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1.
Alterations to habitats that increase the distance at which prey can detect predators can decrease the risk of predation. In grasslands, burning may have this effect for mammalian herbivores by decreasing vegetation height, potentially making burned areas safer habitats. However, few studies have tested the impacts of burning on the perceived predation risk of herbivores. Vigilance can be used as a measure of habitat safety and therefore should be lower in burned areas than unburned areas. We tested the impacts of prescribed burning on vigilance by Thomson's gazelles in Serengeti National Park, Tanzania. Both individual vigilance, proportion of time an individual spends looking, and group vigilance, proportion of a group looking, of Thomson's gazelles was observed in burned and unburned areas before and after presenting a model cheetah to each group. Surprisingly, both individual and group vigilance was the same in both habitats pre‐ and post‐cheetah addition and removal. This is despite the fact that both vegetation height and biomass were lower in burned areas than unburned areas. Thus, it does not appear that Thomson's gazelles perceive burned areas to be safer habitats than unburned areas.  相似文献   

2.
Monthly changes in abundance of Thomson's gazelles at 142 locations on the Serengeti Plains are presented over a 3½ year period. Numbers of gazelles on the eastern plains were strongly correlated with rainfall, whereas numbers in the central and western plains appeared to be related to other variables. Movements of female cheetahs and non-resident male cheetahs corresponded closely to the movements of Thomson's gazelles but those of resident male cheetahs remained relatively independent of the gazelle migration.  相似文献   

3.
During serological surveillance of peste des petits ruminants (PPR) disease, it required capture of randomly selected herds of gazelles as part of a study to determine the epidemiological role of these species in the circulation of peste des petits ruminants virus (PPRV). The study targeted capturing 135 Grant's gazelles (Gazella granti) from the Serengeti ecosystem, Tanzania. A modified netting technique was used aiming at providing safe, efficient and cost‐effective method for capture of gazelles. Locally available materials were used, and wildlife professionals guided the process of manufacturing supporting frame for the nets. Twenty (20) black metal pipes, 20 metal bars, four nets and three vehicles were used in the procedure. A total of 136 Grant's gazelles and nine Thomson's gazelles were captured in three missions. The Grant's gazelles were captured as per sample size calculated in all locations: Loliondo (n = 25), Serengeti National Park (n = 44) and Ngorongoro Conservation Area (NCA) (n = 67) using less time and minimum cost than estimated. Injuries of three fawns (2%) inadvertently captured with the groups of adults and sub‐adult animals were recorded. Comparing with 2014 and other studies, modified netting technique showed high animal and operator safety levels with minimal injuries. With this technique, it was possible to capture even flighty animals that behave nervously because of hunting and other human activities, including Thomson's gazelles, a species previously found to be difficult to capture by netting.  相似文献   

4.
Landscape scale, heterogeneity, and the viability of Serengeti grazers   总被引:1,自引:1,他引:1  
Species persistence can be threatened by substantial temporal variation in food resources over time. On the other hand, spatial heterogeneity in resources at the landscape scale might allow mobile consumers to compensate for temporal variability in resource availability at the local scale. We evaluated this hypothesis, using an extensive data set on foraging, grass growth, and movement by Thomson's gazelles living on the Serengeti Plains. Here we show that modelled populations of Thomson's gazelles can only persist under Serengeti conditions in the face of observed levels of rainfall stochasticity by making adaptive movements to take advantage of ephemeral spatial distributions of food resources. More importantly, our models suggest that Thomson's gazelles in Serengeti require unrestricted access to relatively large areas of grassland (> 1600 km2) to guarantee long‐term persistence, particularly when there is positive spatial autocorrelation in resource abundance, as is the case in Serengeti. If this proves to be true for other species and/or other systems, then understanding of complex behavioural responses to spatially and temporally heterogeneous food supplies may be essential to successful conservation of grazing herbivores.  相似文献   

5.
《Animal behaviour》1986,34(3):663-684
Stotting in Thomson's gazelles (Gazella thomsoni) was found to have a negligible time cost in slow flights and it was normally shown in safe situations when prey were unlikely to be captured. Despite its probable energy cost and time cost during fast flights there was no evidence to show that, once a chase occurred, stotting gazelles were caught more or less often than gazelles that did not stott.Eleven hypotheses concerning the benefits of stotting were tested using a number of predictions about the stotting individual, its conspecifics and the predator (usually cheetahs), some of which were pertinent to several hypotheses. Although a number of hypotheses were supported by some of the predictions, most were refuted by one or more pieces of evidence. Only two were satisfactorily supported by all of them: stotting appears to inform the predator that it has been detected, but it does not invite or deter the predator from pursuing the gazelle. In neonate Thomson's gazelles, stotting probably has a different function, it informs the mother that the neonate has been disturbed and is in need of defence. In addition, mothers whose neonates escaped capture by cheetahs stotted significantly more during the attempt than mothers whose neonates were caught. Hypotheses concerning the prey signalling its health, startling or confusing the predator; group cohesion; anti-ambush behaviour; play in young animals; warning of conspecifics; and pursuit invitation or deterrence were dismissed by data presented here.  相似文献   

6.
Habitat selection and feeding ecology of a reintroduced population of cheetahs Acinonyx jubatus were studied in a 16 000 ha game reserve in the Eastern Cape Province (South Africa). Seventy per cent of the reserve is characterized by very dense thicket vegetation (valley bushveld) and the remainder is open and savanna-like. The results illustrated a strong effect of sex and group size on the behaviour of cheetahs. The coalition (three adult males) killed significantly larger animals (55% of kills weighed more than 65 kg) than single female cheetahs (less than 2% of kills weighed more than 65 kg). Female cheetahs showed temporal and spatial avoidance of lions by hunting at dawn and dusk and positioning their home ranges [95% utilization distribution (UDs)] significantly farther from the pride of lions than did the coalition. The coalition hunted earlier and later than female cheetahs, and 46% of their kills were made in darkness. In addition, their home range overlapped that of the lions and they showed neither temporal nor spatial avoidance of the lions. The rates of kleptoparasitism were lower and the kill retention times were longer than those reported elsewhere in Africa, and it is suggested that this is a consequence of the cover provided by the thicket vegetation and prey size. The home ranges (95% UDs) of female cheetahs incorporated more thicket vegetation than that of the coalition, indicating that the coalition is less susceptible to predation than single females. These data suggest that cheetahs possess greater behavioural flexibility than previously reported, that they can hunt successfully in thicket vegetation, sometimes in darkness, that they are not restricted to killing small to medium-sized prey, and that they may not be savanna specialists.  相似文献   

7.
Recreational big game hunters make a significant contribution to conservation through kills of deer, pigs, chamois and tahr. New opportunities for managing recreational hunting through the proposed Game Animal Council underscore the need to understand the implications of potential changes in recreational hunting participation and harvests. Based on a survey of hunters' recall over a year, hunters averaged 15.63 (SEM = 0.58) big game hunts per year, spending 30.53 (SEM = 0.85) days hunting and killing 8.92 (SEM = 0.69) big game animals. Hunters commonly targeted several species on a single hunt, with highly skewed distributions for hunter effort and kills. Mean monthly expenditure on big game hunting items was $296.78 (SEM = $8.95). Results demonstrate that big game hunting is a significant activity in New Zealand, but this varies considerably among hunters with a small number responsible for the vast majority of kills. These are important considerations for future big game hunting management.  相似文献   

8.
The lappet-faced and white-headed vulture nests in a 1636 km2 study area on the Serengeti Plains were kept under observation from June 1972 to August 1973. Active nests were inspected from a light aircraft at intervals of approximately 2 weeks. The inverse nesting densities were estimated as 43 km2/pair for the lappet-faced vulture and 409 km2/pair for the white-headed vulture. Nests were built of sticks in exposed sites on the crowns of trees, Acacia tortilis being the most popular species. Where the previous history was known, 44% of lappet-faced vulture nests were newly constructed, and the rest re-used from the previous year. The incubation period was about 55 days and the fledging period about 100 days in both species. Juveniles continued to frequent their nests after they could fly, sometimes for several months. Most lappet-faced vultures laid their eggs in April-May, the white-headed vultures in June-August. This means that the lappet-faced vultures raised their young during the dry season, when Grant's and Thomson's gazelles were the only animals present in any numbers on the plains. By contrast, the Ruppell's griffons nesting in the nearby Gol Escarpment colony raise their young during February-May, when the wildebeest and zebra herds are normally on the plains. The survival rate of lappet-faced vultures from laying to fledging was about 40%. The chicks are thought to be vulnerable to predation by tawny eagles, and one was known to have been killed by a leopard. Three adult vultures were killed on their nests, from unknown causes. Food remains from lappet-faced vulture nests showed a heavy preponderance of Grant's and Thomson's gazelles in all cases, with golden jackal the next most commonly occurring species. No food remains were obtained from white-headed vulture nests. The possibility of using aerial counts of vulture nests as an indicator of productivity is discussed.  相似文献   

9.
Rates of chimpanzee predation on mammals are calculated using data on 75 kills recorded during focal observation in Gombe National Park, Tanzania, from January 1972 to April 1975. The chimpanzees were members of two study communities (Kanyawara, or Northern, and Kahama, or Southern, community), and were observed as focal individuals for 14,583 hr by more than 30 researchers and field assistants working in pairs. The rate of predation by females was too low to allow reasonable estimates. For males, the mean rate of killing during the study period was 0.31 kills per male per 100 hr (N=17 males), or 4.65 kills per 100 hr in the two communities. In contrast to results from Mahale Mountains, there was no difference in predation rate between wet and dry seasons. However, predation rates varied over time, increasing by four times between the first three and last four seasons of the sample period. In an average year the 15 adult and subadult male chimpanzees are calculated to have killed 204 prey per year in an area of 16 km2, varying between 99 and 420 prey per year in periods of low and high predation rate. Red colobus were the most frequent prey, followed by bushpig and bushbuck. Predation rates varied greatly on different prey species, and were not related to either the proportion of time spent within 200 m of male chimpanzees, or to their population densities. In relation to encounter rates and population density, baboons, blue monkeys, and redtail monkeys were killed at a fraction of the rate of red colobus monkeys, which suffered severe mortality from chimpanzee predation. Predation on bushpig and bushbuck also appears to have been high in relation to population density. The amount of food provided by predation is estimated to have averaged 600 kg per year for chimpanzees in the two communities (totalling 14–17 adult or subadult males, 18–20 adult of subadult females, and about 19 infants or juveniles). This suggests that adult males consumed around 25 kg of meat per year, although any average figure undoubtedly masks considerable individual variation. Present data suggest that chimpanzees in Gombe and Tai National Park, Ivory Coast, prey on mammals at rates higher than other populations.  相似文献   

10.
This paper presents preliminary evidence that kleptoparasitism by spotted hyaenas may influence optimal hunting group size of lions. In the absence of adult male lions, hyaenas can drive female and subadult lions off their kills provided they outnumber the lions by a factor of four. Hence the larger the group of lions on the kill, the greater their chance of defending their food against invading hyaenas. At Savuti, where there was a shortage of adult male lions, the groups of female and subadult lions lost almost 20% of their food to hyaenas. Losses were most frequent for those living in small groups. These lions were often satiated by the time the hyaenas acquired the kill, so the hyaenas did not cause immediate need, yet constituted a constant energy drain on lions by forcing them to hunt more frequently. The implications of these observations for modelling optimal hunting group size of lions are discussed.  相似文献   

11.
Equine herpesvirus type 9 (EHV-9), which we isolated from a case of epizootic encephalitis in a herd of Thomson''s gazelles (Gazella thomsoni) in 1993, has been known to cause fatal encephalitis in Thomson''s gazelle, giraffe, and polar bear in natural infections. Our previous report indicated that EHV-9 was similar to the equine pathogen equine herpesvirus type 1 (EHV-1), which mainly causes abortion, respiratory infection, and equine herpesvirus myeloencephalopathy. We determined the genome sequence of EHV-9. The genome has a length of 148,371 bp and all 80 of the open reading frames (ORFs) found in the genome of EHV-1. The nucleotide sequences of the ORFs in EHV-9 were 86 to 95% identical to those in EHV-1. The whole genome sequence should help to reveal the neuropathogenicity of EHV-9.  相似文献   

12.
Data collected from 265 cropped Thomson's gazelle in northern Tanzania have permitted development of ageing criteria based on weights, horn growth and dentition. Most deciduous teeth are replaced between 12 and 15 months of age and the third molar becomes fully functional at nearly 2 y. Asymptotic horn length of about 32 cm is reached by males at 20–24 months. Dressed carcass weights were about 60 per cent of live weights, being slightly higher in males and higher in January than February. Females are capable of breeding before 1 y. Only single foetuses were found and these only in the right uterine horn. There was evidence of lambing every month but with May and November peaks.  相似文献   

13.
The conversion of natural ecosystems due to anthropogenic activities has led to the destruction of natural habitats and to the deterioration of habitat quality. Top predators particularly respond sensitively to changes in habitat structures, including the availability of prey. The cheetah Acinonyx jubatus prefers small‐medium‐sized, wild ungulate prey due to the cheetah''s morphological adaptations. However, the majority of the species’ population is found beyond protected areas, where habitat structures, species abundances, and community composition are highly influenced by human activities. Only few studies have analyzed the diet preference of cheetahs in relation to prey availability and abundance for rangelands beyond protected areas in Eastern Africa. The study aimed to determine cheetah prey preference in the rangelands of south‐eastern Kenya based on scat analyses. We compared dietary preference of cheetah with prey availability. For this purpose, we conducted standardized game counts. We analyzed 27 cheetah scat samples collected across the same study area where we also conducted game counts. We found that Grant''s gazelle Gazella granti contributed the highest portion of cheetah''s diet, although Thomson''s gazelle Gazella thomsonii was the most abundant medium‐sized ungulate prey in the study areas. We also recorded two primate species, yellow baboon Papio cynocephalus and vervet monkey Chlorocebus pygerythrus, as well as the rock hyrax Procavia capensis in the cheetah diet. These species have never been documented as cheetah prey before. Furthermore, our results document livestock as potential prey for cheetahs. These observations underline that cheetah use diverse prey in rangelands outside protected areas, and that the abundance of specific prey does not influence cheetah prey preference.  相似文献   

14.
Because hunting disturbance can influence local distribution of ducks and their availability to hunters, managers often limit access to hunting areas to improve hunting success and satisfaction. Few studies have quantified the effectiveness of public area access restrictions on duck hunter activity, harvest, or hunters' satisfaction with their hunting experience. We used a cross-over design over 6 consecutive hunting seasons (2008–2009 through 2013–2014) on State Wildlife Areas (SWAs) in northeastern Colorado, USA, to compare the effects of restricted hunting access regulations and regulations without these restrictions on duck hunter activity, harvest success, harvest levels, and satisfaction. We also considered effects of SWA types, duck abundance, temperature, precipitation, use of equipment by duck hunting parties, and, for hunter satisfaction, hunting success, hunting parties' satisfaction with ducks seen, habitat conditions, crowding from other hunters, and SWA regulations. The number of days when duck hunters had access to restricted properties was about half that on unrestricted properties, and unrestricted properties were used by about twice as many duck hunting parties, but the mean number of hunting parties per available hunting day and mean party size were similar under the 2 types of regulations. Most (56%) duck hunting parties did not bag any ducks; hunting success (harvest of ≥1 duck by a hunting party) was best explained by a model that included a regulation type × hunting season interaction, a SWA type × month interaction, hunter density the previous day, an index of hunter investment (number of decoys used and whether dogs and calls were used), and temperature. Successful hunting parties harvested 1.92 ± 1.60 (SD) ducks/hunter/day (range = 0.1–7.0); the best model predicting the number of ducks harvested per hunter in successful parties included a regulation type × hunting season interaction, a SWA type × month interaction, hunter density the previous day, an index of hunter investment, temperature, and precipitation. Overall satisfaction of duck hunting parties with a day's hunt averaged 3.62 ± 1.20 based on a rank scale of 1 (very unsatisfied) to 5 (very satisfied), and was best explained by a model that included hunting party success; hunter investment; temperature; and satisfaction with duck numbers, habitat conditions, hunting regulations, and crowding. While greatly reducing days available for hunting, access restrictions were associated with improved chances of hunting parties successfully harvesting ≥1 duck in 5 of 6 hunting seasons, and substantially greater numbers of ducks harvested by hunters in successful parties in 1 of 6 hunting seasons. Restrictions did not have a strong direct effect on hunting parties' satisfaction with a day's hunt. Uncontrolled factors, including weather and use of equipment by hunters, had important influences on hunter success, harvest, and satisfaction. Managers should carefully assess hunting activity, hunter expectations and desires, and hunting area characteristics when considering access restrictions on public hunting areas.  相似文献   

15.
Few data are available on the behaviour of leopards in the absence of competing large predators and human impact, both of which are believed to influence leopard activity and movements. Remote camera traps and global positioning system (GPS) collars were used to quantify leopard activity in the Cederberg Mountains, seasonal and sexual differences in their movements, and determine whether nocturnal hunting success was related to lunar activity. Seventy‐seven per cent of camera‐trap photographs were at night, with a strong male bias (69%) in captures. Daily displacement using one location per day suggested that males moved significantly further than females. However, multiple locations (≥6 per day) showed no difference because males moved in a more linear fashion, but not further each day, than females. In the Cederberg Mountains, an open rocky habitat with low human impact and no competing predators, leopards were predominantly nocturnal, mainly hunting diurnal prey species. Hunting success was low: leopards travelled long distances between kills, with nocturnal hunting success higher on darker nights.  相似文献   

16.
Spotted hyenas are successful hunters, but they also scavenge. Their main food competitors are lions. In the Etosha National Park, Namibia hyenas are unable to prevent kleptoparasitism by lions and fail to acquire kills from lions. The reasons are the small ratio of hyenas to female and subadult lions at kills and the presence of adult male lions. Because of the hyenas’ small clan sizes and large territories they seem to be unable to recruit sufficient clan members to take over lion kills or deter lions from their own kills. In Etosha, 71% of hyena mortality was due to lions; four cubs and one adult female hyena were killed by male lions during a 1‐year study. Hyenas have evolved adaptations against lions and initiate aggressive interactions with lions without the immediate availability of food, which is termed mobbing behaviour. Etosha hyenas initiated mobbing attempts when lions were near the hyena's communal den. Possibly, Etosha hyenas mobbed lions to distract lions from the hyenas’ den and their cubs and to warn their dependent offspring to hide from lions.  相似文献   

17.
Dorcas gazelles are believed to use middens to mark their territories and transmit information. Given the commitment to maintaining a midden, it is believed that middens are not placed randomly. We examined how the habitat (tree height and maximum canopy) and anthropogenic disturbance (camel and human presence) influenced the selection of midden sites by Dorcas gazelles in South Sinai, Egypt. Our results showed that Dorcas gazelles did not place middens at larger trees, while favoring relatively smaller trees and shrubs where the anthropogenic disturbance and perceived hunting risk are less. Our results, in light of the previous findings, suggest that selection of midden sites is species context‐dependent behavior. In areas with less anthropogenic disturbance and hunting, Dorcas gazelles have been shown to select the largest trees of the same species as midden sites. In contract, in our study site with high anthropogenic disturbance and no protection from hunting, gazelles did not utilize the presumably optimum landmarks for midden sites. Our study showed that Dorcas gazelles instead utilized smaller trees and some shrubs that are less conspicuous and presumably less effective as advertisement sites, but safer.  相似文献   

18.
PROTEOLYTIC ENZYMES AND EXPERIMENTAL DEMYELINATION IN THE RAT AND MONKEY   总被引:5,自引:2,他引:3  
Abstract— Visible lesions from monkeys with acute experimental allergic encephalomyelitis (EAE) induced by injection of purified myelin basic protein were assayed for acid proteinase, for a neutral proteinase at pH 6·5, and one lesion was measured for cathepsin A. Acid proteinase was increased to 152–176 per cent of levels in normal-appearing brain areas, neutral proteinase increased to 220–258 per cent, and the one lesion assayed for cathepsin A was 840 per cent of control. These enzymes were measured in the brain stem of Lewis rats with acute EAE as a result of basic protein injection and compared to Freund's adjuvant-injected controls. Acid proteinase was increased significantly to an average level of 128 per cent of control, the increase in neutral proteinase was not significant, and cathepsin A levels were 258 per cent of control, a highly significant increase. The rise in cathepsin A levels was not seen until the onset of paralytic symptoms. The brain stem of Wistar rats treated with whole spinal cord which show EAE in a milder form than the Lewis rat did not contain significantly higher enzyme levels than the control. The increases in acid proteinase and cathepsin A in brain stems were compared to levels of these enzymes in lymph nodes of EAE, Freund's adjuvant-injected controls and uninjected controls. The level of acid proteinase of lymph nodes/g protein did not change appreciably in the course of EAE development in the Lewis and Wistar rats and was about 3–4 times the activity in the brain stem. The cathepsin A in the inguinal lymph nodes of Wistar and Lewis rats injected with whole spinal cord in Freund's adjuvant increases to a level 2× that of the lymph nodes of the uninjected control. The cathepsin A levels in these activated lymph nodes was 6–8 × that of the control brain stem. The lymph nodes of Lewis and Wistar rats injected with Freund's adjuvant alone showed the same increase in cathepsin A as those from rats injected with spinal cord. The brain stem of rats undergoing severe demyelination as a result of chronic administration of triethyl tin did not show the enzyme increases. These results are compatible with the theory that proteolytic enzyme increases in EAE (and probably multiple sclerosis) are due to the invasion of mononuclear cells, some of which are probably lymphocytes. Whether or not these enzymes participate in the actual dissolution of myelin is unknown.  相似文献   

19.
The condition and age of Thomson's gazelles ( Gazella thomsoni ) killed by two species of predators were compared. The wild dog, a coursing predator, was predicted to take a greater proportion of young, old and sick animals than the cheetah, a stalker. As measured by the marrow fat content of limb bones, wild dogs captured more Thomson's gazelles in poor condition than cheetahs. This appeared to be a consequence of their preference for male gazelles, which were in worse condition than females. Cheetahs did not capture fewer young and old gazelles than wild dogs.  相似文献   

20.
We studied survival of elk (Cervus elaphus) ≥1 yr old and quantified mortality sources in the Blue Mountains of Washington, 2003–2006, following a period of extensive poaching. The population was managed under a spike-only general hunting season, with limited permits for larger males and for females. We radiomarked 190 elk (82 males and 39 females >1 yr old and 65 males 11 months old), most with rumen transmitters and neck radiocollars; 60 elk only received rumen transmitters. We estimated annual survival using known fate models and explored survival differences among sex and age classes and in 2 potentially different vulnerability zones for males. We found little support for differences in survival between younger (2–3-yr old) and older (≥4-yr old) branch-antlered males or zone differences for yearling males. A model with zone differences for branch-antlered males was the second ranked model and accounted for 14% of the available model weight. From the best-supported models, we estimated annual survival for yearling males at 0.41 (95% CI: 0.29–0.53). We estimated pooled adult female survival at 0.80 (95% CI: 0.64–0.93); when an age-class effect was included, point estimates were higher for prime-aged females (2–11 yr: S = 0.81 [0.70–0.88]) than for older females (≥12 yr: S = 0.72 [0.56–0.83]), but confidence intervals broadly overlapped. Only 1 of 7 models with a female age effect on survival was among the competitive models. For branch-antlered males, survival ranged 0.80–0.85, depending on whether zone variation was modeled. We recorded 78 deaths of radiomarked elk. Human-caused deaths (n = 55) predominated among causes and most were of yearling males killed during state-sanctioned hunts (n = 28). Most subadult male deaths were from tribal hunting (n = 5), and most mature males died from natural causes (n = 6) and tribal hunting (n = 5). We detected few illegal kills (n = 4). Our results suggest that increased enforcement effectively reduced poaching, that unreported tribal harvest was not a trivial source of mortality, and that spike-only general seasons were effective in recruiting branch-antlered males. © 2011 The Wildlife Society.  相似文献   

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