Species Of Similar Size Research Articles

Very low force-generating ability and unusually high temperature-dependency in hummingbird flight muscle fibers

Hummingbird flight muscle is estimated to have among the highest mass-specific power output among vertebrates, based on aerodynamic models. However, little is known about the fundamental contractile properties of their remarkable flight muscles. We hypothesized that hummingbird pectoralis fibers generate relatively low force when activated in a tradeoff for high shortening speeds associated with the characteristic high wingbeat frequencies that are required for sustained hovering. Our objective was to measure maximal force-generating ability (maximal force/cross-sectional area, Po/CSA) in single, skinned fibers from the pectoralis and supracoracoideus muscles, which power the wing downstroke and upstroke, respectively, in hummingbirds (Calypte anna) and in another similarly sized species, zebra finch (Taeniopygia guttata), which also has a very high wingbeat frequency during flight but does not perform a sustained hover. Mean Po/CSA in hummingbird pectoralis fibers was very low - 1.6, 6.1 and 12.2 kN m(-2), at 10, 15 and 20°C, respectively. Po/CSA in finch pectoralis fibers was also very low (for both species, ~5% of the reported Po/CSA of chicken pectoralis fast fibers at 15°C). Q10-force (force generated at 20°C/force generated at 10°C) was very high for hummingbird and finch pectoralis fibers (mean=15.3 and 11.5, respectively) compared with rat slow and fast fibers (1.8 and 1.9, respectively). Po/CSA in hummingbird leg fibers was much higher than in pectoralis fibers at each temperature, and the mean Q10-force was much lower. Thus, hummingbird and finch pectoralis fibers have an extremely low force-generating ability compared with other bird and mammalian limb fibers, and an extremely high temperature dependence of force generation. However, the extrapolated maximum force-generating ability of hummingbird pectoralis fibers in vivo (~48 kN m(-2)) is substantially higher than the estimated requirements for hovering flight of C. anna. The unusually low Po/CSA of hummingbird and zebra finch pectoralis fibers may reflect a constraint imposed by a need for extremely high contraction frequencies, especially during hummingbird hovering.

Dry season factors determining habitat use and distribution of mouse deer (Moschiola indica) in the Western Ghats

Ecology of Asia's smallest ungulate, the Indian chevrotain or mouse deer (Moschiola indica), has been poorly assessed. We used camera-trapping data to investigate habitat use of mouse deer in Mudumalai Tiger Reserve. Presence/absence data, collected under a systematic sampling framework, were used to test a priori hypotheses incorporating covariates believed to influence mouse deer occurrence and detection. The average occupancy rate of mouse deer in the study area was 0.56 (SE = 0.22) with a low detection probability (0.29, SE = 0.14). Model selection indicated that presence of moist bamboo brakes positively influenced while percent leaf litter negatively influenced mouse deer occupancy. Placement of camera-traps along narrow trails positively influenced detection probability of mouse deer. Future conservation efforts in India should focus on preservation of bamboo vegetation and dense forest cover which provide refuge for the mouse deer. Our results illustrate that occupancy can be suitable for monitoring elusive, forest dwelling, small ungulates; however, caution is needed when applying these models on small ranging species, as our study identifies the limitations in our survey design and its improvement for future monitoring which are applicable for similar-sized species across a range of habitats.

Spatial distribution and habitat selection in coexisting species of mountain ungulates

One of the main objectives of community ecology is to understand the conditions allowing species to coexist, which requires identifying how co‐occurring species use and share space and resources. Species of the same trophic level, such as large herbivores, are of fundamental interest in that context because competition for resources is likely. Segregation in space or on some axes of the ecological niche are processes allowing coexistence, yet, both are seldom studied jointly. Based on annual spring censuses collected for 11 yr, we analysed the degree of overlap in spatial distribution among chamois Rupicapra rupicapra and mouflon Ovis gmelini musimon, 2 species of similar size that coexist on the same alpine pastures. We further investigated whether they differed in terms of habitat selection processes, and identified which environmental factors led to species being aggregated or segregated. The areas of intensive use for 2 species were more spatially aggregated than expected by chance. Habitat selection was studied using multivariate methods based on the niche concept, considering the presence of 1 species as an environmental variable for the other. Despite a large overlap in niches (88%), segregation was significant as chamois preferred meadows dominated by Sesleria and Carex sempervirens while mouflon selected meadows dominated by Carex ferruginea and avoided being close to areas affected by human activities. Importantly, habitat selection within each species was not affected by the presence of the other species. Coexistence between these 2 species and spatial overlap may be permitted because resource partitioning occurs at a fine temporal and/or spatial scale. We underscore that joint approaches of spatial and ecological processes are necessary to disclose the type of interaction (neutral, facilitation or competition) at play within a community.

Contrasting feeding patterns of native red deer and two exotic ungulates in a Mediterranean ecosystem

Context Ungulates have been widely introduced in multiple ecosystems throughout the world due to their value as food and for sport hunting. The identification of foraging preferences of exotic and native ungulates living in sympatry is, therefore, becoming increasingly important in order to assess potential impacts of introduced animals on the host ecosystem. Aims To describe species-specific foraging strategies and infer resource selection overlap between native and exotic ungulates. Methods We compared the trophic ecology of three sympatric ungulate species living in a Mediterranean landscape: the native Iberian red deer Cervus elaphus hispanicus, and two exotic bovids, the European mouflon Ovis orientalis musimon and the aoudad Ammotragus lervia. We simultaneously determined herbivore diet through analyses of botanical content in faeces and assessed the nutritional content of these diets. Key results Higher selection of shrubs by deer was sustained throughout the year, while bovids showed seasonal shifts in forage selection. Both bovids displayed a selective dietary strategy directed towards a higher overall nutritional quality than that of deer. Divergent exploitation patterns between the studied cervid and bovids might be related to body mass and physiological adaptations to overcome secondary defence compounds of shrubs, and were largely affected by seasonal changes in the nutritional value of available vegetation. Ecological theory suggests that diet overlap should be greater between similar-sized species. Indeed, both exotics showed similar, sometimes overlapping, dietary patterns that could lead to potential competition in the use of resources. Native red deer preferences only showed some overlap with those of exotic mouflon under constrained summer conditions. Conclusions Dietary overlap between deer and mouflon and between aoudad and mouflon during limiting summer conditions could entail a potential competitive interaction under more even densities of the study species, since a concurrent habitat overlap between those pairs of species has previously been reported. Implications The outcomes of our study suggest the need for an integration of habitat and ungulate management. Management actions in Mediterranean rangelands should be directed towards protecting habitat conditions so that biodiversity is enhanced along with the presence of sustainable communities of large herbivores. Management directed towards ungulates should maintain moderate stocking rates and monitor and control introduced and native populations.

Booming during a bust: Asynchronous population responses of arid zone lizards to climatic variables

The productivity of arid environments and the reproductive success of vertebrates in these systems, are typically thought to be primarily influenced by rainfall patterns. Data from our 15 year study at an Australian arid zone site reveals asynchronous demographic responses to rainfall and other climatic variables among different lizard species. We show that, in addition to precipitation, key demographic rates (fecundity, recruitment and survival) are correlated strongly with temporal variability in temperature, during and prior to the breeding season, and also to the density of sympatric lizard species. There were nine-fold fluctuations through time in the relative abundance of two similar-sized Ctenotus species, and asynchronous recruitment success and survival among other species, despite the absence of direct anthropogenic affects Understanding the drivers and magnitude of the substantial natural variability in arid-zone lizard assemblages is integral to predicting and interpreting their responses to future land use or climate-change scenarios.

Interspecific Aggression for Nest Sites: Model Experiments with Long-Tailed Finches (Poephila Acuticauda) and Endangered Gouldian Finches (Erythrura Gouldiae)

ABSTRACT. For cavity-nesting birds, tree cavities often represent a critical, defendable, and limiting resource that is frequently under intense interspecific competition. However, the dynamics of interspecific conflict resolution, especially between species of similar size, are often unclear. We experimentally tested aggression and nest-defense behaviors in Gouldian Finches (Erythrura gouldiae) and Long-tailed Finches (Poephila acuticauda), two sympatric, cavity-nesting estrildid finches that are very similar in size, ecology, and nest-site requirements. Mounted taxidermie models of conspecific and heterospecific nest-site competitors (black and red Gouldian Finch morph and Long-tailed Finch models), as well as a control noncompetitor (Black-chinned Honeyeater [Melithreptus gularis]), were presented to Gouldian and Long-tailed finches. These two competing species differed in their overall responses to simulated intruders and in their relative aggression toward conspecific and heterospecific intruders. Lo...

A Comparison Of Two Surgical Methods For Chronic Measurement Of Blood Pressure In Juvenile Rats Through Adulthood

Collecting chronic blood pressure (BP) from juvenile animals through adulthood can provide a number of research benefits. The number of animals used, coinciding surgical support, and animal variability can all be reduced by using one BP transmitter model throughout the animal's lifetime. The PA-C40 transmitter (DSI), typically used in rats and similar species is too large in size and catheter diameter for smaller rodent arteries. However, the PA-C10 transmitter (DSI), which is typically implanted in mice or similar-sized species, was chosen as a possible alternative to the larger PA-C40. The PA-C10 was implanted in 12 male, juvenile rats (SD, ~90 grams) to determine the most suitable placement for the catheter and transmitter body to retain catheter patency during the growth period. Two separate surgical procedures were evaluated including direct aortic cannulation with intraperitoneal (IP) transmitter placement in six rats and direct femoral artery cannulation with subcutaneous (SQ) transmitter placement in six rats. BP was monitored and collected three days per week for a total of 16 weeks. Catheter patency was determined by analyzing the collected data and visualizing in vivo catheter placement. At the end of the study, 11 of the 12 rats had viable BP signals. Therefore, BP measurement in growing rats, from juvenile to adult, is a viable experimental design for cardiovascular researchers.

Cuevas de Armadillos (Cingulata: Dasypodidae) en la Amazonía Central: Son Útiles para Identificar Especies?

Abstract Armadillo burrows are important structures for shelter and reproduction, and may be used as a source of information in ecological studies. In regions where several species coexist, it is necessary to know if the burrow measures are useful for species identification. We investigated whether burrow entrance morphometry is useful for differentiating four armadillo species in the central Amazon and evaluated whether entrance size was related to site topography. We registered entrance height and width, and entrance tunnel angle for each burrow encountered in 61 plots. We estimated the elevation and mean declination of the terrain at each burrow site. We measured the entrances of 188 armadillo burrows. Mean entrance height was 19.15 ± 5.04 cm and mean width 22.76 ± 5.85 cm. These variables were positively correlated and therefore not useful to distinguish individual species. Burrow size was not related to site topography. Burrows with similar dimensions may be built by species of similar size or by ind...

Ten new species of the genus Brevisomabathynella Cho, Park and Ranga Reddy, 2006 (Malacostraca, Bathynellacea, Parabathynellidae) from Western Australia

Ten new species of Brevisomabathynella Cho, Park and Ranga Reddy, 2006 are described and illustrated from the arid region of Western Australia. Comparison of the external morphology revealed the presence of three common characters distributed among the 10 species: the five-segmented antenna, the absence of the basipodal seta on the male thoracopod VIII and the absence of a basiventral seta on the uropodal exopod. This character combination is not found in Notobathynella and Billibathynella, but only in Brevisomabathynella, a genus known from two described species both with unusual characters. Despite the three common attributes, the 10 new species differ remarkably from these two described species, but could not be defined by their own synapomorphy. Consequently, and cognizant of a previously performed molecular analysis, we assign the 10 new species to Brevisomabathynella and amend the generic diagnosis. The species inhabit shallow aquifers in groundwater calcretes and each appears to be endemic to a given calcrete formation. The two species previously known and the 10 species now described include four sympatric species pairs, with similar-sized sympatric species differing markedly in body form. Brevisomabathynella inhabit groundwater up to at least marine salinity.

Body coloration and colour alternation among tropical forest mammals

Despite different phylogenetic origins, the mammals of Gabon and Guiana show very similar colour patterns. The coloration is closely correlated with several biological parameters: body weight, diet, and activity rhythm. The less dangerous the living conditions, the more easily perceptible are body colours. Within the same community, the degree of colour convergence between species of similar body size is very low among diurnal carnivores or between they and their prey, that is when interspecific encounters can be dangerous. In contrast, it is higher among diurnal terrestrial frugivores or folivores of similar size, than among those of unequal size. Owing to the few colours available, and to the regular size spacing between species, all species are arranged into narrow unicoloured size strata (indistinct colour or red), regularly alternating along the whole size range. Since most species of similar size are well differentiated from each other by ecology, each solitary animal can be sure that another having both the same size and colour is conspecific. The colour alternation does not exist when it is not useful: nocturnal, arboreal, or flying mammals.

CAN PARALLEL DIVERSIFICATION OCCUR IN SYMPATRY? REPEATED PATTERNS OF BODY-SIZE EVOLUTION IN COEXISTING CLADES OF NORTH AMERICAN SALAMANDERS

A classic paradigm in evolutionary biology is that geographically isolated clades inhabiting similar selective regimes will diversify to create similar sets of phenotypes in different locations (e.g., similar stickleback species in different lakes, similar Anolis ecomorphs on different islands). Such parallel radiations are not generally expected to occur in sympatry because the available niche space would be filled by whichever clade is diversified first. Here, we document a very different pattern, the parallel evolution of similar body-size morphs in three sympatric clades of plethodontid salamanders (Desmognathus, Plethodon, Spelerpinae) in eastern North America. Using a comprehensive, time-calibrated phylogeny of North American plethodontids from nuclear and mitochondrial DNA sequences, we show that these three clades have undergone replicated patterns of evolution in body size and that this parallel diversification occurred in broad-scale sympatry. At the local scale, we find that coexisting species from these clades are more similar in body size than expected under a null model in which species are randomly assembled into communities. These patterns are particularly surprising in that competition is known to be important in driving phenotypic diversification and limiting local coexistence of similar-sized species within these clades. Although parallel diversification of sympatric clades may seem counterintuitive, we discuss several ecological and evolutionary factors that may allow the phenomenon to occur.

Extremely Low Maximal Force-Generating Ability in Hummingbird Flight Muscle Fibers

Hummingbird flight muscle has the highest mass-specific mechanical power output among all vertebrates. The wingbeat kinematics and aerodynamics of hummingbird flight have been studied in multiple species, but little is known about fundamental contractile properties of these remarkable muscles. The objective of this study was to measure the maximal force-generating ability (maximal force per unit of fiber cross-sectional area, Po/CSA) of single muscle fibers from the pectoralis muscle, which powers the wing downstroke, in adult hummingbirds and in another similarly-sized species, zebra finch, which does not hover but also has a very high wingbeat frequency during routine flight. Single, skinned pectoralis fibers were maximally calcium-activated and Po/CSA was measured across a range of temperatures. Po/CSA in hummingbird pectoralis fibers was 1.1 ± 0.4 (mean ± SEM), 5.2 ± 1.6, and 10.8 ± 2.4 kN/m2, at 10, 15, and 20°C, respectively. Po/CSA in zebra finch pectoralis fibers was 2.0 ± 0.4 (mean ± SEM), 10.4 ± 1.6, and 21.6 ± 3.2 kN/m2, at 10, 15, and 20°C, respectively. For comparison, Po/CSA in adult mammalian limb muscle fibers at 15°C is typically 100-120 kN/m2. The mean Po/CSA in hummingbird leg muscles fibers, which are used for perching, was 73.4 ± 11.6 kN/m2 at 10°C. These results indicate that hummingbird pectoralis fibers have an extremely low force-generating ability, compared to mammalian limb muscle fibers and hummingbird leg muscle fibers, even when maximally activated, and have an unusually high temperature-dependence of force generation. The unusually low force-generating ability of hummingbird and zebra finch pectoralis fibers may reflect a constraint imposed by a need for extremely high contraction frequencies, especially during hovering flight in hummingbirds. Supported by the National Science Foundation.

SEISMIC SEXUAL SIGNAL DESIGN OF TWO SYMPATRIC BURROWING TARANTULA SPIDERS FROM MEADOWS OF URUGUAY: EUPALAESTRUS WEIJENBERGHI AND ACANTHOSCURRIA SUINA (ARANEAE, THERAPHOSIDAE)

Abstract Eupalestrus weijenberghi (Thorell 1894) and Acanthoscurria suina Pocock 1903 are two fossorial, sympatric, synchronic, and similar-sized species of tarantulas that inhabit the meadows of Uruguay. Both species use seismic signals for communicating during courtship (body vibrations in males, leg tapping in females), but little is known either about temporal and spectral signal characteristics or effective signal range. Males were elicited to court (body vibrations) by exposing them to sexual pheromones in one end of a terrarium, whereas females were successively placed in burrows at different distances from the courting male. Seismic male signals were registered by using a geophone placed near the females. We found that E. weijenberghi male signals reach at least 135.75 cm, whereas A. suina signals reach at least 110.5 cm. There was no correlation between latency of female response and distances at which the male was courting for either of the spider species. For A. suina, a bout of vibration was c...

Seasonal and diel comparisons of the diets of four dominant fish species within the main channel and flood-zone of a small intermittently open estuary in south-eastern Australia

The diets of four highly-abundant, dominant fish species within the Surrey River, a small intermittently open estuary in south-east Australia, were examined from specimens collected between July 2004 and June 2005. These four, similar-sized species (Atherinosoma microstoma, Galaxias maculatus, Philypnodon grandiceps and Pseudogobius olorum) have limited ability to spatially segregate along the length of the estuary owing to its small size relative to other estuarine habitats. All four species fed on a variety of prey items including crustaceans, insects and detritus. Despite this parity, the four species were demonstrated to occupy differing dietary niches that were concluded to be responsible for reducing interspecific feeding competition. Seasonal variations in the diets were observed for A. microstoma and Philypnodon grandiceps, with these species also exhibiting contrasting diel feeding behaviours. The closure of the estuary mouth led to the flooding of its margins, resulting in an increase in the size of the estuary and providing alternative food resources for the fish to exploit. It appears the inundation of the flood-zone facilitated further significant divergence in the diets of the fish and is likely to be of high ecological value to the estuary.

Body Mass of Long-Tailed Ducks (Clangula Hyemalis) During Incubation

Abstract We investigated body-mass dynamics during incubation of Long-tailed Ducks (Clangula hyemalis) nesting in Canada’s central Arctic, 1998–2003. Long-tailed Duck females (n = 37) lost 7% of pre-incubation body mass during incubation; on average, females weighed 618 ± 15 g (mean ± SE) at clutch completion and 575 ± 11 g at hatch. Given the differences in body size, Long-tailed Ducks relied less on endogenous reserves than sympatric King Eiders (Somateria spectabilis), but lost less mass than similar-sized waterfowl species nesting in temperate climates. Preliminary data suggest that Long-tailed Ducks maintain similar or higher nest-attendance rates than temperate-nesting waterfowl of similar size, and we suggest that access to locally abundant, high-quality foods enable Long-tailed Duck females to maintain high incubation constancy without sacrificing female body condition. Nevertheless, Long-tailed Ducks appear to differ widely from most Arctic-nesting waterfowl in nutritional strategy for nesting. Masse corporelle chez l’Harelde kakawi (Clangula hyemalis) au cours de l’incubation

BODY MASS OF LONG-TAILED DUCKS (CLANGULA HYEMALIS) DURING INCUBATION

Abstract We investigated body-mass dynamics during incubation of Long-tailed Ducks (Clangula hyemalis) nesting in Canada’s central Arctic, 1998–2003. Long-tailed Duck females (n = 37) lost 7% of pre-incubation body mass during incubation; on average, females weighed 618 ± 15 g (mean ± SE) at clutch completion and 575 ± 11 g at hatch. Given the differences in body size, Long-tailed Ducks relied less on endogenous reserves than sympatric King Eiders (Somateria spectabilis), but lost less mass than similar-sized waterfowl species nesting in temperate climates. Preliminary data suggest that Long-tailed Ducks maintain similar or higher nest-attendance rates than temperate-nesting waterfowl of similar size, and we suggest that access to locally abundant, high-quality foods enable Long-tailed Duck females to maintain high incubation constancy without sacrificing female body condition. Nevertheless, Long-tailed Ducks appear to differ widely from most Arctic-nesting waterfowl in nutritional strategy for nesting. M...

Soricid Response to Canopy Gaps Created by Wind Disturbance in the Southern Appalachians

We used drift fences with pitfall traps to compare soricid abundance, richness, and demographic parameters among intact multiple-tree windthrow gaps, salvaged gaps, and mature forest in a xeric southern Appalachian forest type during 1997–1999. We also tested whether capture rates were correlated with rainfall, and whether similar-sized species did not co-occur as predicted by multi-species assemblage rules. We captured six species: Blarina brevicauda (Say) (northern short-tailed shrew), Cryptotis parva (Say) (least shrew), Sorex cinereus Kerr (masked shrew), S. fumeus G.M. Miller (smoky shrew), S. hoyi Baird (pygmy shrew), and S. longirostris Bachman (southeastern shrew). Tree basal area, forest structural features, and arthropod abundance differed among treatments, but species richness and abundance of most shrews did not. Captures during June–October were higher in 1998 than in 1997, although 1998 summer rainfall was low. Rainfall was correlated with shrew activity, but explained little of the variability in capture rates (r2 = 0.05). The sex ratio within each species was similar among gap treatments and controls, but differed from 1:1 for S. hoyi, S. longirostris, and S. fumeus. The soricid assemblage did not conform to multi-species assemblage rules; three small-bodied species co-occurred in similar numbers at all study sites. Our results suggest that forest management that mimics conditions created by multiple windthrows in xeric forest of the southern Appalachians is unlikely to affect shrew communities adversely, at least in the short-term.

Liquid-feeding performances of ants (Formicidae): ecological and evolutionary implications

Disparities in liquid-feeding performances of major ant taxa have likely been important to resource partitioning among ants, to the nature and composition of ant partnerships with plants and sap-feeding trophobionts, and to ecological and evolutionary diversification of ant taxa. We measured performance volumetrically for individual workers of 77 ant species from lowland rain forests of Amazonia and Borneo and three key North American taxa. In trials with 9% sucrose solution, performances were strongly related to body size (and alitrunk length) and to proventricular structure at generic to subfamilial levels. Highly modified proventriculi were associated with disproportionately large load sizes in Formicinae and certain small-bodied Dolichoderinae. These same taxa also ingested liquids more rapidly during foraging than did similar-sized species with plesiomorphic proventriculi. Secondarily reduced foraging performances of several formicines likely reflect ecological or evolutionary trade-offs related to dietary specialization or anti-predator defenses. Across formicines and dolichoderines, performances differed by functional group. Relatively small loads and slow uptake characterized species tending trophobionts (mainly Hemiptera) day and night in large worker aggregations. Large loads and rapid uptake typified solitary, diurnal "leaf-foragers." Intermediate feeding performances characterized a few species that both tended trophobionts in small aggregates and frequently foraged alone.

How dispersal limitation shapes species-body size distributions in local communities.

A critical but poorly understood pattern in macroecology is the often unimodal species-body size distribution (also known as body size-diversity relationship) in a local community (embedded in a much larger regional species pool). Purely neutral community models that assume functional equivalence among species are incapable of explaining this pattern because body size is the key determinant of functional differences between species. Several niche-based explanations have been offered, but none of them is completely satisfactory. Here we develop a simple model that unites a neutral community model with niche-based theory to explain the relationship. In the model, species of similar size are assumed to belong to the same size guild. Within a size guild, all individuals are equivalent in their competition for resources, sensu Hubbell's neutral community model; they have the same speciation rate and dispersal capacities. Between size guilds, however, the total number of individuals, the speciation rate, and the dispersal capacities differ, but using known allometric scaling laws for these properties, we can describe the differences between size guilds. Our model predicts that species richness reaches an optimum at an intermediate body size, in agreement with observations. The optimum at intermediate body size is basically the result of a trade-off between, on the one hand, allometric scaling laws for the number of individuals and the speciation rate that decrease with body size and, on the other hand, the scaling law for active dispersal that increases with body size.

Foraging ecology of the early life stages of four sympatric shark species

Sharks may have an important role in marine ecosystems in relation to populations of fish and invertebrates at lower trophic levels. Fishery management plans stress the need for an ecosystem approach, but few quantitative studies on the foraging ecology of sharks have been published. Stomach contents and catch data of early life stages of Atlantic sharpnose Rhizoprionodon terraenovae, blacktip Carcharhinus limbatus, finetooth Carcharhinus isodon, and spinner sharks Carcharhinus brevipinna taken from fishery independent surveys in Apalachicola Bay, Florida, USA, were examined to test for overlap in resource use. Young-of-the-year Atlantic sharpnose sharks were found to feed mainly on shrimp, juveniles on sciaenids, and adults on clupeids. Young-of-the-year blacktip sharks were found to feed mainly on sciaenids, whereas juveniles fed on clupeids. The primary prey of young-of-the-year and juvenile finetooth and spinner sharks was clupeids. Eight of 10 prey size-selectivity tests showed neutral selection. Compared to relative prey sizes published for teleost piscivores, Atlantic sharpnose and finetooth sharks consume relatively small-sized prey while blacktip sharks consume relatively large prey. Regardless of maturity state and species, diet overlap was high for species-life stage combinations that are similar in size; however, species-life stages did not show significant habitat overlap. Prey categories shared by similar-sized species may not be limiting, although shark species may have alleviated competition pressure by partitioning the resource of time or space.