Similar Habits Research Articles

Morphological adaptations of the digestive tract of tropical cyprinids and cichlids to diet

Eight cyprinids with four different feeding habits fall into two distinct groups according to morphological adaptations of the intestine: (i) carnivorous and omnivorous cyprinids with large gut diameter and large mucosal surface which decreases from the foregut to the hindgut; (ii) benthivorous and phytoplanktivorous cyprinids with small gut diameter and small mucosal surface which is more or less uniformly built along the intestine, although relative gut length may vary considerably (1.45–6.10). Although the intestine of phytoplanktivorous cyprinids is extremely elongated, it appears less adapted for processing a refractory diet than that of cichlids with similar feeding habits.

MICROPROPAGATION OF AZALEAS USING THIDIAZURON

Rhododendron sp., deciduous azaleas are routinely grown in vitro using N°C-(2-isopentenyl)-adenine (2ip) as the cytokinin. Actively multiplying cultures of cvs. 'Gilbraltar', 'Peachy Keen', and 'Tobasco' were placed onto a woody plant medium containing various concentrations of N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron, TDZ) to determine whether TDZ could be substituted for 2iP. The deciduous azaleas tested were highly responsive to TDZ and sensitivity varied with cultivar. Plants were grown on in vivo to observe any affect of TDZ on older plants. Thidiazuron was then tested at a wider range to determine the optimal concentration for proliferation, shoot quality, and growth. Proliferated cultures underwent a cold treatment to determine if TDZ's activity is temperature dependent. TDZ in combination with 2iP was tested to see if there was a synergistic affect using both compounds. TDZ has powerful cytokinin activity, yielding many shoots of lesser quality due to compact vitrified growth. Shoots did not elongate when exposed to cold temperatures. The combination of TDZ and 2iP resulted in greater adventitious shoot production and improved quality (nonvitrious) well formed shoots. Plants grown on in the greenhouse were of similar phenotypic habit regardless of the growth regulator used.

Die Entwirrung desBotrytella(Sorocarpus)-Komplexes (Ectocarpaceae, Phaeophyta)

Sorocarpus Pringsh. is a later synonym forBotrytella Bory. Four species of the genus are known from northern European coasts. Three of them are found at Helgoland (North Sea), type locality of bothBotrytella uvaeformis (Pringsh.) andB. reinboldii (Reinke). A third species, most frequently seen, still remains unnamed. Plants of similar habit, however, have been described from Japan. The type species for the genus,Botrytella micromora Bory, was originally published asEctocarpus siliculosus β.uvaeformis by Lyngbye. A sample from Danish waters proved to be identical with it. In a previous paper (Kornmann & Sahling, 1984), the life history of two species was studied and the investigation is now extended to include the other two, demonstrating the conformity of the four species with the genus characters as to morphological and developmental features.

Renal Structure and Body Size in Heteromyid Rodents

The relationship between body size (i.e., body mass, surface area, and relative surface area) and urine concentrating ability (via renal morphology) was determined using six sympatric species of heteromyids. These rodents share similar feeding habits and life histories but differ in adult body size. When variables such as ecological distribution, dietary habits, and other aspects of an animal's life history are reduced, renal morphology is highly and negatively correlated with body size; small heteromyids have relatively thicker medullae and presumably greater urine concentrating abilities than large ones. Renal medullary thickness is as strongly correlated with body mass as with measurements of surface area and mass-specific surface area.

Trapping Techniques and Attractants for Cetoniinae and Rutelinae (Coleoptera: Scarabaeidae)1

Techniques developed for attractancy tests for the Japanese beetle, popalia Japonica Newman, were used to test synthetic chemicals as lures for species in the subfamilies Cetoniinae and Rutelinae, which are closely related to the Japanese beetle and have similar habits. Of 21 compounds successfully tested, 6 were highly attractive to Cetoniinae, particularly to Oxythyrea spp.; 4 were attractive to the Rutelinae, particularly to Adoretus spp. and Anomala spp .

Environmental Effects on Seed Yield and Other Characteristics of Irrigated Soybeans Differing in Growth Habits

Three soybean cultivars, 'Williams' (Dt,-indeterminate), 'Will' (Dt2-semideterminate), and 'Elf (dt,-determinate), with similar genetic backgrounds but various growth habits, were grown to evaluate their responses to different management practices. Cultivars were grown at two northeastern Kansas irrigated locations (Ashland and Rossville), in two planting dates (May and June), two row widths (38 and 76 cm), and two plant populations (30 and 60 plants/m2) in 1978 and 1979. Cultivar, population, and row width did not significantly influence seed yield in most of the environments. An exception was enhanced yields from narrow rows and high populations in a late planting at one location. Although late planting significantly lowered some seed yields, late plantings showed no yield differences in more than half of the treatments. Lodging scores normally fell within acceptable limits, except when high populations of the tallest cultivar, Williams, was planted in narrow rows. However, height of the first pod of Elf presented a potential problem associated with harvest losses. Considerable research effort has been expended to improve soybean seed yield, especially through breeding new cultivars and developing more efficient productive management practices. Recent research has shown that determinate and semideterminate cultivars adapted to the northern USA production region may have some advantages over taller indeterminate types. Determinate and semideterminate cultivars' reduced plant height resists

Notes on the diet of the carnivorous mammals of the Upper Henty River Region, western Tasmania

All four of Tasmania's large mammalian carnivores (Sarcophilus harrisii, Dasyurus maculatus, D. viverrinus, Felis catus) occur in the Upper Henty River region~ in western Tasmania. A short-term study was undertaken to compare the diet of these species when in sympatry. No data were obtained for D. maculatus. The other species overlapped in their use of small mammals. However each species had a major component of the diet (S. harrisii, large mammals; D. viverrinus, invertebrates and plant material; F. catus,birds)which was not utilized by the other species and hence substantial competition between them is unlikely. The diet reported others for D. maculatus is similar to that found for F. catus. These two species had similar habit preferences and hence it is possible that competition could occur between the native D. maculatus and the introduced F. catus.

Glassy Microspherules from Bomb Combustion of Charcoal

Glassy microspherules, typically 200μm or less in diameter, are well documented from a variety of terrestrial and extraterrestrial sources (Baker, 1959, p 192–198; Glass, 1969; Rost, 1969; McKay, Greenwood & Morrison, 1970; Mueller & Hinsch, 1970; Cross, 1971; O'Keefe, 1980). To these we would add the formation of microspherules of similar habit when wood charcoal is burned in a combustion bomb (Barker, Burleigh & Meeks, 1969; Burleigh, 1973, 1974; Switsur, 1973; Switsur et al, 1974) as a first step in the chemical synthesis of samples for 14C age measurement. The glassy material of these spherules originates from fusion at the high temperatures reached during the combustion, of traces of alkali-metal minerals in the charcoal and silica bodies (phytoliths) within its microstructure. Other materials commonly burned, such as bone collagen, do not yield microspherules. The age and source of the charcoal are immaterial, though different species (and perhaps other woody plant materials) may be more-or-less productive of spherules. Here we give a brief summary of the characteristics of these glassy microspherules, based on optical and scanning electron microscopy and energy-dispersive x-ray analysis.

Comparisons of Growth in Weight of Temperate and Tropical Marine Fish Counterparts

For temperate and tropical marine teleosts I compared growth in mean weight with age with similar trophic positions and ecological habits. Temperate demersal forms generally grew faster than tropical counterparts whereas mesopelagic and pelagic forms were similar. I suggest that differences in growth rates may be related to higher metabolic costs in the tropics in comparison with temperate waters.

Cigarette smoking, physical activity, and alcohol consumption: Relationship to blood lipids and lipoproteins in premenopausal females

A total of 164 premenopausal female subjects were randomly selected for evaluation from a much larger pool of volunteers. The relationships between blood lipid and lipoprotein levels as dependent variables and cigarette smoking, physical activity, and alcohol consumption were determined from partial regression coefficients. A lower HDL-C level (10.1 mg/dL) was seen in smokers v nonsmokers. For each ounce of alcohol consumed, HDL-C level was higher by 2.8 mg/dL, and greater physical activity was associated with a higher HDL-C level of 8.6 mg/dL. An analysis of covariance with covariance adjustments for age and body fat revealed that smokers who regularly exercise or consume alcohol had significantly lower HDL-C levels than nonsmokers with similar habits. Subjects who both exercise and consume alcohol demonstrated higher HDL-C levels than those who indulge in one or the other separately. Results suggest that cigarette smoking may attenuate the effects of chronic exercise or alcohol consumption, or of both, to raise HDL-C levels. Also, chronic exercise and alcohol consumption may exert an additive effect, raising HDL-C level.

Trophic Resource Allocation between Percina sciera and P. ouachitae in the Tombigbee River, Mississippi

Aspects of the trophic ecology of Percina sciera and P. ouachitae from a site on the Tombigbee River, Mississippi, were compared to: (1) determine the extent of seasonal, sexual and size class trophic allocation in the two species; (2) describe the feeding habits of the two species and compare these habits to a syntopic group of benthic fishes, and (3) determine whether a relationship exists between predator morphology and prey characteristics. The two species had similar diets which corresponded closely to diets for darters of similar habitats. There were small qualitative differences in diet, and gut content changed seasonally in both species. Percina sciera took larger prey than P. ouachitae in the autumn, and this was related to differences in fish size (standard length). Males and females differed in prey size selectivity and the differences were greatest in the spring. With the exception of standard length, no morphological trait of the two species was highly correlated with prey size. Trophic competition is likely of minor importance between these species. INTRODUCTION One means by which species of similar habits may coexist is by allocation of trophic resources (Schoener, 1974a). The gut contents of sympatric fishes of similar feeding habits may differ in prey kind (e.g., Hartley, 1948; Keast, 1966; Mathur, 1972), actual prey length (e.g., Northcote, 1954; Tyler, 1972; Ross, 1977; Yoshiyama, 1980); and prey may be selected on the basis of prey size (O'Brien et al., 1976) or prey evasiveness (Vinyard, 1980). Trophic resource partitioning may also be effected by ontogenetic use patterns (Ross, 1978; Nakashima and Leggett, 1978; Fahy, 1980). Limiting morphological similarity relating to the trophic function of the species within the community may also be important (Hartman, 1958; Werner, 1974; Montgomery, 1977; Smartt, 1978; Gatz, 1979b; Ricklefs and Travis, 1980). Studies of resource partitioning are best carried out on functional groups of species, or guilds (Root, 1967; Krebs, 1978), which exploit a common resource base in a similar way and in which competition is expected to be greatest. Comparative studies of the trophic ecology among guilds of fishes are common (e.g., Hartley, 1948; Northcote, 1954; Keast and Webb, 1966; Keast, 1966, 1978; Thomerson and Wooldridge, 1970; Tyler, 1972; Ross, 1977; Yoshiyama, 1980). However, even though the feeding habits of benthic stream fishes have been studied (e.g., Scalet, 1972; Page and Smith, 1970; Page, 1974; Schenck and Whiteside, 1977; Burr and Page, 1978), fewer studies are available which directly compare the food habits of closely related darters (Percidae). Cordes and Page (1980) compared aspects of the trophic ecology of Etheostoma zonale and E. microperca in Illinois. Adamson and Wissing (1977) observed the diets of E. careruleum, E. flabellare and E. zonale in an Ohio stream. Daiber (1956) compared the food habits of the darter E. flabellare with Cottus bairdi in New York, and Thomas (1970) examined diets of four species of darters in Illinois. This study describes aspects of the trophic ecology of two ecologically and morphologically similar darters, Percina sciera and P. ouachitae, from the Tombigbee River in Mississippi. I compare diet complement, prey size and volume and the morphology of trophic structures, as well as seasonal, size class and sexual differences in diet. I evaluate one assumption of the ecomorphological model (Gatz, 1979a) by comparing 'Present address: Department of Entomology, Mississippi Entomological Museum, Drawer EM, Mississippi State, Miss. 39762.

The effects of sample preparation and measuring techniques on the shape and shape characterization of mineral particles: The case of wollastonite

Shape characterization of mineral particle populations based on a regression analysis of log width dependency on log length was previously shown by H. G. Siegrist and A. G. Wylie (1980, Environ. Res. 23, 348–361) to provide a quantitative basis for distinguishing asbestos from other mineral particles. The derived equations are of the form log width = F log length − b, where F is called the fibrosity index. The sensitivity of F to sample preparation and measuring techniques is evaluated for the mineral wollastonite. A sample of wollastonite was ground by five different techniques in commercially available mills. There were two grinding times for several of the mills. The samples were sieved and representative particles were measured by SEM and PLM. The major results are (1) the accuracy of the shape characterization can be affected by sieving and instrumentation, the range over which length measurements are made, and the number of particles measured; (2) the different methods of grinding have only minor effects on the fibrosity index F; (3) F is essentially independent of particle size, i.e., SEM versus PLM; (4) variations in F between groups of minerals of similar habit far exceed variations due to sample preparation and measuring techniques. These results are valid only for wollastonite and further work is necessary before they can be extrapolated to all fibrous minerals, especially to particles collected on air or water monitoring filters.

Photoreactivation in two closely related marine fishes having different longevities

The tautog, Tautoga onitis, and cunner, Tautogolabrus adspersus, are marine fishes which are closely related taxonomically (family Labridae), have similar habits, the same ecological requirements and are found in the same areas. However, they differ markedly in their longevity. The tautog is longer-lived, reaching an estimated average age of 34 years. It attains sexual maturity at 3–4 years of age. The cunner, on the other hand, lives to about 5–6 years of age and is sexually mature at about one year. An examination of their respective capacities for photoreactivation using cells in tissue culture derived from these fishes revealed marked differences in the rate of monomerization of ultravioletinduced pyrimidine dimers from their DNA. Radiochromatographic analysis of dimers in the tautog showed that half the dimers were removed within a period of 10 min of exposure to photoreactivating light whereas a 50-min exposure was required to photoreactivate dimers to this same level in the cunner. Dark repair of dimers was measured by radiochromatography and by endonuclease assay. The two methods showed similar low levels of excision repair in both species.

Resources: Food Waste is Energy Waste

Americans waste energy when they waste energy-intensive food, which requires one-sixth of the nation's energy resources to produce, distribute, and prepare. A two-year University of Arizona study of household food waste that divided refuse into straight waste and plate scrapings found that 9% of purchased food was thrown away, and over half that was discarded untouched. Samplings from schools, restaurants, and other institutions reveal similar habits. More food is discarded in the fields and processing plants. A California group (the Gleaners) is among those trying to eliminate harvesting waste, while urban groups are salvaging store and restaurant throwouts. A conscious effort by an informed public can lead to a more-efficient use of food and energy. (DCK)

Distribution of Palm Fruits on a Rain Forest Floor: Why White-Lipped Peccaries Forage near Objects

Litter and soil disturbance in the wake of white-lipped peccary (Tayassu pecari) herds in southeastern Peru indicates that these animals often forage intensively at the bases of such as trees, exposed roots, logs, and lianas. I sampled the litter and soil near such objects on the forest floor, and found that fruits of the common palm trees were encountered more frequently near objects than in the open. This pattern was especially well marked for seeds of an Astrocaryum palm having a very restricted fruiting season. Where had recently foraged, densities of some fruit types were significantly reduced near objects. Apparently the peccaries are consuming palm fruits that have been scatterhoarded by rodents. WHITE-LIPPED PECCARIES (Tayassu pecari) occur in larger groups than any other terrestrial mammal in neotropical rain forests. Their herds, which may contain over 100 individuals, leave broad areas of overturned litter and disturbed soil wherever they have foraged. During a study of white-lippeds in southeastern Peru, I invariably noted that soil and litter disturbance in the wakes of herds was concentrated near certain objects-at the' bases of plant stems, along logs and exposed roots, and beneath lianas and low shrubs with dense foliage. One possible explanation for this observation was that the were searching for invertebrates in such places, as Ewer (1970) suggested to explain similar habits of the African forest hog Hylochoerus meinertzhageni. However, the extent of the disturbance seemed disproportionate to the small amounts of invertebrate body parts found in white-lipped stomachs (Kiltie 1980). Another possibility was that the peccaries were searching for fruits with hard endocarp at these places, since stomach contents, feeding experiments with captive animals, and anatomical evidence (Kiltie 1980) indicated that are distinguished by their ability to masticate very hard fruits and seeds. This explanation was further suggested by the fact that elsewhere in the neotropics, agoutis (Dasyprocta punctata) and squirrels (Sciurus granatensis) have been observed scatterhoarding fruits along tree bases, logs, roots, and beneath lianas (Smythe 1978: 26; Heaney and Thorington 1978; Morris 1962). Thus it was conceivable that were exploiting hard fruits that had been stored by rodents. The study described in this report was designed to see if palm fruits were more abundant near objects than elsewhere on the forest floor and to see if whitelipped peccaries were harvesting such fruits.

A Reevaluation of the Sorapillaceae

The Sorapillaceae has been placed by some authors either near the Fissidentaceae or in the Eubryales suborder Rhizogoniineae because of its peculiar leaf structure closely resembling that of the Fissidentaceae and what was appar- ently a single peristome. Examination of the peristomes of Sorapilla sprucei Mitt. and S. papuana Broth. & Geh. revealed that the peristome is double and reduced. On the basis of the reduced double peristome, pseudoparaphyllia, complanate leaves, immersed lateral sporophytes, pleurocarpous habit, elongated basal cells in the leaves, and a sparsely hairy calyptra, a placement of the Sorapillaceae in the Isobrvales near the Neckerineae, as advocated by Fleischer, is correct. The genus Sorapilla was established by Spruce and Mitten (in Mitten 1869) to accom- modate a single species, S. sprucei, from Ecuador. In 1900 Brotherus and Geheeb (in Brotherus 1900) described an additional species, S. papuana from New Guinea. The genus was placed by Mitten (1869) in the Skitophylleae (which included Fissidens, Eustichia and Bryoxiphium) primarily on the basis of its distichous and equitant leaves. Fleischer (1907) considered Fissidens and Sorapilla to have little natural relationship to one another. In his view, the leaves of Sorapilla and Phyllogonium were closer to each other than either was to the leaf of Fissidens. Thus, he placed Sorapilla in its own family, the Sorapillaceae, in the Isobryales near the Phyllogoniaceae. According to Fleischer, Sorapilla exhibited a close relationship with the Neckeraceae by its similar habit, its peristome-which he considered to be rudimentary and diplolepideous-and its hairy ca- lyptra. Brotherus (1909), like Mitten, placed Sorapilla in the Fissidentaceae on the basis of leaf structure and the apparent single row of peristome teeth, which have, unlike the exostome of a typical diplolepideous moss a single row of scales dorsally. In 1924, however, Brotherus recognized the family Sorapillaceae, and placed it in the Eubryales, suborder Rhizogoniineae, with which it shares a two-rowed complanate leaf arrangement and erect, regular radially symmetrical sporophytes. Dixon (1932) also maintained the Sorapillaceae in the Eubryales, suborder Rhizogoniineae, which he felt represented a heterogeneous group of variably developed mosses, often with a single peristome ... Sorapilla is a pleurocarpous moss. This is evidenced by the immersed and laterally borne sporophytes and by foliose pseudoparaphyllia (Fig. 1). The latter character is one found only in certain pleurocarpous mosses (Ireland 1971). The distichous and equitant leaves of the Sorapillaceae, which also possess vaginant laminae and both dorsal and ventral laminae, very nearly approach the leaf structure of the Fissidentaceae, as was observed by Salmon (1899). The leaf cells are elongated at the base (Fig. 2), isodiametric above, and enlarged and hyaline along the edge of the vaginant laminae forming a border

Flies associated with cattle in south west Scotland during the summer months

The sheep headfly, Hydrotaea irritans, and Morellia simplex were the species most frequently associated with cattle at pasture and comprised 69.01 per cent and 13.93 per cent, respectively, of the total fly collection made from grazing cattle. The most prevalent biting fly was Haematobosca stimulans which comprised 4.46 per cent of the total catch. A few clegs, Haematopota pluvialis, and horse flies, Hybomitra distinguenda, were also recorded. A few of the headflies swarming around cattle entered milking parlours and byres and made up, at 38.23 per cent, the highest percentage of the total fly collection from these buildings. Headflies congregated on the windows, particularly those in the roof. Lesser numbers of the flies, Hydrotaea albipuncta, Morellia simplex and Trichopticoides decolor, with similar feeding habits to H irritans were also collected from these windows with a number of those species attracted to excrement. The biting muscids, Stomoxys calcitrans and Haematobosca stimulans, were collected mainly from the outside surfaces at the entrance to milking parlours and byres and comprised 23.53 per cent and 11.18 per cent, respectively, of the total fly collection from these buildings. Stomoxys calcitrans, the stable fly was present on every sample taken from calf houses and comprised 63.79 per cent of the total fly collection from these houses. Two other species, Sepsis violacea and the common housefly Musca domestica, were present on occasions in significant numbers and comprised 20.69 per cent and 9.48 per cent, respectively, of the total fly collection from calf houses.

Tobacco smoking habits and attitudes of Australians with oral mucous membrane keratoses

The purpose of this study was to ascertain whether or not a relationship existed between the presence of oral mucous membrane keratoses and tobacco smoking habits. Two groups of tobacco smokers, one group exhibiting oral mucous membrane keratoses, and the other no such changes, were chosen for their similar smoking habits. Detailed tobacco smoking histories of each group were ascertained. Similar results for both groups, in terms of the number of years of smoking, quantity of tobacco consumed dialy, type of tobacco smoked and the method of inhalation and exhalation were found. Eighty per cent of patients wanted to stop smoking with the fear of cancer being the major reason in the subjects with oral keratoses and the continued cost of smoking the major reason in the control subjects. In the affected patients the prevalence of white patches was not related to the quantity of tobacco consumed but rather to the number of years the subject had smoked.

Density and Diversity in Mojave Desert Rodent and Shrub Communities

The mechanisms allowing for coexistence of animal species, and particularly the number of species coexisting in a given habitat, have been explored from many viewpoints. Evolutionary ecologists have investigated the process whereby the species has acquired, the necessary adaptations for exploitation of the habitat (e.g. Bowman 1961; Selander 1966). Biogeographical ecologists have explored the packing of species in an environment and the effects of speciation and immigration upon community composition (e.g. Pianka 1967; Brown 1973). Thirdly, community ecologists have examined species interactions within a relatively stable community to determine how resources are allocated among the species (e.g. MacArthur & MacArthur 1961; Paine 1966; Brown & Lieberman 1973). Most of these studies have concluded that the species composition of a community is the resultant of a complex interaction between all three parameters, i.e. evolutionary, biogeographical and ecological factors. Accordingly, researchers such as Pianka (1967) and Brown (1973) have chosen to simultaneously analyse the effects of all three parameters upon animal species diversity. An alternative method of community analysis, wherein one of the three parameters is observed in closer detail, requires that the remaining two factors be conclusively eliminated as variables. In this study I have chosen to focus upon the ecological mechanisms of granivorous rodent coexistence in the Mojave Desert of southern California. The study transect has been selected to range over a geographically small area of physically similar desert habit such that all rodent species of the study are (at least potentially) evolutionarily and biogeographically able to exploit all study areas. The rodent complpment of each of the study areas is therefore determined by the interactions of the ecologies of the species and, particularly, the effect of certain varying parameters (such as rainfall and seed abundance) upon each species' competitive success. Granivorous rodent species of desert habitats vary remarkably little in general behavior and morphology. The rigors of the desert environment have necessitated physiological adaptations in most species for existence with little or no free water intake. High diurnal temperatures have required that nearly all North American desert rodent species forage at night and spend the day in burrows. Additionally, anti-predatory manoeuvers in areas of sparse vegetation have necessitated adaptations in most species for rapid locomotion in open spaces. The net result of these and other adaptations for desert survival in rodents is convergence toward very similar ecologies. It is the intent of this study to analyze the abundance and diversity of rodents in several Mojave Desert communities in the attempt to uncover predictable patterns related to

Behavioral Character Displacement: Evidence of Food Partitioning in Insectivorous Bats

Two extremely similar insectivorous bats, Myotis evotis and M. auriculas , differ in food preferences when sympatric (Black, 1974). Myotis auriculus preys generally upon moths and some beetles, whereas M. evotis specializes on beetles. Does this specialization of M. evotis persist in allopatry, indicating that it has evolved as a food specialist, or in the absence of its close competitor, does it eat both moths and beetles without a strong preference? What sort of effect, if any, does M. evotis exert on the diet of M. auriculus in areas of sympatry? Both species were captured in areas of allopatry during the summer of 1972. Fecal samples were collected and analyzed using Black's (1974) technique. My results indicate that when in allopatry, M. evotis and M. auriculus have similar food habits. Thus, in sympatry, competition for food is avoided by changes in food preferences of M. evotis . Furthermore, each species exhibits sexual differences in foods taken in areas of allopatry, indicating that intraspecific niche subdivision occurs in each of these bats only in the absence of the potential competitor.