Digestive ecology of two omnivorous Canarian lizard species (Gallotia, Lacertidae) (original) (raw)
Related papers
02. Body size affects digestive performance in a Mediterranean lizard
Herpetological Journal, 2016
Published by the British Herpetological Society Effective digestion is decisive for survival. In nature, where most animals feed sporadically, high digestive performance guarantees they will gain the most out of their infrequent meals. Larger body size implies higher energy requirements and digestion should function properly to provide this extra energy. Comparing Skyros wall lizards (Podarcis gaigeae) from Skyros Island to large ("giant") lizards from a nearby islet, we tested the hypothesis that digestion in large individuals is more efficient than in small individuals. We anticipated that giant lizards would have higher gut passage time (GPT), longer gastrointestinal (GI) tracts and higher apparent digestive efficiencies (ADE) for lipids, sugars and proteins. These predictions were only partially verified. Giant lizards indeed had longer (than expected based on body length) GI tract and longer GPTs but achieved higher ADE only for proteins, while ADEs for lipids and sugars did not differ from the normal-sized lizards. We postulated that the observed deviations from the typical digestive pattern are explained by cannibalism being more prominent on the islet. Giant lizards regularly consume tail fragments of their conspecifics and even entire juveniles. To break down their hard-to-digest vertebrate prey, they need to extend GPT and thus they have developed a longer GI tract. Also, to fuel tail regeneration they have to raise ADEproteins. It seems that larger size, through the evolution of longer GI tract, enables giant lizards to take advantage of tails lost in agonistic encounters as a valuable food source.
Correlating diet and digestive tract specialization: Examples from the lizard family Liolaemidae
Zoology, 2005
A range of digestive tract specializations were compared among dietary categories in the family Liolaemidae to test the hypothesis that herbivores require greater gut complexity to process plant matter. Additionally, the hypothesis that herbivory favors the evolution of larger body size was tested. Lastly, the association between diet and hindgut nematodes was explored. Herbivorous liolaemids were larger relative to omnivorous and insectivorous congeners and consequently had larger guts. In addition, small intestine length of herbivorous liolaemids was disproportionately longer than that of congeners. Significant interaction effects between diet and body size among organ dimensions indicate that increases in organ size occur to a greater extent in herbivores than other diet categories. For species with plant matter in their guts, there was a significant positive correlation between the percentage of plant matter consumed and small intestine length. Herbivorous liolaemids examined in this study lacked the gross morphological specializations (cecum and colonic valves) found in herbivores in the families Iguanidae and Agamidae. A significantly greater percentage of herbivorous species had nematodes in their gut. Of the species with nematodes, over 95% of herbivores had nematodes only in the hindgut. Prevalence of nematodes in the hindgut of herbivores was 2 Â that of omnivores and 4 Â that of insectivores.
Body size affects digestive performance in a Mediterranean lizard Herpetological Journal
Effective digestion is decisive for survival. In nature, where most animals feed sporadically, high digestive performance guarantees they will gain the most out of their infrequent meals. Larger body size implies higher energy requirements and digestion should function properly to provide this extra energy. Comparing Skyros wall lizards (Podarcis gaigeae) from Skyros Island to large (" giant ") lizards from a nearby islet, we tested the hypothesis that digestion in large individuals is more efficient than in small individuals. We anticipated that giant lizards would have higher gut passage time (GPT), longer gastrointestinal (GI) tracts and higher apparent digestive efficiencies (ADE) for lipids, sugars and proteins. These predictions were only partially verified. Giant lizards indeed had longer (than expected based on body length) GI tract and longer GPTs but achieved higher ADE only for proteins, while ADEs for lipids and sugars did not differ from the normal-sized lizards. We postulated that the observed deviations from the typical digestive pattern are explained by cannibalism being more prominent on the islet. Giant lizards regularly consume tail fragments of their conspecifics and even entire juveniles. To break down their hard-to-digest vertebrate prey, they need to extend GPT and thus they have developed a longer GI tract. Also, to fuel tail regeneration they have to raise ADEproteins. It seems that larger size, through the evolution of longer GI tract, enables giant lizards to take advantage of tails lost in agonistic encounters as a valuable food source.
PLOS ONE, 2016
Through 17 years and from a sample of 7,790 faecal pellets and 26,346 prey items, we studied the diet of the Balearic lizard Podarcis lilfordi in Aire Island (Menorca, Balearic Islands, Spain). We analysed the diet in terms of prey frequencies, as well as by their volume and biomass contributions. The diet of the Balearic lizard was extremely variable through the years, months and areas under study. The dominance of small clumped prey, particularly ants, was confirmed. However, the main contribution by volume corresponded to beetles, with a relevant role for Diplopoda and terrestrial Isopoda during some months and at particular areas of the island. Several prey items were probably captured at the base of shrubs, under stones or inside rock crevices. Therefore, our estimations of electivity would only be reliable for epigeal and flying prey. The capacity of the Balearic lizard to include marine subsidies in its diet, such as coastal crustaceans, is noteworthy. Also, its consumption of carrion from carcasses of gulls and rabbits and leftovers from human visitors is remarkable. Juvenile conspecifics can also be a sporadic food resource, especially during the second half of summer, whereas the consumption of vegetal matter is constant for each whole year. The shifts of vegetal exploitation among areas of the island and months take place according to availability of different plant species at each area or during a given period. Thus, lizards are able to conduct a thorough monitoring of plant phenology, exploiting a large variety of plant species. Omnivory does not imply the indiscriminate inclusion of any edible food in its diet. Rather, the inclusion of several food items means the adoption of a wide range of foraging behaviours adapted to the exploitation of each food resource.
Physiological and Biochemical Zoology, 2010
Dietary shifts have played a major role in the evolution of many vertebrates. The idea that the evolution of herbivory is physiologically constrained in squamates is challenged by a number of observations that suggest that at least some lizards can overcome the putative physiological difficulties of herbivory on evolutionary and even ecological timescales. We compared a number of morphological and physiological traits purportedly associated with plant consumption between two island populations of the lacertid lizard Podarcis sicula. Previous studies revealed considerable differences in the amount of plant material consumed between those populations. We continued the investigation of this study system and explored the degree of divergence in morphology (dentition, gut morphology), digestive performance (gut passage time, digestive efficiency), and ecology (endosymbiont density). In addition, we also performed a preliminary analysis of the plasticity of some of these modifications. Our results confirm and expand earlier findings concerning divergence in the morphology of feeding structures between two island populations of P. sicula lizards. In addition to the differences in skull dimensions and the prevalence of cecal valves previously reported, these two recently diverged populations also differ in aspects of their dentition (teeth width) and the lengths of the stomach and small intestine. The plasticity experiment suggests that at least some of the changes associated with a dietary shift toward a higher proportion of plant material may be plastic. Our results also show that these morphological changes effectively translate into differences in digestive performance: the population with the longer digestive tract exhibits longer gut passage time and improved digestive efficiency.
The effect of plant consumption in the overall diet of an omnivorous lizard
Salamandra
During the blooming period of the thistle Carlina corymbosa L. (Asteraceae) on Aire Island (Menorca, Balearic Islands, Spain), the Balearic lizard, Podarcis lilfordi, climbs the plant and forages on its inflorescences. We studied this foraging behaviour by means of observation. We collected data on fourteen variables belonging to three groups: movements and foraging strategy, use of C. corymbosa as a trophic resource, and foraging behaviour of P. lilfordi on this plant species. Analysis of these variables shows that P. lilfordi employs a mixed strategy of licking and plucking C. corymbosa flowers, probably due to a low nectar production and/or its difficulty of access. Interestingly, some behavioural traits are similar to those observed while foraging on carcasses. We also studied the diet of P. lilfordi through analysis of faecal samples. We found that C. corymbosa is a key food resource during summer. Foraging on C. corymbosa led to consumption not only of plant elements, but also...
Frugivory in polychrotid lizards: effects of body size
Oecologia, 2004
As more data have become available on lizard diets in the past few decades, researchers have stressed the importance of lizards as pollinators and seed dispersers. Whereas large body size has been traditionally put forward as a major biological factor "allowing" herbivory and frugivory in lizards, a recent review of frugivory and seed dispersal by lizards showed that frugivory might be considered to be a typical island phenomenon, independent of body size. Here we show that frugivory is correlated with lizard body size among a group of syntopic Anolis species in Jamaica, with larger species eating more fruit. Additionally, the size of the fruits consumed is significantly related to lizard body size. Multiple regression analyses show that this is largely a pure body size effect as head shape or residual bite force are uncorrelated to overall fruit size. Moreover, we demonstrate that among polychrotid (Anolis-like) lizards in general, those that consume fruit are on average larger than those that do not. Lizards from the mainland were not significantly different in body size from island species. We thus suggest that fruit consumption in polychrotid lizards is mediated by large body size whether living on islands or not.
Spatial, Ontogenetic, and Sexual Effects on the Diet of a Teiid Lizard in Arid South America
Journal of Herpetology, 2011
Most lizard species feed on small arthropods, and although some are omnivorous, only a few species are strict herbivores. We studied the diet of Dicrodon guttulatum, a teiid lizard endemic to the arid coastal deserts and dry forests of northern Peru. Herbivory by this lizard has been identified as a potential limiting factor in the regeneration of plant communities in these dry ecosystems. We collected gastric and fecal samples of adult males, adult females, and juveniles of D. guttulatum in different plant communities. Based on the ontogenetic shift from insectivory to herbivory observed in other herbivorous lizards, we hypothesized that juvenile D. guttulatum would have an omnivorous or insectivorous diet. We found D. guttulatum to be almost exclusively herbivorous (78-100%) and to feed largely (12-95%) on mesquite (Prosopis pallida) leaves and flowers across all plant communities and locations. Contrary to our predictions, there was a large overlap in diet between adult males and juveniles, whereas adult females were most likely to include plant species other than P. pallida in their diet. The consistency of herbivory in both juveniles and adults makes the origin of herbivory in D. guttulatum very interesting. We discuss potential factors promoting the evolution of herbivory in this species and the importance of lizard herbivory in the dry ecosystems of northern Peru. 4 Corresponding Author.