Patterns of association, nestedness, and species co-occurrence of helminth parasites in the greater kudu, Tragelaphus strepsiceros, in the Kruger National Park, South Africa, and the Etosha National Park, Namibia

The helminth parasites of the greater kudu from the Kruger National Park (KNP), South Africa, and the Etosha National Park (ENP), Namibia, were examined to determine the major patterns of spatial and demographic variation in community structure and to evaluate nonrandomness in parasite community assembly. Nonmetric multidimensional scaling ordination procedures were used to test for differences in parasite community composition between hosts of the 2 parks and between hosts of different demographic groups within KNP. Infracommunities within KNP were also examined for patterns of nonrandomness using 2 null models, i.e., nestedness and species co-occurrence. Infracommunities of KNP and ENP were significantly different from each other, as were infracommunities of different host demographic groups within KNP. Parasite species in the greater kudu from KNP displayed significant levels of nestedness and were found to co-occur less frequently than expected by chance; however, this lack of co-occurrence was significant only when all demographic groups were considered. When restricted to any particular age class, co-occurrence patterns could not be distinguished from random. Overall, these data suggest that biogeography and host demographics are important factors in determining community organization of helminth parasites in the greater kudu.     

Hepatic lesions associated with Cooperioides hepaticae (Nematoda: Trichostrongyloidea) infection in impala (Aepyceros melampus) of the Kruger National Park

Intrahepatic biliary lesions were observed in two of 12 lambs, seven of 12 yearlings and 10 of 25 adult impala (Aepyceros melampus) surveyed in the Kruger National Park, Republic of South Africa. Lesions were associated with the nematode Cooperioides hepaticae, a trichostrongyloid parasite that inhabits the bile ducts of impala, and ranged from a mild chronic-eosinophilic cholangitis to foci of florid hyperplastic cholangitis with duct ectasia. The latter almost always contained viable worms and, after the worms died, the lesions appeared as foreign-body granulomas. Infection was acquired early in life; severe lesions were seen most frequently in yearlings. Adults were less severely infected, which suggested an acquired immunity. Although the incidence of infection was high, cooperiiasis did not appear to be a serious herd-health problem at the time of this study.     

A new filarial nematode (Onchocercidae) from warthogs (Phacochoerus aethiopicus) of the Kruger National Park

Fifty-five warthogs [Phacochoerus aethiopicus (Suidae: Artiodactyla)] from the Kruger National Park, Republic of South Africa, were examined for parasites. Adult filarial nematodes were found in lymphatic vessels adjacent to peripheral and visceral lymph nodes, and microfilariae were found in lymph nodes and circulating blood. Both the adult parasite and the microfilaria are described. Specific identification is pending confirmation and recovery of intact adult specimens and microfilariae identical to those described herein.     

黑斑羚粪便中碳同位素揭示的食性变化

利用稳定碳同位素数据(δ13C)分析了南非克鲁格国家公园混食性黑斑羚(Aepyceros melampus)时间和空间尺度上的食性变化,验证了两个假说,即有蹄类食性变化是由生境中木本植物与草本植物的相对配比导致;降雨控制有蹄类生态。结果表明:黑斑羚的食性涵盖了精食者-粗食者采食谱系,且食性中木本与草本比例在不同月间、季节、年度和区域间存在很大变化。栖息于开放性热带稀树草原和草原中的黑斑羚通常采食比生境中更高比例的草本,但在时间尺度上并不恒定。在克鲁格北部的一个区域(Punda Maria) ,黑斑羚采食的草本比克鲁格国家公园中其它任何区域都多。与其它生境相比,在河边的黑斑羚采食草本数量更少,尤其是在食性空间变化更为明显的旱季。因此,我们的数据不支持有蹄类食性组成变化是由生境中木本与草本比例不同造成的假说,食性与降雨量间也无明显的关系。我们的结果支持草本中蛋白含量增加引起黑斑羚采食比例的增加这一模型。粪便中氮含量在时间和空间上的变化很小,揭示在可利用食物中,无论木本还是草本,黑斑羚进行选择采食以保证最好的食物质量。基于这些结果,我们认为更具体的食物选择和可利用性最适采食理论能够更好地解释这种生态学变化。     

White rhinoceros range size in the south-western Kruger National Park

White rhinoceros range size was ascertained telemetrically in the south-western Kruger National Park. The mean annual range size of territorial males was 9.86 km² compared to 22.83 km² for adult females. White rhinoceros females' summer wet season range was larger (21.44 km²) than the winter dry season range (11.64 km²). It is argued that abundant field-water during the wet season enables animals to range further from permanent water supplies and to utilize larger foraging areas. White rhinoceros have core areas in their individual ranges that usually are situated along riverbanks in the preferred grazing regions. These core areas also include some favourite resting spots on high-lying areas. White rhinoceros range sizes in the south-western Kruger National Park were similar to those of other reserves with comparable white rhinoceros densities. In the Umfolozi Game Reserve, which has a higher white rhinoceros density than the Kruger National Park, the individual ranges are much smaller.     

Nested assemblages resulting from host size variation: the case of endoparasite communities in fish hosts

Nested species subsets are a common pattern in many types of communities found in insular or fragmented habitats. Nestedness occurs in some communities of ectoparasites of fish, as does the exact opposite departure from random assembly, anti-nestedness. Here, we looked for nested and anti-nested patterns in the species composition of communities of internal parasites of 23 fish populations from two localities in Finland. We also compared various community parameters of nested and anti-nested assemblages of parasites, and determined whether nestedness may result simply from a size-related accumulation of parasite species by feeding fish hosts. Nested parasite communities were characterised by higher prevalence (proportion of infected fish) and intensities of infection (number of parasites per fish) than anti-nested communities; the two types of non-random communities did not differ with respect to parasite species richness, however. In addition, the correlation between fish size and the number of parasite species harboured by individual fish was much stronger in nested assemblages than in anti-nested ones, where it was often nil. These results were shown not to be artefacts of sampling effort or host phylogeny. They apply to both assemblages of adult and larval parasites, which were treated separately. Since species of larval parasites are extremely unlikely to interact with one another in fish hosts, the establishment of nestedness appears independent of the potential action of interspecific interactions. The species composition of these parasite communities is not determined from within the community, but rather by the extrinsic influence of host feeding rates and how they amplify differences among parasite species in probabilities of colonisation or extinction. Nested patterns occur in parasite communities whose fish hosts accumulate parasites in a predictable fashion proportional to their size, whereas anti-nested communities occur in parasite communities whose fish hosts do not, possibly because of dietary specialisation preventing them from sampling the entire pool of parasite species available locally. Thus, nestedness in parasite communities may result from processes somewhat different from those generating nested patterns in free-living communities.     

Distributional niche of relatively rare sable antelope in a South African savanna: habitat versus biotic relationships

The geographic distribution of a species is governed by climatic conditions, topography, resources and habitat structure determining the fundamental niche, while the local distribution expressed via home range occupation may be compressed by biotic interactions with competitors and predators, restricting the realised niche. Biotic influences could be especially important for relatively rare species. We investigated how rainfall, geology, land type and abundance of other ungulate species serving as competitors or prey for predators contributed to the patchy distribution of sable antelope herds within Kruger National Park. Data were provided by annual aerial surveys of ungulate populations conducted between 1978 and 1988. Sable herds were more commonly present on granitic and sandstone substrates than on more fertile basalt. They occurred both in the moist south‐west and dry north of the park. They were most abundant in sour bushveld and mopane savanna woodland, and mostly absent from knob thorn‐marula parkland. The presence of sable was negatively associated with high concentrations of impala and wildebeest, less consistently related to the abundance of zebra, and positively associated with the occurrence of buffalo herds. Best supported models included the separate effects of the most abundant grazers along with land type. Interspecific relationships seemed more consistent with vulnerability to predation as the underlying mechanism restricting the distribution of sable herds than with competitive displacement. Sable favoured land types distinct from those where wildebeest, the most preferred prey of lions, and impala, numerically the most important resident prey species, were most abundant. Hence the risk of predation, associated with habitat conditions where abundant prey species are most concentrated, can exert an overriding influence on the distribution of rarer species in terms of their home range occupation.     

Host sex and ectoparasites choice: preference for, and higher survival on female hosts

1. Sex differences in levels of parasite infection are a common rule in a wide range of mammals, with males usually more susceptible than females. Sex-specific exposure to parasites, e.g. mediated through distinct modes of social aggregation between and within genders, as well as negative relationships between androgen levels and immune defences are thought to play a major role in this pattern. 2. Reproductive female bats live in close association within clusters at maternity roosts, whereas nonbreeding females and males generally occupy solitary roosts. Bats represent therefore an ideal model to study the consequences of sex-specific social and spatial aggregation on parasites' infection strategies. 3. We first compared prevalence and parasite intensities in a host-parasite system comprising closely related species of ectoparasitic mites (Spinturnix spp.) and their hosts, five European bat species. We then compared the level of parasitism between juvenile males and females in mixed colonies of greater and lesser mouse-eared bats Myotis myotis and M. blythii. Prevalence was higher in adult females than in adult males stemming from colonial aggregations in all five studied species. Parasite intensity was significantly higher in females in three of the five species studied. No difference in prevalence and mite numbers was found between male and female juveniles in colonial roosts. 4. To assess whether observed sex-biased parasitism results from differences in host exposure only, or, alternatively, from an active, selected choice made by the parasite, we performed lab experiments on short-term preferences and long-term survival of parasites on male and female Myotis daubentoni. When confronted with adult males and females, parasites preferentially selected female hosts, whereas no choice differences were observed between adult females and subadult males. Finally, we found significantly higher parasite survival on adult females compared with adult males. 5. Our study shows that social and spatial aggregation favours sex-biased parasitism that could be a mere consequence of an active and adaptive parasite choice for the more profitable host.     

Mammal road‐type associations in Kruger National Park,South Africa: Common mammals do not avoid tar roads more than dirt roads

The majority of Africa''s parks and conservation areas have a vast road network, facilitating motorized vehicle game viewing. These roads have an influence that is both road type‐ and species‐specific, on the surrounding ecosystem. Due to their higher traffic volumes, we hypothesized that tar roads and their immediate surrounds within the Kruger National Park, South Africa, are avoided to a greater extent by medium‐to‐large mammals than comparable dirt roads in the park. We systematically recorded the presence of medium‐to‐large mammal species from our vehicle, recording data at 401 tar and 369 dirt road stops in the Kruger National Park. In addition to species presence, we also estimated the proximity of animals to the road, as well as herd sizes. Our results indicate an equal likelihood of viewing the commonly recorded medium‐to‐large mammal species from both road types. The likelihood of observing larger herd sizes was also similar between tar and dirt roads for the three most commonly observed species, African elephant (Loxodonta africana), impala (Aepyceros melampus), and plains zebra (Equus quagga), and the likelihood of viewing impala and zebra close to the road also did not differ between tar and dirt roads. However, elephant was observed more often close to tar roads, compared to dirt roads. We interpreted this as the result of potentially increased woody cover associated with more water runoff in close proximity to tar roads compared with dirt roads. Our results not only have ecological significance, supporting the notion that many of the park''s species are habituated to human infrastructure, but also management implications, informing park officials about the influence of road traffic and road type on wildlife distributions.     

Comparative growth of wild male and female lions (Panthera led)

Lion growth was studied by fitting sex specific Von Bertalanffy curves and linear regressions to data on body mass, heart girth, shoulder height and vertebral column length. Measurements were recorded for 344 lions ( Panthera leo ) (158 ♂♂ and 186 ♀♀), from Kruger National Park, South Africa. Growth in mass for males and females was linear up to about 36 months of age 0 = 0–98 and 0–99 respectively). The other age-specific measurements were clearly curvilinear. Mean weights for adult lions (excluding stomach contents) were 187–5 kg (♂♂) and 124–2 kg (♀♀) respectively. Lions tended to continue growing up to about seven years in males and nine to 10 years in females after which they usually started to lose condition. Body mass and heart girth measurements of Kruger Park lions were compared with samples from three other populations. These showed that lions from East Africa were smaller than those from more southern populations in Rhodesia, Kalahari and Kruger Park.     

The functional importance of parasites in animal communities: many roles at many levels?

Past research on parasites and community ecology has focussed on two distinct levels of the overall community. First, it has been shown that parasites can have a role in structuring host communities. They can have differential effects on the different hosts that they exploit, they can directly debilitate a host that itself is a key structuring force in the community, or they can indirectly alter the phenotype of their host and change the importance of the host for the community. Second, certain parasite species can be important in shaping parasite communities. Dominant parasite species can directly compete with other parasite species inside the host and reduce their abundance to some extent, and parasites that alter host phenotype can indirectly make the host more or less suitable for other parasite species. The possibility that a parasite species simultaneously affects the structure of all levels of the overall community, i.e. the parasite community and the community of free-living animals, is never considered. Given the many direct and indirect ways in which a parasite species can modulate the abundance of other species, it is conceivable that some parasite species have functionally important roles in a community, and that their removal would change the relative composition of the whole community. An example from a soft-sediment intertidal community is used to illustrate how the subtle, indirect effects of a parasite species on non-host species can be very important to the structure of the overall community. Future community studies addressing the many potential influences of parasites will no doubt identify other functionally important parasite species that serve to maintain biodiversity.     

Community ecology of the parasites of adult spot, Leiostomus xanthurus, and Atlantic croaker, Micropogonias undulatus (Sciaenidae) in the Cape Hatteras region

Twenty-three species of metazoan parasites were recorded from adult spot and 26 from adult croaker. Of the 33 parasitic species found, 17 occurred in both spot and croaker. No significant differences in intensity of parasites occurred between sexes of either spot or croaker. All of the parasites had over-dispersed, or clumped, distributions among hosts. Adult spot and croaker collected offshore had much greater species-richness, diversity, and total number of individual parasites than juvenile fishes collected in adjoining estuaries during another study. The juvenile spot and croaker had less time to acquire parasites and inhabited less diverse and more confined habitats in inshore estuaries, which resulted in less diverse parasite communities than offshore fishes. The number of species and diversity of parasites in adult fish was greater in croaker than spot. However, when only gastrointestinal helminths were considered, spot had greater species-richness as well as greater numbers of individual helminths, suggesting that they had a more diverse diet and that they fed on more infected intermediate hosts than croaker. In both adult spot and croaker the mean number of parasitic species was greater than those of freshwater fishes and fewer than those for birds and mammals. The total number of individual parasites was similar to that of freshwater fishes. The opportunistic diet and the migratory habits of both spot and croaker contribute to their diverse parasite faunas. Comparison of adult spot and croaker parasite faunas collected offshore indicated that their respective parasite component communities were distinct and that similar parasite infracommunity variability existed in both hosts and that their communities were not ‘random’ samples, but restricted subsets of the compound community. Although the parasite dominance hierarchy in adults of both species varied slightly between areas and seasons sampled, there appeared to be a predictable dominant species that was accompanied by subordinate, less predictable species. However, the variability in both relative intensities and presence-absence of parasites within communities resulting from their diverse diets make them less predictable than those of other vertebrates with less diverse diets such as the lesser scaup duck and more like those of other marine fishes.     

Polystomatidae (Monogenea) of African Anura: Polystoma dawiekoki n. sp. parasitic in Ptychadena anchietae (Bocage)

Polystoma dawiekoki n. sp. is described as a new species of the Polystomatidae parasitic in the urinary bladder of the plain grass frog Ptychadena anchietae. This parasite was collected at Mkuze town and Mkuze Game Reserve in northern Kwazulu-Natal Province, in the Kruger National Park in Mpumalanga Province, South Africa, and at Bulwa in Tanga Province, East Usambara Mountains, Tanzania. It is distinguished from other African Polystoma species by a combination of characters, including the body size, size and shape of marginal hooklets and the haptor length to body length ratio. The presence of adult, as well as subadult, parasites in the same individuals, as is known for Eupolystoma, represents a significant evolutionary departure from the pattern of transmission typical of Polystoma in most of the other anuran hosts.     

Fire frequency drives habitat selection by a diverse herbivore guild impacting top–down control of plant communities in an African savanna

In areas with diverse herbivore communities such as African savannas, the frequency of disturbance by fire may alter the top–down role of different herbivore species on plant community dynamics. In a seven year experiment in the Kruger National Park, South Africa, we examined the habitat use of nine common herbivore species across annually burned, triennially burned and unburned areas. We also used two types of exclosures (plus open access controls) to examine the impacts of different herbivores on plant community dynamics across fire disturbance regimes. Full exclosures excluded all herbivores > 0.5 kg (e.g. elephant, zebra, impala) while partial exclosures allowed access only to animals with shoulder heights ≤ 0.85 m (e.g. impala, steenbok). Annual burns attracted a diverse suite of herbivores, and exclusion of larger herbivores (e.g. elephant, zebra, wildebeest) increased plant abundance. When smaller species, mainly impala, were also excluded there were declines in plant diversity, likely mediated by a decline in open space available for colonization of uncommon plant species. Unburned areas attracted the least diverse suite of herbivores, dominated by impala. Here, herbivore exclusion, especially of impala, led to strong declines in plant richness and diversity. With no fire disturbance, herbivore exclusion led to competitive exclusion via increases in plant dominance and light limitation. In contrast, on triennial burns, herbivore exclusion had no effect on plant richness or diversity, potentially due to relatively little open space for colonization across exclosure treatments but also little competitive exclusion due to the intermediate fire disturbance. Further, the diverse suite of grazers and browsers on triennial burns may have had a compensating effect of on the diversity of grasses and forbs. Ultimately, our work shows that differential disturbance regimes can result in differential consumer pressure across a landscape and result in heterogeneous patterns in top–down control of community dynamics.     

Halfway up the trophic chain: development of parasite communities in the sparid fish Boops boops

We examined the patterns of composition and structure of parasite communities in the Mediterranean sparid fish Boops boops along a gradient of fish sizes, using a large sample from a single population. We tested the hypothesis that species forming the core of the bogue parasite fauna (i.e. species which have a wide geographical range and are responsible for recognizable community structure) appear early in the fish ontogeny. The sequential community development observed supported the prediction that core species appear in the fish population earlier than rare and stochastic species. There was also a strong correlation between the order of 'arrival' of the species and their overall prevalence. Six key species were responsible for recognizable community structure across size/age cohorts; the addition to this baseline community of key parasite species resulted in a nested structure that is linked to differential species abundance rather than fish size. Information on the life-cycles, distribution and host range of the parasites is used to explain the observed patterns of parasite community structure. We conclude that the small mouth size of B. boops coupled with suction feeding may provide a setting for passive sampling as a mechanism leading to non-random parasite community structure.     

Dispersal and seasonal distributions of black-faced impala in the Etosha National Park, Namibia

Factors affecting the seasonal distribution of the vulnerable black‐faced impala at Etosha National Park, Namibia and the spread of the impala in the park since their translocation there in the 1970s were studied in the hot dry season of 2000 and the wet season of 2001 in order to provide information for future translocations of this antelope. In the 30 years since their release in the park, black‐faced impala appear to have dispersed a maximum of 31.5 km from their initial release sites, effectively forming five subpopulations based on their five initial release sites. The mean minimum distance that impala had dispersed between water holes since their release was 7.11 ± 1.47 km. Black‐faced impala concentrated strongly around water holes; more than 50% were within 1 km of water holes in both seasons. Changes in population densities in different habitats may have resulted from seasonal movements of impala between adjacent habitats. The role of initial release sites in determining the distribution of threatened species such as the black‐faced impala is discussed in light of its importance for future translocations.     

Infracommunity structure of parasites of Hemigymnus melapterus (Pisces: Labridae) from Lizard Island, Australia: the importance of habitat and parasite body size

This study describes the community of all metazoan parasites from 14 individuals of thicklip wrasse, Hemigymnus melapterus, from Lizard Island, Australia. All fish were parasitized, and 4,649 parasite individuals were found. Twenty-six parasite species were identified although only 6 species were abundant and prevalent: gnathiid isopods, the copepod Hatschekia hemigymni, the digenean Callohelmis pichelinae, and 3 morphotypes of tetraphyllidean cestode larvae. We analyzed whether the body size and microhabitat of the parasites and size of the host affected understanding of the structure of the parasite community. We related the abundance, biovolume, and density of parasites with the host body size and analyzed the abundances and volumetric densities of some parasite species within microhabitats. Although the 2 most abundant species comprised 75% of all parasite individuals, 4 species, each in similar proportion, comprised 85% of the total biovolume. Although larger host individuals had higher richness, abundance, and biovolume of parasites than smaller individuals, overall parasite volumetric density actually decreased with the host body size. Moreover, parasites exhibited abundances and densities significantly different among microhabitats; some parasite species depended on the area available, whereas others selected a specific microhabitat. Parasite and habitat size exhibited interesting relationships that should be considered more frequently. Considerations of these parameters improve understanding of parasite community structure and how the parasites use their habitats.     

Variation in intensity of a parasitic mite (Spinturnix myoti) in relation to the reproductive cycle and immunocompetence of its bat host (Myotis myotis)

Given the intimate association in host–parasite systems, parasites are expected to initiate their own reproduction when vulnerable hosts become abundant and/or when adult hosts are less resistant. In this study, we examined the variation in the intensities of a blood-sucking mite ( Spinturnix myoti , Acarina) with respect to the reproductive cycle and immunocompetence of its host, the greater mouse-eared bat Myotis myotis . Reproductive, pregnant females were less immunocompetent and harboured more parasites than nonreproductive females, whilst, during lactation, immunocompetence was positively associated with female body mass. There was a dramatic increase in the T-cell response of gravid females with the advancement of gestation, which coincided with a diminution of individual parasite loads and a progressive switch of parasites from adults to juveniles. The latter not only harboured greater numbers of mites than adult female bats, but they also exhibited gravid parasites in higher proportions, indicating that juvenile hosts are more attractive for parasite reproduction than adult females.     

Geographical variations in the jack mackerel Trachurus symmetricus murphyi populations in the southeastern Pacific Ocean as evidenced from the associated parasite communities

The composition of the metazoan parasite communities within 2 fishing zones along the Chilean coast were compared to determine the population structure of the jack mackerel Trachurus symmetricus murphyi (Nichols) in these 2 geographical locations. More than 7,780 parasites belonging to 15 taxa were collected between 1990 and 1996 in 71 samples comprised of 3,946 hosts. The same taxa were found in both fishing zones. However, jack mackerel from northern Chile had a higher abundance of cymothoid isopods, Ceratothoa spp., whereas those from southern Chile had more Rhadinorhynchus trachuri, Hysterothylacium sp. larvae, and Anisakis type I larvae. Results were similar at all community levels because all parasites had low prevalence and infracommunities had low total abundance and richness. Analyses at the component community level may be more adequate for stock identification when infracommunities are simple. There were significant differences in composition of parasite communities between years in each fishing zone, presumably as a result of the increase in offshore catches since 1994. These results reinforce the hypothesis that more than 1 ecological stock of the jack mackerel exists in the southeastern Pacific and contradict the current assumption of a single stock in the management of this heavily exploited fish species.     

The Sicker Sex: Understanding Male Biases in Parasitic Infection,Resource Allocation and Fitness

The “sicker sex” idea summarizes our knowledge of sex biases in parasite burden and immune ability whereby males fare worse than females. The theoretical basis of this is that because males invest more on mating effort than females, the former pay the costs by having a weaker immune system and thus being more susceptible to parasites. Females, conversely, have a greater parental investment. Here we tested the following: a) whether both sexes differ in their ability to defend against parasites using a natural host-parasite system; b) the differences in resource allocation conflict between mating effort and parental investment traits between sexes; and, c) effect of parasitism on survival for both sexes. We used a number of insect damselfly species as study subjects. For (a), we quantified gregarine and mite parasites, and experimentally manipulated gregarine levels in both sexes during adult ontogeny. For (b), first, we manipulated food during adult ontogeny and recorded thoracic fat gain (a proxy of mating effort) and abdominal weight (a proxy of parental investment) in both sexes. Secondly for (b), we manipulated food and gregarine levels in both sexes when adults were about to become sexually mature, and recorded gregarine number. For (c), we infected male and female adults of different ages and measured their survival. Males consistently showed more parasites than females apparently due to an increased resource allocation to fat production in males. Conversely, females invested more on abdominal weight. These differences were independent of how much food/infecting parasites were provided. The cost of this was that males had more parasites and reduced survival than females. Our results provide a resource allocation mechanism for understanding sexual differences in parasite defense as well as survival consequences for each sex.