Showing papers in "Journal of Zoology in 1982"

Factors affecting population density, group size and territory size of the European badger, Meles meles

Abstract: This paper discusses the relationship between the distribution and biomass of the main prey of European badgers, Meles meles and the badgers group size, territory size and population density. The distribution of areas rich in earthworms, Lumbricus spp., is correlated with badger range size, whilst badger group size increases with the biomass of worms per badger territory and badger density increases with overall worm biomass. Regulation of badger density in an area is likely to take place through regulation of group size, in the absence of other factors such as persecution and lack of suitable sett-sites.

The biology of Portia fimbriata, a web‐building jumping spider (Araneae, Salticidae) from Queensland: utilization of webs and predatory versatility

Abstract: The biology of a primitive salticid spider, Portia fimbriata (Doleschall), is described from observations in a Queensland rain-forest and the laboratory. Locomotory specializations enable the spiders to move about readily on webs; and all stages of life history are associated with webs, both alien and two types they build themselves. The more flimsy Type 1 webs are used as resting sites similar to the nests employed by more familiar jumping spiders. Type 2 webs are more substantial structures in which the spider moults, mates, oviposits, broods its eggs and remains for as long as 48 days. The predatory strategy of Portia includes the use of distinct alternative tactics in the pursuit of varied types of prey. Most of these tactics are ones not usually associated with salticids. Portia invaded diverse types of webs without difficulty, including adhesive and non-adhesive, cribellate and ecribellate, and two-and three-dimensional ones. Once in the web, Portia produced vibratory stimuli by specialized but varied movements of the legs and palps. Web spiders responded to these in a manner more appropriate for a potential prey item or a conspecific in its web than a potential predator. Sometimes vibrations lured the spider to the waiting Portia. Other times, localized movements were elicited which assisted Portia in remaining orientated toward the spider as it stalked across the web. Outside webs, Portia stalked other species of salticids, moving in a very slow and “mechanical” fashion and arresting forward motion whenever faced by the prey. Evidently, the salticids did not recognize Portia as another salticid and a potential predator. Although Portia pursued insects, they pursued spiders more readily, persistently and successfully. Portia captured insects outside webs, on their own webs and on the webs of other species. Those on their own webs adhered temporarily to the silk. In webs of other spiders, insects were sometimes taken directly from the chelicerae of the host. Also, their own webs assisted Portia in capturing other spiders. Eggs of spiders were fed upon both on and off webs. Different attack tactics tended to be employed with different types of prey: web spiders, lunge; salticids, swoop; insects, pick-up. Egg-cases were opened by means of specialized movements involving the chelicerae and the eggs were raked toward the mouth with the legs. Most prey were seized after the attack, but sometimes they were stabbed with fangs and ran several centimetres before immobilized. Portia maintained its orientation, then walked to the stabbed prey and fed. Vision of the prey seemed to be of major importance for most aspects of predatory behaviour. In the rain-forest habitat, webs of Portia, pisaurids, pholcids, and theridiids are often contiguous and facilitate the tactic of web-invasion. It is proposed that the pervasive use of webs by Portia is a primary character conserved from ancestral salticids, and that in the evolution of the family, invasion of contiguous webs could have led to selection for a sophisticated visual system that assisted in the localization of their residents. The developed visual system could then have allowed vagrant predation en route to more distant webs, and finally emancipation from dependence on webs altogether.

Behavioural ecology of the Greater one-horned rhinoceros (Rhinoceros unicornis)

Abstract: In the Chitawan Valley of Nepal there were estimated to be between 270 and 310 Greater one-horned or Indian rhinoceroses (Rhinoceros unicornis L.). Population densities reached 4.85 rhinos/km2 in the favoured areas of high diversity of early successional vegetation types on the valley floor. The overall population composition was 32.3% adult females, 19.9% adult males, 21.2% sub-adults and 26.6% calves. Females first calved at a mean age of 7.1 years and the median intercalving interval was 2.8 years. Causes of death included poaching, tiger predation on calves and fighting among males. The population was increasing. Rhinos fed from 183 species of plants belonging to 57 botanical families but grass (50 species) made up between 70 and 89% of their diet according to the season. Considerable seasonal variations in food availability resulted in movements of rhinos between vegetation types. Rhinos' ranges were smallest in the areas of greatest vegetational diversity. Rhinos rarely formed groups. The most common type consisted of sub-adults–mainly males. Ten auditory displays were distinguished and visual displays, although less striking, included baring the lower incisor tusks. Scents were carried in the dung, the urine and the pedal scent glands. Squirt urination and foot-dragging displays were performed by breeding males only. There was some degree of range exclusivity among breeding males but no true territoriality. Poor visibility and the relatively unpredictable distribution of resources in time and space have perhaps selected against a territorial mating system. Relationships between ecology and social organization are discussed with reference to other rhino species. Threats to the continued survival of the Indian rhino include poaching, agricultural encroachment and erosion. In order to spread the risk of a catastrophe, reintroductions of rhinos to other protected areas are proposed.

The underground passages and storage pits used in foraging by a nest of the termite Macrotermes michaelseni in Kajiado, Kenya

Abstract: Part of the system of underground passages and storage pits used in foraging by a nest of Mucrofermes michaelseni was excavated and is described in detail, and an attempt is made to quantify it. Densities as high as 1.9 m of passage and 21.4 storage pits per m2 were recorded in the main foraging zone, which is 10–35 m from the nest. The estimated total for the whole nest was just under 6 km of passage and 72,000 storage pits, in an area of about 8000m2

Effects of lactation on feeding behaviour and habitat use in wild Red deer hinds

Abstract: In many mammals, the energetic costs of lactation double a female's daily energy requirements on her activity budgets, food choice and ranging behaviour–but the effects of lactation have rarely been documented. In this paper, the ecological consequences of lactation in free-ranging Red deer (Cervus elaphus) hinds on the lsle of Rhum is examined by comparing the feeding behaviour, habitat use and ranging behaviour of hinds that were supporting calves (milk hinds) with hinds that did not have calves (yeld hinds). In summer, milk hinds graze for approximately two hours longer per day then yeld hinds. This difference has disappeared by the latter half of the winter, when the grazing budgets of milk and yeld hinds are similar. Both in summer and winter milk hinds spend more time grazing on the most strongly selected plant communities (short, herb-rich greens) where standing crops are low but food quality is comparatively high. Inter-year variation in habitat use by milk hinds is also closely related to variation in rainfall—while this is not the case among yeld hinds. Both in summer and winter, yeld hinds range more widely than milk hinds.

Patterns of breeding behaviour and plasma levels of hormones in a free‐living population of Pied flycatchers, Ficedula hypoleuca

Abstract: Plasma levels of luteinizing hormone (LH) and steroid hormones were measured by radioimmunoassay in a series of plasma samples collected from a free-living population of Pied flycatchers, Ficedula hypoleuca. Both males and females have similar circulating levels of LH and testosterone when they arrive in the breeding area. However, as territories and pair bonds are established, and as courtship and nest-building ensue, the plasma levels of testosterone in males become elevated over those of females, although a lesser peak also occurs in females. As the egg laying phase and incubation begin, plasma levels of LH and testosterone decline sharply in both sexes. On the other hand polyterritorial males, that establish secondary territories, maintain higher levels of LH and testosterone than males remaining in the home-territory, at least until they return to the home-territory, usually at the middle part of the incubation period. By this time polyterritorial males also have basal levels of these hormones. Curiously, females on home-territories show a small, but significant, rise of circulating LH and testosterone at the time the males return. In males, plasma levels of corticosterone are elevated from the time of arrival on the breeding grounds until the end of the nest-building period. Thereafter corticosterone levels decline in males staying on the home-territory but remain elevated in polyterritorial males until the latter return to the home-territory. In contrast, circulating levels of corticosterone in females are only elevated for brief period during egg laying.

Reproductive and social behaviour of the Dhole, Cuon alpinus (Canidae)

Abstract: A pack of Dholes living in the Bandipur Tiger Reserve Karnataka, India was observed between August 1976 and July 1978. The home range of the pack was 40 km2, the average density was 0·35-0·9 Dholes/km2 in the 20 km2 core area. The hunting range of the pack during the denning period was 11 km2 and at other times the range was over 15 km2. Mean number of adults in the pack averaged 8·3 and including pups, the mean pack size was 16. Adult sex ratio consistently favoured ♂♂ with a 2:1 ratio. Preexisting dens were used during this study. Pups left the den when 70 to 80 days old and at seven months of age actively took part in killing prey. Means of communication, types of play, and response to other species are described. Determinants of pack size and features of pack size regulation are discussed and data are compared with those of Canis lupus and Lycaon pictus.

The role of tendon elasticity in the locomotion of the camel (Camelus dromedarius)

Abstract: Several ofthe distal leg muscles ofcamels have very short or even rudimentary muscle fibres. This makes it possible to calculate the elastic extensions of tendons that occur in running, from the leg positions observed in films. A series of experiments have been performed for this purpose on the dissected legs of a camel. The initial conclusions derived from them are modified in the light of estimates of the forces that act on the tendons, and of measurements of the elastic properties of one tendon. Evidence for movement at the intertarsal and tarso-metatarsal joints. and the corresponding joints of the fore leg, is examined. The importance of the various tendons as elastic energy stores in running is assessed.

Autumn and winter feeding ecology of waterfowl at the Ouse Washes, England

Abstract: The potential foods available to waterfowl at the Ouse Washes in autumn and winter are described. All were commonly found in the river, pool, marsh and flooded grassland habitats of the washes and in the surrounding arable fields. Gadwall Anas strepera, Wigeon A. penelope, Moorhen Gallinula chloropusand Coot Fulica atramainly consumed vegetative foods, especially the leaves of grasses and in the case of the first named, water plants. Mallard A. platyrhynchos, Pintail A. acuta, Teal A. crecca, Pochard Aythya ferinaand Moorhen fed extensively on fruits and seeds with the first three species supplementing their diets with cereal grains from stubbles. Shoveler A. clypeata, Tufted duck Aythya fuligula, Pochard and Moorhen consumed the largest amounts of invertebrates. Within these three groupings there were further interspecific differences in diet. With most species diets also differed under low and high floods, being most similar under the latter. Amongst the dabbling ducks Anasspp. there were differences, probably minor, in foods taken attributable to differences in the bill lamellae on the outer margins of the upper jaw. The feeding methods used under low and high floods are described and some differences may further serve to ecologically separate the waterfowl. There was a high degree of adaptability, especially amongst the dabbling ducks, with some species changing the feeding postures completely under high floods. All species fed diurnally. Wigeon, Gadwall, Coot and Moorhen all fed for at least 90% of the daylight hours. Shoveler, Teal, Mallard and Pintail were most active in the mornings and afternoons. A partially objective analysis of ecological niches shows that all but two species pairs were clearly separated by either habitat or food factors. There is some overlap between Pochard and Tufted duck and greater overlap between Mallard and Pintail. This may be because they are utilizing the temporarily abundant foods present at this site.

Dynamics of oviposition in Danaus plexippus (Insecta: Lepidoptera) on milkweed, Asclepias spp

Abstract: Where a butterfly chooses to lay an egg will influence the subsequent survival of her offspring. In this paper we report on the effect of a number of variables which influence the choice of oviposition site in Danaus plexippus L. Experiments were conducted under both flight cage and field conditions. The field observations consisted of recording the within and between plant egg dispersions across different patch sizes. Laboratory experiments looked at egg laying preferences as affected by plant species, age and condition. Butterflies were selective in their choice of oviposition site. Eggs were laid singly on the underside of medium sized leaves towards the top of a plant. More eggs were laid per plant on single isolated plants than on plants within a patch. The number of eggs per plant increases with plant height but decreases with plant age. Females preferred young plants or plants with fresh regrowth of leaves. These characteristics could override species preferences which were, in decreasing order, Asclepias curassavica. A. fruticosa and A. physocarpa. Species preferences varied between butterflies and with female age. Neither the presence of eggs nor larvae on a plant deterred oviposition. These results are compared with previous observations of egg laying in this species.

Factors affecting group size and territory size of the Brown hyaena, Hyaena brunnea in the southern Kalahari

Abstract: The paper describes how the dispersion pattern of food affects group size and territory size in the brown hyaena in different ways. Territory size is affected by the distribution of the food, group size by the quality of the food in the territory.

Studies on the growth, structure and abundance of the Mediterranean spur‐thighed tortoise, Tesudo graeca in field populations

Abstract: The blackness and physical appearance of Mediterranean spur-thighed tortoises (Testudo graeca L.) are recorded in field populations. The inter-relationships between carapace and plastron length, fourth vertebral scute width and other morphometric characters are related to growth. The rear fontanelle is larger in males and the plastron length correspondingly smaller. The relationship between carapace length (y) in mm and body mass (x) in g is strongly allometric and given by y= 16.63 x0–34. The maximum carapace lengths recorded for male and female T. graeca graeca L. in NW. Africa are 151 and 198 mm, and for larger T. graeca ibera Pallas in W. Turkey and NE. Greece 208 and 218 mm, respectively. The growth annuli of epidermal scutes are deposited yearly until external growth ceases. The number is used to assess the age of wild animals. Tortoises can be full-grown by 19 years but some, especially slower growing ones, deposit further annuli. The biggest mean growth increments occur up to 7 years with the largest in individuals over the 5–12 year period. The proportion of immature tortoises, adult sex ratios, size and body mass structure, age distribution, annual recruitment and survivorship until full-grown, and abundance (sighting frequency) are compared in northern and southern range populations of NW. African T. g. graeca and S. Anatolian and SE. European (Thrace and Macedonia) ones of T. g. ibera. These are discussed in relation to other tortoise species.

Feeding behaviour and feeding ecology of the Octocorallia (Coelenterata: Anthozoa)

Abstract: The feeding behaviour of some 30 species of Octocorallia was examined in the laboratory and in the field. All of the species from the Orders–Alcyonacea, Gorgonacea, Stolonifera and Telestacea, appear to have a common, basic feeding strategy. Fine particulate matter and zooplankton were captured in a raptorial manner by the tentacles and pinnules. Upon capture of food particles, the tentacles were flexed rapidly inwards and closed or wiped across the mouth. At the same time the mouth opened and ingestion was accomplished by directional ciliary currents in the mouth and the pharynx. Food capture by means of mesenterial filaments, mucus strands or ciliary currents was not observed. The examination of gut contents of Alcyonacea showed that they feed upon zooplankton. Epibenthic copepods from the demersal coral reef zooplankton were an important element of the diet of alcyonaceans.

The wing musculature of the Brown kiwi Apteryx australis mantelli and its bearing on ratite affinities

Abstract: Most previous accounts of the wing muscles of the kiwi have only dealt with the proximal muscles. The few accounts that have treated the distal muscles are incomplete in other respects and sufficient uncertainty exists to warrant the present study. The wing musculature of the kiwi is closely similar to that of other ratites but markedly dissimilar to that of the carinates. In this regard the wing muscles differ from those of the leg. Ratites have far fewer wing muscles than carinates. Significantly, they lack propatagial muscles (and almost certainly propatagia), and neither the M. pectoralis nor the M. supracoracoideus is well developed; in carinates these two flight muscles comprise the bulk of the wing musculature. Furthermore, the insertion tendon of the M. supracoracoideus does not loop through a triosseal canal to effect wing elevation as it does in the carinates. In all of these regards the ratite condition is closer to that of reptiles than of carinates. This raises the question of whether ratites should be regarded as primitive birds, rather than as advanced birds that evolved from carinates. The present skeleto-muscular data, taken with other evidence, suggests that ratites are primitive birds that evolved from a primitive, volant ancestor. The elements of the pectoral skeleton show a greater degree of individual variation than those of the pelvic skeleton. Aside from its extreme curvature the humerus is the most rudimentary element and few of its features can be compared with those of the carinate humerus. Few of the wing muscles have attachments that can be identified with specific osteological features. Myological data for the kiwi are therefore virtually irretrievable from osteological material, as noted previously for the pelvic muscles. While this might be peculiar to the kiwi (which seems unlikely) the fact should serve as a cautionary note to palaeontologists attempting to reconstruct the muscles of extinct animals.

Pyrrolizidine alkaloids sequestered by Solomon Island Danaine butterflies. The feeding preferences of the Danainae and Ithomiinae

Abstract: The plant sources and identity of pyrrolizidine alkaloids sequestered by six species of Solomon Island Danainae have been investigated. The secretions of the pheromone-disseminating hairpencils of the males have also been analysed and the componenets, including pyrrolizidine metabolites, have been identified. The first confirmed example of Danaine larvae, rather than adults, acquiring pyrrolizidine alkaloids is reported and its relevance to hypotheses concerning the origin of the requirement of Danaine and Ithomiine butterflies for pyrrolizidine alkaloids is discussed.

Causes of mortality in the Mute swan Cygnus olor on the River Thames

Abstract: Over the last 20 years there has been an unprecedented decline of the Mute swan on the River Thames. Between August 1979 and October 1981 a systematic attempt was made to collect as many swan corpses as possible. Of 94 swan corpses examined at post-mortem 57% died from lead poisoning due to ingestion of anglers' weights. Birds dying from lead poisoning had significantly higher liver and kidney lead levels. Kidney proved to be the most useful indicator tissue, the median lead level in birds with lead weights in their gizzard was 908 μg/g DM compared to 8 μg/g DM in birds without weights. More immature birds die from lead poisoning than other factors and significantly more corpses were found between the months of July-October. Ultra-structure examinations revealed electron dense intra-nuclear inclusions in the cells of proximal convulated tubules of the kidney and X-ray analysis confirmed that these structures consisted of lead.

The pace of growth: An allometric approach to comparative embryonic and post embryonic growth

Abstract: Embryonic and post-embryonic growth times are scaled to body size in a fashion quantitatively similar to physiological time scales. Previous studies have either perceived the allometry of physiological time only as a crude approximation or overlooked it entirely. Allometric analysis offers considerable promise for understanding comparative growth dynamics.

Seasonal variations in infestations of parasites in a Wood mouse Apodemus sylvaticus population in the West of Ireland

Abstract: Seasonal variation in most of the metazoan parasites of a Wood mouse population was investigated by a statistical analysis of their frequencies in 11 samples of about 30 mice trapped regularly over one year. Numbers of the flea Ctenophthalmus nobilis, most mesostigmatid mites and the beetle Leptinus testaceus were correlated with breeding in the mouse population and may have been directly linked with it as all ofthese arthropods are common in Wood mouse nests. The tick Ixodes ricinus was abundant over the summer but scarce in winter. Its preponderance on male hosts is doubtless because they cover more ground than females. Flukes were commonest in summer, probably as a result ofthe period of intensive feeding on invertebrates by the mice which usually occurs in early summer. Female mice were more heavily infected, perhaps because of their increased food requirements in the breeding season. Abundance of flukes declined with the turnover in the mouse population in autumn. The infestation pattern of the nematode Capillaria muris sylvatici is similar and the possibility of an invertebrate vector is discussed. While older mice were generally more heavily infected with helminths than were young, this was least marked in the tapeworm Cataenotaenia lobata (which most likely has a mite as an intermediate host and may be picked up as soon as juveniles start grooming) and the roundworm Syphacia stroma (eggs of which are almost certainly transferred by body contact between hosts)

Predation by Tawny owls (Strix aluco) on Bank voles (Clethrionomys glareolus) and Wood mice (Apodemus sylvaticus)

Abstract: During 1954–56 we made a study of the numerical relationships between a population of Tawny owls (Strix aluco) and populations of their main prey species, the Bank vole (Clethrionomys glareolus) and the Wood mouse (Apodemus sylvaticus), in a 48.6-ha area of mainly deciduous woodland near Oxford. The owls were censused by plotting their territorial challenges (hooting), the rodents by the capture-mark-recapture technique. Since the rodents were marked with numbered monel metal leg rings, we were able to recover a proportion of these in the pellets of undigested material cast by the owls. The results for Bank voles, which were the more numerous of the two prey species, indicated that 20–30% of the standing crop was removed by owls in any two-month period. We also made an independent estimate of predation rate from the number of rings recovered from owl pellets in relation to the number of ringed rodents released into the population each two months. This coincided with the limits indicated by the first method for voles (20-30% removed of the standing crop each 2 months). Wood mice were scarcer than Bank voles and were not amenable to satisfactory capturemark-recapture analysis but, when treated on the system of recovery of rings in owl pellets, we found that they were preyed upon relatively more heavily than were the voles. Of the latter 18–46% of the marked animals were recovered in the owl pellets compared with 28–70% of the marked mice. Either the mice were preferred prey or they were more vulnerable to owl predation by reason of their preference for more open habitats.

Ecological observations on epomorphorine fruit‐bats (Megachiroptera) in West African savanna woodland

Abstract: Three species of Megachiroptera were studied in Mole National Park, Ghana, by systematic netting in various habitats and by observations of bats in the field and in captivity. This study, undertaken in July-August 1974 and 1975, is a preliminary attempt to elucidate how these species partition the resources available to them, with particular emphasis upon roosting habits, food resources, and temporal and spatial differences in foraging behaviour. All three species give birth towards the beginning of the wet season and are probably polyoestrus. The larger species, Epomophorus gambianus, does not appear to compete with the other two due to differences in roosting habits and the food resources available to it consequent upon its larger size. The two smaller species, Micropteropus pusillus and Nanonycteris veldkampi, are similar in size. N. veldkampi is presumed absent from Mole in the dry season when food is scarce; in the wet season it may minimise competition by being better adapted for nectarivory, foraging later, and foraging at a greater height than M. pusillus.

Sexual reproduction in Epistomia bursaria (Bryozoa: Cheilostomata), an endozooidal brooder without polypide recycling

Abstract: Epistomia bursaria L. is unusual amongst cheilostomes in that there is only one polypide generation per autozooid, together with endocoelomic embryonic brooding and larval viviparity. This combination, which gives the minimum possible fecundity of one larva per gynozooid is only known for one other cheilostome species, the majority of the rest being extracoelomic ovicellate brooders with polypide recycling. The greater fecundities exhibited by ovicellate and non-brooding recyclers may offset the smaller degree of protection afforded by these reproductive strategies. Spermatogenesis and oogenesis are examined ultrastructurally. Whereas spermatogenesis is similar to that of other cheilostomes studied previously, oogenesis is very different. The egg at maturity is small and alecithal. Evidence suggests that endozooidal self-fertilization occurs. Whereas nutrient for spermatogenesis and oogenesis is probably intrazooidal in origin, that for embryogenesis is derived inter-zooidally. It is suggested that the combination of endocoelomic brooding, larval viviparity and one polypide generation may be a primitive feature from which recycling and extracoelomic brooding may have evolved.