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Showing papers in "Journal of Animal Ecology in 1971"


Journal Article•DOI•
TL;DR: Hassell & Varley (1969) have recently proposed a new population model for insect parasites in which the searching efficiency of the adult parasites declines exponentially as the density of searching adults increases.
Abstract: The theory of Nicholson (1933) and Nicholson & Bailey (1935) assumes that the searching efficiency of a parasite as measured by its 'area of discovery' is a constant and thus independent of both host and parasite density. Major drawbacks to this simple hostparasite model are (1) the instability of the interactions and (2) that, even if stabilized with an additional density-dependent mortality acting on the host, it is not possible for two or more specific parasites to coexist on the same host species (Varley & Gradwell 1970). Hassell & Varley (1969) have recently proposed a new population model for insect parasites in which the searching efficiency of the adult parasites declines exponentially as the density of searching adults increases. They base this model on the published experimental data for five species of parasites all of which show such a relationship. Fig. 1 reproduces these results and includes an additional relationship for Pseudeucoila bochei Weld. (Cynipidae) parasitizing Drosophila melanogaster Meig. larvae. The range of searching parasite densities in each of these experiments is certainly much higher than one would expect under natural conditions. However, in two of them (a and e) the lowest parasite densities are below ten/m2, which is a density exceeded by some parasites in the field. The model of Hassell & Varley is derived from the linear equations describing the data in Fig. 1: log a = log Q-m logp (la)

258 citations


Journal Article•DOI•
TL;DR: The subject was taken up by Thienemann, and, in 1934, he published a paper on the fauna of various tropical phytotelmata contrasting it with that known from similar water-bodies in the temperate zone.
Abstract: In 1928 Ludwig Varga described the various small water bodies found in or upon plants. He reviewed the observations published up to 1928 and described his own work on the water-bodies found in the leaf-axils of teasels (Dipsacus sylvestris Huds.). He named all such 'plant-waters' 'phytotelmata' (singular: 'phytotelma'). The subject was taken up by Thienemann, and, in 1934, he published a paper on the fauna of various tropical phytotelmata contrasting it with that known from similar water-bodies in the temperate zone. More recently, Thienemann (1954) published a review of all work done in these habitats with reference to the Chironomidae. Thienemann observed that by far the greater variety of phytotelmata were to be found in the tropics but they were also common, although with less variety, in the temperate zone. He classified these habitats on the basis of their position in or on the plant and on the nature of the liquid they contain. To avoid confusion I shall retain his classification in describing the occurrence of phytotelmata. In attempting to collate the information available to date I have listed only those plants from which water-bodies containing or likely to contain animal life have been reported. The survey cannot be complete but is intended to show the wide range of occurrence of these habitats.

200 citations



Journal Article•DOI•

166 citations


Journal Article•DOI•
TL;DR: The fish populations in one soft water and three hard water streams were investigated to determine their growth and mortality rates and, from these parameters and population estimates, their annual production.
Abstract: The fish populations in one soft water and three hard water streams were investigated to determine their growth and mortality rates and, from these parameters and population estimates, their annual production. Previous workers have usually confined their attention to a single species (Ricker & Foerster 1948; Allen 1951; Johnson & Hasler 1954; Watt 1960; Gerking 1962; Warren et al. 1964; Chapman 1965 and Libosvarsky 1968) although Mann (1965) computed the annual production of five species of fish in the River Thames at Reading. In our studies the annual production of the more abundant fish were estimated at each site, the species involved being trout (Salmo trutta L.), salmon (S. salar L.) bullhead (Cottus gobio L.), minnow (Phoxinus phoxinus (L.)), three-spined stickleback (Gasterosteus aculeatus L.) and stone-loach (Nemacheilusbarbatula (L.)). The eel (Anguilla anguilla (L.), brook lamprey (Lampetraplaneri (Bloch)) and, very occasionally, pike (Esox lucius L.) were also caught, but no attempt was made to measure their growth and production. Production is here defined as the total quantity of fish flesh elaborated in a year, regardless of whether or not all of it survives to the end of the year (Ivlev 1966). The units used are grams fresh weight per square metre of stream bed per year. The paper is based on data collected during the period April 1964-June 1967, but the duration of study at any one site never exceeded 2 years (Table 1). Where data on population densities and growth are available for more than 1 year, these have been combined to give mean production estimates for that site.

165 citations






Journal Article•DOI•

125 citations


Journal Article•DOI•
TL;DR: In this paper, the authors investigated the upstream movements of benthic invertebrates in a stony stream and found that these upstream movements were quantitatively unknown and were not related to downstream drift.
Abstract: Benthic invertebrates in lotic systems drift downstream in large numbers (see references in Bishop & Hynes 1969a; Waters 1969), but little is known about compensatory upstream movements. In amphibiotic insects the upstream flight of females may partially compensate for the drift of eggs and larvae (Roos 1957). Muller (1954) proposed the term 'Colonization Cycle' for the whole process of females migrating upstream, oviposition near the source of the stream, and larvae drifting downstream. This hypothesis is applicable to some species of Trichoptera (Roos 1957; Waters 1968; Elliott 1969), but imagines of most species fly in the same direction as the wind and show no persistent upstream movement (Elliott 1967; Bishop & Hynes 1969a). An alternative mechanism is the upstream movement of benthic invertebrates, and this is the only possible mechanism for species which are aquatic throughout their lives. Upstream movements have been recorded for gammarid amphipods (Macan & Mackereth 1957; Minckley 1964; Muller 1966; Kureck 1967; Lehmann 1967; Hultin 1968), crayfish (Momot 1966), stonefly nymphs (Stehr & Branson 1938), and mayfly nymphs (Traver 1925; Neave 1930; Harker 1953; Macan 1957; Leonard & Leonard 1962). Ball, Wojtalik & Hooper (1963) studied the upstream dispersion of radiophosphorus in a Michigan stream and concluded that the radiophosphorus was probably carried upstream by benthic invertebrates. These upstream movements were quantitatively unknown and were not related to downstream drift. Recent studies in a Canadian river (Bishop & Hynes 1969b) and in a Swedish stream (Hultin, Svensson & Ulfstrand 1969) have shown that substantial numbers of invertebrates move upstream. The purpose of the present study was to investigate the upstream movements of benthic invertebrates in a stony stream. This work is part of a general study of invertebrate drift and benthos in the Wilfin Beck, a small stony stream in the English Lake District.


Journal Article•DOI•
TL;DR: Results indicate that, in those natural habitats having a continuous abundant supply of food, young salmon are probably less aggressive than in habitats where they are constantly hungry and meals are sporadic.
Abstract: The distribution and density of every species of animal is at least loosely controlled by the distribution and abundance of its food. Particular attention has been paid recently to the distribution of salmonids as affected by selection of the site of the fish's feeding territory (Chapman & Bjornn 1969) and to their numbers as affected by varying abundance of food in different streams (Egglishaw 1967). Evidence that food supply does more than permit or prevent a population of salmonids from inhabiting a stream is as yet equivocal. Mason & Chapman (1965) found that the biomass and numbers ofjuvenile coho salmon (Oncorhynchus kisutch Walbaum) remaining in two stream channels from which they could emigrate were greater in the channel which had a greater food supply. However, since there was no replicate in which the varying rations were switched between channels, the possibility remained that the channel with the greater food supply retained more fish because of a greater number of hiding places, better cover, etc. In comparing two streams, one of which had three times as much food as the other, Egglishaw (1967) found that there were fewer trout in his food-poor stream, but more salmon, so that the total density of salmonids differed little (about 0 45 fish/m2 in the poor compared to 0 55 fish/m2 in the rich stream). Biomass differed even less. The streams were different in other respects besides food, however, which, in this case, may have masked the effect of food supply on density. Le Cren (1965) suggests that while a population of fish may be limited by food in the long run, in some instances other regulatory mechanisms usually reduce the importance of food supply as a regulatory factor. Effects offood supply on behaviour, in contrast to those on population density, have been reasonably well defined. In laboratory experiments with young salmon (Salmo salar L.), provision of food in two daily feedings was followed shortly afterwards by an increase in aggression which subsided gradually 30 min later (Keenleyside & Yamamoto 1962). Symons (1968) found when aggression was measured after immediate effects of feeding had waned, that fish deprived of food for 18-66 h were more aggressive than those receiving an abundance of food. Together these results indicate that, in those natural habitats having a continuous abundant supply of food, young salmon are probably less aggressive than in habitats where they are constantly hungry and meals are sporadic. Chapman (1962) has postulated that aggression of some territorial fish may cause the emigration of others with inferior fighting ability. Presumably an increase in aggression would speed this emigration process. Symons (1968) also suggested that the increase in aggression associated with food-deprivation might, in a natural environment, result in an


Journal Article•DOI•
TL;DR: This paper, which is part of a 4-year study on the ecology of L. lugubris, attempts to elucidate the close association of this spider with woodlands.
Abstract: Wolf spiders belong to the family Lycosidae, a group of ground-dwelling spiders which are among the largest and most conspicuous members of the terrestrial invertebrate fauna of temperate regions. Adult females of the European representatives of the genus Lycosa are about 6 mm in length. Lycosids have relatively good eyesight, by spider standards (Homann 1931) they are good sprinters and they do not make use of silk to catch their prey. They are said to chase and catch their prey (Savory 1928; Nielsen 1932; Bristowe 1958) although this has been questioned (Edgar 1969). The egg mass is wrapped in a layer of silk and this cocoon or egg sac is carried by the female, attached to her spinnerets. Their large size, conspicuousness and high density in favourable habitats, makes them very suitable for population studies. The wolf spider, Lycosa lugubris (Walckenaer), occurs over the whole of Western Europe, from Finland in the north to Spain and Italy in the south. It is found in Asiatic as well as European Russia (Bristowe 1939), and has also been recorded in Japan (Yaginuma 1962). Most authors describe its habitat as being in or near woods (Dahl 1908; Norgaard 1945; Locket & Millidge 1951; Wiebes 1959; Hallander 1967a). Locket & Millidge say 'it never seems to occur far from woods' while Wiebes says it is 'very common in clearings in woods'. All the specimens of L. lugubris which I have taken in Scotland have been collected in or near deciduous woodland. This paper, which is part of a 4-year study on the ecology of L. lugubris, attempts to elucidate the close association of this spider with woodlands. This has been done by studying the life-cycle, and the habitats occupied by the spider at different stages in its life-cycle. Most of the field work was carried out in an oak woodland (Quercus petraea (Matt.)) near Glasgow University Field Station on the Ross Peninsula on the east bank of Loch Lomond. The average height of the trees was between 40 and 50 ft and they were 70-100 years old. Clearings had been made in a number of areas to allow for the planting of conifers. Vaccinium myrtillus L. is the dominant plant over large areas of the Peninsula while Pteridium aquilinum (L.) is dominant in places. In this paper frequent reference is made to whether the sampling areas are shaded or whether they are situated in clearings. Reference is made to eight sampling areas. Areas I and 2 were partly shaded, areas 3-6 were shaded and areas 7 and 8 were in clearings.



Journal Article•DOI•
TL;DR: This account will compare and contrast the changes occurring in two populations of Neophilaenus lineatus at the edge of the species' range on the Pennine hills (over a period of 9 years) with a population from lowland southern England during 6 years.
Abstract: The majority of published population studies of animals consider the circumstances pertaining to a single population in a given type of habitat. Yet authors such as Huffaker (1958), Clark et al. (1967) and Klomp (1962) have emphasized the importance of distinguishing between 'salubrious and hazardous environments' (Huffaker 1958), in interpreting a study and in particular when attempting to reconcile the seemingly polarized views of the theorists. Of course, it will not necessarily be possible in a particular case to define a habitat as salubrious or hazardous since there will be every gradation between these extremes. It should, however, be possible to study a population living in a habitat which is representative of the broad conditions under which this species is observed to live and thrive and to contrast this with a population which has been specifically chosen because it is living at the extreme edge of the species' range. In 1965 I published an account of a short-term study of a cercopid (Neophilaenus lineatus (L.)) living at high altitude in the Pennine hills of northern England (Whittaker 1965a, b). This did appear to be on the verge of extinction as judged by the fact that it became temporarily extinct at only slightly higher altitudes. This same species occurs throughout Britain in areas of uncultivated grassland. The study has since been extended with the aim of comparing these populations with one in a low-altitude grassland in southern England at Wytham Woods, Berkshire. As far as can be judged from knowledge of the distribution and biology of N. lineatus, this latter habitat is favoured by the species whilst the populations on the Pennines are living in a peripheral, hazardous environment. The grassland known as Upper Seeds at Wytham Woods also supports two other species of cercopid, and one of these, Philaenus spumarius (L.), shares a pipunculid parasite Verrallia aucta Fallen with Neophilaenus lineatus. They differ, however, in the important respect that N. lineatus feeds exclusively on monocotyledons and Philaenus spumarius on dicotyledons. This account will compare and contrast the changes occurring in two populations of Neophilaenus lineatus at the edge of the species' range on the Pennine hills (over a period of 9 years) with a population from lowland southern England during 6 years.

Journal Article•DOI•
TL;DR: Pollination in Pancratium was studied, under the unique climatic conditions of the sea shore habitat, especially the effects of wind on pollination and seed setting.
Abstract: Pancratium maritimum L. grows wild in the light soil belt of the coastal plain of Israel, from the sea-shore to the sandy plains further inland. The habitat of P. maritimum in the immediate vicinity of the sea is characterized by direct exposure to sea breezes and to continuous sprays or salt water droplets carried by the wind, by strong radiation and by high air humidity. These characteristics become less pronounced as the distance increases from the sea. In close vicinity to the sea, Pancratium participates in the plant association of Sporobolus arenarius (Gou.) Duv.-Jouv.-Lotus creticus L. which occupies the sandy beach and the high sandy-loam shores (Eig 1939). Here, this species often produces dense stands. Our present purpose was to study pollination in Pancratium, under the unique climatic conditions of the sea shore habitat, especially the effects of wind on pollination and seed setting.



Journal Article•DOI•
TL;DR: The populations in colonies of Vespula vulgaris and V. germanica adults collected in suction traps at Rothamsted during 1960-61 (Taylor 1963) were examined and the number of generations of wasps produced per cell was determined by counting the faecal pellets in each.
Abstract: Total counts and estimates of the populations of wasp colonies have been made by several authors (e.g. Weyrauch 1935; Richards & Richards 1951; Blackith & Stevenson 1958; Kemper 1961; and Kemper & Dohring 1961) and their population dynamics have been discussed by Bodenheimer (1937) and Brian (1965). The only information about seasonal changes in vespine colonies is a little on hornets by Janet (1895), Ishay (1965), and by Ishay, Bytinski-Salz & Shulov (1968). This paper describes the populations in colonies of Vespula vulgaris (L.) and V. germanica (F.). In 1961, fifty-nine colonies of V. vulgaris and thirty colonies of V. germanica were collected within a 10 km radius of Rothamsted Experimental Station. A further twenty-three colonies were discovered but not sampled. Colonies were killed at intervals during the season with dieldrin or chloroform. Returning wasps that remained outside the nest overnight were caught. The combs, cells, immature stages and adults were counted in each nest, and the number of generations of wasps produced per cell was determined by counting the faecal pellets in each. Cells were measured with calipers. In each foundress queen, the six pairs of ovarioles were examined; and in each ovariole the number of eggs equal in size to, or larger than, the nurse cells ('ovariole index', Cumber (1-949)) was determined. V. germanica adults collected in suction traps at Rothamsted during 1960-61 (Taylor 1963) were also examined.

Journal Article•DOI•
TL;DR: The ecological distributions and general behaviour of the species are described from field observations, and their feeding habits and important morphological adaptations are briefly considered, and the correlations between the distribution in nature and each species' behaviour towards certain habitats under laboratory conditions are described in an effort to determine whether there are differences which might be due to competition for space or food.
Abstract: Brachyuran crabs of the families Grapsidae and Ocypodidae usually have a rectangular, more or less straight-sided carapace with a wide anterior edge and prominent eyestalks reaching to the lateral angles. They are typically intertidal animals and in Tasmania are the most abundant and diverse crabs of this zone. Nine species of grapsid crabs and two ocypodids occur in Tasmania. At many localities several of the eleven species can be found on the one area of beach flat under the same boulder or under adjacent stones or in adjacent burrows. Ovigerous (egg-bearing) females of most species can be found together in summer. Some species seem to be equally abundant on a number of different types of shore whereas others are found on one or, at most, two types of shore. Some of the now familiar questions arising from such observations are the following. What factors are determining the distributions of the species? Are there any differences between the species' potential distributions and their observed distributions, i.e., are their distributions importantly limited by interspecific competition? If not, how is competition avoided in those situations where several species occur together. It is with answers to these kinds of questions that this study is concerned. The term 'competition' is used here in the sense preferred by Birch (1957) to describe the situation where a number of animals (of the same or different species) utilize common resources the supply of which is short, or if the resources are not in short supply, when the animals seeking those resources nevertheless harm one another in the process-see also Andrewartha & Browning (1961), Browning (1962) and Park(1962). The term 'niche' is used here as defined by Hutchinson (1958) to mean the multidimensional hypervolume delimited by all the environmental states which allow that species to exist indefinitely. In this paper the ecological distributions and general behaviour of the species are described from field observations, and their feeding habits and important morphological adaptations are briefly considered. The temporal fluctuations in intensities of breeding are briefly described, the number and relative volume of the gills, the structure of the mouthparts and arrangement of hairs on them are considered in relation to each species' behaviour and the habitat in which it occurs. Finally, the correlations between the distribution in nature and each species' behaviour towards certain habitats under laboratory conditions are described in an effort to determine whether there are differences which might be due to competition for space or food. The nine grapsids occurring in Tasmania are listed below by their scientific name and their common name (where one is available).

Journal Article•DOI•
TL;DR: In this article, it was shown that females that have completed oviposition are much less attractive to males on contact and though about 35% of post-oviposition females copulate as a result of their first encounter, only about half of them will have begun genital contact even if allowed six encounters with males.
Abstract: Females in all stages of their reproductive cycle around dung are equally attractive in eliciting encounters from searching males. On contact, all females which still have eggs to lay are mated (or remated), generally (i.e. over 75%) in their first encounter. All such females copulate for a normal duration, irrespective of previous matings. However, females which have completed oviposition are much less attractive to males on contact and though about 35% of post-oviposition females copulate as a result of their first encounter, only about half of them will have begun genital contact even if allowed six encounters with males. The female behaviour does not appear to be involved in this effect. Matings with post-oviposition females last only 43% of the normal duration. This effect may be due at least in part to the side to side ('swaying') movement performed by the female. It is extremely rare in nature for females to oviposit without a male mounted in attendance (i.e. in the 'passive phase'), though females will do so quite readily if separated artificially. The female initiates separation only after all the egg batch is laid, and after separation she flies immediately upwards and away from the dropping. Female quiescence appears to be necessary for the male to adopt the passive phase; swaying during genital contact and immediately after precedes separation without a passive phase. Females remain quiescent if they still have eggs to lay (even when already mated) and fresh dung is present, though the continuous reception of fresh dung is not necessary. Females sway fairly persistently if they have completed oviposition or there is no dung stimulus. Most females examined on arrival at the dropping (and before being found by a male) already had sperm in their spermathecae, presumably from matings at previous ovipositions since all females mate on arrival at the dung and there are several successive batches of eggs. It is predicted that receptivity before all the eggs are laid may now be of selective advantage to the female. The performance of non-receptivity as exhibited by post-oviposition females involves the female in an average rejection delay of 2.7 min. per encounter. At the average density of searching males present on the dung this rejection delay time would involve the female in much more time waste than full receptivity, since after mating the passive male undertakes the rejection of other males during oviposition. Even allowing for time wasted in recopulation following take-over (i.e. when a second male takes possession of the female), a female with full receptivity would save about 50 min. per oviposition cycle compared to one showing rejection. The passive phase is presumably of advantage to the male in preventing further inseminations, sperm from which could compete with his own for the fertilisation of the female's eggs. After oviposition, the female initiates termination of the passive phase by swaying reactions which cause the male to dismount. She then flies from the dropping.

Journal Article•DOI•
TL;DR: The present study deals with the production and energetics of Leptopterna dolabrata, a mirid bug, with this characteristic, which has been studied and the various stages described.
Abstract: There is little published information on annual production and energy flow in low density insect populations. Most natural populations are of low density and the present study deals with the production and energetics of Leptopterna dolabrata (L.), a mirid bug, with this characteristic. The lifecycle has been studied and the various stages described by Osborne (1918), Tullgren (1919), Garman (1926), Kullenberg (1946) and Jewett & Townsend (1947). Briefly L. dolabrata is univoltine, the eggs, laid in late June and early July, enter diapause at a very early stage of embryogenesis (Cobben 1968) and do not hatch until the following May. The nymphal stages are of short duration and adults first appear in mid-June. These mature in about 10 days and the females usually lay all their eggs into the bases of the grass stems within 24 h. The detailed numerical population data will be published in a separate paper.

Journal Article•DOI•
TL;DR: A population model of the cabbage aphid, its parasite, and other natural enemies is put to work to examine stochastic variation of population numbers, the parasite's strategy and a field test of the model's predictions for biological control.
Abstract: This paper describes three developments of our studies on aphid populations. A previous paper (Hughes & Gilbert 1968) described a population model of the cabbage aphid (Brevicoryne brassicae L.), its parasite (Diaeretus rapae Curtis), and other natural enemies. The model uses a physiological time-scale with aphid instar-periods as units. Here we put the model to work to examine (1) stochastic variation of population numbers, (2) the parasite's strategy and (3) a field test of the model's predictions for biological control. In the original model the development time of the mature parasite was given as nine aphid instar-periods. This was known to be rather too long, but, as the parasite had such scant effect on the aphid population, a more accurate estimate was not sought. No generally applicable value can be given because of the difference in the apparent temperature thresholds of parasite and aphid (Hughes 1963), but at the ambient temperatures of the local populations, parasite development lasting 71-8 instar periods is more realistic.

Journal Article•DOI•
TL;DR: To evaluate the incidence and intensity of predation on each of the four species of triclad in habitats ranging from stony to weedy shores, a serological approach was used which produced four specific antisera which reacted with the remains of ingested triclads but not against the predator itself or other prey organisms.
Abstract: It is the purpose of this paper to evaluate the incidence and intensity of predation on each of the four species of triclad in habitats ranging from stony to weedy shores with particular reference to two questions. Firstly, can predation on either a stony or weedy shore reduce populations of triclads below the level atwhichcompetition for food operates; secondly, are some species of triclads preyed on more heavily than others? A direct study of predation by the examination of the gut contents of predators or their faecal pellets cannot be used successfully for soft-bodied prey such as triclads. For the detection of such non-visually identifiable remains of triclads consumed by predators, a serological approach was used. In essence, four specific antisera, one against each species of triclad were produced which reacted with the remains of ingested triclads but not against the predator itself or other prey organisms. Initial cross reactions were absorbed out and specific rabbit antisera produced against Polycelis nigra, and Dendrocoelum lacteum. Loss of sensitivity after absorption prevented the preparation of a specific anti-Polycelis tenuis serum and therefore an antiserum which retained sensitivity but cross-reacted with P. nigra to a slight degree was used. Until recently (Reynoldson & Davies, in press) distinction between Dugesia polychroa and D. lugubris was not made, the two species being recorded under the name D. lugubris. The anti-D. polychroa serum reacted with D. lugubris but this is unlikely to have influenced the data since most habitats contained only D. polychroa. In the three habitats which supported both species D. lugubris was very much in the minority. For all serological tests Morris's (1964) version of the modified Oakley-Fulthorpe method (Preer 1956) was employed with the macerate


Journal Article•DOI•
TL;DR: To obtain if possible a more general correlation between age and root development, an attempt was made to stain the calcium being laid down in the roots at standard intervals of time, by injecting the voles with sodium alizarine sulphonate, a water-soluble and acid dye, used for gross skeletal staining.
Abstract: In the bank vole (Clethrionomys glareolus (Schr.)) the relatively large first molar in the mandible has been a natural choice as an indicator of age (Zimmermann 1937; Wasilewski 1952; Koshkina 1955; Zejda 1961; Mazaik 1963), chiefly because, although rootless when it first erupts, an oral and aboral root are developed subsequently, and these then continue to grow throughout life until, in old age, only the roots remain, the entire crown having been worn away. Various estimates of the time taken for roots to develop and of their subsequent growth rate have been made by different authors, some using large samples of animals from the field, collected after different intervals of time, while others have used laboratory animals of known age, or a combination of both sources of material. Partly because of the different methods used, and partly for other reasons, discussed later, estimates of the age at which the molars first begin to develop roots have varied widely, ranging from 2 months (Wasilewski 1952) to 6 months (Zimmermann 1937), and the rate of growth of the roots has been estimated to vary between 0-12 and 0-161 mm/month, averaging 0d15-016 mm/month (Zejda 1961), but only teeth from individuals 11-16 months of age were measured. To obtain if possible a more general correlation between age and root development, an attempt was made to stain the calcium being laid down in the roots at standard intervals of time, by injecting the voles with sodium alizarine sulphonate, a water-soluble and acid dye, used for gross skeletal staining. Both laboratory and field populations were used in these experiments, which were carried out under licence from the Home Office at the Bureau of Animal Population in Oxford, and in some nearby woodlands on the Wytham estate between 1954 and 1957.