African Journal of Ecology 

About: African Journal of Ecology is an academic journal published by Wiley-Blackwell. The journal publishes majorly in the area(s): Population & National park. It has an ISSN identifier of 0141-6707. Over the lifetime, 3304 publications have been published receiving 70418 citations.

Age criteria for the african elephant: loxodonta a. africana

Abstract: Summary 1. The paper is based on a collection of 385 lower jaws of the African elephant (Loxodonta a. africana Blumenbach) from western Uganda. 2. Thirty age groups are described and illustrated, which are related to the progress of eruption and wear of the six teeth in each side of the lower jaw. 3. Correct identification of individual teeth in the series is essential and several checks are described. Thus, when length is plotted against width for the six teeth the points fall into six well - defined groups. Frequency distributions of laminary indices and lamella numbers support the belief that teeth have been correctly identified, but overlapping, distributions preclude identification on these characters alone. 4. The presence of abnormal seventh molars in four jaws is described. 5. Chronological ages have been assigned to the relative age groups. Information on age and growth of captive animals has been considered and the general form of the growth curve established. Arbitrary estimates of the intervals between successive age groups were made and subsequently checked against growth and seasonal ridges on the roots. These indicate an upper age limit of about 60 years, which is compatible with fuller information on Indian elephants. 6. Growth curves support the validity of the ages assigned. Asymptotic heights at shoulder (∞) are respectively 317 cm and 298 cm for males from Murchison Falls and Queen Elizabeth National Parks. For females no distinction is made (because the sample from the latter area is small) and ∞ is 272 cm. 7. Growth in weight has also been established but shows no significant differences between the two populations. The mean maximum weight of females is 2766 kg (6100 lb), and of males 5450 kg (12000 lb). Growth apparently continues throughout life. 8. Tusk growth is analysed. There is a linear increase in weight of female tusks from eruption at 1–3 years up to the oldest group, with an indicated mean combined weight of 17.7 kg (39 lb) at 60 years. Male tusks show an increasing rate of growth throughout life to a mean combined weight of about 109 kg (240 lb) at 60 years. Big tusks are generally the result of prolonged growth; extremely big tusks probably result from prolonged and above average rate of growth. 9. Seasonal and annual incremental layers on the root 3 of the teeth are briefly described; these give an objective estimate of the chronological intervals between the relative age groups. 10. Field age criteria are presented which are derived from these growth curves. 11. The age at puberty in the female elephant is discussed and compared with earlier conclusions. There is evidence of a retardation in recent years in the Murchison Falls National Park (South bank) population and of a lengthening of the mean calving interval. This considerable depression of the reproductive rate, which is almost certainly density dependent, agrees with the observed lower recruitment in this population. 12. Survivorship curves constructed from material representing 325 natural deaths are presented for the two populations. If estimates of the age at puberty and the reproductive rate are taken into account, the expected differences in recruitment are found. 13. The calculated mean expectation of life is less than 15 years. 14. Mean individual weight is estimated at about 3800 lb.

Water availability and its influence on the structure and dynamics of a savannah large mammal community

Abstract: Summary The Amboseli ecosystem is in a semi-arid savannah environment in which water availability is highly seasonal, a feature which has an important bearing on the structure and efficiency of the large mammal community. Data are presented to show that the seasonal movements, a wet season dispersal and dry season concentration of water-dependent species (obligate drinkers) can be related to the seasonality of rainfall and water availability, but that similar patterns do not prevail in the water-independent species. Evidence suggests that water availability is a crucial parameter in calculating the carrying capacity of a range, and that the duration of ephemeral supplies, which reflect rainfall seasonality, evapotranspiration, and soil water storage capacity, is equally important. A simplified model is presented which calculates the carrying capacity of water-bound communities–taking into account these two limiting factors. There appears to be a physiological barrier to a heavy utilization of the low water content grasses beyond reach of the water-dependent species, since most water-independent species select high water content browse in order to maintain a positive water balance. Significantly, while the water-independent community is almost exclusively composed of browsers, most water-dependent species are grazers. The biomass density of large mammals beyond 15 km from water, a radius which encloses 99-5% of the biomass of water-dependent species, is extremely low compared to areas within 10 km of water. As a consequence of the physiological barrier to a heavy utilization of low water content forage in water-deficient areas, the food chain efficiencies are appreciably lower than those with permanent water sources. Livestock development programmes have long appreciated this constraint and employed water development schemes to increase range-carrying capacity. Seasonality in the movement patterns of Amboseli is compared to other large mammal communities and management implications are discussed.

Size, life history and ecology in mammals

Abstract: ummary Allometric laws which scale numerous biomechanical and physiological processes to size in mammals have long been recognized and widely used in biology. There is now sufficient evidence to suggest that those life history parameters such as growth and maximum rates of reproduction, which depend in part on metabolic rate, are also scaled to size. Data are presented which, coupled with a literature review, show that gestation time, growth rates, age at first reproduction, lifespan, the intrinsic rate of natural increase, birth rate, net reproductive rate and litter weight are allometrically scaled to size and are, in consequence, inter-related. The exponents of the scaling functions are similar in all mammalian orders but in some taxa such as the primates, the species grow slower, live longer and reproduce at a lower rate. For these taxa the differences in life history parameters can be explained by differences in brain size and an existing hypothesis that the maximum rate of neural tissue growth constrains the maximum rate of growth and development of the entire organism. It is then argued that because size scales the main life history parameters of mammals it should also be a central theme in ecology from the individual to the community level of organisation. Examples are presented to show that size is ubiquitous in ecology and accounts for most of the variation in life history parameters between species. Size scaling offers a method of reducing species of varying size to similar dimensions of time, space and rates of action. It is therefore fundamental in distinguishing those life history parameters which arise as a consequence of size, the first order strategies, from those that vary between populations and according to environmental circumstances, the second order strategies. From this approach should develop a broader biological synthesis in which genetic and physiological determinants will inevitably feature more centrally than they do in ecological and behavioural theory. Resume Les lois allometriques unissant les processus biomecaniques et physiologiques avec la taille chez les mammiferes ont ete reconnues depuis longtemps et largement utilisees en biologic Il y a maintenant assez de certitude pour suggerer que les parametres biologiques tels que croissance et taux maximal de reproduction, qui dependent partiellement du rendement metabolique, sont aussi fonctions de la taille. Les donnees presentees ici, couplees avec une revue de la litterature, montrent que la duree de gestation, le taux de croissance, l'âge a la premiere reproduction, la duree de vie, le taux intrinseque d'accroissement naturel, le taux de natalite, le taux de reproduction net et le poids de la portee sont en relation allometrique avec la taille et, par consequent, sont en interrelation.

Ecological separation of the large mammal species in the tarangire game reserve, tanganyika†

Abstract: Summary The ecological separation of 14 common ungulate species living in close contact with each other in a Tanganyika game reserve is shown to be achieved by six different factors: 1. the occupation of different vegetation types and broad habitats; 2. the selection of different types of food; 3. the occupation of different areas at the same season; 4. the occupation of the same area at different seasons; 5. the use of different feeding levels in the vegetation; 6. the occupation of different dry season refuges in the Masai area when the competition for food is greatest (zebra and wildebeest). Habitat preferences are indicated by the frequency distribution of each species along the central of three 8,000 yard parallel transect paths which were traversed nearly daily for four years. Characteristic patterns of frequency are apparent for each of the species in the vegetation zones represented in the transect area. Certain species show a tendency, sometimes strong, to concentrate along the boundaries between adjoining vegetation zones and in the ecotones between the zones. This is ascribed to a greater diversity of food, availability of shelter from the sun and/or greater protection from predators. Records of the animal species eating particular plant species are shown and (qualified in the light of other observations) used to deduce food preferences. The species are classified broadly into grass-eaters, browsers and mixed feeders (grass and browse). In the case of the three common grass-eaters, buffalo, wildebeest and zebra, a percentage analysis of the grass species eaten indicates that little differential preference is shown but that they take the palatable grasses largely in proportion to the frequency in which they occur in the habitats most used by the ungulate concerned. Buffalo are separated by their preference for denser vegetation. Wildebeest and zebra largely overlap ecologically in all respects except that the bulk of the populations of each species move to different dry season areas. Those species which are able to live without drinking free water, notably impala and Grant's gazelle, are able to make use of wild areas of waterless country when the animals requiring water are forced to move into dry season concentration areas near water. The influence of the animals on the habitats and on other species is discussed and instances are given of species helping to shape the habitat to the advantage of both themselves and other species. Elephants are the main habitat modifiers and their capacity to improve water supplies and change the vegetation, and their facilitation of the feeding of other species is described. The formation of mixed herds is interpreted as being protective to one or both species concerned and is a further important facilitation. Little or no hindrance of one ungulate species by another was seen although herbivores show antagonistic behaviour towards carnivores smaller than themselves.

Rainfall, soil nutrient status and biomass of large African savanna mammals

Abstract: ummary Published estimates of population densities of large savanna herbivores are used to relate biomass to rainfall, and soil nutrient status as determined by geomorphology (after Bell, 1982). This reveals that the positive correlation between total large herbivore biomass and rainfall in arid/eutrophic savannas (Coe, Cumming & Phillipson, 1976) also applies for nineteen out of twenty-three individual herbivore species. Herbivores are divided into two groups, arid and moist savanna species, on the basis of the rainfall at which their peak population densities occur on soils of low nutrient status (< 820 and ≥ 1000 mm, respectively). These groups reflect the division between arid/eutrophic) and moist/dystrophic) savannas. Arid savanna herbivores, which dominate total herbivore biomass, include grazers, mixed feeders and browsers and are less selective feeders. Their biomass tends to decline at higher levels of rainfall on low nutrient status soils and only the larger species, such as elephant, buffalo and hippopotamus, are widespread in moist/dystrophic savannas where mean annual rainfall exceeds 1000 mm. Moist savanna species are mainly highly selective grazers and occur widely in moist/dystrophic) savannas. Their biomasses are usually low and show a positive correlation with rainfall on soils of low nutrient status. Large carnivore biomass is positively correlated with rainfall in arid/eutrophic) savannas, reflecting a positive relationship to prey biomass. The biomass of individual carnivore species is most closely correlated with the biomass of the preferred size class of prey. These relationships suggest that natural populations of large savanna mammals tend to be close to the limits set by their food resources. Resume Les estimations publiees de densites de population des grands herbivores de savane sont utilisees pour mettre en relation la biomasse avec les chutes de pluie et la composition du sol en nutriments, telle qu'elle est determinee par la geomorphologie (d'apres Bell, 1982). Ceci revele que la correlation positive entre la biomasse totale de grands herbivores et la chute de pluie dans les savanes arides/ eutrophiques (Coe, Cumming & Phillipson, 1976) s'applique egalement pour dix-neuf des vingt-trois especes d'herbivores. Les herbivores sont divises en deux groupes–especes de savanes arides ou humides–selon le niveau de chutes de pluie auquel correspond leur densite de population maximale sur des sols pauvres en nutriments (< 820 et ≥ 1000 mm respectivement). Ces groupes refletent la division entre les savanes arides/eutrophiques) et humides/dystrophiques). Les herbivores de savane aride, qui dominent la biomasse totale des herbivores, comprennent des brouteurs d'herbe, des brouteurs mixtes, des brouteurs de feuilles et des brouteurs moins selectifs. Leur biomasse tend a diminuer aux plus hauts niveaux de pluies sur sols pauvres et seules quelques grandes especes comme l'elephant, le buffle et l'hippopotame sont repandus dans les savanes humides/dystrophiques) ou la quantite de pluie depasse 1000 mm. Les especes de savane humide sont principalement des brouteurs d'herte tres selectifs. Leurs biomasses sont generalement faibles et presentent une correlation positive avec les chutes de pluie sur sols pauvres en nutriments. La biomasse des grands carnivores est en correlation positive avec les chutes de pluie en savanes arides/eutrophiques, illustrant la relation positive avec la biomasse de leurs proies. La biomasse de chaque espece de carnivore est beaucoup plus intimement liee a celle de son type de proie. Ces relations suggerent que les populations naturelles de grands mammiferes de savane tendent aetre proches des limites fixees par leurs ressources alimentaires.