceptional case of historical outbreeding in African sable antelope populations.

Empirical investigations of intraspecific outbreeding and subsequent introgressive hybridization in natural populations are rare, particularly among conspecific populations of large mammals. Using mitochondrial DNA data [partial control region (496 basepairs - bp) and cytochrome b gene (343 bp) sequences analysed from 95 individuals representing 17 sampling locations scattered through the African miombo (Brachystegia) woodland ecosystem] and phylogeographical statistical procedures (gene genealogy, nested cladistic and admixture proportion analyses), we (i) give a detailed dissection of the geographical genetic structure of Hippotragus niger; (ii) infer the processes and events potentially involved in the population history; and (iii) trace extensive introgressive hybridization in the species. The present-day sable antelope population shows a tripartite pattern of genetic subdivision representing West Tanzanian, Kenya/East Tanzanian and Southern Africa locations. Nested clade analysis revealed that past allopatric fragmentation, caused probably by habitat discontinuities associated with the East African Rift Valley system, together with intermediary episodic long-distance colonization and restricted, recurrent gene flow have played an predominant role in shaping the extent of maternal genetic diversity (10.4%) and population structure. An extensive (average rate of admixture = 20.0%), but geographically circumscribed and unidirectional hybridization event in the past was inferred, resulting in an extreme (the highest discovered so far in mammals) intraspecific difference of 18.2% among morphologically monotypic sable antelopes from West Tanzania. The results are used to provide an evolutionary framework within which taxonomic implications and conservation decisions can be evaluated.