Common section

Chapter Ten

Urban Ecology


There is a school of thought that defines urban ecology as the interaction of the urban organism with its environment. The organism is the town or city itself which consumes the resources of surrounding areas, excretes its waste, and has its own circulatory and digestive system. This organism has been further described as a parasite on its host, the natural environment (White 1985). In areas where urbanization, and associated land loss, food supply, migration, waste, energy and water shortages are serious problems, this concept together with a systems analysis approach can be extremely important in the development of urban areas. Jakarta, as one of the world's largest cities, deserves this kind of attention. It may be appropriate to analyse the different forms of growth, resource use and waste1 from urban centres in Sulawesi (Waworoentoe 1984), but this chapter treats urban ecology as the study of interactions between organisms and the urban environment.

Urban ecology is a vastly underexploited field of study in Indonesia. Budgetary and time constraints act against conducting ecological studies in remote areas but neither of these can be used as excuses against the initiation of ecological projects in any school grounds or university campus. It is not enough to learn about ecology from books: direct and personal observation of ecological interactions is essential. More attempts at teaching and learning about the ways urban organisms react to changes in their environment would lead in time to a greater familiarity with ecological concepts. Presentation of the results from studies on urban ecology to an increasingly well-informed planning sector could promote changes that would make towns and cities increasingly dynamic, attractive and hygienic and improve the well-being and mental satisfaction of the urban dwellers.

Towns comprise numerous habitats and opportunities for adaptable species:

• rubbish heaps provide nocturnal scavenging civet cats with a dependable food resource;

• these tips and houses are occupied by rats which are potential carriers of disease;

• eaves of roofs provide alternatives to tree holes for nesting birds;

• drainage water with high organic loads are exploited by toads, fish and mosquitoes, the last of which are important disease vectors;

• ponds around fountains are exploited by various small animals and plants;

• bare plots of rubble in building plots are colonized by plants with distinctive life histories;

• and house walls provide specialized niches for a few pioneer plants and animals.

Numerous ideas for imaginative research by dedicated school and university teachers can be found in urban ecology textbooks and guides (Collins 1984; Smith 1984; Hammond and King 1985) which, although written to promote urban studies in Europe, would serve as valuable guides to work that could be achieved in Sulawesi.



Urban trees provide aesthetic pleasure and shelter for humans, as well as a habitat for many animals such as birds, that use them as sites for nesting, feeding and roosting. Relatively few species of trees are planted and many of the species planted now are more or less the same as those planted over the last one or two hundred years. There have been some changing fashions in species, however; for example, many of the older streets in the major towns are dominated by mahoganies Swietenia planted about 70 years ago, but the modern fashionable tree is the quick-growing Acacia auriculiformis.

Few of the species planted are indigenous2 (table 10.1) and perhaps more efforts could be made to plant more Sulawesi species. There are indeed no indigenous species that could compete with the beautiful shape of the rain tree Samanea saman or the stunning red flowers of the flamboyant Delonix regia3 but it is certainly not true that Sulawesi has no species to offer, it is rather that landscape gardeners rarely make the effort to find appropriate trees and bring them into cultivation. Examples of under-exploited indigenous trees with great ornamental potential are Elaeocarpus teysmannii (Elae.), E. cf macroceras, Deplanchea bancana (Bign.), Knema celebica (Myri.), Terminalia supitiana (Comb.) and Macadamia hildebrandii (Prot.) (p. 513) (van Balgooy and Tantra 1986). It is probably correct that indigenous plants would be more attractive to birds than introduced plants, but some of the introduced species of trees have greater potential for attracting birds than some local species (table 10.1).

Legumes and Casuarina are obvious choices of trees because both possess the capability of fixing atmospheric nitrogen in root nodules. This means that the trees can grow on young or infertile soils and help to improve the soil for other plants. The choice of tree is determined by the aim of the planting. Parks personnel and horticulturalists are largely concerned with whether a particular species is aesthetically pleasing. Ecologists, on the other hand, are more concerned with the appropriateness of the plants in relation to other components of the environment.

Students and teachers should be encouraged to identify urban trees (Corner 1952) and other plants (van Steenis 1981) in order to become acquainted with plant characters and the classification of plants. Identifying trees in natural ecosystems will then be much easier. Most of the epiphytic ferns are also quite easily identifiable (Piggott 1979).

EoS teams made a survey of epiphytic ferns on roadside trees in a 1 km2 area of residential Ujung Pandang, centred on the junction of Jalan Hasanuddin, Jalan Botolempangan and Jalan Arief Rate. Each tree was marked and the following were recorded: fern species present, their substrate (branch, trunk, etc.), and density. In addition, the species of each tree was noted together with its height, crown cover and diameter at breast height.

A total of 175 trees from six species were examined and four species of epiphytic fern were found (table 10.2; fig. 10.1). No more than two species were found on one tree although epiphytic pigeon orchids Dendrobium crumenatum were found on 6% of the trees.

The ferns were found most commonly on the trunks, and these were in fact the only sites for Drymoglossum piloselloides. Drynaria sparsisora was found on all parts of the trees. All bark-covered parts of the trees had some epiphytes (table 10.3), but the densest growth of ferns was on the trunks 4-8 m from the ground.

Exposure brings two problems: rapid drying and few sources of nutrients although exposed habitats are colonized by air-borne algae particularly the nitrogen-fixing blue-green algae which colonize bark (Wee 1982). Drynaria sparsisora clearly has advantages over other ferns growing in exposed places because its dried nest-leaves collect small pieces of decomposing organic material which break down releasing nutrients and retaining moisture. It is interesting that D. piloselloides is found beneath branches, where water and the nutrients it contains are likely to remain longest. Also, the observation that the densest growths are on the trunks 4-8 m above the ground may be because of the relatively nutrient rich water flowing down the trunk. Davillia denticulata is most common in moist, humus-rich microhabitats such as the axis between bough and trunk. The creeping rhizome is very thick and can store water.

Figure 10.1. Urban epiphytic ferns, a - Davillia denticulata, b - Drymoglossum piloselloides, c - Drynaria sparsisora, d - Phymotodes sp.

Of great interest is the fact that Acacia auriculiformis was never, and the flamboyant Delonix regia was hardly ever, found bearing epiphytic ferns. Half of the ferns on D. regia appeared to be dead, and these and the living ones were sparsely distributed on only the younger specimens. Both species have relatively smooth bark and none of the urban ferns is able to establish itself. Bark texture is unlikely to be the whole reason, however.

One of the most common epiphytic orchids on big urban trees is the pigeon orchid Dendrobium crumenatum, all plants of which tend to flower at the same time. Similar gregarious flowering in dipterocarp trees is probably a response to some environmental cue, possibly water stress (p. 367). The major trigger for pigeon orchids is also environmental but in this case it is a rapid fall in temperature, usually associated with a rainstorm. Nine days after that drop in temperature all the pigeon orchids will bear white, sweet-smelling flowers (Burkill 1917; Coster 1926). The reasons the pigeon orchids flower simultaneously is presumably to increase the likelihood of cross-pollination by insects.

If the crowns of urban trees, particularly fruit trees, are examined closely it may be noticed that parts are dominated by leaves other than the tree's leaves. These may be the leaves of mistletoes Scurrula, Viscum and Dendrophthoe (Lora.) (fig. 10.2), which are parasites whose roots penetrate the host bark and grow into the living tissue beneath. They are thereby able to absorb water and nutrients for their own use. Unlike certain other parasites that have no green leaves, the mistletoes do have green leaves and photosynthesize. Mistletoe flowers are relatively long and the four or five petals remain closed until touched by a visiting flowerpecker Dicaeum celebicum. As the bird sucks nectar from the newly-opened flower, pollen from the anthers is deposited on the base of the bill, and is then carried to another flower where it may be transferred to a receptive stigma. This same bird also eats the mistletoe fruit which comprises a single seed covered by a sticky 'glue' enclosed in a sweet pulp. The pulp is digested by the flowerpecker but the 'glue' is not, so that when the seed is voided it sticks to the branch on which the bird is sitting. It has been reported that the seeds are very large for the intestinal tract of the bird (whose major food is spiders) and the bird has to hop along a branch knocking the seeds from its anus (Dammerman 1929). It appears that germination only occurs after passage through a bird's gut.

One garden shrub indigenous to forest edges of Sulawesi is the white-flowered Costus speciosus (Zing.), a relative of ginger. Like ginger, its rhizome has a host of traditional uses particularly as a medicine (Burkill 1966). The lanceolate leaves are arranged spirally on a stem which itself grows in a spiral manner. The flowers open one by one from an elongate mass of red bracts, with one opening each day. In the centre of the flower the fine stamens fuse to form an upturned yellow-white tongue or lip which hides the throat of the flower. The flowers are visited by large female carpenter bees Xylocopa at about 0600 hrs. to 0800 hrs., from which the bees gather nectar for their nests. To obtain the nectar they have to push up the flower's tongue, and in so doing their backs are dusted with pollen, which in turn is rubbed on to the stigma. Males are rarely seen at flowers.

Figure 10.2. Mistletoes. Left - Dendrophthoe growth habit, right - germination of Macrosolen. Scale bars indicate 1 cm.

After Holttum 1969

Carpenter bees are solitary bees and the males are said to be territorial (Frankie and Daly 1983; Louw and Nicholson 1983). Females visit the same flower locations every day (called 'trap-lining') and will generally visit different species in a regular order. Such trap-lining species tend to be large, have long life-spans, exhibit plasticity in their behavioural patterns, have powerful flight abilities, and clearly have a good knowledge of their surroundings (Janzen 1983). The nest tunnels which the females bore into timber are over 1 cm in diameter and 30 cm long and are bitten out along the grain of dead timber that is in a vertical or horizontal, rather than diagonal, position. The female deposits a ball of nectar and pollen at the end of the tunnel and then lays a large egg next to it. She then closes off this cell with a portion of chewed wood (Frankie and Daly 1983).

One of the largest garden spiders is the black and yellow Nephila maculata, whose huge webs of tough silk are constructed between trees, telephone wires and bushes. Most spiders eat their webs in the morning to avoid them being broken by larger animals such as birds. The web is rich in protein and represents a considerable investment on the part of the spider. Nephila does not eat its conspicuous yellowish web but remains instead in the web's centre, strikingly obvious to passing birds. Some smaller spiders also do not eat their webs, but these advertise them against birds by constructing zigzag or other patterns near the centre thereby making the web much more obvious (Eisner and Nowick 1983).


In general the bird fauna of towns tends to have a lower species richness and diversity than nearby forests, but the biomass and density are higher, and there are a very few dominant species. In addition, the major guild4 shifts from the bark- and canopy-insect eaters to ground feeders (Ward 1968; Beissinger and Osborne 1982; Yorke 1984). These changes are not surprising since relatively few urban trees exceed 10 m in height, and they are often widely dispersed between large areas of grass or hedges. The total number of individual birds and bird species is low in Sulawesi's urban centres. Part of the reason is the predatory habits of young children with catapults, but ecological reasons include the lack of fruit suitable for birds and the few insects able to utilize the 'foreign' trees, leading to less food being available for insectivorous or partially-insectivorous birds (p. 369).

Lists of birds were collected for Manado and Ujung Pandang5 forty years ago (Coomans de Ruiter and Maurenbrecher 1948) and although there have been some changes and additions as species have spread or been introduced (Escott and Holmes 1980), they provide useful baseline information. The totals counted are very similar to those reported for Kuala Lumpur and Singapore (McClure 1961; Ward 1968) (table 10.4).

An examination of the natural habitats of urban and suburban birds of Ujung Pandang (table 10.5) suggests that over half originate from coastal habitats, only about 5% from lowland forest and a similar percentage are normally cliff or cave-mouth nesters. About 25% have been introduced or are recent immigrants. The similarity between cliffs and buildings are obvious, and the swifts and swiftlets have clearly taken advantage of that. The similarity between coastal habitats and towns is not so clear, however, although a common factor is their simple plant communities containing relatively few species (Ward 1968). Because of this, generalized foragers rather than species with specialized niches are the major town invaders. In parts of Africa where savannah vegetation is common, birds in the relatively open urban environment are far more diverse. Sulawesi has no large areas of natural open country or savannah which might be expected to form a source of urban birds and so the number of urban birds originating from indigenous natural habitats is limited (p. 480).

The tree sparrow has spread widely in Indonesia. It is a native of Europe, Russia and China, and probably first arrived in Ujung Pandang aboard ships in the 16th and 17th centuries. It has now found throughout most of the southwest peninsula, to Palu, to Manado and elsewhere in Minahasa and Bolaang Mongondow, but has not so far been reported from Poso, Kolonodale or Kendari (L. Clayton pers. comm.).

The most frequent feeding preference is for insects, accounting for 24 of the 39 species above. Some of these eat insects as a major part of their diet, while others eat insects as an important component of their diets when a higher protein intake is required such as during moulting or breeding, or when they are feeding young. Insects are more abundant on trees with finely-divided leaves such as Samanea, Casuarina, Delonix, Parkia and Albizia, probably because of the greater number of potential resting places. Insect-rich microhabitats are also created by the growth of epiphytes, creepers and climbers on the trees.

The proportion of nectarivorous birds is very small, but they are attractive to urban dwellers because of their bright colours and their pleasing songs. In addition, the flowers from which they suck nectar are generally large and showy. To attract these birds (as well as butterflies) to heights at which they can be easily seen, plants such as Hibiscus rosasinensis (Malv.) (the wild red rather than the cultivated forms), Ixora (Rubi.) and Calliandra (Legu.) can be planted.

Birds need not only food, but also places and materials for nesting. Two of the most favoured nesting materials are the fluffy seeds from kapok Ceiba pentandra (Bomb.) and long grass. Certain swiftlets also use the dead leaves of Casuarina. Thus, these plants must be available in any area where birds are being encouraged to live. Hole-nesting birds can also be encouraged by leaving dead boughs in place, but only where human life is not endangered. In summary, the best way to attract birds to urban areas is to provide areas of heterogeneous vegetation—tall and short trees, shrubs and undergrowth, including long grass—and protection from catapults.

Birds represent excellent subjects of urban ecology studies. Observation conditions are as near ideal as one could wish for and the number of food species and competing birds species are relatively few. The study of such topics would not have island-wide environmental significance, but it would furnish those involved with an invaluable awareness of ecological complexity and principles (Ward and Poh 1968; Ward 1969, 1970; Hails 1984), of great use when required to work in more complex ecosystems on an environmental impact assessment or similar study.

* This includes 13 species of raptors and 10 species of coastal or rice-field birds.

** This is low partly because relatively few birds of prey and coastal/rice-field birds were seen.

After Coomans de Ruiter and Maurenbrecher 1942; McClure 1961; Ward 1968; Escott and Holmes 1984

(I) - Insectivore, (G) - Granivore, (F) - Frugivore, (C) - Carnivore, (N) - Nectarivore.

After Coomans de Ruiter and Maurenbrecher 1948; Nisbet 1968; Ward 1968; K.D. Bishop pers. comm.


At first sight, bats in flight all look the same but, with a little time and patience, different groups or species can be distinguished (Gould 1978). The medium-sized, roof-dwelling, long-winged tomb bat Taphozous longi-manus is usually the first to start flying at dusk and can be seen flying with sharply bent wings about 25m above the streets. Before it leaves its roost it becomes quite vocal and is easily heard in the house below. It and other smaller insectivorous bats fly rather erratically as they swoop to catch insects. Frugivorous bats generally fly in a more direct manner.6 Soppeng, in the middle of the southwest peninsula, has a famous roost of fruit bats near the Bupati's office in the centre of town. Local legend states that if the bats leave the roost the town will fall.

When watching bats forage at night it is clear that many of them fly slower than birds. The amount of lift produced by a flying animal, or indeed an aircraft, depends on the speed of the animal relative to the air (the airspeed), the wing area and the coefficient of lift, which in turn depends on the shape or efficiency of a particular wing shape. Bats and birds can change their coefficient of lift by altering the shape of their wings in the same way that the change in shape of an aircraft wing affects the airspeed. An animal that flies fast therefore needs less wing area for a given wing shape and weight than one that flies slowly and needs more lift. Fruit bats often carry quite heavy fruit from of a fruit tree to a feeding roost and consequently need a large wing area to increase lift. If one compares two urban flying animals of similar weight considerable differences can be seen (table 10.6).

Thus the sparrow carries more weight for its wing area than the fruit bat, and has a relatively long, thin wing typical of relatively fast-flying creatures. The bat therefore has some leeway to enable it to carry a 20 g guava, for example, to a feeding roost.

Bat wings are often a mosaic of scars, cuts and holes and urban bats are sometimes found with missing thumbs or feet. Exactly what causes these injuries is not known.

The usefulness of bats in producing fertilizer (p. 553), controlling fruit flies (p. 423), pollinating fruit trees (p. 561), and consuming vast numbers of insects (p. 549) has been described elsewhere and it is possible that some of these benefits, certainly the first, could be engineered by the building of bat towers or bat boxes. The first bat tower was built in 1908 in Texas but it took six years to design a tower that was truly attractive to bats. The purpose behind it was to control mosquitoes and hence improve the health of the surrounding population. Malaria did become less prevalent, and the roosts created a reasonable income from the sale of guano. Local governments and the Ministry of Health encouraged the building of towers and they were even exported to Europe but with little success. The American free-tailed bat Tadarida brasiliensis which occupied the towers has a relative, T. plicata in Sumatra, Java and Borneo. Bat towers were used with some success in Sumatra decades ago but it is not known which species colonized them (Anon. 1985). Sulawesi has a single species of Tadarida (p. 41) which does not seem to be particularily common, but it could probably be encouraged.

Building a tower is probably overly ambitious, and bat boxes are rather more practicable. Bat Conservation International, an interest group based at the University of Texas, U.S.A., recommends two types of boxes of slightly different sizes (fig. 10.3), that can be hung on trees 3 m or more above the ground. The different sized gaps should accommodate bat species of different sizes, but it may take several months before the boxes are colonized. Bat boxes could be erected in the grounds of schools or university departments, and the bats inhabiting them should be monitored.

After Yalden and Morris 1975; B. GasHeii pers. comm

Figure 10.3. Bat boxes adapted from the design recommended by Bat Conservation International. Numbers indicate measurements in centimetres. Bats enter and leave through the bottom which is open. The wood used should be as rough as possible so that the bats can grip the surface with their feet. The top of the box can be covered with heavy plastic tacked down firmly at the edges. Boxes should be hung in relatively shady situations to prevent the bats getting too hot during the day.


Walls are an integral part of the urban environment and are not utilized as much as they might be for the teaching of ecology. They represent a major habitat: it would be instructive to measure the area of exterior walls present in a defined area of town, remembering that many boundary walls have two external faces.

A wall has essentially four zones: the base, the lower level, the upper level and the wall top. Of these, the wall base is the wettest, most shaded and most nutrient-rich since rain and other material from the upper zones run into it. It is onto the soil adjacent to the wall base that seeds are excreted by birds or are blown by wind. Many of the seeds grow into plants that climb up walls forming a number of micro-habitats. The wall top differs from the other zones by being generally horizontal, and this has profound effects on the rate and type of colonization.

Numerous factors influence the colonization of a wall such as aspect (the direction it faces), shading, age and type of building material, and age and type of paints (if any). New walls are not immediately colonized because cement and red brick are quite strongly alkaline and unfavourable to all but the most specialized algae. Gradual decomposition, the roughening of the surface and the formation of cracks set the stage for colonization. If the process of succession is left undisturbed, algae tend to colonize first, followed by mosses, ferns and then flowering plants.

White-washed or emulsion-painted walls quickly discolour. Areas of green, black and orange appear in patches or streaks, some in shade, some in the open. The 'stains' are caused by green and blue-green algae and by diatoms. The black stains are usually blue-green algae that have caught airborne dust particles in their mucilaginous sheaths. The distribution of these microscopic plants on buildings has been investigated in Singapore (Chua et al. 1972) and an identification key is available (Lee and Wee 1982). Algal cells and filaments are dispersed in the air, and samples of Singapore air have been found to contain 21 species of algae, some of which are known to cause allergic reactions in humans (Wee 1982). Some of the algae are able to fix atmospheric nitrogen and as more dust and soil particles become attached, so a favourable habitat is formed for flowering plants to colonize. This obviously takes time, and regular maintenance of the wall prevents succession from proceeding.

Some of the oldest standing walls in Sulawesi are those of Fort Rotterdam in Ujung Pandang. The first walls were built in 1545 during the reign of the first Gowa king. The walls were rebuilt in 1634 and the Fort was surrendered to the Dutch in 1667. The walls are formidable: up to 6 m high and over 10 m thick in places. The Fort was partially restored in the 1920s and after the Japanese Occupation, then in the early 1970s the whole Fort underwent major repairs to house a provincial museum and offices of the Department of Education and Culture. There are 25 lengths of wall, seven of which have been repaired recently. The others comprise a mixture of the original blocks, coral blocks and cement.

Thirty species of moss, lichens and flowering plants were found growing on the walls during the rainy season in February 1986, and the distribution of the 23 species most commonly found was investigated (table 10.7). Eleven of these species were present on all the walls and the distribution of the other twelve did not seem to relate to aspect (the direction faced).

By far the most common plants during the wet season are an unidentified moss and the small South American herb Pilea microphylla (Urti.) each of which covered nearly 20% of some walls. The next most abundant plant is Hedyotis corymbosa (Rubi.), which was found at densities of 20/m2 in the sample quadrats, followed by Peperomia pellucida (Pipe.), Urtica urens (Urti.) and Eragrostis amabilis (Gram.) all of which averaged 2-3/m2. Only one plant, the fern Cheilanthes farinosa (Polp.), appeared to have any clear preference for microclimate; it was found only on the lower parts of walls close to other buildings, where shade and humidity were high.

By the middle of the dry season in June, only 12 of the 30 species found in February were still present, but even these were less abundant (table 10.7). Two species, the widespread fodder plant Alysicarpus vaginalis (Legu.) and seedlings of the small tree Muntingia calabura (Elae.) whose seeds are dispersed by birds and bats, were relatively rare in the wet season but, because they persisted, were dominant in the dry season although their numbers did not increase. Some of the species of the wet season were clearly annuals, setting seed and then dying, but the EoS team watered the 'dead', brown remains of some other plants, particularly the common moss and Pilea microphylla and found that within five minutes the plants had become green and were becoming turgid. This ability to recover from droughts, known as poikilohydry, is also known from natural habitats such as limestone cliffs which are also subject to periodic droughts (p. 477).


Urban roadside ditches are regarded by many as simply a means of preventing floods or of removing household waste water to larger water courses. To an ecologist, a ditch is a simple, small river, the life in which can give indications of water quality.

Where ditches are obstructed and where water flows sluggishly, mosquitoes may breed. Their preference for still water is the major reason that they are more common in the dry season than in the wet season. In the latter the eggs and larvae are swept away. The frequency of mosquito-borne diseases is usually higher in urban areas than elsewhere because of the availability of suitable breeding habitats and biting targets.

There are about 125 species of mosquito in Sulawesi but only the genera Anopheles, Culex, Mansonia and Aedes (represented in Sulawesi by 38, 21, 5 and 35 species respectively) have species known to spread debilitating diseases such as dengue, filariasis and malaria (fig. 10.4) (O'Connor and Sopa 1981; Hii et al. 1985). The disease organisms are spread when female blood-sucking mosquitoes7 inject a small quantity of saliva into the bloodstream of the host. If the mosquito is not yet carrying the disease organism, she may pick it up in the blood sucked from an infected host. The identification of those species that spread disease is far from easy, and suggestions that posture or leg colour alone can be used to distinguish species accurately are ill-founded. There are considerable differences between and within genera in behaviour, and the habitat preference of larvae and adults (table 10.8). In the towns of southern South Sulawesi, for example, Anopheles sundaicus, A. subpictus and A. barbirostris are the most important vectors of malaria; the peak biting period for A. sundaicus is between midnight and 0100 hrs, for A. subpictus the biting peak is between 2200 hrs. and 2300 hrs., but A. barbirostris bites through the night until 0500 hrs. with no clear activity peak. A. sundaicus prefers human targets over cattle and buffalo, whereas A. subpictus prefers to take blood from cattle and buffalo. Both these species are tolerant of brackish-water and so are common in locations close to coastal tambak fishponds (p. 187). The normal method of controlling mosquitoes in Indonesia is by spraying with a 75% solution of DDT at a rate of 2 g/m2 (Collins et al. 1979). No one appears to have studied the effect of the use of this infamous chemical on other aquatic organisms or on organisms, such as humans, higher up the food chain in Sulawesi.

Ditches are commonly inhabited by two species of small fishes, the mosquito fish Aplocheilus panchax and the guppy Poecilia reticulata (fig. 10.5). Both species have been introduced to Sulawesi from South America by people in attempts to control mosquito larvae. Mosquito fish are primarily eaters of small aquatic insects whereas guppies are primarily eaters of algae, but will also prey on insects.

Figure 10.4. Differences in larval shape and position in water, adult posture, wing-spotting, mouth parts, and shape of scutellum between anopheline (Anopheles) and culicinine (Aedes, Culex, Mansonia) mosquitoes.

After Anon. 1967

After M. Rachmat pers. comm.

Figure 10.5. Mosquito fish Aplocheilus panchax (a), guppy Poecilia reticulata female (b), and male (c). Note the different positions of the dorsal fins, and the long anal fin of A. panchax. Also, A. panchax has a shiny silvery spot on the top of the head.

Both these fish are most obvious in urban ditches when they mouth at the surface, looking as though they are breathing air. Some fish can use atmospheric oxygen (pp. 301 and 580) but the two species are in fact taking in water from the air-water interface where the concentration of dissolved oxygen is greatest (Kramer and Mehegan 1981). This 'aquatic surface respiration' is generally only used where oxygen levels are low (such as slow-moving ditch water with a high organic content), and when the oxygen levels of water are raised the fish respire normally. Aquatic surface respiration does not allow them to stay alive for long periods in highly deoxygenated water but it does confer an advantage such that these fish can survive where other fishes cannot, and they can thus be used as indicators of water quality.


Spiders and Ants

Spiders are a ubiquitous group of predators found in houses. Some of the most common are the often brilliantly-coloured jumping spiders which form the world's largest spider family (Salticidae) with over 4,000 species. These bold beasts can leap up to 40 times their body length, and not surprisingly have more acute vision than any other spider. The large middle pair of eyes at the front that give these animals such a surprisingly endearing look, act like telephoto lenses with a narrow field of vision but high resolution. There are remarkably like human eyes but, since the eyes are unable to move, the retina rather than the eyeball is moved to change the field of view. The other three pairs of small eyes (two at the back and one at the front), have a much wider field of vision and the pair at the front give these spiders some degree of binocular vision, thus enabling them to judge distances when jumping and hunting. The small eyes are probably the first to pick up movements of potential prey and the main eyes are used for the fine hunting techniques. Since at least one pair of their eyes look behind them, jumping spiders are very hard to catch. They do not make webs but, like all spiders, they trail behind them a strand of 'silk' which is attached to the ground at intervals so that they are saved from falling after an unsuccessful leap or pounce on flies and other prey (Preston-Martin and Preston-Martin 1984).

Kitchens often harbour a number of ant species. The smallest is the yellowish Pharaoh's ant Monomorium pharaonis with a black tip to the abdomen. It has been carried unintentionally all over the world and is quick to find sugar if left in open containers. Once it has found a food source it may keep other species away with a repellent odour secreted from the poison gland.


There are few houses or other buildings in towns without a resident community of geckos and they are unusual amongst the animals living alongside man in that they are not, for the most part, regarded as dangerous or undesirable.

Five gecko species8 regularly inhabit houses but the two larger species, Gekko monarchus and G. gecko, are relatively rarely seen. The 'to-kay' call of the latter species is quite frequently heard, however, particularly in suburban villages where palm-leaf roofs are still used.

The other three geckos are remarkably similar in size and diet although Gehyra mutilata appears to shun brightly-lit locations (Church 1962). In many suburban areas Hemidactylus frenatus is the most common species followed by H. platurus and G. mutilata although H. platurus is often the most common species on well-lit walls inside houses, with H. frenatus most common on outer walls. The females of each species lays two hard, white eggs at a time in cracks, behind pictures, etc., and these take about three months to hatch. At least a year is required for the hatchlings to reach adult size although they become mature after the snout-to-vent length exceeds 3.5 cm (Chou 1978). Their primary food is insects but the stomach of one H. platurus examined in Bandung contained a H. frenatus tail. H. platurus also appear very partial to rice, honey, juices from fruit, bread crumbs, meat and fish. Most lizards develop fat bodies under their skin the size of which is determined by the abundance of food, but none of the geckos in the Bandung study were ever found to contain such fat bodies. This may be due to the year-round supply of scraps from the humans with which they share houses, and this also results in the absence of breeding seasons (Church 1962). Geckos have relatively short tails and this is typical of lizards that are habitat specialists (the ability to run upside down is taken to be a speciality), relatively cryptic, and have a sit-and-wait strategy for hunting (Vitt 1983). The bright green, diurnal, and very long-tailed lizard Calotes cristatellus of suburban gardens would be placed at the opposite end of the spectrum.

It is a frequent matter of debate how geckos manage to climb on vertical surfaces and run upside down on a ceiling. The feet do not have suckers but instead have small overlapping flaps of skin. These flaps are covered with minute, closely-set hairs which make contact with the slight irregularities of a surface and enable geckos to cling where other animals would fall. Geckos are also known for their ability to shed their tails when caught—a response designed either to enable them to break free if caught by the tail, or to distract the 'predator' with a wriggling tail, or perhaps both The shedding of the tail is obviously extremely important for geckos since they divert a great deal of energy into the growth of a new tail, and the majority of geckos appear to have lost their original tail. Regenerated tails are rather larger than the original but often not so long or so symmetrical (Vitt et al. 1977). Tail shedding is also known in some other lizards and in snakes, and in all cases it involves muscular contractions which causes a fracture to occur across a vertebra, rather than between two vertebrae.

Possible Urban Ecology Studies

Plots of land awaiting development, roadsides, the gardens of unoccupied houses, and neglected corners of towns represent opportunities to study the process of plant succession. Which plants colonize open ground? How does exposure affect colonization rates? Which plants are the first to arrive? How quickly does the organic content of the soil increase? Assuming the first plants are grasses and herbs, how long until the first woody plant appears? Measure samples of the above-ground biomass at different times. Is the rate of increase constant? Does it show changes related to the seasons? What animals are associated with different stages of the succession?

Investigate different urban ditches, and try to catch one of each of the fish species present. Remember that some fish are mainly nocturnal in their habits. It is more informative if the fishes caught can be given a scientific name (Schuster 1952; Alfred 1961, 1966; Mohsin and Ambak 1983), but simply the total number of different species provides useful data. Plot a graph of the number of species against the biological oxygen demand or the oxygen concentration of the water. Repeat in a different section of town and in irrigation canals. Is it possible to show a correlation between the results? What other parameters are important? Use the same procedure for other aquatic organisms.

Select a number of walls of different ages (either absolute age or age of most recent paint), and quantify the differences in algae and higher plants growing on them. Is exposure more important than aspect? Pay attention to the base of the walls. Are there plants which probably grew from seed carried by birds? Drill holes of different sizes and lengths into a wall and monitor the rate at which these are colonised by wasps and other animals (Darlington 1981).

Stand outside at dusk and watch for bats, noting the times the different species appear. Where do they seem to come from? Finding roosts is sometimes easier at dawn when bats fly around them before settling. Over a series of days, try to pin down the actual roosts. Do the bats emerge at the same time each day? What effect does rain have? Are roosts available all over the town or are they concentrated in one area? How many bats emerge from each roost? Is it the same number day after day? Take a series of 1 ha plots in a town and collect data to estimate the number of resident bats. Attempt an estimate of the quantity of fruit and insect food the bats ingest each night. If bat boxes have been made (p. 614), attempt to determine why some boxes are inhabited and others are not.

The three most common species of house gecko are more or less the same size. What forms of competition and niche separation allow them to coexist? Collect several of each species at intervals of several weeks over a period and analyze the stomach contents. Without necessarily identifying the animal food remains to genus or even family, is it possible to detect differences in composition or size of prey between species. Watch the geckos. How do their hunting strategies and prey differ? Do any of them catch food during daylight hours? How do the species space themselves around light bulbs? Are resting places (in cracks, behind pictures and mirrors, under stones, in thatch roofs, in corners of ceilings or behind cupboards and curtains) different between species?

Ants frequently take advantage of scraps of food left in kitchens. Deliberately leave small quantities of sugar, meat, oily nuts or other food and notice which ants are attracted to which food. If the foods are mixed, which ant reaches the pile first and which dominates? Place a known, weighed quantity of food in a small pile—monitor how quickly it is removed. Is there any difference between the rate at which food piles are found between day and night time? Follow a trail of ants. How far does it extend? How long does it last in any one pattern? In what ways can ants be regarded as useful?

If you find an error or have any questions, please email us at Thank you!