Quagga Research Articles

Mammalian body size changes and Plio-Pleistocene environmental shifts: implications for understanding hominin evolution in eastern and southern Africa

This study examines geographic and temporal variation in three mammalian taxa co-occurring in eastern and southern Africa. The selected taxa—the spotted hyena ( Crocuta crocuta), the plains zebra ( Equus burchellii), and the impala ( Aepyceros melampus)—are geographically widespread in modern times and are abundant in eastern and southern African Plio-Pleistocene fossil sites. Craniodental measurements of modern conspecifics from known geographic locations are compared using multivariate statistical methods to discern patterns of modern geographic variation within taxa. Modern and fossil samples are statistically compared to assess the nature and extent of inferred shifts in body size, both between modern samples and through time in each region. These results indicate that modern spotted hyenas and plains zebras exhibit mainly size variation between regions, with southern African samples possessing statistically larger craniodental metrics than eastern African samples. Comparison of fossil and modern samples reveals that the fossil assemblages do not show the same pattern of geographic variation. Significant temporal changes are more numerous between fossil and modern eastern African samples, and these changes are not mirrored by similar changes in the southern African samples. The changes experienced by taxa in eastern Africa appear to have been more extreme and wide-ranging than those in southern Africa, a presumed refugium. This result accords well with genetic studies of several large mammal species and paleoenvironmental studies suggesting that eastern African localized environments were more affected by tectonism and volcanism than were those in southern Africa. This study suggests that different evolutionary scenarios may have existed within Africa during the Plio-Pleistocene, but that both regions played unique and complementary roles in the evolution of African hominins and the broader faunal community.

Characterization of Streptococcus equi subsp. ruminatorum isolated from spotted hyenas ( Crocuta crocuta) and plains zebras ( Equus burchelli), and identification of a M-like protein (SrM) encoding gene

Thirteen strains of Streptococcus equi subsp. ruminatorum from free-ranging spotted hyenas ( Crocuta crocuta) and plains zebras ( Equus burchelli) in Tanzania were characterized by biochemical and molecular-biological methods. Although the colony appearance of the S.e. ruminatorum wildlife strains differed from that of the S.e. ruminatorum type strain CECT 5772 T, all biochemical reactions of the wildlife strains were similar to those of the type strain. In addition, all wildlife strains produced hyaluronidase and were capable of hydrolysing arginine, three strains (23%) synthesized acetoin, but only eight strains (62%) produced acid from ribose. rep-PCR indicated that different clones of S.e. ruminatorum were distributed among the hyena and zebra populations in the study area. Identical rep-PCR patterns in hyena and zebra strains suggest that a direct transmission of S.e. ruminatorum between these species may occur. The presence of a M-like protein (SrM) gene was demonstrated in all S.e. ruminatorum strains including the type strain. Sequencing of the M-like protein gene revealed a hypervariable region within the deduced amino acid sequence. Most of the strains clustered with previously described strains based on the hypervariable region of the S.e. zooepidemicus SzP protein. Sequencing also demonstrated that identical SrM protein sequences were shared among S.e. ruminatorum strains from different host species.

A genetic index for stripe-pattern reduction in the zebra: the quagga project

The quagga project aims to breed plains zebra that phenotypically resemble the extinct quagga (Equus quagga quagga), by selective breeding to aggregate desirable characteristics, particularly a reduced striping pattern. The purpose of this study was to produce a genetic selection index to improve stripe-pattern reduction, and hence to produce an efficient and objective selective breeding protocol, which will hopefully be of use in future selection experiments. From images of selectively bred zebras, striping ratios for three regions were calculated. Correlations of parent-offspring relationships resulted in narrow-sense heritabilities. Data from two regions (R1 and R3) were used to create an index to improve selection and reduce striping. The index I = 3.1875 (R1) 4.8134 (R3) and the response to selection using the index, R = 0.6047 i.

A note on motor laterality in plains zebras (Equus burchellii) and impalas (Aepyceros melampus)

This observational field study used intermittent still photography to examine the distribution of motor laterality in images of two African grazing quadruped species: plains zebras (Equus burchellii) and impalas (Aepyceros melampus). Zebra images (n=708) had a laterality index of −6.21 and a Z-score of −1.65 (p=.098). Impala images (n=318) had a laterality index of −18.87 and a Z-score of −3.36 (p=.0008). The weak left motor bias in zebras aligns with that reported in domestic horses using a related method.

Karyotypic relationships among Equus grevyi, Equus burchelli and domestic horse defined using horse chromosome arm-specific probes

Using laser microdissection we prepared a set of horse chromosome arm-specific probes. Most of the probes were generated from horse chromosomes, some of them were derived from Equus zebra hartmannae. The set of probes were hybridized onto E. grevyi chromosomes in order to establish a genome-wide chromosomal correspondence between this zebra and horse. The use of arm-specific probes provided us with more information on the mutual arrangement of the genomes than we could obtain by means of whole-chromosome paints generated by flow sorting, even if we used reciprocal painting with probe sets from both species. By comparison of our results and results of comparative mapping in E. burchelli, we also established the chromosomal correspondence between E. grevyi and E. burchelli, providing evidence for a very close karyotypic relationship between these two zebra species. Establishment of the comparative map for E. grevyi contributes to the knowledge of the karyotypic phylogeny in the Equidae family.

An isthmus at the caecocolical junction is an anatomical feature of domestic and wild equids

The isthmus at the caecocolical junction in domestic equids is well described. Like another isthmus between the ansa proximalis coli (the colonic fermentation chamber or ‘large colon’) and the colon transversum (the distal or ‘small’ colon), this spot represents not only a potential anatomical feature contributing to particle ingesta retention but also an explicit predilection site for intestinal obstructions. The question whether this anatomical feature also occurs in wild equids is therefore of both physiological and medical interest but has not been addressed so far. In this paper, we report dissections of the large intestine of a domestic pony (Equus caballus f. dom.), a Przewalski horse (Equus przewalski) and a plains zebra (Equus burchelli). The intestinal tract section of all three animals were similar in length; each species displayed the caecocolical isthmus as well as the abrupt narrowing of the intestinal tract between the ‘large’ and the ‘small’ colon. Graphical descriptions of wild equid gastrointestinal anatomy should include these features.

Habitat use and movements of plains zebra (Equus burchelli) in response to predation danger from lions

Prey species must adapt their behavior to avoid predation. As a key prey item for lions (Panthera leo), plains zebras (Equus burchelli) were expected to respond to immediate threats posed by lions in their area. In addition, zebras were predicted to exhibit behavior tuned to reduce the potential for encounters with lions, by modifying their movement patterns in the times of day and habitats of greatest lion danger. We studied a population of approximately 600 plains zebra living in Ol Pejeta Conservancy, Kenya. We found that zebra abundance on or near a grassland patch was lower if lions had also been observed on that patch during the same day. Predation danger was highest in grassland habitat during the night, when lions were more active. Zebra sightings and global positioning system radio collar data indicated that zebras also reduced their use of grassland at night, instead using more woodland habitat. Zebras moved faster and took sharper turns in grassland at night. It is hypothesized that these more erratic movements assist zebras in avoiding detection or capture by lions.

Savanna herbivore dynamics in a livestock-dominated landscape: I. Dependence on land use, rainfall, density, and time

Ecosystem processes in African savannas can be better conserved if management is based on a mechanistic understanding of wildlife dynamics in livestock-dominated landscapes. For Laikipia District, a non-protected savanna region in northern Kenya, we used spatially explicit estimates of density to characterize factors influencing the dynamics of large herbivores on three land-use types: commercial ranches that favor wildlife, communal ‘group ranches’ practicing pastoralism, and the remainder (‘transitional’ properties). For 21-year time series of nine wild and two domestic species, linear model selection was used to ascribe between 45% (Grant’s gazelle) and 95% (plains zebra) of observed variation in biomass density to land use, rainfall-dependence, density-dependence, and trends over time. Strongly opposing patterns of variation across the landscape in wildlife and livestock densities affirmed the primacy of land use among factors influencing wildlife abundance in non-protected areas. Rainfall limited densities of only the dominant grazing species throughout the monitoring period (plains zebra and cattle), and of most other species while their densities were high. Regulating effects of density were detected only for the dominant wild grazing and browsing species (zebra and giraffe). All but two wild species (zebra and Grant’s gazelle) declined on at least one land-use type, for reasons that varied among land uses. Where favored, diverse and abundant wild herbivores (mean of 1.7 t km −2 on pro-wildlife ranches) can thrive even when sharing the landscape with a slightly higher biomass density of livestock (mean of 2.7 t km −2). Where not favored, only a few resilient wild species (e.g. gazelles and plains zebra) persist with high densities of livestock (mean of 4.6 t km −2 on transitional ranches). Maintaining higher wild species diversity in the landscape will depend on the creation of a network of unfenced conservation areas in which livestock densities are persistently low or zero, which are sufficiently large to act as ‘sources’ of wild species that are prone to displacement by humans and livestock, and which generate benefits to community members that exceed opportunity costs.

Savanna herbivore dynamics in a livestock-dominated landscape. II: Ecological, conservation, and management implications of predator restoration

Conserving African wildlife in human-occupied landscapes requires management intervention that is guided by a mechanistic understanding of how anthropogenic factors influence large-scale ecological processes. In Laikipia District, a dry savanna region in northern Kenya where wildlife share the landscape with humans and livestock, we examined why five of nine wild ungulate species suffered protracted declines on properties receiving the greatest conservation investment. Of 10 alternative causes examined, only an increase in predation, interacting with brief periods of high and low rainfall, was consistent with the timing, synchrony, duration and species composition of observed ungulate declines. The principal factor causing predation to increase was a shift in land use from cattle ranching, under which predators and plains zebras were severely suppressed, to wildlife conservation and ecotourism. This prompted a 5-fold increase in plains zebra abundance, and created a demand for living predators. Plains zebras ultimately comprised more than half the available prey biomass, and supported a substantial predator community, but were not limited by predators. We infer that increasing predation pressure caused predator-susceptible prey species to decline, via mechanisms that included apparent competition. Herbivore dynamics in Laikipia shared features with previously reported responses by prey communities to predator manipulation in Kruger and Serengeti National Parks. All featured one or a few numerically dominant herbivore species, which were primarily limited by rainfall and density, supporting a predator community that in turn limited the abundance of other prey species. In each case, predation had a profound effect, but on only a subset of prey species, reducing the evenness component of prey diversity. The presence of cattle in the landscape may affect predator–prey dynamics in both direct and indirect ways, depending on rainfall. In extreme years (floods or drought), episodic die-offs temporarily subsidize scavenging predators. In low rainfall years, competition between plains zebras and cattle, which negligibly support predators, may indirectly limit predator carrying capacity. Consequently, removal of cattle may favor not only zebras, but also their predators, and further depress predator-susceptible prey species.

Social relationships and reproductive state influence leadership roles in movements of plains zebra, Equus burchellii

In animal groups, collective movements emerge from individual interactions. Biologists seek to identify how characteristics of actors in these groups, and their relationships, influence the decision-making process. We distinguished two basic factors determining leadership in group choices: identity and state. We hypothesized that identity is more important to leadership in groups with stable relationships, which permit the development of habitual roles. In groups with fluid membership, particular individuals or subgroups are less likely to emerge as consistent leaders. Instead, we predicted that movement initiation in unstable groups depends on individual state at the time of the decision. We characterized how identity and reproductive state influenced leadership patterns in the movements of plains zebra. As in many other mammals, lactation in this species significantly alters water and energy needs. We investigated leadership in tightly knit harems and loosely bonded herds of multiple harems. Harem females tended to have habitual roles in the initiation of harem movement. In herds, however, we found no consistent leaders among harems. At both levels of social organization, lactation was a key determinant of leadership. In harems, lactating females were more likely to initiate movement than nonlactating females. In turn, harems containing lactating females were more likely to lead herd movements. Thus, we conclude that social relationships and reproductive state together shape the interactions that produce group behaviours. One benefit to lactating females of leading herd movements is preferential access to scarce water. Thus, leadership roles in group decisions may have fitness consequences.

Anthrax outbreak among Grevy's zebra (Equus grevyi) in Samburu, Kenya

AbstractAn anthrax outbreak occurred in the Wamba area of southern Samburu, Kenya, between December 2005 and March 2006. The outbreak affected equids including the endangered Grevy's zebras (Equus grevyi), plain zebras (Equis Burchelli) and donkeys (Equus asinus). Most of the deaths were localized in Nkaroni area just west of Wamba town. The diagnosis of anthrax was rapidly confirmed by bacteriological methods. The relevant government departments, including the Kenya Wildlife Service and Veterinary Department, and other stakeholders were promptly informed. Fifty‐three Grevy's zebra and 26 plains zebras died from anthrax. An equal number (eighteen) of adult male and female Grevy's zebras succumbed to the disease. The outbreak affected immature and mature individuals equally. The dead plain zebras included fifteen adult females, two adult males and nine immature individuals. The Veterinary Department responded by vaccinating livestock while Kenya Wildlife Service vaccinated 620 Grevy's zebras within southern Samburu. Examination of sites at which carcasses of animals which succumbed to the disease were burnt, revealed that unsupervised burning did not eliminate anthrax spores in 42% of the cases (n = 14). There is an urgent need to incorporate strategic wildlife disease monitoring in the struggle to save Grevy's zebras and other endangered species.

Bottom‐up and top‐down processes in African ungulate communities: resources and predation acting on the relative abundance of zebra and grazing bovids

African ungulate populations appear to be limited principally by their food resources. Within ungulate communities, plains zebras coexist with grazing bovids of similar body size, but rarely are the dominant species. Given the highly effective nutritional strategy of the equids and the resistance of zebras to drought, this is unexpected and suggests that zebra populations may commonly be limited by other mechanisms. Long‐term research in the Serengeti ecosystem and in the Kruger National Park suggests that zebra could be less sensitive to food shortage, and more sensitive to predation, than grazing bovids: if this is a general principle, then, at a larger scale, resource availability should have a weaker effect on the abundance of zebra than on grazing ruminants of similar body size (wildebeest and buffalo), and zebras should be relatively more abundant in ecosystems where predators are rare or absent. We test these expectations using data on 23 near‐natural ecosystems in east and southern Africa. The abundance of wildebeest is more closely related to resources than is that of zebra; buffalo are intermediate. We show that hyena densities are closely correlated with those of lions, and use the abundance of lions as an index of predation by large predators. The numerical response of lions to increases in the abundance of their prey was linear for mesoherbivores, and apparently so for the three species alone. Finally, the abundance of zebra relative to grazing bovids is lower in ecosystems with high biomasses of lions. These results indicate that zebras may commonly be more sensitive to top‐down processes than grazing bovids: the mechanism(s) have not been demonstrated, but predation could play a role. If it is true, then when numbers of the large mammalian predators decline, zebra populations should increase faster than buffalo and wildebeest.

Changes in large herbivore populations across large areas of Tanzania

AbstractWe collated aerial census data collected during the late 1980s to early 2000s for large herbivore populations in eight large census zones in Tanzania. Of the ungulate populations that showed significant changes in densities at the start versus end of this decade, most declined; very few populations increased significantly. Thomson's gazelle, Grant's gazelle, hartebeest, reedbuck, roan antelope, sable antelope, warthog and zebra, for example, declined in over 50% of the zones where they were surveyed. Interestingly, small‐bodied species fared particularly poorly in many census zones, whereas elephant and giraffe generally fared well across the country. Most populations of all herbivores declined in some portions of the country (e.g. Burigi‐Biharamulo, Katavi, Greater Ruaha and Tarangire census zones). These surveys suggest that, even in a country renowned for its protected areas and conservation commitment, some large herbivore populations need more conservation attention in order to remain stable.

Adjacent pastoral areas support higher densities of wild ungulates during the wet season than the Lake Mburo National Park in Uganda

The small size of many African protected areas makes adjacent rangelands potentially important in the local survival of wild animals. In order to assess the importance of pastoral areas to wild ungulates, we studied density and habitat choice of wild ungulates and cattle in Lake Mburo National Park, Uganda, the adjacent exclusively pastoral Nshara Dairy Ranch and on private land consisting of a mixture of ranching and subsistence farms. Transects, in the three land-use zones, were walked during the wet season and the data were analysed by DISTANCE sampling technique. We found significantly higher total density of wild ungulates on the dairy ranch compared with the National Park and private land. There was no significant difference in total wild animal density between the National Park and private land. Impala (Aepyceros melampus), zebra (Equus quagga), bushbuck (Tragelaphus scriptus) and waterbuck (Kobus ellipsiprymnus) had significantly higher densities on the dairy ranch compared to the National Park. Only eland (Taurotragus oryx) density was higher in the National Park compared to private land. Wild ungulates and cattle showed a high degree of habitat overlap, generally preferring open grassland. Our study shows that high densities of wild ungulates are not necessarily associated with protected areas. Pastoral areas may be important for populations of wild herbivores during the growing season despite a pronounced presence of livestock.

Sex of the foetus determines the time of weaning of the previous offspring of captive plains zebra ( Equus burchelli)

We examined if captive plains zebra ( Equus burchelli) mares change the timing of weaning according to the sex of the suckling foal and of the new impending foetus. We observed 19 captive plains zebra foals, in three different formations, at the Dvůr Králové Zoo. The earliest time for weaning of any foal was recorded at the age of only 243 days. The latest suckling that was ever recorded occurred 83 days before the dam's next delivery, when the foal was at the age of 355 days. We found that pregnant mares weaned their foals sooner than the non-pregnant mares. Survival analysis revealed that the sex of the foetus was the most influential factor in determining the weaning age of the current foal. Hence, if the foetus was a male, then weaning occurred sooner than if the dam was carrying a female foetus. This finding is the first of this kind among ungulates. The reproductive state of the mare and the sex of her foetus should be considered when interpreting weaning times of equids.

Prey preferences of the spotted hyaena (Crocuta crocuta) and degree of dietary overlap with the lion (Panthera leo)

AbstractSpotted hyaenas Crocuta crocuta were once considered mere scavengers; however, detailed research revealed that they are very efficient predators. Information on what spotted hyaenas actually prefer to prey on and what they avoid is lacking, as well as the factors that influence prey selection. Data from 14 published and one unpublished study from six countries throughout the distribution of the spotted hyaena were used to determine which prey species were preferred and which were avoided using Jacobs' index. The mean of these values for each species was used as the dependent variable in multiple regression, with prey abundance and prey body mass as predictive variables. In stark contrast to the rest of Africa's large predator guild, spotted hyaenas do not preferentially prey on any species. Also surprisingly, only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyaena most prefer prey within a body mass range of 56–182 kg, with a mode of 102 kg. The dietary niche breadth of the spotted hyaena is similar to that of the lion Panthera leo, and the two species have a 58.6% actual prey species overlap and a 68.8% preferred prey species overlap. These results highlight the flexible and unselective nature of spotted hyaena predation and are probably a reason for the species' success throughout its range, despite a large degree of dietary overlap with lions.

Influence of drought on predation of elephant (Loxodonta africana) calves by lions (Panthera leo) in an African wooded savannah

AbstractData were collected on species killed by lions Panthera leo in Hwange National Park, Zimbabwe between 1998 and 2004. Lions killed predominantly large to medium‐sized herbivores, concentrating on buffalo Syncerus caffer, elephant Loxodonta africana, giraffe Giraffa camelopardalis, wildebeest Connochaetes taurinus and zebra Equus burchelli. These species made up 83% of all lion kills found and 94% of the biomass of kills actually observed. Elephant calves made up an unusually large proportion of lion prey during the study period (23% of kills recorded). All elephants killed were dependent juveniles. Elephant calves appear more vulnerable during the dry months of the year, particularly in years of below average rainfall. Elephant calves are usually well protected. However, high‐density aggregations of elephants around limited water sources during the dry season may deplete local food resources, forcing elephant herds to travel large distances between water and forage. Under these circumstances, elephant calves may become lost or separated from family groups, accounting for their high incidence in lion diet.

Embedded systems in the wild

The Princeton ZebraNet project is a collaboration of engineers and biologists to build mobile, wireless embedded systems for wildlife tracking. Over the lifetime of the project, we have implemented a number of compression, communication, and data management algorithms specifically tailored for the small memory, constrained energy and sparse connectivity of these long-lifetime systems. We have gone through three major generations of hardware and software implementations, and have done two successful real-world deployments on Plains Zebras in Kenya, with a third deployment planned for Summer, 2007. In this talk, I will discuss our real-life experiences with crafting embedded systems hardware and software, and our deployment experiences in Africa. I will also put forward a vision for how portability, reliability, and energy-efficiency can be well-supported in future embedded systems.

Geographic distribution of an extinct equid (Equus hydruntinus: Mammalia, Equidae) revealed by morphological and genetical analyses of fossils

Equus hydruntinus inhabited Europe and the Middle East for more than 300 000 years. For a long time, palaeontological data failed to place E. hydruntinus into the equid phylogenetic tree, confronted with the fact that it shares primitive Equus characters with both zebras and asses, and derived characters with asses and hemiones. However, the study of a recently discovered skull points to a relationship with hemiones. Extraction of DNA from ancient samples from Crimea (E. hydruntinus) and Iran (E. cf. hydruntinus) yielded 134-288 bp of the mtDNA control region and 143 bp of the cytochrome b gene. This DNA analysis supports the proximity of E. hydruntinus and Equus hemionus suggested by skull and limb bone analyses, and rejects proximity to either Equus burchelli or the asses suggested by tooth morphology. Dental morphology may thus be of poor taxonomical value if used alone for establishing equid phylogenetic relationships. Furthermore, the small genetic distance between E. cf. hydruntinus of Iran and the classical E. hydruntinus of Crimea suggests that both samples belong to the same species. Accordingly, the geographic range of E. hydruntinus -- until now believed to be restricted to Europe, Israel, and Turkey -- can be extended towards East as far as Iran.

TNF‐α SNP haplotype frequencies in equidae

Tumour necrosis factor alpha (TNF-alpha) is a pro-inflammatory cytokine that plays a crucial role in the regulation of inflammatory and immune responses. In all vertebrate species the genes encoding TNF-alpha are located within the major histocompatability complex. In the horse TNF-alpha has been ascribed a role in a variety of important disease processes. Previously two single nucleotide polymorphisms (SNPs) have been reported within the 5' un-translated region of the equine TNF-alpha gene. We have examined the equine TNF-alpha promoter region further for additional SNPs by analysing DNA from 131 horses (Equus caballus), 19 donkeys (E. asinus), 2 Grant's zebras (E. burchellii boehmi) and one onager (E. hemionus). Two further SNPs were identified at nucleotide positions 24 (T/G) and 452 (T/C) relative to the first nucleotide of the 522 bp polymerase chain reaction product. A sequence variant at position 51 was observed between equidae. SNaPSHOT genotyping assays for these and the two previously reported SNPs were performed on 457 horses comprising seven different breeds and 23 donkeys to determine the gene frequencies. SNP frequencies varied considerably between different horse breeds and also between the equine species. In total, nine different TNF-alpha promoter SNP haplotypes and their frequencies were established amongst the various equidae examined, with some haplotypes being found only in horses and others only in donkeys or zebras. The haplotype frequencies observed varied greatly between different horse breeds. Such haplotypes may relate to levels of TNF-alpha production and disease susceptibility and further investigation is required to identify associations between particular haplotypes and altered risk of disease.