Do snakes exhibit shifts in feeding ecology associated with the presence or absence of potential competitors? A case study from tropical Africa

2003 ◽  
Vol 81 (2) ◽  
pp. 228-236 ◽  
Author(s):  
Luca Luiselli
Keyword(s):  
Feeding Ecology ◽  
Prey Size ◽  
Prey Type ◽  
Swamp Forest ◽  
Southeastern Nigeria ◽  
Predator Species ◽  
Predatory Behaviour ◽  
Ecological Requirements ◽  
Predator Size ◽  
Potential Competitor

Two species of rain-forest snakes, the colubrids Natriciteres fuliginoides and Natriciteres variegata, are potential competitors, because they attain, on average, the same body size (20–30 cm long), have similar habits and ecological requirements (they are both diurnal and nocturnal, often semi-aquatic), and have similar dietary spectra ( including both small vertebrates and invertebrates). I studied prey type and predator size – prey size relationships of these snakes in four swamp-forest areas of southeastern Nigeria (West Africa): only N. fuliginoides was found in two of these areas, whereas both species were common in the other two areas. The feeding ecology of N. fuliginoides shifted greatly in the presence of its potential competitor, N. variegata, in terms of prey-type preferences and predatory behaviour as well as in terms of predator size – prey size relationships. In particular, the effects of the potential competitor on the feeding ecology of N. fuliginoides were (i) a shift toward eating many invertebrates from a diet based on many small vertebrates, (ii) a shift toward eating many terrestrial organisms from a diet based on many aquatic organisms, and (iii) a shift in mean prey size for females toward relatively larger prey from a diet based on smaller prey. The resulting effect was a clear partitioning of food resources between the two predator species in both the areas where they are sympatric, whereas N. fuliginoides had a wider dietary spectrum (covering that of the two species together) in the areas where its competitor is not found. The role of intraspecific competition seems less strong, as no apparent resource partitioning in prey type or prey size was observed between males and females of either species or in any study area. However, mean prey size was significantly greater for females than for males of both species and in all study areas, but depended on the significant reverse sexual size dimorphism observed in both species.

The Relationship Between Prey Size and Handling Time and Prey Size and Capture Success in 3 Sympatric Species of Dasyurid Marsupials

1988 ◽  
Vol 15 (6) ◽  
pp. 615 ◽  
Author(s):  
MC Calver ◽  
JS Bradley ◽  
DR King
Keyword(s):  
Linear Regression ◽  
Prey Size ◽  
Handling Time ◽  
Prey Type ◽  
Sympatric Species ◽  
Niche Separation ◽  
Simple Linear Regression ◽  
Predator Species ◽  
The Relationship ◽  
Better Than

Regressions of handling time on prey weight were determined for the dasyurids Srninthopsis hirtipes, S. ooldea and Ningaui spp. preying on grasshoppers and cockroaches in the laboratory. In all cases, a simple linear regression fitted the relationships better than logarithmic models. The slopes of the regression lines were steeper for grasshopper prey than for cockroach prey in all species, and for each prey type the slopes for the predators were ranked in order of predator weight. Capture efficiency, defined as the proportion of successful attacks, did not vary significantly between predator species and prey types, and all predators showed declining capture efficiencies with increasing prey size. Niche separation in these dasyurids does not appear to be based on different optimal prey sizes for each species.

The allometry of cannibalism in piscivorous fishes

2003 ◽  
Vol 60 (5) ◽  
pp. 594-602 ◽  
Author(s):  
Francis Juanes
Keyword(s):  
Upper Bound ◽  
Prey Size ◽  
Trophic Niche ◽  
Large Prey ◽  
Predator Species ◽  
Size Dependent ◽  
Predator Size ◽  
Large Databases ◽  
Widespread Phenomenon ◽  
Large Predators

Cannibalism is a widespread phenomenon that can have strong population and community effects. In this study, I compare the prey size – predator size relationships of diets with and without cannibalized prey for four piscivorous species and five populations that are commonly cannibalistic and where large databases exist. I then examine the resultant trophic niche breadths (range of relative prey size consumed) to quantify whether inclusion of cannibalized prey in the diet slows down the decline in trophic niche breadth that many large predators exhibit as they grow. When comparing diets including cannibalized prey with those without, consistent differences were found among all predator species. In all cases, the slope of the upper bound of the predator size – prey size scatters was larger for cannibal predators compared with noncannibals, suggesting selectivity for larger cannibal prey, which may be driven by higher rates of size-dependent capture success with familiar prey. The slopes of the upper bounds of the cannibal relative prey size vs. predator size scatter also tended to be larger than the upper-bound slopes for diets without conspecific prey. Finally, for all species, mean trophic breadth of diets including cannibalized prey were larger than those not including cannibal prey, suggesting that relatively large prey sizes may always be available for cannibals.

Predatory plasticity in nephilengys cruentata (araneae: tetragnathidae): relevance for phylogeny reconstruction

Behaviour ◽  
2002 ◽  
Vol 139 (4) ◽  
pp. 529-544 ◽  
Author(s):  
Carmen Viera ◽  
Hilton Ferreira Japyassú
Keyword(s):  
Phylogenetic Analysis ◽  
Foraging Behaviour ◽  
Single Species ◽  
Prey Type ◽  
Phylogeny Reconstruction ◽  
Behavioural Plasticity ◽  
Analysis Method ◽  
Predator Species ◽  
Predatory Behaviour ◽  
Cluster Analysis Method

AbstractThe plasticity of behavioural expression has been used as an argument against the use of behavioural characters in the reconstruction of phylogenetic patterns. Nevertheless, plasticity itself may vary strongly among taxa, so that phylogenetic considerations about behavioural data must be complemented by an analysis of behavioural plasticity. Plasticity may also vary among distinct behavioural domains in a single species. We have studied the foraging repertoire in N. cruentata using a cluster analysis method, in order to identify the behavioural sequences employed by the spider when preying upon either distinct prey types or distinct prey sizes. Foraging behaviour varies less with prey size than with prey type. Variation in predatory sequences is obtained through (1) repetitions of one same sequence of categories, (2) the use of one same sequence at distinct phases of the predatory behaviour, or (3) the arrangement of behavioural categories in new sequences. Despite this plasticity in spider responses to prey, almost 40% of the predatory repertoire is common to both large and small prey items; this percentage lowers to 20% when we compare the predation of distinct prey types. These results suggest that phylogenetic analysis of predatory behaviour should focus on building ethograms for one single prey type. Small variations in prey/predator size among the predator species selected for a behavioural phylogenetic analysis are preferred to variations of prey type among predator taxa. We discuss the implications of this 'single prey-type' approach to the phylogenetic analysis of behaviour.

Feeding behaviour of predatory larvae of Atherix lantha Webb (Diptera: Athericidae)

1994 ◽  
Vol 72 (10) ◽  
pp. 1695-1699 ◽  
Author(s):  
Fiona F. Hunter ◽  
Astrid K. Maier
Keyword(s):  
Feeding Behaviour ◽  
Prey Species ◽  
Prey Size ◽  
Prey Type ◽  
Predator Prey ◽  
Size Classes ◽  
Predator Size ◽  
Oxygenated Water

Larvae of Atherix lantha Webb (Diptera: Athericidae) are piercing – sucking predators. Predator–prey experiments were conducted in beakers containing gravel substrates and airstone-oxygenated water. The predator:prey ratio used in all experiments was 5:5. One prey type was tested at a time. Prey tested included large and small heptageniid mayflies, hyalellid amphipods, and hydropsychid caddisflies. The effect of predator size was examined using two size classes of A. lantha larvae. Large A. lantha consumed more mayflies than did small A. lantha. However, amphipod mortality was the same with large as with small A. lantha. The effect of prey size on predation success was tested using two size classes of mayflies. Statistically, small A. lantha fed on equal numbers of small and large mayflies, whereas large A. lantha consumed more large than small mayflies. Data for species-wise comparisons are only available for small A. lantha; according to our results, hydropsychid caddisflies (average mortality (m) = 0.5346) are more vulnerable to predation than are hyalellid amphipods (m = 0.2041) and heptageniid mayflies (m = 0.1135–0.1813). However, the mortality of large mayflies caused by large A. lantha larvae (m = 0.5375) is the same as that of caddisflies caused by small A. lantha larvae. Thus, the vulnerability of prey species depends, in part, on predator size.

Predatory behaviour and prey-capture decision-making by the web-weaving spider Micrathena sagittata

2005 ◽  
Vol 83 (2) ◽  
pp. 268-273 ◽  
Author(s):  
Francisco Díaz-Fleischer
Keyword(s):  
Prey Item ◽  
Prey Capture ◽  
Prey Size ◽  
Prey Type ◽  
Optimal Foraging Theory ◽  
Choice Test ◽  
Large Prey ◽  
Predatory Behaviour ◽  
Hunting Behaviour ◽  
The Web

Optimal-foraging theory predicts how a predator would feed most efficiently when faced with a choice of two types of prey differing in profitability and density in the habitat. The predator should focus only on the more profitable prey, since any prey item eaten by the predator has a cost in terms of the time and resources taken to subdue and eat it. A study of the hunting behaviour and prey-type selection of the web-weaving spider Micrathena sagittata (Walckenaer, 1841) (Araneae: Araneidae) in the field is documented. In the first part of the study, prey of two sizes were offered in four sectors of the web (top, bottom, right, and left). A prey item was provided at one position of the web at a time. Attack time was recorded at each position. Also, choice and no-choice tests were carried out by offering prey in opposing web sectors (top and bottom) simultaneously. Large prey were more successfully captured in the upper parts than in the bottom parts of the web. In the choice test, spiders always preferred large prey to small prey, while in the no-choice test, spiders always responded to the first stimulus received. Two different attack strategies, depending on prey size, were observed. Hunting strategies and prey-size preference can be related to the cost of web construction and profitability of the prey type.

Larval sand lance (Ammodytes sp.) in the diet of small juvenile wolffish (Anarhichas spp.): predatory interactions in frontal water masses off western Greenland

2002 ◽  
Vol 59 (11) ◽  
pp. 1759-1767 ◽  
Author(s):  
Peter Munk
Keyword(s):  
Fish Larvae ◽  
Stomach Contents ◽  
Prey Type ◽  
Ontogenetic Changes ◽  
Sand Lance ◽  
Larval Size ◽  
Predatory Behaviour ◽  
Dietary Shift ◽  
Abundance Estimates ◽  
Anarhichas Lupus

The predatory behaviour of two species of juvenile wolffish (Anarhichas lupus and Anarhichas minor) was studied during a field campaign across a frontal area off western Greenland. The study focused on ontogenetic changes in prey-type and -size preference of the wolffish and their predatory impact on a cohabiting population of larval sand lance (Ammodytes sp.). Sampling took place along a cross-shelf transect at latitude 66°20' N, and the analysis is based on stomach contents of assembled wolffish (2–5 cm in length) and abundance estimates of plankton and fish. An ontogenetic change in wolffish prey preference was evident as a dietary shift from copepods and smaller amphipods to larger amphipods and fish larvae. The inclusion of fish larvae in the wolffish diet led to a marked increase in prey biomass, and fish larvae constituted up to 77% of diet biomass in the largest juveniles caught. Wolffish selectively targeted the smaller-sized part of the larval sand lance population; hence, larval vulnerability increased with decreasing size. Comparison between estimated predation rates and abundances of predator and prey indicated larval predation mortalities of up to 5% per day, with mortality peaking in the vicinity of a hydrographic front. Hence, findings suggest substantial predation pressure on larvae, primarily related to larval size and distribution.

scholarly journals Predator size and prey size-gut capacity ratios determine kill frequency and carcass production in terrestrial carnivorous mammals

Oikos ◽  
2018 ◽  
Vol 128 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Annelies De Cuyper ◽  
Marcus Clauss ◽  
Chris Carbone ◽  
Daryl Codron ◽  
An Cools ◽  
...  
Keyword(s):  
Prey Size ◽  
Predator Size

Feeding habits of cockfish, Callorhinchus callorhynchus (Holocephali: Callorhynchidae), in Patagonian waters (Argentina)

1996 ◽  
Vol 47 (6) ◽  
pp. 801 ◽  
Author(s):  
EE Di Giacomo ◽  
MR Perier
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Feeding Habits ◽  
Food Composition ◽  
Commercial Fishing ◽  
Bivalve Molluscs ◽  
Invertebrate Prey ◽  
Selective Foraging ◽  
Predator Size ◽  
Two Factors

Morphology of the main digestive features of cockfish, Callorhinchus callorhynchus, is described and linked to feeding habits. Composition of the diet and size-selective foraging of this species on scallops was studied in northern Patagonian waters and analysed in relation to depth, sex and size. Three species of bivalve molluscs (Pitar rostratus, Aequipecten tehuelchus and Ennucula puelcha) and flabelligerid polychaetes were predominant in the diet of males. The scallop Zygochlamys patagonica dominated the diet of females. The diet of juveniles consisted of small gastropods (Olivella sp.), bivalves with fragile shells (e.g. Pandora cistula), amphipods and polychaetes. Differences in food composition between sexes and between juveniles and adults are attributed to two factors: extrinsic (concerning prey availability) and intrinsic (concerning the morphology and behaviour of the predator). Size-selective foraging on two species of scallops, Aequipecten tehuelchus (subject to commercial fishing) and Zygochlamys patagonica, was found in adults; it is argued that maximum scallop prey size is constrained by the strength of the crushing apparatus of the cockfish. The diet of the cockfish is compared with that of other holocephalans. It is concluded that species of Callorhinchus can be generally characterized as benthic foragers that specialize in crushing shelled invertebrate prey.

The uneasy coexistence between Carpet Pythons and Cane Toads

2020 ◽  
Author(s):  
Gregory P. Brown ◽  
Jeremy Hemphill ◽  
Richard Shine
Keyword(s):  
Negative Impact ◽  
Prey Type ◽  
Direct Costs ◽  
Cane Toad ◽  
Predator Species ◽  
Indirect Benefits ◽  
Negative Impacts ◽  
Monitor Lizards ◽  
A Site ◽  
Free Ranging

We describe a case of a free-ranging Carpet Python Morelia spilota consuming a toxic Cane Toad Rhinella marina, and dying as a result. Such an encounter would not be surprising at the toad invasion front, where predators first confront this novel prey type. However, the encounter we describe occurred at a site near Darwin where toads have been present for fifteen years. Other reports suggest that the behaviour we observed occurs across the snake’s range. Lethal ingestion of toads has been suggested to threaten the viability of populations of Carpet Pythons, but paradoxically, our surveys at this site reveal a twofold increase in abundance of Carpet Pythons since the arrival of toads. Toad invasion likely has favoured pythons by reducing the abundance of large monitor lizards, that are both predators and competitors of Carpet Pythons. That advantage has outweighed occasional cases where a snake is fatally poisoned by consuming a toad. Thus, the overall impact of Cane Toads on Carpet Pythons (and likely, other predator species) is a balance between direct costs and indirect benefits. Negative impacts on individuals may not necessarily translate to a negative impact on the species.

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