Variations in the demographic structure and dynamics of gelada baboon populations

Summary A comparative analysis of demographic variables for three populations of gelada baboons (Theropithecus gelada) showed that these were determined by a combination of environmental, demographic and social factors interacting in complex ways. Both birth rates and survivorship were found to be adversely influenced by the severity of local climatic conditions. These independently influenced adult sex ratio, which in turn determined the proportion of multimale reproductive units in the population. Mean harem size was found to be independent of all environmental and demographic factors with the sole exception of the proportion of harem-holding males, suggesting that it is mainly a consequence of social factors related to harem fission rates. Migration rates and band fission rates were related to population growth rates, these in turn being determined largely by local mortality and birth rates.     

Determinants and evolutionary consequences of dominance among female gelada baboons

Summary Dominance relations among free-living female gelada baboons (Theropithecus gelada) are shown to depend on the individual's aggressiveness, modified by coalitionary support from female relatives. Relatives rank adjacent to each other more of often than expected by chance.Females are more willing both to give coalitionary support and to do so on an asymmetric basis to females with whom they interact socially (usually relatives) than to those with whom they rarely interact.The number of offspring that a female has is shown to be a function of her dominance rank. This phenomenon is probably due to the fact that females harass individuals subordinate to them when the latter are in oestrus. It is suggested that the stress caused by this harassment appears to disrupt the female's reproductive physiology, thereby inducing a high rate of anovulatory cycles and amenorrhea. In consequence, subordinate females take longer to conceive than do dominants.Simulation is used to show that females who form coalitions gain a life-time reproductive advantage over those who do not because coalitions with younger females help to prevent the decline in rank that would otherwise occur in old age.It is argued that females prefer to form coalitions with caughters rather than unrelated females because the mother-daughter relationship is the only bond of sufficient strength to provide the basis for an investment which is asymmetric in the short-term and reciprocal only over the length of a life-time. Any benefits that accrue from kin selection are considered to be secondary.     

Time as a constraint on group size in spider monkeys

An animal can only survive in a given habitat if it has enough time to find, process and digest food whilst avoiding predation. The time it has for food acquisition is affected by the vegetation and competition with conspecifics, which depends on aggregation tendencies. We used the relationships between time allocations, on the one hand, and climatic variables (as a proxy for habitat quality) and group size, on the other, to develop a model that predicts maximum ecologically tolerable group size at different locations for spider monkeys. Spider monkeys are particularly interesting because the social communities often split up into small units. Temperature variation and rainfall variation were the main determinants of time budgets. Community size and average annual rainfall determined party size. The model correctly predicted presence or absence of spider monkeys at 78–83% of 217 New World forest sites. Within the geographical range of the species, this time budget model predicted the presence of spider monkeys better than a model based directly on climate variables. Predicted community and party sizes were significantly larger at sites where spider monkeys are present than at sites where they are absent. As required by the model, predicted maximum community sizes were significantly larger than observed community sizes. Moving time showed a U-shaped relationship with party size, which suggests that moving time is the factor that keeps spider monkey communities from travelling together in a tight group.     

Trade-offs between time, predation risk and life history, and their implications for biogeography: A systems modelling approach with a primate case study

Group sizes are often considered to be the result of a trade-off between predation risk and the costs of feeding competition. We develop a model to explore the interaction between different ecological constraints on group sizes, using a primate (baboons) case study. The model uses climatic correlates of time budgets to predict maximum ecologically tolerable group size, and climatic predictors of predation risk (reflected mainly in predator density and female body mass) to predict minimum tolerable group size for any given habitat. As well as defining the range of sustainable group sizes for a given habitat, the model also allows us to reliably predict our exemplar taxon's biogeographical distribution across Africa. We also explore the life history implications of the model to ask whether baboons form group sizes which maximise survival or fecundity in the classic trade off between these two key life history variables. Our results indicate that, within the range of study sites in our sample, baboons prefer to maximise fecundity. However, the data indicate that in higher predation risk habitats they would switch to maximising survival at the expense of fecundity. We argue that this is due to the fact that interbirth interval and developmental rates have a ceiling that cannot be breached. Thus, while females can shorten interbirth intervals to compensate for increased predation risk, there is a limit to how much these life history variables can be altered, and when this is reached the best strategy is to maximise survivorship.     

Reducing mine water network energy requirements

Increasing energy efficiency and reducing water consumption are two of the key requirements in moving toward a more sustainable mining industry. This paper demonstrates a method of determining the lowest energy option for a mine/mill water system network. The method uses a linear programming algorithm to compare different possible combinations of supplying water to mine and mill consumers. First, a site water balance is determined and then every major water consumer and source is specified. Water sources may require pumping, cooling and/or treatment before the water meets the specifications of the water consumer. The amount of energy required for each water source to supply each consumer is calculated and then the model is solved to minimize power consumption. An example is used to illustrate the method.     

Classifying the Health of Connecticut Streams Using Benthic Macroinvertebrates with Implications for Water Management

Bioassessments have formed the foundation of many water quality monitoring programs throughout the United States. Like many state water quality programs, Connecticut has developed a relational database containing information about species richness, species composition, relative abundance, and feeding relationships among macroinvertebrates present in stream and river systems. Geographic Information Systems can provide estimates of landscape condition and watershed characteristics and when combined with measurements of stream biology, provide a useful visual display of information that is useful in a management context. The objective of our study was to estimate the stream health for all wadeable stream kilometers in Connecticut using a combination of macroinvertebrate metrics and landscape variables. We developed and evaluated models using an information theoretic approach to predict stream health as measured by macroinvertebrate multimetric index (MMI) and identified the best fitting model as a three variable model, including percent impervious land cover, a wetlands metric, and catchment slope that best fit the MMI scores (adj-R ² = 0.56, SE = 11.73). We then provide examples of how modeling can augment existing programs to support water management policies under the Federal Clean Water Act such as stream assessments and anti-degradation.     

Female territoriality and the function of scent-marking in a monogamous antelope (Oreotragus oreotragus)

In monogamous species, females often choose between males according to the quality of the territories they defend, but the extent to which females themselves contribute to territory defence is frequently underestimated. Here we test for differences in male and female roles during paired scent-marking bouts, a key component of territorial defence, in a monogamous antelope. In two populations (Kenya, Zimbabwe) of klipspringer, Oreotragus oreotragus, both males and females usually scent-marked at the same site, but there were significant differences between sexes in terms of investment within bouts. Females initiated most bouts, thus dictating the marking strategy of the pair. Males initiated relatively few bouts, but deposited more scent marks per bout than females and were usually the last to scent-mark before leaving the site; they marked on the same branches as the female and thus overmarked her scent. Both sexes deposited more marks during paired than solo visits. Immediately preceding and following scent-marking bouts, males approached females and females left males more often than expected. Female scent-marking rates were higher when they were receptive than at other times, and this increase was matched by elevated marking rates of males. Females may increase marking rates when they are receptive in order to test the quality of their mate or to incite male competition. However, these ideas are unlikely to explain female scent-marking behaviour outside the mating season, which appears to be related primarily to territorial defence. We suggest that these differences in investment in scent-marking bouts are consistent with predictions that females may be autonomously territorial and that overmarking of female scent by males is a form of mate-guarding. Received: 17 November 1999 / Received in revised form: 24 February 2000 / Accepted: 13 March 2000     

Time: a hidden constraint on the behavioural ecology of baboons

Summary Data from wild populations of baboons are used to derive functional equations relating time budget components, day journey length and group size to environmental variables. This set of equations predicts both time budgets in an independent sample of populations and the geographical distribution of baboon populations extremely well. I then use these equations to examine the maximum ecologically tolerable group size for baboons occupying different habitats. Groups which exceed this value exhibit signs of ecological stress: they spend less time resting and in social activity than would be expected for their size and environment, they are more likely to fragment during foraging and they travel faster. Populations living in poor quality (low rainfall) habitats are more likely to live in groups that are stressed in this way.     

Territory size and defendability in primates

Mitani and Rodman (1979) showed that a simple measure of the defendability of the range area could differentiate fairly successfully between territorial and non-territorial species of primates. Their analysis has, however, been much criticised on the grounds that it considered only the day journey length and the diameter of the range area. We develop a number of more realistic indices of territory defendability that take into account both the length of the boundary to be defended and the detection distance as well as linear measures of range size. These indices (a) discriminate between territorial and non-territorial species more successfully than the Mitani-Rodman index and (b) allow the results to be extended to species which do not forage in cohesive groups. However, our results suggest that the Mitani-Rodman analysis was in many ways correct.