J. Willem H. Ferguson

Seasonal change in the distribution and density of seals in the pack ice off Princess Martha Coast, Antarctica

During the period 9 December 1991–4 February 1992 shipboard and aerial surveys of seals in the pack ice off the Princess Martha Coast were made. All aerial surveys were flown from the MV SA Agulhas at the edge of the fast ice opposite SANAE at 70°19′S, 02°26′W. A total of 18 1/2-nm-wide transects were flown censusing 481.3 nm 2 of pack ice within which 1437 seals were counted. The species composition of the seals was 94.4% crabeater, 3.4% Ross, 1.4% leopard and 0.8% Weddell seals. The density of seals nm −2 for the early season surveys (December) in the inner pack was 1.92 for crabeater, 0.0 for leopard; 0.026 for Weddell and 0.057 for Ross seals. The density for the late season surveys throughout the pack was 4.02 for crabeater, 0.10 for leopard, 0.029 for Weddell and 0.122 for Ross seals. These data support the thesis that seal densities increase as the amount of pack ice diminishes with the advance of summer. Leopard seals were largely found near the retreating outer edge of the pack, and Weddell seals associated closely with the inshore fast ice, whilst both crabeater and Ross seals showed no statistically significant preference either for any part of the pack ice or for any particular geographical area covered during the surveys in the present study. The high densities (0.45−2.91 seals nm −2 ) and percentage species contribution (9.7−32.4%) of Ross seals determined by shipboard censuses in the same area during the early 1970s could not be confirmed in the present study, and it is likely that a real decrease in Ross seal numbers has taken place.

Mating ecology of the nonpollinating fig wasps of Ficus ingens

The males of many fig wasps fight fatally for mating opportunities. The concentration of females in space has been proposed as one factor selecting for their aggressive behaviour. We studied the temporal distribution of receptive females to obtain a clearer impression of the operational sex ratio in figs. Females of nonpollinating species emerged from figs over a protracted period of time and this resulted in an extremely male-biased operational sex ratio, conducive to extreme fighting. Since there were so few receptive females at any one time, a male could defend an eclosing female. Consequently, the largest, Otitesella longicauda male in a fig had a much higher mating success than smaller males. This suggests that larger males have a larger fitness advantage than larger females and a Trivers-Willard effect could have important implications for sex allocation. Apterous and seemingly nondispersing males routinely left their figs. Such dispersal can affect both (1) sex allocation by reducing the degree of local mate competition between brothers and (2) male dimorphism by reducing the mating opportunities of males with a dispersing morphology. We show that the wingless digitata males of the Otitesella digitata species group disperse on to leaves close to their natal fig. An extremely male-biased sex ratio resulted in almost all O. longicauda females being mated. These findings suggest that the classical concept of the fig wasp mating system is too simplistic and that important assumptions of sex allocation models are violated. Copyright 1999 The Association for the Study of Animal Behaviour.

Characterization and evolution of the mitochondrial DNA control region in hornbills (Bucerotiformes)

Abstract. We determined the mitochondrial DNA control region sequences of six Bucerotiformes. Hornbills have the typical avian gene order and their control region is similar to other avian control regions in that it is partitioned into three domains: two variable domains that flank a central conserved domain. Two characteristics of the hornbill control region sequence differ from that of other birds. First, domain I is AT rich as opposed to AC rich, and second, the control region is approximately 500 bp longer than that of other birds. Both these deviations from typical avian control region sequence are explainable on the basis of repeat motifs in domain I of the hornbill control region. The repeat motifs probably originated from a duplication of CSB-1 as has been determined in chicken, quail, and snowgoose. Furthermore, the hornbill repeat motifs probably arose before the divergence of hornbills from each other but after the divergence of hornbills from other avian taxa. The mitochondrial control region of hornbills is suitable for both phylogenetic and population studies, with domains I and II probably more suited to population and phylogenetic analyses, respectively.

The Groenvaly grassland fragmentation experiment: design and initiation

Abstract An experiment designed to study the effects of habitat fragmentation on biological diversity in the montane grasslands of Southern Africa was launched in September 1994. The Groenvaly experiment is positioned on the western slopes of the Drakensberg escarpment in Mpumalanga, South Africa. The hypotheses being tested are: (1) that fragmentation reduces biological diversity; (2) that fragmentation alters community composition (invasion); (3) that the reduction in diversity is dependent on fragment size; (4) that species viability is differentially affected by distances between fragments; and (5) that afforestation causes irreversible community change. In addition, the experiment evaluates the relevance of mainland–island, metapopulation and source–sink models for describing the population characteristics of the grassland taxa. The experimental design comprises two fragment sizes (0.25 and 1.5 ha) replicated 12 times. Six replicates were retained as grassland fragments surrounded by newly established Pinus elliottii plantations. A further six replicates served as control fragments in an adjacent designated grassland conservation area. Sampling to monitor community composition (vegetation, Coleoptera, Orthoptera, arachnida, small mammals) and the population dynamics (mark–recapture) of selected taxa (small mammals to date) was conducted. Monitoring of the population dynamics of selected Coleoptera and Orthoptera taxa, identified as suitable models for further study, and the soil micro-fauna in fragments will commence in 1997. Two years following plantation establishment effective fragmentation has not yet been achieved. However, the analysis of pre-treatment data is used to evaluate the effectiveness of the experimental design. The analyses suggest that there is a sound basis for future interpretation of experimental results because no significant differences between the experimental and control plots were detected. The presence of some variation within experimental and control plots underscores the importance of adequate replication in ecological field experiments, a strength of the experimental design employed here.

Spawning and non-breeding activity of adult giant bullfrogs (Pyxicephalus adspersus)

Abstract Populations of the giant bullfrog (Pyxicephalus adspersus) have been poorly monitored due to the unpredictable appearance of this species aboveground. To better understand the activity of P. adspersus we quantified spawning by a population during five summers, and the activity of twenty adult frogs radio-tracked at the same site ca. twice weekly during the first three summers. In addition we examined animal activity, and population spawning in relation to meteorological variables, day of season, and moonlight. During the six-month summer period, males and females, respectively, spent 10±7 and 3±2 days at water, and 22±5 and 13±5 nights active. Greater proportions of radio-tracked animals moved overland, and/or foraged at night, around full moon, after heavy rainfall, when cooler, and less windy conditions prevailed. More animals were found at water, or on land during the day, and population spawning was more likely, earlier in summer, following heavier rainfall. Spawning occurred most frequently, in descending order, during December, January, and November, and was triggered by 40±16 mm rain in 24h. Spawning events lasted 2±1 days, but were prolonged around full moon. Numbers of males at spawning events varied between 30 and 500 males, and were positively correlated with the previous days rainfall. Annually 6±1 spawning events occurred, and numbers of annual spawning events were positively correlated with total summer rainfall. Results of this study show that single counts of spawning adults will often result in gross underestimates of population size, and therefore, long-term adult counts are necessary to detect real population trends. Due to the unpredictable activity of adults, however, it may be more practical to monitor, within certain areas, the number of aquatic sites where breeding occurs, for improved conservation management of P. adspersus.

Composition and foraging behaviour of mixed-species flocks in two adjacent African woodland habitats: a spatial and temporal perspective

We examined temporal and spatial effects on (1) overall flock composition, and (2) aspects of the foraging behaviour of three bird species commonly participating in mixed-species flocks in mixed and Acacia woodland across the winter season in South Africa. Foraging observations were compared when birds were alone or with conspecifics, against when in mixed-species flocks. The two habitats differed with respect to the presence of the Southern Black Tit Parus niger, a leader species in mixed woodland but largely absent from Acacia woodland. Flock species richness within mixed woodland, but not Acacia woodland, increased significantly as the season progressed. Enlarged flock size resulted from a general increase in flocking tendency of all species. At the species level, the Long-billed Crombec Sylvietta rufescens and the Chinspot Batis Batis molitor showed clear feeding benefits within flocks, whereas tits obtained no feeding benefit. Crombecs and batises also changed foraging location when entering mixed flocks by converging on the foraging height of tits in mixed woodland and on each other in Acacia woodland. Furthermore, batises and tits showed marked temporal changes in feeding techniques, due to the changing vegetation structure, a fact that should be considered in future flocking studies.

Conservation Implications of Spatial Habitat Use by Adult Giant Bullfrogs (Pyxicephalus adspersus)

Abstract In South Africa, particularly Gauteng Province, populations of the large, explosive-breeding Giant Bullfrog (Pyxicephalus adspersus) are suffering increasing habitat loss due to encroaching urbanization. To investigate the spatial habitat requirements of this regionally threatened species, 70 adult frogs were radio- or spool-tracked during five summers around a periurban breeding site. Male and female P. adspersus moved a maximum overnight distance of 350 m when returning to their burrows postspawning. On average, animals of either sex used one long-term burrow (LTB) in a summer. Four males each used a single LTB or burrowing area for two or three consecutive summers. The LTBs of females were situated almost 4 times further (mean  =  446.8 m) from the seasonal dams where spawning occurred than those of males (mean  =  131.0 m). Female body condition was significantly positively correlated with distance of their burrows from the seasonal dams (rs  =  0.77). Limited evidence indicated that adult P. adspersus probably forage mostly within 20 m of their burrows. To protect the LTBs of all radiotracked animals a 950-1,000-m wide buffer would be necessary around the seasonal dams. Because adult P. adspersus seem to be philopatric, juvenile dispersal is predicted to be largely responsible for gene flow among populations.

Unique Combinations of Stakeholders in a Transfrontier Conservation Area Promote Biodiversity-Agriculture Integration

The world seeks to balance biodiversity protection and food production. Transfrontier conservation areas (TFCAs) provide unique opportunities for strategies that combine agriculture with biodiversity conservation at a landscape level, known as ecoagriculture. We identified and consulted ecoagriculture stakeholders in a smallholder farming community within a TFCA. Data were obtained through key informant interviews and questionnaire surveys. Eighty-eight percent of key informants indicated that planned ecoagriculture was feasible in the area and 95% of interviewed farmers positively considered to plan the integration of biodiversity conservation and farming. Potential conflicts of interest were revealed among stakeholders but to a large extent, stakeholder roles and interests were complementary, creating an environment conducive to effective coordinated ecoagriculture planning.

Towards more equal footing in north-south biodiversity research : European and sub-Saharan viewpoints

Research collaboration between developed countries from the northern hemisphere and developing countries in the southern hemisphere is essential for the understanding and protection of the major proportion of biodiversity located in the tropics. Focusing on the case of sub-Saharan Africa, we here assess the real involvement of northern versus southern contributors, and caution against unequal academic benefit sharing arising from non-commercial biodiversity research that may ultimately hamper sustainable knowledge transfer and long-term biodiversity conservation. We discuss possible drivers that may have led to a business of raw biodiversity data. While we fully support the current efforts to stamp out biopiracy through international biodiversity policies and agreements, we illustrate that such legislative frameworks may further constrain biodiversity research, especially in countries where regulations are poorly streamlined and bureaucracy remains rather inert. We therefore ask for workable solutions towards more equal footing in north–south biodiversity research, and propose a number of steps to transgress the current barriers towards a more fair and equitable sharing of benefits arising from biodiversity research.

STRUCTURE OF AN AFRICAN RED-BILLED HORNBILL (TOCKUS ERYTHRORHYNCHUS RUFIROSTRIS AND T. E. DAMARENSIS) HYBRID ZONE AS REVEALED BY MORPHOLOGY, BEHAVIOR, AND BREEDING BIOLOGY

Abstract The distributions of southern African (Tockus erythrorhynchus rufirostris) and Damaraland (T. e. damarensis) Red-billed Hornbills overlap in northern Namibia. Allopatric populations of the taxa have diagnosable differences in habitat, morphology, vocalizations, and displays. We investigated the structure of the hybrid zone using data from morphology, behavior, and breeding biology. The morphological characteristics—eye color and facial plumage color—were summarized as hybrid index scores, which showed a significant positive regression against distance from southwest to northeast across the hybrid zone. Vocalizations also showed a positive relationship between the first principal component (extracted from 12 call variables) and distance across the hybrid zone. However, there appears to be introgression of a T. e. damarensis call into T. e. rufirostris, but not vice versa. In addition, female T. e. damarensis-male T. e. rufirostris breeding pairs occur more frequently than male T. e. damarensis-female T. e. rufirostris pairs. The asymmetrical call introgression may result either from asymmetry in mating or from genetic control of call inheritance. Finally, heterospecific pairs show lower fitness, in the form of reduced hatching success, even when female fitness attributes are included as covariates. Although we are uncertain whether the Red-billed Hornbill hybrid zone is stable, the apparent biological processes operating within it conform to predictions of both the “mosaic” and the “tension zone” models, because both habitat characteristics and a balance of dispersal and selection appear to determine its structure.