Research Article |
Corresponding author: Gabriela de Araujo Pereira ( gapereira@unifesp.br ) Corresponding author: Marcelo José Sturaro ( marcelosturaro@gmail.com ) Academic editor: Lukas Landler
© 2023 Gabriela de Araujo Pereira, Célio F. B. Haddad, Marcelo José Sturaro.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
de Araujo Pereira G, Haddad CFB, Sturaro MJ (2023) Trophic ecology of the Atlantic Forest endemic tree frog Boana bischoffi (Boulenger, 1887) (Anura, Hylidae). Herpetozoa 36: 23-29. https://doi.org/10.3897/herpetozoa.36.e95863
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Studies of natural history are important to accumulate knowledge about aspects of diet, reproduction, and habitat use, which can assist the conservation biology for endangered groups, such as amphibians. Here we evaluated the trophic ecology and sexual size dimorphism of Boana bischoffi, a widely distributed and endemic tree frog species of the Brazilian Atlantic Forest. We analysed 80 individuals, covering the distribution of the species and combined our data-set with data from the literature. Gastrointestinal items were separated, accounted, and identified to the highest possible taxonomic resolution. Subsequently, the size and mass of prey items were measured. Afterwards, we calculated rates of relative importance for each prey category. The items of greatest relative importance were beetles (Coleoptera), termites (Isoptera), crickets (Orthoptera) but also harvestmen (Opiliones). We did not find a relation between female snout-vent length, mouth width and length with prey length. In males, the mouth length and width are related to prey length. We found a sexual dimorphism in size typical for hylid frogs, with females being larger than males. Our data expand the knowledge about the alimentary biology of B. bischoffi, but further research focusing on other aspects of the natural history such as possible intersexual dietary divergence and food niche overlapping, environmental prey availability and selection is still needed.
amphibians, diet, sexual dimorphism, trophic ecology
Data about alimentary biology are essential to understand several aspects of an animal’s life history and functional interaction between organisms, including energy flow and food webs as well as the development of conservation strategies (
Anurans play a fundamental role in the ecosystem since they are a source of food for several other animals, such as spiders (
Even though B. bischoffi is a widely distributed species, aspects related to its natural history have been poorly studied, with only a single study describing the diet of a population in the Rio Grande do Sul, Brazil (
We examined 80 adults of Boana bischoffi from 26 localities in total (Fig.
We determined the sexes through direct observation of the gonads and secondary sexual characteristics of males such as the presence of a vocal sac and/or vocal slits. We measured the snout-vent length (SVL), mouth width (MW), and mouth length (ML) following
We analysed the composition of the diet examining both stomachs and intestines of each specimen to increase the efficiency to find a respective gut content (following
To evaluate whether the sampling used was sufficiently representative, we performed two rarefaction curves with prey categoric frequency, one using only our data and a second compiling data set from
We also analysed the possible influence of frog snout-vent length, mouth width, and length in relation to the length of the prey ingested, represented by a simple regression between frog measurements, by sex, and the length of the largest prey item found in each gastrointestinal tract. For this analysis, we only considered intact prey to avoid bias.
All analyses were performed using the R program (R CORE TEAM, 2018).
For the analysis of the sexual dimorphism relative to the SVL, we sampled 80 adult specimens (38 females and 42 males) of Boana bischoffi. Females were larger (SVL ranged from 43.9 to 61.1 mm; mean 54.9 ± 3.7 mm) than males (SVL range 34.4–46.2 mm, mean 39.9 ± 2.6 m; t = 20.639, DF = 66.641, p = 0.0001) and had wider (females: 16.2–22.3 mm, mean 19.0 ± 1.4 mm; males: 11.1–16.4 mm, mean 14.1±1.2 mm; t = 16.493, DF = 73.739, p < 0.0001) and longer mouth (females: 14.5–20.1 mm, mean 17.6 ± 1.4 mm; males: 10.7–15.5 mm, mean 12.7±1.1 mm; t = 17.745, DF = 771.752, p < 0.0001). The size dimorphism index also shows that females were larger than males (SDI = 0.376).
We analysed the gastrointestinal contents of 38 females and 42 males of B. bischoffi. Of these, 43 (six only with fragments of plants) had their digestive tracts with prey (53.8%), of which 18 were females and 25 males. The percentages of gastrointestinal tracts with some contents were relatively higher in the summer (54%) and spring (64%) than in the fall (45%) and winter (42%). We identified 112 alimentary items in total distributed into 13 prey categories (Table
Diet composition of the frog Boana bischoffi (n = 43). O = total number of each prey category in the gastrointestinal tract; N = frequency of gastrointestinal tracts containing a given category; M = total mass (g) of each prey category; IRI = Index of Relative Importance; % = percentage value over total.
Prey Categories | O | O% | N | N% | M | M% | IRI% |
---|---|---|---|---|---|---|---|
Araneae | 6 | 5.4 | 6 | 13 | 29.63 | 2.1 | 5.8 |
Opiliones | 6 | 5.4 | 5 | 10.9 | 339.39 | 24.1 | 13.4 |
Blattaria | 1 | 0.9 | 1 | 2.2 | 2 | 0.1 | 0.1 |
Coleoptera | 14 | 12.5 | 12 | 26.1 | 199.32 | 14.1 | 36 |
Diptera | 1 | 0.9 | 1 | 2.2 | 0.81 | 0.1 | 0.1 |
Hymenoptera (ants) | 3 | 2.7 | 3 | 6.5 | 0.69 | 0 | 1.3 |
Hemiptera | 1 | 0.9 | 1 | 2.2 | 58.21 | 4.1 | 0.4 |
Isoptera | 63 | 56.3 | 2 | 4.3 | 4.93 | 0.3 | 18.9 |
Lepidoptera | 1 | 0.9 | 1 | 2.2 | 516.2 | 36.6 | 2.5 |
Larvae of Coleoptera | 1 | 0.9 | 1 | 2.2 | 1.3 | 0.1 | 0.1 |
Larvae of Lepidoptera | 6 | 5.4 | 4 | 8.7 | 25.84 | 1.8 | 4 |
Neuroptera | 1 | 0.9 | 1 | 2.2 | 4.42 | 0.3 | 0.2 |
Orthoptera | 8 | 7.1 | 8 | 17.4 | 228.42 | 16.2 | 17.2 |
Plant matter | 27 | – | 16 | – | 37.87 | – | – |
In the gastrointestinal tracts of B. bischoffi, we observed 13 prey categories increasing to 20 when we included data from references. In the richness of prey estimative, we found 30 categories for our data and 21 compiling data from Moser et al. (Fig.
Female Boana bischoffi were larger than males in agreement with the findings of other congeneric species such as B. albopunctata, B. cordobae, and B. curupi (
The absence of prey in about half of the gastrointestinal tracts may be due to the use of specimens deposited in collections of natural history museums, which were collected for many other purposes but were not specifically collected for diet biology studies. Specimens to be used in alimentary biology studies must be euthanized and fixed immediately after being collected (following e.g.,
We found 13 prey categories in the diet of B. bischoffi, two less than that reported earlier by
Coleoptera, Orthoptera, Isoptera and Opiliones were the most important prey categories in the diet of B. bischoffi in accordance with congeners, where Araneae and Diptera also have high representativity (
We found plant material (seed and fragments of leaves) in the gastrointestinal tract of B. bischoffi, which was previously reported for other species of Boana (
We did not find a relation between snout-vent length, mouth width and length to prey length in females of B. bischoffi. However, in the males, the mouth length and width are related to prey length, which was also reported earlier for the congener B. albomarginata (
Boana bischoffi is a generalist feeder; i.e., its diet is mainly based on several major arthropod groups such as Coleoptera, Isoptera and Orthoptera but also Opiliones. It has an accentuated sexual size dimorphism with females being larger than males.
Future studies comparing alimentary biology are necessary to elucidate possible intersexual dietary divergence or food niche overlapping. Furthermore, environmental prey availability and selection are other important aspects to be evaluated in the future. Our study contributes to understanding the trophic ecology of anurans in the Atlantic Forest and reinforces the importance of including literature data in the analysis.
We thank Fabiana E. Casarin dos Santos and Cibele Bragagnolo for helping in the identification of some preys. Also, Adriano Oliveira Maciel, Cinthia Aguirre Brasileiro, Katia Pellegrino and Isabel Bonatelli for helpful feedback and suggestions to improve the manuscript. MJS and the study were financially supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, process # 434362/2018–2).
Adults of the frog Boana bischoffi in this study
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