Body temperature variation of South African antelopes in two climatically contrasting environments

To understand the adaptive capacity of a species in response to rapid habitat destruction and climate change, we investigated variation in body temperature (T_b) of three species of antelope, namely eland, blue wildebeest and impala, using abdominally-implanted temperature data loggers. The study was conducted at two climatically contrasting environments in South Africa, one with a less seasonal and mild winter (Mapungubwe National Park) and the other with a more seasonal, long and cold winter (Asante Sana Game Reserve). Since the habitat with long and cold winters would be suboptimal for these African antelopes, which evolved in less seasonal and hot environments, antelopes in Asante Sana were expected to exhibit a larger amplitude in T_b and a lower minimum body temperature (Min T_b) during winter to reduce T_b and the ambient temperature (T_b−T_a) gradient to save energy. In both eland and impala, 24-h body temperature amplitude did not differ between the study sites, regardless of season. Conversely, wildebeest in Mapungubwe showed a higher variability in the 24-h amplitude of body temperature and also a lower Min T_b during winter and spring than the wildebeest in Asante Sana. This variation in T_b among Mapungubwe wildebeest was influenced by both the amplitude of ambient temperature (positive) and cumulative rainfall (negative), which was not the case for wildebeest in Asante Sana. We propose that the low Min T_b of wildebeest in Mapungubwe was the result of nutritional stress during winter and spring; an evident response even during a year of average rainfall. Therefore, these wildebeest apparently live in a physiologically stressful environment. With the predicted increase in the frequency and intensity of drought periods in southern Africa, wildebeest and other grazers, will likely experience greater nutritional stress in the future.     

Energy advantages of orientation to solar radiation in three African ruminants

Animal orientation relative to incident solar radiation allows an animal to effectively adjust the amount of radiant heat gained from an environment. Yet recent literature found ruminants to primarily orientate north/south and proposed magnetic alignment as the most parsimonious explanation. To test whether such northerly orientation has an energy advantage, we used heated cylindrical models to estimate energy costs of thermoregulation associated with north and east orientations of three species of African ruminants under cool winter conditions. Concurrent behavioural observations revealed that eland, blue wildebeest and impala did not preferentially orientate north/south during warm summer or cool winter conditions. Instead, all three species preferred to orientate perpendicular to incident solar radiation during winter and parallel to incident solar radiation during summer, throughout the day. On clear winter days with little wind, more than 60% of animal orientation preference could be accounted for by the energy savings associated with that orientation. Thus energy demands are likely to be the primary driver of animal orientation preferences.     

Adaptive heterothermy and selective brain cooling in arid-zone mammals

Adaptive heterothermy and selective brain cooling are regarded as important thermal adaptations of large arid-zone mammals. Adaptive heterothermy, a process which reduces evaporation by storing body heat, ought to be enhanced by ambient heat load and by water deficit, but most mammals studied fail to show at least one of those attributes. Selective brain cooling, the reduction of brain temperature below arterial blood temperature, is most evident in artiodactyls, which possess a carotid rete, and traditionally has been considered to protect the brain during hyperthermia. The development of miniature ambulatory data loggers for recording body temperature allows the temperatures of free-living wild mammals to be measured in their natural habitats. All the African ungulates studied so far, in their natural habitats, do not exhibit adaptive heterothermy. They have low-amplitude nychthemeral rhythms of temperature, with mean body temperature over the night exceeding that over the day. Those with carotid retes (black wildebeest, springbok, eland) employ selective brain cooling but zebra, without a rete, do not. None of the rete ungulates, however, seems to employ selective brain cooling to prevent the brain overheating during exertional hyperthermia. Rather, they use it at rest, under moderate heat load, we believe in order to switch body heat loss from evaporative to non-evaporative routes.     

Black wildebeest seek shade less and use solar orientation behavior more than do blue wildebeest

Many ungulates, including wildebeest, seek shade and orient their bodies relative to incoming solar radiation in order to reduce environmental heat loads. Blue (Connochaetes taurinus) and black wildebeest (Connochaetes gnou), which co-exist artificially in some reserves in South Africa, are thought to adopt different thermoregulatory behaviors to mitigate high environmental heat loads. However, whether or not blue and black wildebeest use different behaviors to reduce heat loads in regions where they co-occur has never previously been examined. We compared the shade seeking and solar orientation behavior of free-ranging blue and black wildebeest in summer at three locations in South Africa where both species co-occur. We found that blue wildebeest exhibited more shade seeking behavior than did black wildebeest at all times of day, at all study sites. Black wildebeest remained in the sun but were more likely than blue wildebeest to orient their bodies parallel to the sun at all study sites, a behavior which reduces the amount of surface area exposed to incoming radiation. Black wildebeest were most likely to employ parallel solar orientation during the hottest times of the day when the sun was not directly overhead (i.e., solar noon ± 1 hour). We thus demonstrate that co-occurring blue and black wildebeest use different thermoregulatory behaviors to reduce high heat loads. It is possible that the lack of shade in the historical distribution of black wildebeest led to selective pressure for reliance on solar orientation. Differences in thermoregulatory behavior can affect species-specific heat loads, habitat use, body mass, fitness and grazing activity. Such differences may also allow blue and black wildebeest to inhabit separate microclimates within the same habitat, provided there is sufficient heterogeneity in vegetation structure, potentially facilitating reproductive isolation.     

Validation of a biotelemetric technique, using ambulatory miniature black globe thermometers, to quantify thermoregulatory behaviour in ungulates

Behavioural thermoregulation is an animal's primary defence against changes in the thermal environment. We aimed to validate a remote technique to quantify the thermal environment behaviourally selected by free-ranging ungulates. First, we demonstrated that the temperature of miniature, 30 mm diameter, black globes (miniglobes) could be converted to standard, 150 mm diameter, black globe temperatures. Miniglobe temperature sensors subsequently were fitted to collars on three free-ranging ungulates, namely blue wildebeest (Connochaetes taurinus), impala (Aepyceros melampus) and horse (Equus caballus). Behavioural observations were reflected in animal miniglobe temperatures which differed from those recorded by an identical miniglobe on a nearby exposed weather station. The wildebeest often selected sites protected from the wind, whereas the impala and the horse sheltered from the sun. Nested analysis of variances revealed that the impala and horse selected significantly less variable environments than those recorded at the weather station (P<0.001) over a 20-min time interval, whereas, the microclimates selected by wildebeest tended to be more variable (P=0.08). Correlation of animal miniglobe against weather station miniglobe temperature resulted in regression slopes significantly less than one (P<0.001) for all species studied, implying that, overall, the animals selected cooler microclimates at high environmental heat loads and/or warmer microclimates at low environmental heat loads. We, therefore, have developed an ambulatory device, which can be attached to free-ranging animals, to remotely quantify thermoregulatory behaviour and selected microclimates.     

Experience with drugs for capture and restraint of wildebeest, impala, eland and hartebeest in Kenya

Two hundred and sixteen wildebeest (Connochaetes taurinus), 111 impala (Aepyceros melampus), 39 eland (Taurotragus oryx) and 9 hartebeest (Alcelaphlus buselaphus cokii) were drug-immobilized for capture or for handling in captivity. Drugs used for capture were combinations of xylazine, etorphine and acepromazine, or xylazine and fentanyl, with or without the addition of azaperone. For restraint in captivity, xylazine alone proved to be satisfactory in most instances. Drugs were injected with projectile syringes. Recommendation on dosage are given.     

Effects of body size on the diurnal activity budgets of African browsing ruminants

We compared the diurnal activity budgets of four syntopic species of African browsing ruminant that differ widely in body size. These were concurrently studied through all phases of the seasonal cycle, in the same area, using the same methods. We tested five predictions from the literature on how body size is expected to influence the behaviour of tropical ungulates: the smallest members of the browsing ruminant guild exhibit (1) the lowest allocation of diurnal time to activity; (2) the greatest hour-to-hour variation in activity and resting time; (3) the greatest reduction in activity time during the hottest days; (4) the least change between wet and the dry seasons in the ratio of feeding: ruminating time; and (5) the greatest time budget allocation to vigilance. Prediction 1 was supported in that the smaller species spent less time being active during the day. Prediction 2 was also supported in that the smaller species were more variable in their relative allocations of time to activity and resting through successive hours of the day. Contrary to Prediction 3, however, the greatest reduction in activity with increasing temperature was found for the largest guild member. The smaller species can achieve their daily food intake requirements by feeding at night and in the cool hours of the day, while the larger species have to feed during all hours of the day and are thus more susceptible to thermoregulatory constraints on foraging. Prediction 4 was partially upheld in that the largest species (giraffe) displayed the widest variation in feeding: ruminating time through the seasonal cycle. Prediction 5 was not supported, indicating that multiple factors interact with body size in determining vigilance behaviour.     

NAIROBI NATIONAL PARK GAME CENSUS, 1966

1. The monthly game counts of Nairobi National Park in 1966 are compared with those of 1961 to 1983 inclusive. It appears that the mean an-nual population of wild ungulates has remained constant at about 4000 animais after a severe decline during the drought of 1961.
2. Wildebeest have continued to decline since the drought and there is no evidence of the former migration to the Athi-Kapiti plains. Reasons for these phenomena are proposed.
3. Kongoni have continued to in-crease since their decline in 1961 and little migration to the plains could be detected in 1966.
4. The mean yearly population of zebra has remained constant since their decline in 1961. At present this is the only species to migrate in large num-bers to and from the plains with the onset and cessation of the rains.
5. Other ungulates were less affected by the drought and their numbers in 1966 appear to have changed relatively little since the beginning of 1961.
6. Females predomInate in the adult populations of all the common plains ungulates.
7. In 1966 lions killed wildebeest at a rate four times greater than would be expected from the percentage of wildebeest in the population. Reasons for this are suggested. As the wildebeest have declined in numbers, the lion have included higher percentages of zebra, warthog, kongoni and eland in their diets.     

Evolution of the ungulate dewlap: thermoregulation rather than sexual selection or predator deterrence?

Background

Dewlaps are iconic features of several ungulate species and, although a role in signalling has been postulated, their function remains largely unexplored. We recently failed to find any age-independent link between dewlap size and social status in the common eland (Tragelaphus oryx), pointing to the possibility that sexual selection may not be the primary cause of dewlap evolution in ungulates. Here I use a two-pronged approach to test hypotheses on the function of ungulate dewlaps: an interspecific comparative analysis of bovids and deer, and an intraspecific study of eland antelopes in the wild.

Results

Across species, the presence of dewlaps in males was not found to be associated with sexual size dimorphism, a commonly used measure of the intensity of sexual selection. The presence of dewlaps was, however, linked to very large male body size (>400 kg), which agrees with a thermoregulatory function as lower surface/volume-ratio counteracts heat dissipation in large-bodied species. In eland antelopes, large dewlap size was associated with higher, rather than lower, incidence of claw-marks (independently of age), a result which speaks against the dewlap as a predator deterrent and rather indicates a predation cost of the structure.

Conclusion

The findings suggest that, although an additional function in communication should not be ruled out, the dewlap of ungulates may contrast with that of lizards and birds in thermoregulation being a primary function.

     

The pathogenicity of bovine strains of foot and mouth disease virus for impala and wildebeest.

Impala (Aepyceros melampus) and wildebeest (Connochaetes taurinus) were infected with bovine strains of foot and mouth disease virus by intradermolingual inoculation. No clinical signs developed in the impala but mild atypical lesions developed in the tongues of the wildebeest with generalized spread to one foot in two of the eight animals exposed. All the impala but only some of the wildebeest developed viraemia. No virus could be isolated from any tissues in either species after the 7th day following virus inoculation. Immune response occurred in both species. A field survey revealed few animals of either species with significant antibody titers and no virus 'carriers' were found.     

Influence of diet on the rumen protozoal fauna of indigenous African wild ruminants

A study was carried out to determine if the protozoal fauna of indigenous African wild ruminants was different from that found in their domestic counterparts and if the animal's diet influenced the number and types of protozoa. Samples of rumen contents were collected in 1997 and 2001 from various indigenous African wild ruminants in Kenya. All three ruminant feeding types were sampled: browsers or concentrate selectors (giraffe and Guenther's dik-dik); intermediate or adaptable mixed feeders (impala, Thomson's gazelle, Grant's gazelle and eland); grass or roughage eaters (hartebeest and wildebeest). Total concentration of ciliate protozoa and percentage generic distribution were determined. In general, protozoal concentrations were higher in concentrate selectors, followed by the intermediate or opportunistic mixed feeders and lowest in the grass and roughage eaters. Both Thomson's and Grant's gazelle were protozoa-free in the 2001 samples. Entodinium percentages were considerably higher in concentrate selectors and intermediate mixed feeders, compared to roughage eaters. Two genera of protozoa previously found in only a few African ruminants, Epiplastron and Opisthotrichum, were observed in several additional animal species and represent new host records. A difference was noted in the protozoal species composition of the indigenous wild ruminants from that previously observed in African domestic ruminants.     

Bush selection along foraging pathways by sympatric impala and greater kudu

In order to identify the selection mechanism of two sympatric African browsers, we analysed encounter rates and selection of bushes along foraging pathways. We monitored the tracks, left overnight, by kudu and impala on an experimental plot of natural Acacia nilotica and Dichrostachys cinerea in the highveld of Zimbabwe, and recorded the number of bushes attacked in each category. Both ungulates were selective for the bush categories, but kudu were consistently more selective than impala, and showed a higher preference for the larger A. nilotica and D. cinerea bushes, which had a significantly greater number of bites which were not reachable by impala. For both kudu and impala, the probability of attacking larger bushes increased significantly with the proportion of large bushes encountered along the foraging pathways, whereas the consumption of smaller bushes was apparently unpredictable. For the most abundant food item (medium D. cinerea), the probability of attack by impala along a pathway decreased with increasing proportions of larger bushes in the experimental area, but was also dependent on impala group size and season. In addition, we found that encounter rates with larger bushes were significantly higher for kudu than for impala. Experimentally reducing the availability of the larger bushes had little effect on both impala and kudu during the following rainy season. However, during the following cool dry season, kudu showed an increased selectivity with a strong preference for the remaining large bushes (large A. nilotica), followed by a sharp decrease in selectivity in the hot dry season when they also fed from significant numbers of medium trees. Impala had little reaction to the experimental changes in the availability of bush categories in either season. We suggest that both kudu and impala selected bushes on the basis of the potential number of bites they can provide, and this resulted in different search strategies. Kudu focussed on the larger bushes which have a larger number of twigs which are out of reach of impala and kudu also probably directed their path preferentially towards the few larger bushes to maximize encounter rates with this favoured bush category. These differences in bush selection process lead to a low overlap in resource use between the two browsers in this type of savanna.     

Chinko/Mbari drainage basin represents a conservation hotspot for Eastern Derby eland in Central Africa

One of the largest of antelopes, Derby eland (Taurotragus derbianus), is an important ecosystem component of African savannah. While the western subspecies is Critically Endangered, the eastern subspecies is classified as least concern. Our study presents the first investigation of population dynamics of the Derby eland in the Chinko/Mbari Drainage Basin, Central African Republic, and assesses the conservation role of this population. We analysed data from 63 camera traps installed in 2012. The number of individuals captured within a single camera event ranged from one to 41. Herds were mostly mixed by age and sex, mean group size was 5.61, larger during the dry season. Adult (AD) males constituted only 20% of solitary individuals. The overall sex ratio (M:F) was 1:1.33, while the AD sex ratio shifted to 1:1.52, reflecting selective hunting pressure. Mean density ranged from 0.04 to 0.16 individuals/km², giving an estimated population size of 445–1,760 individuals. Chinko harbours one of the largest documented populations of Derby eland in Central Africa, making Chinko one of its potential conservation hotspots.     

Knee-clicks and visual traits indicate fighting ability in eland antelopes: multiple messages and back-up signals

Background  

Given the costs of signalling, why do males often advertise their fighting ability to rivals using several signals rather than just one? Multiple signalling theories have developed largely in studies of sexual signals, and less is known about their applicability to intra-sexual communication. We here investigate the evolutionary basis for the intricate agonistic signalling system in eland antelopes, paying particular attention to the evolutionary phenomenon of loud knee-clicking.     

Evaluation the possibility of ex situ conservation of plateau antelopes according to food content with stable isotope C and N analysis

Tibetan antelopes, Pantholops hodgsoni, are endemic to the high-altitude Qinghai-Tibet Plateau of western China. Because of human activities and illegal hunting, the population has decreased sharply in recent years. So the population conservation and enlargement becomes a puzzle to the scientists and government. There are some individuals in several zoos in high altitude area, however, ex situ conservation has never been carried out on a large scale. There are two questions that should be popularized before ex situ conservation is performed. Whether the food content in ex situ area similar to native area or not is the preliminary one, and the other is that whether Tibetan antelope can coexist with other ungulates distributed in ex situ or not. The aim of this study was to identify the food habit of Tibetan antelope in native (Kekexili area, KA) and ex situ (Tiebujia area, TA) areas and the food competition between Tibetan antelope and ungulates in KA and TA. The data indicate that fecal samples provide the most convenient and uninjurious sources to predict the food habit of Tibetan antelope. C3 plants, such as Gramineae, Cyperaceae, Compositae, Leguminosae and Cruciferae, were selected by antelopes both in KA and TA tested with stable isotope analysis method. Tibetan antelopes have high competition with ungulates distributed in KA but low competition with ungulates living in TA. Our results provide a tempting foreground for chiru’s ex situ conservation integrated protecting strategies into the development of appropriate grazing, especially in brittle ecosystem.     

Population trends of large non-migratory wild herbivores and livestock in the Masai Mara ecosystem, Kenya, between 1977 and 1997

The total of all non-migratory wildlife species in the Masai Mara ecosystem has declined by 58% in the last 20 years. This decline ranges from 49% in small brown antelopes to 72% in medium brown antelopes. In individual wildlife species, the decline ranges from 52% in Grant's gazelle to 88% in the warthog. Declines of over 70% have been recorded in buffalo, giraffe, eland and waterbuck. Only elephant, impala and ostrich have not shown any significant decline or increase. Overall, there has not been any significant difference in decline of all wildlife population sizes inside and outside the reserve, except for Thomson's gazelle and warthog. Livestock have not significantly declined over the entire analysis period. However, livestock and cattle populations significantly declined during the 1983–88 period. Donkey declined by 67%, while shoats (goats and sheep) remained stable. In the case of wildlife, land use and vegetation changes, drought effects and poaching are considered to be among the potential factors that may have been responsible for the decline; the decline in livestock during the 1983–84 period was probably due to drought effects.     

The biomass of game animals in Nairobi National Park, 1960–66

The large animals of Nairobi National Park have been censused intermittently once a month from mid-1960 until the end of 1966. Of the 23 species discussed, the density per kilometre has been determined accurately for the following: Grant's gazelle, Thomson's gazelle, water-buck, impala, wildebeest, hartebeest, eland, buffalo, warthog, giraffe, zebra and ostrich. From these figures the biomass has been calculated for each species each year. After a peak biomass of 12,775 kg/sq. km during the drought of 1960–61 the population declined to and remained fairly level at about 5690 kg/sq. km from 1962 to 1966. This figure includes about 1050 kg/sq. km of cattle and sheep. The large predators account for only about 1.4 % of the total biomass of wild animals while removing about 15.5% from this group annually.     

How Rainfall Variation Influences Reproductive Patterns of African Savanna Ungulates in an Equatorial Region Where Photoperiod Variation Is Absent

In high temperate latitudes, ungulates generally give birth within a narrow time window when conditions are optimal for offspring survival in spring or early summer, and use changing photoperiod to time conceptions so as to anticipate these conditions. However, in low tropical latitudes day length variation is minimal, and rainfall variation makes the seasonal cycle less predictable. Nevertheless, several ungulate species retain narrow birth peaks under such conditions, while others show births spread quite widely through the year. We investigated how within-year and between-year variation in rainfall influenced the reproductive timing of four ungulate species showing these contrasting patterns in the Masai Mara region of Kenya. All four species exhibited birth peaks during the putative optimal period in the early wet season. For hartebeest and impala, the birth peak was diffuse and offspring were born throughout the year. In contrast, topi and warthog showed a narrow seasonal concentration of births, with conceptions suppressed once monthly rainfall fell below a threshold level. High rainfall in the previous season and high early rains in the current year enhanced survival into the juvenile stage for all the species except impala. Our findings reveal how rainfall variation affecting grass growth and hence herbivore nutrition can govern the reproductive phenology of ungulates in tropical latitudes where day length variation is minimal. The underlying mechanism seems to be the suppression of conceptions once nutritional gains become insufficient. Through responding proximally to within-year variation in rainfall, tropical savanna ungulates are less likely to be affected adversely by the consequences of global warming for vegetation phenology than northern ungulates showing more rigid photoperiodic control over reproductive timing.     

Ultrasonographic-guided retrieval and in vitro maturation of eland (Taurotragus oryx) and bongo (Tragelaphus eurycerus isaaci) antelope oocytes

The limited availability of gametes is a major factor hindering the development and application of assisted reproductive technologies (ART) in large non-domestic ungulates. This is partly due to the small number of captive animals and handling difficulties associated with procedures for gamete recovery. In the present study, results are reported of multi-year studies on ovarian stimulation and oocyte retrieval by ultrasonographic-guided transvaginal follicular aspiration and subsequent in vitro maturation (IVM) in eland and bongo antelopes. All procedures were conducted on sedated females handled in a hydraulic chute without inducing general anesthesia. Five estrous synchronization/ovarian stimulation protocols were evaluated and data are presented on 73 and 15 procedures in eland and bongo, respectively. Repeating procedures (< or =once/month) on the same female did not affect ovarian response or number oocytes recovered in either species. Eland females, but not the ovarian stimulation treatment, affected ovarian response. Ovarian stimulation treatment affected oocyte recovery rate in eland, but not in bongo. In both species, ovarian hormone stimulation treatment affected the distribution of follicles by size and the status of expansion of the cumulus cell investment of oocytes, but not the frequency of metaphase II oocytes during IVM. The timing of extrusion of the first polar body during IVM was more synchronous in bongo than in eland oocytes. It is concluded that Transvaginal oocyte retrieval (TVOR) can be safely and repeatedly applied in gonadotropin-treated eland and bongo females to recover oocytes that can mature in vitro. The methods described for the present study can be adapted to improve the availability of non-domestic ungulate oocytes for basic and applied studies.     

The pattern of lion predation in Nairobi Park

The feeding habits of lions in Nairobi National Park have been observed between 1968 and 1972. Nairobi Park is briefly described and the herbivore and predator populations are discussed. The relationship between the changing status of the prey population for the period 1968-72 and the feeding habits of the lions is examined and compared with data from earlier years. Selection ratio (preference ratio) for three of the most important prey species is more closely adjusted to the abundance of these species in the total ungulate population than was the case prior to 1968. Only warthog and eland form an exception. Predation on wildebeest shows the most marked decrease although this species has been increasing during the last 5 years. Wildebeest, kongoni, zebra and warthog have provided 80% of total kills throughout the study on the basis of numbers killed. On this basis, warthog has the highest preference rating. However, the largest contribution to the lions' diet expressed in kg is by kongoni, followed by zebra, wildebeest, eland and warthog, in that order. Kongoni and wildebeest contribute most during the first half of the year and zebra and eland during the last 6 months. Selection for males is significant in zebra and eland and highly significant in kongoni, whilst only in zebra is selection for juveniles evident.