Main Habitat Types Research Articles

ORIBATIDA OF CANADIAN PEATLANDS

AbstractThis paper reviews and summarizes preliminary data on the taxonomy, distribution, and ecology of oribatid mites of Canadian peatlands, primarily those of eastern Canada. This fauna is a heterogenous assemblage comprising 71 species in 49 genera and 34 families, found in four main types of habitats: aquatic, mesic, xeric, and epigeal. About half of the oribatid fauna of peatlands, and most aquatic species, are restricted in distribution to the Nearctic. Oribatid taxa known or suspected to be parthenogenetic are much better represented in peatlands than in the general Canadian fauna. Data on the feeding habits of odonate larvae in Newfoundland bog pools, based on gut content analysis, show that oribatid mites, in particular species of Limnozetes Hull and Hydrozetes Berlese, are common prey of species of Aeshna Fabricius, Leucorrhina Brittinger, and Libellula L. A synopsis of available data suggests that assemblages of Limnozetes species may be useful in characterizing peatlands.

Utilization of floodplain water bodies by the fishes of the Fly River, Papua New Guinea

The Fly River, southern Papua New Guinea, is bordered by extensive floodplains in the lowland reaches. There are four main habitat types within these floodplains: blocked-valley lakes created by fl...

Density‐related features of natterjack toad (Bufo calamita) population in Britain

We have studied a series of natterjack populations with varying densities of adults on the three main habitat types (lowland heaths, coastal dunes and coastal marshes) occupied by this species in Britain. Animals were aged by skeletochronology, condition was assessed by measuring weight length ratios in autumn and home ranges were determined by individual‐marking and by radiotelemetry. Female longevity was inversely correlated with population density, but no similar effect was observed for males. Uniformity of growth rates, absolute growth rates and mean condition for both sexes were also inversely related to population density, whereas mean home range showed a positive correlation. Taken together the data indicated that in high‐density populations natterjack toads grew more slowly and erratically, were in poorer condition and foraged much more widely than their counterparts in low‐density populations.

The relative importance and distribution of Aedes polynesiensis and Ae. aegypti larval habitats in Samoa.

In preparation for a Filariasis Control programme in Samoa, during 1978 monthly larval surveys of the vector mosquito Aedes polynesiensis were carried out in four study villages in the main island of Upolu. A more extensive survey of larval habitat distribution was then made in twenty-two villages of Upolu and eighteen of Savai'i island, to determine the importance of habitat types according to their abundance, volume of water and whether their productivity was permanent or seasonal. Ae.aegypti larval densities and habitat distribution were also monitored and the occurrence of predatory Toxorhynchites amboinensis larvae in northern Upolu was recorded from forty-one collections. Aedes Breteau and container indices fluctuated with the pattern of rainfall in two coastal villages and an inland bush village, but not in a coconut plantation community. The five main Aedes larval habitat types encountered were: 200 litre water-storage drums, discarded tins and bottles, coconut shells, automobile tyres and treeholes. Aedes immatures occurred perennially in drums and tree holes, but breeding discontinued in tins, bottles and coconut shells during the driest month of July. For Ae. polynesiensis in Upolu the Breteau and container indices of 104.5 +/- SD 80.9 and 35.3 +/- 12.4 respectively were significantly higher than those in Savai'i: 33.1 +/- 25.0 and 24.3 +/- 20.0 respectively. Likewise for Ae.aegypti the Breteau and container indices of 50.8 +/- 32.5 and 23.9 +/- 15.6, respectively, were also significantly higher than those in Savai'i: 12.7 +/- 17.1 and 9.4 +/- 13.2 respectively. Habitat types greater or lesser importance were determined by plotting the percentage of each type of cotnainer utilized for Aedes breeding against the percentage of ech type amongst all larva-positive containers. Ae.polynesiensis preferred tree-holes but not water-storage drums. Ae.aegypti preferred drums and tyres; mixed populations of larvae of both species were commonest in these two types of habitat. Ae.polynesiensis occurred in every village. Ae.aegypti was encountered in all twenty-two villages surveyed in Upolu and nine of eighteen villages in Savai'i. Total larval surveys revealed that drums and tree-holes contained the highest numbers of Aedes larvae. The study provided criteria for planning a control programme.

Replacement events among tetrapods: expansion or competition?

Many macroevolutionary patterns have been explained in the past on the basis of expectations and prejudice rather than quantitative testing. Large-scale ecological replacements have been a prime example, where expectations of progress and competitive advantage have coloured interpretations. Equally, no doubt, others have looked for, and found, evidence for entirely noncompetitive processes to explain major replacements (reviewed, Benton 1987).A partially quantitative approach is presented, based on a study of tetrapod families, marine and nonmarine, through the interval from Devonian to the present day. New data bases of the history of tetrapod diversification have the advantage over older attempts of (1) a fully cladistic phylogeny, and hence monophyletic families; (2) a detailed overview of stratigraphy and improved range data; (3) palaeobiogeographic control; and, (4) definition of ecological categories in terms of mean body size categories, diet, main habitat types (fully marine; partially marine/ coastal; freshwater; aquatic/terrestrial; lowland; upland; arboreal, aerial).The bulk of the diversification of tetrapods is correlated with increases in the ranges both of habitats occupied and of diets (Benton 1990). However, tetrapod families came and went, and a large proportion of the diversification could have been driven by competition and progressive replacement of archaic families by competitively superior ones in ecological relays. In order to test this, the ranges of all tetrapod families were plotted against time and sorted into a variety of habitat, dietary, and palaeogeographic categories.The results do not support a generalised view of competitive ecological relays. The majority of families appear to have arisen within new cells of the matrix, and did not apparently overlap in time with, or follow closely after, any potential competitors. This would be the minimum requirement for a postulate of competition. Only some 5% of cases could be open to a competitive explanation, and these include certain well known examples, such as multituberculates/ rodents, plesiadapiforms/ rodents, ichthyosaurs/ mosasaurs. The present study has narrowed the odds againt large-scale competition as a significant motor of large-scale biotic replacements. Most new taxa of tetrapods appear to have arisen in response to the availability of empty adaptive space.Environmental shifts may also be detected during the course of tetrapod evolution, with expansions offshore to ever more fully aquatic lifestyles among marine tetrapods (because they all arose from terrestrial ancestors!), and with expansions from lowland tropical zones to temperate belts, uplands, and marginal lifestyles (burrowing, climbing, flying) among nonmarine tetrapods.

Landscape Ecology of Lyme Disease in a Residential Area of Westchester County, New York

The landscape ecology of Lyme disease was studied in 1989 on 67 residences in an endemic area of Armonk, Westchester County, a northern suburb of New York City. Four main habitat types were defined, and each property was surveyed for immature and adult lxodes dammini ticks; 98.6% of 1,790 ticks collected were I. dammini. Overall, 67.3% were collected from woods, 21.6% from ecotone (unmaintained edge), 9.1% from ornamental vegetation, and 2% from lawns. Larval ticks were concentrated in woods, but nymphs and adults were widely dispersed in all habitats. Tick abundance was positively correlated with property size. Larger properties (greater than or equal to 0.5 acre) were more likely to have woodlots and, hence, more ticks. Dark-field and direct fluorescent microscopic examination of tick midgut tissues revealed that 29.6% of nymphs and 49.7% of adults were infected with Borrelia burgdorferi. Infected nymphs and adults were found on 36% and 60% of properties, respectively. These data indicate that the abundance of ticks capable of transmitting Lyme disease spirochetes is related to landscape features of the suburban residential environment.

The role of protective understorey in the regeneration system of a heavily browsed woodland

The paper tests an apparent relationship between young understorey of Ilex aquifolium and the presence of seedlings of the canopy species Fagus sylvatica and Quercus species, in heavily browsed woodland in the New Forest, southern England. A small block of woodland was searched and mapped, and the information collected subject to graphical and statistical analyses. Regeneration, though of low frequency, is present and shows non-random patterns of distribution. Older seedlings appear to be located in or near areas of understorey, or near fallen branches, logs, etc. Principal components analysis of woodland characteristics suggests six main habitat types are available to seedlings, and predictions are made about likely regeneration patterns associated with these habitats, according to a model based on the hypothesis of a protective understorey and heavy browsing pressure. Chi-square tests of actual seedling occurrences versus habitat types demonstrate marked associations of regeneration with non-trampled areas, including young Ilex understorey but also other forms of protective barrier. The association is more marked for larger seedlings. The implications for a wider understanding of regeneration processes and community dynamics in heavily browsed forest are discussed. It is concluded that regeneration theories appropriate to such forests are required, since the dominant gap-phase theories are not successful in predicting regeneration patterns when browsing is a major factor.

Growth of Australian bass Maquaria novemaculeata (Perciformes : Percichthyidae) in the Sydney Basin

Habitat type and sex are the principal determinants of the variable length-at-age of M. novemaculeata. Growth was studied in three main habitat types: lagoons, gorge streams, and freshwater estuarine habitats, and a total of 1071 adult bass and 644 young fish were examined. Observations were made on the growth of young wild bass, and their rapid growth after stocking in isolated lentic waters was measured. The three von Bertalanffy growth parameters were estimated for populations from the main habitat types. A growth curve generated from tag-return data provided comparable values. Variation in length was tested by three-way ANOVA using age, habitat type and sex as independent variables. Female bass grew faster than males towards a larger asymptotic size (L∞ = 396 mm). Lagoon populations grew the most rapidly, and those in freshwater tidal sites grew slowest. T'he proportion of variarion in bass length that was due to habitat type, sex, and age was 15, 10, and 56% respectively. Marked flexibility of the growth, diet and reproduction of M. novemaculeata is seen as an adaptive response to variable environmental conditions.

Criteria for protected areas and other conservation measures in the Antarctic region

The Antarctic region is threatened by three major anthropogenic influences: climatic change brought about by increases in atmospheric carbon dioxide, the effects of persistent pollutants carried into the region via atmosphere and ocean, and the increase in Man's activities. Vulnerable ecosystems can be considered as those which are under direct pressure from Man's activities, whereas fragile ecosystems are the more likely to suffer irreversible change when perturbed, but are not necessarily threatened at present. Three of the main habitat types, terrestrial, inland waters, and islands, are likely to be fragile. However, all these can be conserved reasonably adequately with a system of protected and managed areas, so long as the area covered is adequate and representative. The fourth habitat type, the oceanic ecosystem, contains few fragile elements because it is dominated by the highly dynamic physical oceanic processes. Elements of the ecosystem are vulnerable to further exploitation, and although only the whales and some of the fish stocks can be regarded as fragile, there is considerable uncertainty as what synergistic effects exploitation of apparently key elements of the ecosystem, such as the krill, will have on other important components of the communities. The highly dynamic structure of oceanic environments renders the concept of conservation based on limited protected areas developed for terrestrial environments ineffective in the majority of marine environments. Instead the whole marine environment of the Antarctic region must be considered to be a single entity and managed as such.

On the ecological status of the Barbary macaque Macaca sylvanus L. in North Morocco: Habitat influences versus human impact

This paper analyses the ecological status of the Barbary macaque in the Djebala region of North Morocco. Results are presented of vegetation surveys and of preliminary studies on resource availability, diet and habitat use of the Barbary macaque in the four main habitat types where the species occurs.Factors affecting the distribution and abundance of the monkeys are considered and data on the past and present distribution in the Djebala habitats are discussed in relation to the influence of man. An assessment is made of whether current monkey populations reflect real differences in the suitability of habitats (i.e. habitat quality and productivity) or whether they are restricted purely by human interference. The latter term is defined both as direct predation and indirect action through modification of habitats via grazing of domestic stock, burning and tree-felling.

Microdistribution and habitat selection in Drosophila subobscura Collin

Microdistribution and habitat selection were investigated in a population of Drosophila subobscura near Leeds, Yorkshire. Microdistribution was examined along a transect running through a deciduous woodland. Two main types of habitat were recognized, those with dry soil and a closed canopy of mature trees (dry and dark) and those with wet soil and an open canopy of mature trees (wet and light). Flies were much more frequent, judged by their attendance at baited traps, in the dry/dark habitat. Flies taken from both habitat types, marked with different coloured fluorescent dust and released at a point mid-way between the original habitats, tended to return to their area of initial capture.

Fauna of the Comoé National Park, Ivory Coast

The Comoé National Park occupies an area of ca 12, 500 km 2. Its main habitat types are, in the west, the Comoé valley, with riparian forest and adjoining floodplain grassland, and, in the east, hill country covered with savanna woodland. In the woody vegetation Leguminous species are dominant, while the tall-grass cover is mainly comprised of Andropogon and Hyparrhenia species. Of the larger animals, Western Hartebeest, Senegal Kob, Grey Duiker, Oribi, and Baboon, are numerous, whereas African Elephant, Buffalo, Roan Antelope, Waterbuck, Warthog, and Hippopotamus, are present only in small numbers. In the south, species characteristic of the high forest occur—especially duikers and primates. The animal biomass of the Comoé valley habitat is estimated at ca 2,550 kg/km 2, and that of the savana woodland at ca 500 kg/km 2.

VAUCHERIA SPECIES FROM THE DUTCH BRACKISH INLAND PONDS “DE PUTTEN”

SUMMARY Data are given on the distribution and periodicity of fifteen Vaucheria species in three main types of habitat: a ditch, drainage ditches, and pond banks. At five stations a detailed analysis of Vaucheria growth was made. On the shores of the ponds from mean water level upwards, four groups of species can be discerned. The occurrence of most Vaucheria species shows a seasonal periodicity.

Observations on the distribution of surface-living land arthropods on the Subantarctic Île de la Possession, Îles Crozet

Summary Collecting by various methods in Jan.–April, 1968, of surface-living arthropods on Île de la Possession, Îles Crozet most of which were already known from the efforts of previous collectors, were made in order to determine to what extent the 46 species are confined to the three main land habitat types distinguished. The results were as follows: The sea-edge habitat is relatively rich, with 10 species, 8 apparently confined to it. Peat-clothed moorland and bog occupying lower ground (about 25–40 km2 in area) has 26 species, including 6 species of Diptera, while the fell-field habitat above about 100 m altitude (120–135 km2 area) with very scanty vegetation, has 24 species. The relatively species-rich fell-field was surprisingly rich in individuals, particularly ectemnorrhine weevils totalling 7 species (some rare), of carabid beetles (3 spp.). About 8 species showed wide distribution in both moorland and fell-field. The existence in the depauperate fauna of the island of at least 5 pairs or triplets of congeneric endemic species pose important problems in understanding its history and ecology.

The feeding habits of Alestes baremose and Hydrocynus forskali (Pisces) in Lake Albert, East Africa

The stomach contents of 1922 Alestes baremose Joannis and 1184 Hydrocynus forskali Cuvier caught in Lake Albert, East Africa were examined. The fish were caught in gill nets in three main different types of habitat; in lagoons, inshore in the main body of the lake and offshore. Zooplankton, ephemeropteran imagines and higher plant species constituted almost the whole diet of A, baremose, although the relative importance of these three items varied with habitat. In the lagoons and inshore Hydrocynus forskali was mainly piscivorous, but offshore where the largest specimens occur it was feeding mainly on Caridina nilotica. The role of Hydrocynus species as predators in Lake Albert is discussed and it is shown that in this lake predation intensity bythis genus must be considered entirely in terms of H.forskali.

NOTES ON THE BIOLOGY AND ETHOLOGY OF THE NATAL ROBIN COSSYPHA NATALENSIS

Summary.A preference for bushy evergreen undergrowth determines both the local and the general distribution of Cossypha natalensis. The lack of such undergrowth makes equatorial rain‐forests unsuitable. Tropical and subtropical evergreen forests provide excellent conditions from this point of view, and they are thus the main habitat type from which C. natalensis has secondarily extended into tropical and subtropical deciduous forests with evergreen undergrowth.Adult birds remain in or close to their territories throughout the year. First‐year birds undertake longer movements during the winter. Breeding territories are relatively small, from 2,500 up to (exceptionally) 10,000 square yards (2,100‐8,400 sq. m).Breeding begins in October. Both sexes build the nest, but only the female incubates. In southern Africa there is one brood a year, and the care of the offspring is protracted. The juvenile moult begins in the third and ends in the sixth month; adults have only one (post‐breeding) moult a year.The begging behaviour of the young is somewhat different from that of most other turdine birds, and is considered to be more primitive. The ontogeny of the adult displays is described as observed in young birds kept in captivity.The development of vocal behaviour is described. Special attention is given to the different functional forms of the song, and to two of its special features, imitation and a tonal quality termed vox humana.

THE TROPICAL FOREST EDGE AVIFAUNA OF IBADAN, NIGERIA

SummaryThe main types of habitat to be found in the Ibadan area are briefly described and their interrelationships considered. The relative degree of shade and cover afforded by each is discussed in relation to human influences.The avifauna, comprising 266 species so far identified in the area, is classified as comprising forest, savanna, widespread and aquatic forms. The status and frequency of each species is indicated.It is shown that the terrestrial element in the Ibadan avifauna is very evenly balanced between forest and savanna forms.The ability of forest forms to emerge from the forest and occupy less shaded habitats is contrasted with the converse ability of savanna forms to enter forested habitats.A number of species are separately noted in a supplement to Appendix 1 that show points of interest concerning their taxonomy, status or range.

THE GOLDEN EAGLE IN RELATION TO ITS FOOD SUPPLY

SummaryThe population of Golden Eagles was assessed in four different areas of the Scottish Highlands. The average area per pair varied from 11,400 to 17,884 acres, excluding country that was not used by the eagles.Eagle food in these areas consists largely of Red Grouse, Ptarmigan, Mountain Hares and Rabbits, and also dead Red Deer and dead sheep.The numbers and biomass of the four main species of living prey were assessed by representative counts in three main types of habitat; and of dead deer and sheep partly from counts but mainly from published data on stocking densities, mortality and weights.The annual food requirement from a home range was estimated at 249 kg. of meat, calculated from data on the food consumption of eagles, allowing for known breeding success and for the presence of some immature eagles and unmated adults; and this was compared with the total food potential in the four Study Areas, allowance being made for the inedible portions of carcases.The average food potential in all areas is greatly in excess of the requirements. In the three western areas living prey is very scarce, but amounts of carrion are large and the eagles in these areas depend mainly on carrion. Large differences in food potential between areas do not correspond with differences in eagle density. Two examples are cited where a drastic reduction in food supply had no effect on eagle density, which remains remarkably constant in spite of seasonal and annual fluctuations in food supply.Golden Eagle nest‐sites are used over many years, and the home ranges are big enough to supply a more than adequate food supply at all times of year. Evidence is provided of territorial or home‐range defence, which generally takes the form of display flights but occasionally involves more overt aggression. The home‐range size is fixed so high that a critical food level is probably very rarely reached.