Ecological Interactions in Dinosaur Communities: Influences of Small Offspring and Complex Ontogenetic Life Histories

Because egg-laying meant that even the largest dinosaurs gave birth to very small offspring, they had to pass through multiple ontogenetic life stages to adulthood. Dinosaurs’ successors as the dominant terrestrial vertebrate life form, the mammals, give birth to live young, and have much larger offspring and less complex ontogenetic histories. The larger number of juveniles in dinosaur as compared to mammal ecosystems represents both a greater diversity of food available to predators, and competitors for similar-sized individuals of sympatric species. Models of population abundances across different-sized species of dinosaurs and mammals, based on simulated ecological life tables, are employed to investigate how differences in predation and competition pressure influenced dinosaur communities. Higher small- to medium-sized prey availability leads to a normal body mass-species richness (M-S) distribution of carnivorous dinosaurs (as found in the theropod fossil record), in contrast to the right-skewed M-S distribution of carnivorous mammals (as found living members of the order Carnivora). Higher levels of interspecific competition leads to a left-skewed M-S distribution in herbivorous dinosaurs (as found in sauropods and ornithopods), in contrast to the normal M-S distribution of large herbivorous mammals. Thus, our models suggest that differences in reproductive strategy, and consequently ontogeny, explain observed differences in community structure between dinosaur and mammal faunas. Models also show that the largest dinosaurian predators could have subsisted on similar-sized prey by including younger life stages of the largest herbivore species, but that large predators likely avoided prey much smaller than themselves because, despite predicted higher abundances of smaller than larger-bodied prey, contributions of small prey to biomass intake would be insufficient to satisfy meat requirements. A lack of large carnivores feeding on small prey exists in mammals larger than 21.5 kg, and it seems a similar minimum prey-size threshold could have affected dinosaurs as well.     

Prey size selection and cannibalistic behaviour of juvenile barramundi Lates calcarifer

This study assessed the cannibalistic behaviour of juvenile barramundi Lates calcarifer and examined the relationship between prey size selection and energy gain of cannibals. Prey handling time and capture success by cannibals were used to estimate the ratio of energy gain to energy cost in prey selection. Cannibals selected smaller prey despite its capability of ingesting larger prey individuals. In behavioural analysis, prey handling time significantly increased with prey size, but it was not significantly affected by cannibal size. Conversely, capture success significantly decreased with the increase of both prey and cannibal sizes. The profitability indices showed that the smaller prey provides the most energy return for cannibals of all size classes. These results indicate that L. calcarifer cannibals select smaller prey for more profitable return. The behavioural analysis, however, indicates that L. calcarifer cannibals attack prey of all size at a similar rate but ingest smaller prey more often, suggesting that prey size selection is passively orientated rather than at the predator's choice. The increase of prey escape ability and morphological constraint contribute to the reduction of intracohort cannibalism as fish grow larger. This study contributes to the understanding of intracohort cannibalism and development of strategies to reduce fish cannibalistic mortalities.     

Egg cannibalism by Coleomegilla maculata lengi neonates: preference even in the presence of essential prey

Abstract 1. Egg cannibalism among coccinellids has been reported widely, however reasons why this type of behaviour is observed so frequently have been neglected. This experiment was undertaken to clarify whether cannibalistic behaviour is advantageous to Coleomegilla maculata lengi Thimberlake neonates and to understand the reasons for high levels of egg cannibalism.
2. Benefits gained by neonate cannibals were ascertained by comparing survival, developmental time, and second-instar weight of C. maculata larvae that were allowed to cannibalise conspecific eggs or not. Preference and behaviour tests were also conducted to assess the reasons for high levels of egg cannibalism.
3. Cannibal neonates grew faster and were heavier than non-cannibals. The developmental time of neonates was influenced more by prey vulnerability than by prey quality.
4. In choice tests, where three different proportions of conspecific eggs and aphids were offered (33–67, 50–50, and 67–33%), C. maculata neonates always consumed significantly more eggs. Manly's preference indexes indicated that neonates showed a consistent preference for conspecific eggs.
5. Seventy-five per cent of neonates observed went directly towards eggs and 90% of the first prey consumed by neonates were an egg. When aphids were painted with extract of crushed eggs and eggs with crushed aphids to determine whether neonates found eggs by chemical cues, neonates preferred aphids painted with egg extract to eggs painted with aphid extract.
6. It was concluded that C. maculata neonates benefited from cannibalistic behaviour. Moreover, egg cannibalism is not related only to frequency of encounter; chemical cues are also involved in egg searching.     

Cannibalism in Arctic charr: do all individuals have the same propensity to be cannibals?

By comparing large Arctic charr Salvelinus alpinus , which had shown a persistent cannibalistic response varying from zero to very high in succeeding laboratory trials, with their individual cannibalistic behaviour after release into a natural lake inhabited by small Arctic charr, it was found that all Arctic charr had the potential to become cannibalistic, irrespective of their laboratory behaviour. More specifically, Arctic charr that never fed on prey fishes when offered them in the tank experiments turned to cannibalism when released in the lake, highlighting the potential difficulties in extrapolating laboratory results to natural settings. This was also true for naive fish that had no prior experience of eating live food. Since no significant increase in the number of prey consumed during each of the succeeding laboratory trials was found, and naive fish showed a response under natural conditions similar to that of their counterparts, the training of the Arctic charr (or experience or learning) probably had no effect upon the piscivorous or cannibalistic response after stocking. Thus, the study appeared to demonstrate that most variations in cannibalism in Arctic charr was simply a function of environmental conditions, depending on the density of conspecifics v . alternative prey, and the relative size difference between predator and prey, rather than any genetic influence.     

A late-surviving basal theropod dinosaur from the latest Triassic of North America

The oldest theropod dinosaurs are known from the Carnian of Argentina and Brazil. However, the evolutionary diversification of this group after its initial radiation but prior to the Triassic-Jurassic boundary is still poorly understood because of a sparse fossil record near that boundary. Here, we report on a new basal theropod, Daemonosaurus chauliodus gen. et sp. nov., from the latest Triassic 'siltstone member' of the Chinle Formation of the Coelophysis Quarry at Ghost Ranch, New Mexico. Based on a comprehensive phylogenetic analysis, Daemonosaurus is more closely related to coeval neotheropods (e.g. Coelophysis bauri) than to Herrerasauridae and Eoraptor. The skeletal structure of Daemonosaurus and the recently discovered Tawa bridge a morphological gap between Eoraptor and Herrerasauridae on one hand and neotheropods on the other, providing additional support for the theropod affinities of both Eoraptor and Herrerasauridae and demonstrating that lineages from the initial radiation of Dinosauria persisted until the end of the Triassic. Various features of the skull of Daemonosaurus, including the procumbent dentary and premaxillary teeth and greatly enlarged premaxillary and anterior maxillary teeth, clearly set this taxon apart from coeval neotheropods and demonstrate unexpected disparity in cranial shape among theropod dinosaurs just prior to the end of the Triassic.     

Body Size Distribution of the Dinosaurs

The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.     

Bite traces on dicynodont bones and the early evolution of large terrestrial predators

Nied?wiedzki, G., Gorzelak, P. & Sulej, T. 2010: Bite traces on dicynodont bones and the early evolution of large terrestrial predators. Lethaia, Vol. 44, pp. 87–92. Dicynodont (Synapsida: Anomodontia) bones from the Late Triassic (late Norian/early Rhaetian) of Poland yield characteristic tooth marks that can be attributed to three ichnotaxa (Linichnus serratus, Knethichnus parallelum and Nihilichnus nihilicus). The general shape and dimension of these traces perfectly match the dental morphology of a co‐occurring carnivorous dinosaur. It is therefore concluded that early carnivorous dinosaurs were feeding on dicynodonts. This discovery constitutes one of the oldest evidence of dinosaur predator–prey interaction. It is suggested that an evolutionary increase in the size of dicynodonts across the Late Triassic may have been driven by selection pressure to reach a size refuge from early dinosaur predators. □Bite traces, dicynodonts, dinosaurs, predation, Triassic.     

Maternal cannibalistic preferences affect offspring preferences and development in Menochilus sexmaculatus Fabricius (Coleoptera: Coccinellidae): A transgenerational investigation

Cannibalism has been widely reported across taxa. However, the heritability and expression of cannibalistic traits have been least explored. The variation in the expression of cannibalism is likely to exist amongst the population affecting the propensity of cannibalism. Thus, to know whether the mother has any role in the transgenerational transmission of this trait in a ladybird beetle, Menochilus sexmaculatus, we studied the interaction between maternal and offspring prey preferences and its effect on, development duration and body weight of offspring over generations. An insignificant effect of maternal dietary history on offspring prey preference was observed across generations except for the non-cannibalistic adults who significantly preferred aphids over eggs. The long-term detrimental effect of cannibalism was found in cannibals with increased developmental duration and decreased body weight of offspring over generations. In conclusion, the results show that maternal diet did not affect the offspring preferences in M. sexmaculatus but cannibalism had a profound generational effect on the cannibalistic propensity, development and body weight of offspring across generations shows that larval dietary history and nutritional composition of prey contribute to the expression of cannibalistic behaviour across generations.     

Onset and development of cannibalistic behaviour in early life stages of yellowtail

The onset and development of cannibalistic behaviour were observed in early life stages of yellowtail Seriola quinqueradiata . Cannibalistic behaviour was divided into four actions, i.e aim, chase, nip and ingestion. The frequency of chase was used as an index of cannibalistic behaviour because it always appeared in every sequence of cannibalism, although a sequence of cannibalistic behaviour sometimes stopped before nip or ingestion. No cannibalistic behaviour was observed during the larval phase until day 22 after hatching (when fish were 9.6mm T.L.) either in a rearing pond or in experimental tanks. The onset of cannibalistic behaviour was observed on day 23, coinciding with metamorphosis from the larval to juvenile phase, and it developed until day 39, with a tentative decrease between day 33 and day 36. This inverted peak corresponded roughly to the development of schooling behaviour after day 33, which was determined by distance to the nearest neighbour. In the rearing pond, suffocation of a cannibal by its prey, appeared from day 23. Field observation of juvenile yellowtails aggregating around floating seaweeds showed that cannibalism occurred in three out of 10 schools, in which six cannibals were found among 194 fish. Cannibalistic behaviour in early life stages of yellowtail may occur as a final phase of inter-individual interference and may have a role for size selection of a School member.     

Ontogenetic isolation favours sibling cannibalism in mites

Inclusive fitness theory suggests that cannibalistic individuals should preferentially eat unrelated prey when given a choice between related and unrelated individuals. Using the predatory mite Phytoseiulus persimilis, I investigated whether having contact with siblings during a sensitive ontogenetic phase or not determines whether cannibalistic protonymphs tend to eat more sibling or nonsibling larvae in choice situations. Cannibals reared with siblings preferentially ate nonsibling larvae when these had been reared in a sibling group but showed no preference when the larvae had been reared in isolation. Cannibals reared in isolation showed no preference when the larvae had been reared in a sibling group and preferentially ate sibling larvae when these had been reared alone. The occurrence of preferential sibling cannibalism when both cannibal and prey had been reared in isolation suggests the use of self-referent phenotype matching to distinguish between siblings and nonsiblings.     

Approach Strategy by which Male Mediterranean Tarantulas Adjust to the Cannibalistic Behaviour of Females

In sexually cannibalistic species, selection is thought to have favoured the evolution of male approaching behaviour that reduces the probability that the female will kill the male. However, investigations of behaviours that could reduce the probability of sexual cannibalism are few. We examine the hypothesis that male wolf spiders, Lycosa tarantula (L.) (Araneae, Lycosidae), decides to approach females in periods when they are less dangerous. Males of this species approach females for mating during the daytime only. While attending females, males stay farther from the female's burrow at night than during the daytime. In field experiments, we offered a grasshopper (typical prey) or a male L. tarantula to females at night and during the day, and our findings show that the diel changes in the male's approaching behaviour matches diurnal changes in the female's tendency to attack both the grasshopper and the male spider. These findings support our hypothesis that a diel change in female responsiveness to prey has been a selection pressure influencing the evolution of male approach behaviour in a sexually cannibalistic species.     

Furculae in the Late Triassic theropod dinosaur<Emphasis Type="Italic">Coelophysis bauri</Emphasis>

Furculae have been identified in many dinosaurs and are synapomorphic in some clades (e.g., dromaeosaurids). All coelophysid dinosaurs exceptCoelophysis bauri have been shown to possess furculae. To date, the oldest well-documented furculae have been those of the Early Jurassic coelophysids,Coelophysis kayentakatae andCoelophysis rhodesiensis. The confirmation of furculae in Apachean-agedC. bauri further documents appearance of these elements in the Late Triassic and shows that furculae are synapomorphic in the Coelophysidae. A total of five furculae have been found in New Mexico Museum of Natural History’s (NMMNH) Ghost Ranch, New Mexico Whitaker Quarry block C-8-82. We describe three furculae in articulated juvenile skeletons; two that are missing fragments but are nearly complete, and one apparently complete, a small fragment of a furcula associated with an adultC. bauri, and one complete but isolated furcula. We access the morphology and allometry of the scapulocoracoid and furcula and show that they grow, at least in juveniles, in isometry with the humerus. The furcula ofC. bauri has a widely opened U shape that subtends an angle of ∼ 120°. All the furculae have groove-like epicleidial facets at the distal ends of the rami and some possess a small centrally located hypocleideal process. We reconstruct the complete Shoulder girdle ofC. bauri with proper spacing and angles between the elements and find that the coracoids are very close together under the center of the furcula.     

To be an intra‐guild predator or a cannibal: is prey quality decisive?

Abstract.  1. Many cannibalistic species are also intra-guild predators. Such predators will often face the decision whether to consume a conspecific or a heterospecific prey from the same guild. This decision may depend on the relative quality and abundance of the prey but also on other factors such as relatedness by descent, prey-specific defence and the probability of the victim harbouring shared diseases.
2. Here, intra-guild interactions among two cannibalistic species of predatory mites, Iphiseius degenerans and Neoseiulus cucumeris (Acari: Phytoseiidae) that belong to closely related genera were studied.
3. Individuals of I. degenerans were offered a diet of conspecifics or heterospecifics. Because I. degenerans is capable of recognising kin individuals from non-kin, and they were exclusively offered conspecifics that were either distantly related or non-kin, it was expected that it would not refrain from cannibalising for reasons of possible relatedness.
4. When corrected for numbers of victims eaten, survival, and juvenile development of predators fed with intra-guild prey was higher than that of cannibals. This was probably caused by a higher quality of heterospecific victims, even though conspecific victims were larger and therefore potentially contained more food. This led to the prediction that the predators should strongly prefer heterospecific prey. This was indeed borne out in independent choice experiments. Thus, the choice of predators between heterospecific and conspecific prey is not only affected by avoidance of consuming conspecifics, but also by relative prey quality.     

Differentiated egg size of the cannibalistic salamander <Emphasis Type="Italic">Hynobius retardatus</Emphasis>

Larvae of the salamander, Hynobius retardatus, are carnivorous, and even though there are two morphs, a typical morph and a broad-headed or “cannibal” morph, both are cannibalistic. They also sometimes eat other large prey, for example larvae of the frog, Rana pirica. In natural habitats, use of both conspecific and R. pirica larvae as food may contribute more strongly to high survival and substantially to fitness when larval densities are higher, because early-stage H. retardatus larvae sometimes experience scarcity of their typical prey. In cannibalistic oviparous amphibians, larger individuals that developed from larger eggs can more efficiently catch and consume larger prey and thus their survival may be better than that of smaller individuals developed from smaller eggs. Populations might therefore diverge in respect of egg size in response to variation in the density of conspecific and R. pirica larvae in natural ponds, with eggs being larger when larval density is higher. I examined how variance in hatchling size correlated with the incidence of cannibalism, and whether increasing larval density in natural ponds correlated with increasing egg size. Variance in initial larval body size facilitated cannibalism, and egg size increased as larval density in the ponds increased. In ponds with high larval density, where cannibalism and large prey consumption is a critical factor in offspring fitness, the production of fewer clutches with larger eggs, and thus of fewer and larger offspring, results in greater maternal fitness. Variation among the mean egg size in populations is likely to represent a shift in optimum egg size across larval density gradients.     

Observations on the feeding behaviour of the Antarctic Gammarid Eusirus perdentatus Chevreux, 1912 (Crustacea: Amphipoda) in aquaria

Summary The feeding behaviour of adult Eusirus perdentatus was observed in aquaria. These observations and the analysis of gut contents of preserved specimens demonstrate that this species is a carnivorous predator feeding on polychaetes, amphipods and other small crustaceans. Apparently the localization and capture of prey in aquaria follows a fixed pattern.     

Allometric growth in juvenile cod (Gadus morhua) and possible effects on cannibalism

Cod juveniles of about 20 mm had the lowest potential predator: prey length ratio based on mouth gape of the predator and the body height of the prey. This implies that the cannibalistic potential is maximized in this size range.     

Cannibalistic interactions in two co-occurring decapod species: Effects of density, food, alternative prey and habitat

Cannibalism is a potentially important factor in the regulation of populations in a range of habitats. The intensity of this biotic factor may be determined by both intra and interspecific interactions. Cancer pagurus and Porcellana platycheles are two co-occurring decapods on Atlantic rocky shores. In laboratory mesocosms, we investigated intra and intersize class cannibalistic and interspecific predatory behaviours in those species. We addressed the effects of prey and predator densities, food, starvation, alternative prey and habitat type. No agonistic behaviour was noted in P. platycheles, suggesting a non-aggressive co-existence between gregarious individuals. Predation of C. pagurus on P. platycheles was intense, possibly accounting for the spatial segregation observed in the natural environment. Cannibalism among C. pagurus juveniles was low and only on vulnerable prey (i.e. at moulting), suggesting a non-aggressive co-existence among juveniles. However, intersize class cannibalism in C. pagurus was intense (ontogenetic shift), possibly reflecting the juvenile-adult segregation in the natural environment. Prey and predator densities, food and habitat type strongly influenced this behaviour. Possible interference among cannibals was noted, with lower prey consumption at high predator density. Food supply alone had more effect on cannibalistic rate than did alternative prey (P. platycheles) and predator starvation. Structurally complex habitats (small pebble and Fucus serratus habitats) yielded higher prey survival than the sandy habitat, and the behaviours of both prey and cannibals reflected the small-scale spatial distribution of individuals in the wild. Intersize class cannibalism and interspecific agonistic relationships may account for the intertidal distribution of crab species at low tide.     

Dental histology of Coelophysis bauri and the evolution of tooth attachment tissues in early dinosaurs

Studies of dinosaur teeth have focused primarily on external crown morphology and thus, use shed or in situ tooth crowns, and are limited to the enamel and dentine dental tissues. As a result, the full suites of periodontal tissues that attach teeth to the jaws remain poorly documented, particularly in early dinosaurs. These tissues are an integral part of the tooth and thus essential to a more complete understanding of dental anatomy, development, and evolution in dinosaurs. To identify the tooth attachment tissues in early dinosaurs, histological thin sections were prepared from the maxilla and dentary of a partial skull of the early theropod Coelophysis bauri from the Upper Triassic (Rhaetian‐ 209–201 Ma) Whitaker Quarry, New Mexico, USA. As one of the phylogenetically and geologically oldest dinosaurs, it is an ideal candidate for examining dental tissues near the base of the dinosaurian clade. The teeth of C. bauri exhibited a fibrous tooth attachment in which the teeth possessed five tissues: enamel, dentine, cementum, periodontal ligament (PDL), and alveolar bone. Our findings, coupled with those of more recent studies of ornithischian teeth, indicate that a tripartite periodontium, similar to that of crocodilians and mammals, is the plesiomorphic condition for dinosaurs. The occurrence of a tripartite periodontium in dinosaurs adds to the growing consensus that the presence of these tissues is the plesiomorphic condition for the major amniote clades. Furthermore, this study establishes the relative timing of tissue development and growth directions of periodontal tissues and provides the first comparative framework for future studies of dinosaur periodontal development, tooth replacement, and histology. J. Morphol. 277:916–924, 2016. © 2016 Wiley Periodicals, Inc.     

Evidence of Cannibalism in Macrolophus pygmaeus, a Natural Enemy of Whiteflies

Cannibalism and the effects of host plant, sex, time and food resources on its expression were studied for the zoophagous mirid Macrolophus pygmaeus Wagner (Hemiptera: Miridae). Cannibalistic behaviour was studied by offering 5 conspecific larvae (first instar) to newly emerging adults. Four treatments were studied: without water, with water only, with a host plant (tobacco) and with both a host plant and prey (eggs of Ephestia kuehniella). Cannibalism was observed in all treatments. In the “host plant + eggs of E. kuehniella” treatment, very few individuals displayed cannibalistic behaviour. The proportion of cannibalism was only reduced when eggs of E. kuehniella were offered. Water (free or via a host plant) was very important for both survival and feeding. The cannibalistic behaviour of M. pygmaeus should be taken into account when planning a release strategy in the context of biological control.     

Biological pest control using cannibalistic predators and with provision of additional food: a theoretical study

Cannibalism is a conspecific lethal interaction, a typical phenomenon in many natural populations, which is used as a “life-boat strategy” to avoid circumstances leading to extinction. It is observed in many experimental studies that the cannibalistic nature of natural enemies deters the outcome of biological pest control programmes. One of the ways to deviate natural enemies from conspecific lethal interactions is to provide them with additional food. In this paper, using the theory of dynamical systems, we analyse the dynamics of a cannibalistic predator-prey system when predators are provided with additional food. A detailed mathematical analysis is carried out to study the permanence, stability and various bifurcations occurring in the system. The system analysis reveals several interesting phenomena. Depending on the choice of quality (characterised by the predator’s handling time towards additional food, and prey) and quantity of additional food, the system can exhibit multiple coexisting equilibria, leading to the emergence of a homoclinic loop. Further, it is observed that by varying the quality and quantity of additional food, one can not only limit and control the pest but also eradicate the predators. In the context of biological control programmes, the current theoretical study aids eco-managers in choosing the appropriate additional food that is to be supplied for enhancing the biocontrol efficiency of cannibalistic predators.