Seasonal variation in the diet of South African Galagos

The feeding behavior and diet of two species of bushbaby, Galago senegalensisand Galago crassicaudatus,in South Africa were examined in relation to seasonal changes in climate. The populations studied were allopatric, but both fed predominantly on Acaciagum and invertebrates. Data on their diet were collected by direct observation of a radiocollared female of each species and by analysis of fecal samples. Differences in diet were found between the species within seasons and within species between the seasons. Both spent more time gum-feeding in winter than in summer. Prey size and type differed between the species in summer but converged in winter. The quantity of insects taken was fairly similar between seasons for G. senegalensisbut dropped considerably for G. crassicaudatusin winter. These observations are interpreted in terms of interspecific differences in feeding strategies, which are considered to be a function of the difference in body size of the two galago species.     

Diet composition and food consumption of the grey heron (Ardea cinerea) from breeding colonies in northern Poland

The diet of the grey heron (Ardea cinerea) was investigated in three colonies in northern Poland (Mosty, Kiersity and Kty Rybackie) varying in size, habitat type and composition of feeding areas used by birds. The diet was assessed during the breeding season on the base of pellets and regurgitated food. Pellets from all studied colonies consisted mainly of mammal hair (almost 100% of samples), bone remains (20–24%) and invertebrate remains (26–51%, mainly water beetle, Dytiscus marginalis). Bones and hair of water vole (Arvicola terrestris) and Microtus voles were the most common remains of mammals recorded in pellets. Remains of other animal taxa were found sporadically. In the colonies at Mosty and Kiersity, fish composed more than 95% of collected regurgitated prey items. Food consumption of herons from the biggest colony at Kty Rybackie was estimated to exceed 100 t per season. Herons from Mosty consumed ca 46–52 t, from Kiersity 30–38 t of food per season. The impact of herons on fish communities was much lower than other losses due to predation (herons from Kty Rybackie caught only 6% of fishermen bycatch, birds from Mosty took 10–14% of round gobies eaten by cormorants).     

Gregarious foraging in barn swallows after the breeding season

Aerial vertebrate foragers, e.g. insectivorous bats, martins and swallows, often show gregarious behavior such as colonial breeding, communal roosting and aggregating behavior during foraging. Studies of gregariousness in aerial foragers have mostly focused on colonial breeding or communal roosting, and only a few intensive studies have dealt with gregariousness during foraging. Here, we report on large and stable aggregations of barn swallows, Hirundo rustica, observed during daytime after the breeding season in Japan. Relatively large aggregations of 20 or more birds were located around poultry, pig and cattle farms and mounds of manure. The aggregations were stable in size both within-days and between-days. Their activities consisted only of repeated cycles of foraging and resting around the farms where their prey, the large black soldier fly Hermetia illuceus (>10 mm) and other medium (5–10 mm) flies, was dense. Distributions of swallows around the farms overlapped with the distributions of prey, and the size of the aggregations significantly correlated with the abundance of prey.     

The photoperiodic clock in blackheaded buntings (Emberiza melanocephala) is mediated by a self-sustaining circadian system

Three experimental protocols were employed to clarify whether the circadian system is involved in photoperiodic time-measurement in the blackheaded bunting, Emberiza melanocephala. In a single-pulse paradigm, one 8-h light pulse was delivered at different times to groups of birds across three days of constant darkness (DD). Photoperiodic induction, as measured by a rise in plasma luteinizing hormone (LH), showed clear circadian rhythmicity. The second experiment examined the LH responses in birds exposed to lighting cycles using a Nanda-Hamner type of protocol and confirmed full photostimulation under 6L:30D. The third experiment measured the time of the first photo-induced rise in LH in birds subjected to 30 h of continuous light following entrainment under short days (6L:18D). This experiment aimed to identify the position of the photoinducible phase ( _i). LH first rose at hour 18 following dawn indicating that _i lies in the middle of the day. Plasma concentrations of melatonin were also measured under 6L:18D and 6L:30D light cycles as another physiological marker of the circadian system in buntings. The pattern of melatonin secretion under these LD cycles showed properties consistent with the driving oscillator being circadian in nature. It is concluded that the circadian pacemaker driving the photoinducible rhythm in blackheaded bunting is strongly self-sustaining and free-runs under constant conditions.     

Energetics and food requirements of the female snake Phillodryas chamissonis during the breeding season

Summary 1.The energetic performance and food requirements of female Phillodryas chamissonis was determined during its breeding season at different ambient temperatures. 2. If the long tailed snake is active for 24 weeks, 25 to 32 30-g rodents are required for reproduction and maintenance. This is slightly more than one rodent per week. 3. The energy cost of reproduction (38 to 48% of total metabolism) is close to the values reported for fish (35% of metabolizable energy). 4. Due to their low metabolic rates, the theoretical predation pressure (on a prey biomass basis) exerted by the snakes should be 2 to 2.5% of that expected for endothermic predators of similar body size.     

Agonistic and grooming behavior of captive crowned lemurs (Lemur coronatus) during the breeding season

Captive breeding of rare and endangered prosimians may be enhanced by an increased understanding of all aspects of their seasonal mating behavior. In this study, the agonistic and grooming behaior of captiveL. coronatus were studied during their annual breeding season. Between October and March, selected aspects of agonistic and grooming behavior of four male-female groups were recorded. Males initiated significantly more allogrooming than females. The frequency of this behavior pattern increased significantly in the weeks of estrus. Females performed significantly more agonistic behavior patterns than males. The mean frequency of agonistic interactions decreased significantly during the breeding season. In successfully reproducing groups males showed much less agonism towards females, than they did in unsuccessful groups. Inter-specific comparisons demonstrated that the patterns of agonistic interactions during the breeding season are very different among closely related species of lemurids. The conclusions drawn from this study are that captive breeding of crowned lemurs may be enhanced by keeping permanent multi-male, multi-female groups.     

Pattern analysis in Belgian limestone grasslands

Pattern analyses were made in several limestone grasslands of Belgium. Vegetation has been sampled in continuous transects. Monospecific patterns are defined by means of two non-parametric indices; multivariate analysis (reciprocal averaging) completed the analysis. The following kinds of pattern are described and explained: random, aggregate, clump, gap, stationary density variation, non-stationary density variation, gradient and many complex patterns. The multivariate analysis leads to a careful phytosociological study of the transects and to the definition of floristically homogeneous regions. Some particular points of pattern analysis, the problem of vegetation sampling and some perspectives are discussed.     

Temporal variations in the feeding habits of the Purple Heron Ardea purpurea during the breeding season

The foraging strategies of adult Purple Herons Ardea purpurea from an increasing colony in northern Spain were studied in the feeding areas (nonagricultural habitats) during the breeding season (May-July). In this area, herons were mainly piscivorous, and there was no seasonal variation in prey type. Small fish (<12.5 cm) were more abundant in the diet in June and medium-sized fish (12.5–25 cm) in May and July. Foraging strategies varied seasonally: (1) More time was spent by the herons in the feeding areas in June than in May or July, whereas foraging time was only significantly greater in June than in July. (2) The biomass captured by the adults in each foraging session was similar in May and June but greater in July. (3) Feeding attempts were more numerous (but not more successful) in shallow water in June and July. (4) Aggression rates between conspecifics were higher in June than in both May and July. Probably the hatching of chicks (June) was the cause of these changes in diet and foraging strategies as well as increased intraspecies competition for foraging habitat.     

Dry season diets of sympatric ungulates in lowland Nepal: competition and facilitation in alluvial tall grasslands

Based on microhistological analyses of faecal material, we compared the early dry season diets of greater one-horned rhinoceros Rhinoceros unicornis, swamp deer Cervus duvauceli and hog deer Axis porcinus, which inhabit the same alluvial grassland habitat complex in lowland Nepal. Their diets were quite similar, both at the forage category level and within subcategories of graminoids and woody plants. Early successional tall grasses, especially Saccharum spontaneum, were the dominant food of all three species, underlining the key role of the threatened alluvial floodplains in large mammal conservation in South Asia. The two deer species ate significantly more graminoids (>66.5%) than did rhino (45.5%), and although they did not differ in proportions of graminoids, swamp deer ate significantly more late successional tall grasses (Narenga porphyrocoma and Themeda spp.) and short grasses (mainly Imperata cylindrica) than hog deer. The two deer consumed almost equal proportions of woody browse (ca. 10%), significantly less than that of rhino (33.0%). The prediction of the Jarman–Bell hypothesis, that large-bodied herbivores are less selective and subsist on lower quality graminoids than smaller ruminants, was not supported by the data. Based on this and previous studies in the same area we propose a conceptual model where the larger megaherbivores (rhino and elephant Elephas maximus) facilitate the smaller swamp deer and hog deer during the monsoonal growing season, while the smaller and more selective deer species outcompete the larger during the dry season when food is more limited. Owing to the all-year sprouting ability of S. spontaneum, facilitation may occur also in the dry season with low numbers of megaherbivores, thus accentuating competitive exclusion at higher deer densities.     

Movements of radio-tagged Grey Herons Ardea cinerea during the breeding season in a large pond area

This paper describes the strategies of resource utilization in the course of the breeding season by five radio-tagged Grey Herons Ardea cinerea. The seasonal changes in exploitation of the environment by two breeding adults, one non-breeding adult and two non-breeding first-year birds were studied from March to August 1982, near Zonhoven in Belgium. Two adult breeding birds could be followed continuously from the end of March until the middle of June. During the first month they explored an extended area all around the colony, but each concentrated its search in a specific direction. From the end of April until the beginning of June, most probably from egg-hatching until the end of breeding activities, each bird spent a very large proportion of its time at a particular feeding site, from which other herons were actively excluded. In the first part of June they again visited different sites, each maintaining its preferred direction. From the middle of June onwards they seemed to have left the fish-pond area. The pattern of movements of the first-year birds differed markedly from that of the breeding adults. In April, although both non-breeding and breeding birds explored large areas, only the areas used by non-breeders were centred on the colony. From the end of April onwards, probably after general egg-hatching in the colony, the non-breeders very rarely revisited the colony, and from May till August their ranges became more and more restricted to very small areas at an increasing distance from the colony. They were never observed defending particular sites. The results are discussed with regard to recent speculations about the evolution of colonies as an adaptation for the exploitation of food resources. Breeding herons seem to explore a large part of the environment during incubation and defend a particular site while feeding their young. Choice of feeding site by non-breeding birds may be influenced by the site defence of the breeding birds. Non-breeding birds exploit a large area when breeding birds occupy feeding territories. Perhaps they are forced to forage in less suitable places at this time. Colonies might have evolved as a strategy to minimize effort in resource esploitation as, especially at the beginning of the breeding season, the colony could act as an assembly point in the exploration of the environment. However, its importance as an assembly point diminishes in the course of the season, as non-breeding birds no longer visit the colony and adults defend territories.     

Diet of the golden eagle Aquila chrysaetos during the breeding season in Sweden

During a five-year period, 1975–1979, a total of 2881 prey individuals of 65 prey species were collected at 162 golden eagle nests from northern Sweden and from the island of Gotland. In northern Sweden birds are taken in higher numbers than mammals but calculated as weight the two categories are of equal importance, The main prey during the breeding season are capercaillie, black grouse, willow grouse, ptarmigan, mountain hare and reindeer fawns which together form 91% of the total food biomass. The capercaillie and the black grouse are taken more in the southern part of the coniferous region than in the northern. In contrast, in northern areas, reindeer fawns are more preyed upon than in the South, Ptarmigan and willow grouse are the most commonly captured prey species in mountain areas. The total number of reindeer fawns taken (dead and/or alive) by the Swedish golden eagle population during one summer is estimated at 600 individuals. On Gotland the golden eagles take mammals more often than in its northern distribution area. Rabbit and hedgehog arc the most important species.     

Diet does not affect intercolonial fighting in Leptothoracine ants

Summary An experiment examined the effects of diet on brood rearing in colonies ofLeptothorax ambiguus andL. longispinosus and on fighting between colonies of the two species. Colonies fedDrosophila and honey reared more pupae than colonies fed the Bhatkar and Whitcomb (1970) diet. However, diet had no effect on intercolonial fighting.     

Variation in enamel development of South African fossil hominids

Dental tissues provide important insights into aspects of hominid palaeobiology that are otherwise difficult to obtain from studies of the bony skeleton. Tooth enamel is formed by ameloblasts, which demonstrate daily secretory rhythms developing tissue-specific structures known as cross striations, and longer period markings called striae of Retzius. These enamel features were studied in the molars of two well known South African hominid species, Australopithecus africanus and Paranthropus robustus. Using newly developed portable confocal microscopy, we have obtained cross striation periodicities (number of cross striations between adjacent striae) for the largest sample of hominid teeth reported to date. These data indicate a mean periodicity of seven days in these small-bodied hominids. Important differences were observed in the inferred mechanisms of enamel development between these taxa. Ameloblasts maintain high rates of differentiation throughout cervical enamel development in P. robustus but not in A. africanus. In our sample, there were fewer lateral striae of Retzius in P. robustus than in A. africanus. In a molar of P. robustus, lateral enamel formed in a much shorter time than cuspal enamel, and the opposite was observed in two molars of A. africanus. In spite of the greater occlusal area and enamel thickness of the molars of both fossil species compared with modern humans, the total crown formation time of these three fossil molars was shorter than the corresponding tooth type in modern humans. Our results provide support for previous conclusions that molar crown formation time was short in Plio-Pleistocene hominids, and strongly suggest the presence of different mechanisms of amelogenesis, and thus tooth development, in these taxa.     

Life-history styles of fishes in South African estuaries

Synopsis Fish utilizing South African estuaries may be divided into two major groups according to the location of their spawning sites. The marine group comprises large species which spawn at sea, enter estuaries mainly as juveniles, and return to the sea prior to attaining sexual maturity. The estuarine group is dominated by small species which have the ability to complete their life cycle within the estuarine environment. They tend to produce relatively few, demersal eggs, or exhibit parental care, which facilitates the retention of eggs and young within the estuary, whereas the marine group release large numbers of small pelagic eggs during spawning and exhibit no parental care. This is contrary to the theory that estuaries (unpredictable environments) should favour altricial life-history styles and the marine inshore zone (a more predictable environment) should favour precocial styles. However, if the total ichthyofauna of South African estuaries is considered, then altricial species predominate. The fact that both altricial and precocial traits are well represented within the overall estuarine fish community suggests that the various taxa have adapted their life-history styles, in different ways, to ensure the utilization of abundant food resources available within these fluctuating systems. A detailed comparison of the life-history styles of the estuarine teleostGilchristella aestuaria and the marine fishMugil cephalus is used to illustrate the contrasting manner in which these two species have succeeded in exploiting South African estuaries.     

Bird pollination in South African species ofSatyrium (Orchidaceae)

Field observations showed that three South African orchid species,Satyrium carneum, S. coriifolium andS. princeps, are pollinated by sunbirds. Foraging sunbirds insert their bills into the labellum chamber of the flowers and suck nectar from the labellum spurs with their tongues. The column overarches the entrance to the labellum and pollinaria become affixed to the upper mandible of the bill. Birds often attempt to remove pollinaria by rubbing their bills against a branch, but are mostly unsuccessful due to the large plate-like viscidia which attach the pollinaria very firmly to the bill. Other modifications for bird pollination in theseSatyrium species may include the red, carmine or orange colour of the flowers, sturdy inflorescence stems used for perching and large amounts of dilute nectar in the spurs. EachSatyrium species was pollinated by several species of sunbird, and despite some differences in flowering time, occasional hybrids occur at a site whereS. carneum andS. coriifolium share the same sunbird pollinators.     

Ear-rot fungi and mycotoxins in South African corn of the 1989 crop exported to Taiwan

A shipment of South African corn (1989) exported to Taiwan, was analyzed for various ear-rot fungi andFusarium mycotoxins. Two sets of samples, one from the points of origin in South Africa prior to shipment, and the other from the end-point distributors in Taiwan, were studied. Surface-sterilized kernels were plated onto two different agar media and the fungal colonies identified. High Performance Liquid Chromatography was used to analyze mycotoxin levels. The predominant ear-rot fungi, in decreasing order of isolation frequency, wereFusarium subglutinans, F. moniliforme, Diplodia maydis andF. graminearum. Aspergillus flavus andA. parasiticus were not isolated from samples prior to export, but a small number ofA. flavus isolates were found after shipment. The predominant mycotoxins were fumonisins B₁ (0–865 ng/g) and B₂ (0–250 ng/g). Low levels of moniliformin (390 ng/g) were detected in some samples before shipment. Zearalenone (25 ng/g), and nivalenol (120 ng/g) were detected in two out of 32 samples taken in Taiwan. The samples contained no detectable levels of either aflatoxins (>0.5 ng/g) or deoxynivalenol (>100 ng/g) before or after shipment.Abbreviations RSA South Africa(n) - FB₁ fumonisin B₁ - FB₂ fumonisin B₂ - ETVL eastern Transvaal - WTVL western Transvaal     

Spatial distribution and time budget of radio-tagged grey herons, Ardea cinerea, during the breeding season

Spatial distribution of foraging grey herons during the breeding season seemed to be determined by a trade-off between costs and benefits of area sampling versus site fidelity. Breeding birds with little experience of the area spent more time exploring than birds with more experience in the early stages of reproduction. Non-breeding herons and first-year breeders showed little site fidelity. Time budgets appeared to be affected mainly by daily changes in food availability and, for breeding birds, by demands of the brood.     

Upper Molar Cusp Dimensions of South African Australopithecines

Recently, a number of articles have been published on the mechanisms of dental development, and in particular on the genetic control of dental formation. As a specific example of the potential of this kind of research for paleoanthropological studies, cusp areas of upper molars of two species of South African Australopithecines (Australopithecus africanus, A. robustus) have been examined. The results suggest notable differences between the two species, possibly related to markedly different developmental pathways that are still far from clear in their details.     

Feeding,Diet, and Jaw Form in West African Colobus and Procolobus

The functional link between mandibular morphology and masticatory stress has been documented by both experimental and comparative investigation. Somewhat more tenuous is the purported connection between dietary variation and the form of the jaws in primates. Several factors complicate the inference of such a connection, including anecdotal or incomplete dietary data from field studies and allometric effects on skeletal form that may have little to do with diet per se. We compared the jaws of sympatric colobines from West Africa to test the effect of diet on mandibular form. Procolobus badius and Colobus polykomos occupy the same habitat yet differ in diet primarily due to the exploitation of hard seeds by C. polykomos. The fact that the two taxa are comparable in body size also obviates the need for allometric qualifications. Colobus polykomos is expected to possess more robust mandibular corpora than Procolobus badius. In fact, the jaws of Colobus polykomos do not differ consistently from those of Procolobus badius in terms of biomechanical function. This apparent failure of mandibular morphology to reflect differences in diet and feeding behavior may be due to a variety of factors. We suspect that functional demands related to canine tooth support are contributing to obliteration of the expected biomechanical signal. Successful prediction of dietary effects on mandibular form requires consideration of competing structural and functional demands. The influence of diet on mandibular corporeal morphology is not equivalent across different primate species.