Does Body Size Affect the Diet Composition of a Sand Dune Lizard? Insights from Liolaemus Occipitalis Boulenger, 1885

Herpetology Notes, volume 12: 1211-1213 (2019) (published online on 12 December 2019) Does body size affect the diet composition of a sand dune lizard? Insights from Liolaemus occipitalis Boulenger, 1885 Alexandro M. Tozetti1,* and Laís S. Martins2 Data about the process of food acquisition and prey 1999). Its diet is based on insects and eventually other selection represent an elementary contribution to small arthropods (Bujes and Verrastro, 2006; Verrastro understand the ecological traits of any animal species and Ely, 2015). Our hypothesis is that, due to their (Sih and Christensen, 2001). The analysis of the low ability in capturing, subduing and ingesting larger relationships between prey consumption and the body prey, smaller individuals will exhibit a less diverse size of a predator is one example of the ecological composition of consumed prey than larger ones. We consequences of feeding ecology (MacArthur and conducted the study in a wide coastal sand dune system Pianka, 1966; Charnov, 1976). Some studies pointed sparsely covered by grasses at Cassino beach (Oliveira et out that larger predators are able to capture, handle al., 2013), in the municipality of Rio Grande in southern and consume both large and small prey (Peters, 1983; Brazil (between coordinates -32.2 to 32.25S and -52.17 Costa, 2008; Sales et al., 2012). On the other hand, to -52.23W). The local climate is classified as sub- larger predators could be inefficient in dealing with tropical humid, with an average annual temperature of small prey, despite being able to do that. Considering 18.1ºC (Maluf, 2000). Lizard captures were performed this, larger predators would try to maximize their energy during the summer, spring and autumn from 2014 intake by capturing preferentially larger prey, which is to 2015. Lizards were located by visual search and supported by the optimal foraging hypothesis (Costa, manually captured. We conducted daytime searches 2008). As a consequence, individuals of different sizes between 9:00 AM and 5:00 PM, which corresponds to will exhibit differences in their set of consumed prey the peak of lizard activity (Martins et al., 2014). Only (diet composition) due to differences in their ability active lizards (lizards observed on surface of sand dunes) to capture prey. As an ultimate analysis, scientists were captured for dietary evaluation. Individuals were assume that food acquisition is a remarkable driver to gently handled for body measures (CRC, head height the evolutionary process (Pianka and Vitt, 2003; Des and head width). Immediately after capture, all lizards Roches et al., 2015). Unfortunately, this approach is were submitted to a stomach flushing (Legler, 1977). poorly studied for many of Neotropical lizard species. We used this method instead of dissecting euthanatized In this study, we investigated the relationship between specimens since L. occipitalis is an endangered species dietary composition and body size in the sand dune in Brazil (ICMBio, 2016). The stomach flushing lizard Liolaemus occipitalis Boulenger, 1885. This is protocol was authorized by the Institutional Ethical a small terrestrial lizard that occurs in southern Brazil Committee for Animal Experimentation (PPCEUA- and Uruguay and spends its entire life in the sand dunes 72016) and by the federal wildlife service (SISBIO (Verrastro and Bujes, 1998; Verrastro and Krause, license # 44829-1). In the laboratory, the stomach content of each specimen was examined and prey items were identified at the lowest possible taxonomic level (order). As many prey items were fragmented, we were not able to perform an evaluation based on prey 1 Laboratório de Ecologia de Vertebrados Terrestres, counting. Instead, we relisted prey composition based on Universidade do Vale do Rio dos Sinos, UNISINOS, Campus volume estimation of each category of consumed prey, São Leopoldo, 93020-190 Rio Grande do Sul, Brazil. following a protocol proposed by Hellawell and Abel ² Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Avenida Itália, Km 8, CEP 96201-900, Rio Grande, (1971). This procedure consists in measuring the area Rio Grande do Sul, Brazil. occupied by the entire content of each prey item spread * Corresponding author. E-mail: [email protected] over a Petri dish, multiplied by the height of the spread 1212 Alexandro M. Tozetti & Laís S. Martins Table Table1. Total 1. volumeTotal volume of consumed of consumed prey itemsprey items by Liolaemus by Liolaemus occipitalis occipitalis of different of different body body size size categories. categories. Lizard size Prey items Small (n = 8) Medium (n = 8) total Large (n = 7) total total volume (mm3) volume (mm3) volume (mm3) Araneae 70 56 77 Coleoptera 200 90 245 Diptera 740 891 439 Heteroptera 0 2 2 Homoptera 0 150 0 Hymenoptera 130 81 26 Orthoptera 3 120 385 Not identified 610 815 413 material (approximately 1 mm). We analysed 23 adult type in lizards of all size categories (Table 1). Median lizards (10 males and 13 females) and identified seven diversity of consumed prey was greater for medium categories of consumed prey (Table 1). Some material and large lizards (Shannon Diversity Index = 7) than with a high degree of fragmentation was described as for small ones (Shannon Diversity Index = 6; Figure 1). “not identified”. We compared the total volume of each Median dominance of consumed prey was lower for large category of consumed prey between three size classes lizards (0.28) than for small and medium ones (median of lizards: small (body size varying from 32 mm to 42 dominance = 0.42 and 0.43, respectively; Figure 2). Our mm), medium (43 mm to 48 mm) and large (49 mm to findings point out, that lizards of different sizes have 53 mm). similar diets, with a similar set of consumed prey. On the We calculated the Shannon Diversity Index of prey other hand, we found differences in terms of diversity items to each lizard size class through a rarefaction and dominance in diet between lizards of different sizes method. To examine the participation of each prey item with lower values of diversity of consumed prey in in the diet composition of each lizard group, we also small lizards. We suggest that small lizards have a more calculated dominance with the rarefaction method. All restrict dietary composition than medium or large ones, analyses were carried out with EcoSim 7.72 software probably due to the inability to capture a wide range (Gotelli and Entsminger, 2001), based on 1,000 of prey types. This interpretation is reinforced by the iterations. Diptera was the most representative prey fact that dominance was lower for large lizards, which suggests an ability to consume a wide range of prey Figure1 1. Median values of the Shannon Diversity Index Figure 2. Median values of dominance obtained by a obtained by a rarefaction method based on samples of rarefaction method based on samples of consumed prey items consumed prey items by three different size classes of by three different size classes of Liolaemus occipitalis in Liolaemus occipitalis in southern Brazil. southern Brazil. Does body size affect the diet composition of a sand dune lizard? 1213 categories. This result is expected since larger lizards Martins, L.S., Verrastro, L., Tozetti, A.M. (2014): The influences are able to capture, subdue and consume a wide range of habitat on body temperature control in a southern population of prey types, including a high variety of taxa (Costa of Liolaemus occipitalis (Boulenger, 1885) in Brazil. South American Journal of Herpetology 9: 9–13. et al., 2008). We performed a linear regression between Oliveira, M.C.L.M., Santos, M.B., Loebmann, D., Hartman A., total body length and head size for the examined lizards, Tozetti A.M. (2013): Diversity and associations between coastal which reinforced this positive relationship (body sizes × habitats and anurans in southernmost Brazil. Anais da Academia head length: Spearman test = 0.67; p = 0.049; body size Brasileira de Ciências 85: 575–582. × head width: Spearman test 0.95; 0 = 0.0002). Since Peters, R.H. (1983): The ecological implications of body size. larger lizards have larger heads, probably they are prone Cambridge, UK, Cambridge University Press. to subdue and consume a wider range of prey items than Pianka, E.R., Vitt, L.J. (2003): Lizards: windows to the evolutionof diversity. University of California Press, Berkeley. smaller lizards. As we captured lizards of all sizes in all Sales, RFD, Ribeiro, L.B, Jorge, J.S, Freire E.M.X. (2012): Feeding locations, we believe that variation in prey availability Habits and Predator-Prey Size Relationships in the Whiptail has a low interference in our results. Our results indicate Lizard Cnemidophorus ocellifer (Teiidae) in the Semiarid an intraspecific variation in the feeding behaviour of Region of Brazil. South American Journal of Herpetology 7: Liolaemus occipitalis. This reinforces the relevance of 149–156 an individual evaluation of diet, which encompasses an Sih, A., Christensen, B. (2001): Optimal diet theory: when does open field for studies in the Neotropical ecozone. it work, and when and why does it fail? Animal behaviour 61: 379–390. Verrastro, L., Bujes, C.S. (1998): Rhythm of activity of Liolaemus Acknowledgments. We thank the Conselho Nacional de occipitalis (Sauria, Tropiduridae) at the Quintão beach, Rio Desenvolvimento Científico e Tecnológico (CNPq) and the Grande do Sul, Brazil. Revista Brasileira de Zoologia 15: 913– Coordenação de Aperfeiçoamento de Pessoal de Nível Superior 920. (CAPES) for financial support. Verrastro, L., Ely, I. (2015): Diet of the lizard Liolaemus occipitalis in the coastal sand dunes of southern Brazil (Squamata- References Liolaemidae). Brazilian Journal of Biology 75: 289–299. Bujes, C.S., Verrastro, L. (2006): Thermal biology of Liolaemus Verrastro, L., Krause L. (1999): Ciclo reprodutivo de machos de occipitalis (Squamata, Tropiduridae) in the coastal sand dunes Liolaemus occipitalis Boulenger (Sauria, Tropiduridae). Revista of Rio Grande do Sul, Brazil.

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