NORTH-WESTERN JOURNAL OF ZOOLOGY 14 (1): 71-75 ©NWJZ, Oradea, Romania, 2018 Article No.: e171507 http://biozoojournals.ro/nwjz/index.html Calling perch selection and body condition in Dendropsophus jimi (Anura: Hylidae). Pietro Longo Hollanda DE MELLO1,2*, Guth Berger Falcon RODRIGUES2, Wáldima Alves da ROCHA2 and Reuber Albuquerque BRANDÃO2,3 1. Biodiversity Institute, Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, USA, 66045. 2. Departamento de Zoologia, Instituto de Ciências Biológicas (IB), Universidade de Brasília, Brasília, Distrito Federal, Brazil, CEP 70910-900. 3. Laboratório de Fauna e Unidades de Conservação, Departamento de Engenharia Florestal, Universidade de Brasília, Distito Federal, Brazil, CEP 70910-900. * Corresponding author, P.L.H. De Mello, E-mail: [email protected] Received: 10. October 2016 / Accepted: 19. April 2017 / Available online: 29. July 2017 / Printed: June 2018 Abstract. Calling is a key behavior in anuran ecology, associated with individual reproductive success and territory maintenance. Sites that allow better sound propagation, with higher intensity and less energy consumption, are a resource that males will compete for. We used body condition (BC) as a proxy for competitive performance to test the hypothesis that Dendropsophus jimi males with superior BC occupied better perches for calling in a pond with simple vegetative structure. Because grassy layer density and height are inversely correlated, presumably facilitating sound propagation, we expected a positive correlation between BC and perch height in open-field specialists. We also identified which morphological features were associated with higher perching. In addition, if calling males are depleting energy reserves during the breeding season, they should maintain BC through food consumption. To test this hypothesis, we performed a correlation between stomach volume and food item abundance with BC. We found perch height to be positively correlated with BC. Higher calling males were also characterized by having longer legs, shorter carpus and smaller heads. However, we found no correlation between BC and food intake. We suggest that calling males are depleting previously accumulated energy stocks. Higher calling perches are apparently actively disputed by D. jimi, as superior BC males are using mainly higher perches. We suggest that our findings on the small D. jimi are also expected for other open field Hylinae in the Cerrado. Key words: advertisement call, body condition, diet, intrasexual competition, morphology, Cerrado. Introduction morphometric features associated with perching height. For that, we sampled males of Dendropsophus jimi (Napoli & Anuran advertisement calls hold several social roles, such as Caramaschi, 1999) (Fig. 1) from a species poor pond (four promoting spacing among males in a chorus, and attracting anuran species) dominated by grasses, in the Brazilian Cer- reproductive mates (Wells 1977, Wells & Schwartz 2007). rado Savanna (Myers et al. 2000). The lack of congeneric spe- Calling is among the most energetically demanding activi- cies in the pond allowed the locally abundant D. jimi males ties in ectotherms (Taigen & Wells 1985) and its effectiveness to use all possible perch heights, thus releasing this feature depends on efficient signal transmission (i.e. reaching the re- from potential interspecific competition (e.g. Brasileiro et al. ceiver). Therefore, optimization of call efficiency should be 2005, Martins et al. 2006). We expected males with superior under selection in frogs (Crump 1974, Sinsch et al. 2012), and BC to call from higher perches, an indication that intraspeci- males should compete for sites that allow better sound fic competition may be playing a role in intraspecific habitat propagation, higher intensity, and lower energy expenditure partitioning; and to have longer legs, used for both jumping (Wells & Schwartz 1982). Since sound degradation is in- (Choi et al. 2003), or in physical combats (e.g. Noer & Mardi- versely correlated to perch height, calling from higher ansya 2014, Méndez-Narváes & Amézquita, 2014). perches is an alternative to improve call efficiency (Kime et Since anuran metabolic costs increase with calling effort al. 2000, Schwartz et al. 2016). (Taigen & Wells 1985), we additionally tested the hypothesis The competition for resources during the breeding sea- that calling males are using previously stored energy stocks son is common in anurans (e.g. Wells 1977, Arak 1983), and through the breeding season (Jiménez & Bolaños 2012), in- might include aggressive vocalization and/or physical com- stead of maintaining BC via frequent intake of energy, i.e. bats (Wells 1988, Gerhardt & Huber 2002). When such in- food ingestion. To test this hypothesis, we performed a cor- traspecific interactions cannot be directly observed in the relation between stomach volume and food item abundance field, body condition (BC), a measure for the energetic status with BC. If calling behavior is kept by depletion of stocks, of an organism (Jakob et al. 1996, Labocha et al. 2013, but see we expect a lack of correlation and a high frequency of Wilder et al. 2016) can be used as a surrogate for several fit- empty stomachs. ness parameters, such as fighting capacity (Thorpe et al. 1995). The scaled mass index (SMI) (Peig & Green 2009) is one of multiple methods developed to estimate BC (e.g. Ja- Material and methods kob et al., 1996). We chose SMI since MacCracken & Steb- bings (2012) tested this method on anurans and salaman- Study system & sampling We conducted our study in a permanent pond (15°53'52"S and ders, and showed that it does accurately reflect the speci- 47°56'38"W, 1100 m a.s.l.) located in a suburban neighborhood of men’s energy storage, i.e. it’s BC, in these taxa. SMI may Brasília, Brazil. The climate in Brasília is tropical (Köppen’s Aw), thus be used as a proxy for competitive performance, help- with a dry season from April to September, and a rainy season from ing identify patterns that may result from intraspecific com- October to March (Peel et al. 2006). Habitat structure in the pond is petition. simple, with the predominance of a grassy layer over wet soil and Herein, we tested the hypothesis that male BC is posi- scattered bushes surrounding the pond. Although males can call tively correlated with higher perches, and characterized the from grasses, the sparse bushes provide the higher calling perches 72 P.L.H. De Mello et al. through a linear regression, followed by an evaluation of the whole data set (all specimens) for outliers by examining scatter plots. We chose this method because it has successfully been applied to quan- tify energy storage in amphibians (MacCracken & Stebbings 2012), and because it accommodates error in measurements for both ‘M’ and ‘L’, as well as differences in the magnitude of natural variability and measurement error between these variables (see Peig & Green 2009). We performed a linear regression between BC and perch height to test the hypothesis that male BC was positively correlated with better, thus higher, perches. To test if frogs were maintaining calling behavior by depleting previously stocked energy, we performed two general linear models, one between BC and the number of ingested food items, and a second between BC and stomach volume. We determined which morphometric measures were associated with perch height use through a multiple regression with automatic Figure 1. Male Dendropsophus jimi perching at study locality. model selection, using the single best Akaike Information Criterion Photo: Wáldima Rocha. (AIC) (Burnham & Anderson 2002) in package MASS (Venables & Ripley 2002). To correct for correlation, we represented all variables through PCA axes (Tabachnick & Fidell 2001). We performed all surrounding the pond. Macrophytes are found around and up to analysis using R software (R Core Team 2015). ~1m away from the margin. Water depth can reach ~1m. Dendropsophus jimi is a small hylid (males SVL 17.6 – 20.9 mm) with a green dorsum, typically associated with permanent ponds in Results open areas (Napoli & Caramaschi 1999). This species concentrates its reproductive effort in wet season (Brasileiro et al. 2005) and pro- We captured and analyzed the stomach of 58 Dendropsophus duces free-living tadpoles that live in lentic water bodies (mode 1, jimi males. These males showed snout-vent length (SVL) av- Haddad & Prado 2005). Three other frog species, including Boana al- bopunctata (Spix, 1824), Leptodactylus fuscus (Schneider, 1799), and erage of 18.78 ± 0.93 mm, and body mass of 37.24 ±7.20 mg. Physalaemus cuvieri (Fitzinger, 1826) were also found in our study Averages and standard deviations of the other morphologi- pond. B. albopunctata could putatively outcompete with D. jimi for cal measures collected are presented in Table 1. As hypothe- perches due to its larger body size (Vieira et al., 2016). However, B. sized, we found a significant positive correlation between albopunctata was never seen calling from Macrophytes, presumably body condition (BC) and perch height (79.24; t = 3.465; p < due to its larger body weight that would not be supported by leaves 0.005). The morphometric variables that best explained the of these plants. B. albopuncatata males were not abundant at the pool, use of higher perches were (AIC = 548.62): Carpus length and the few observed males were scattered along the pond margins. We sampled for four consecutive nights in February, 2013, ob- (CL), tibia length (TL) and head width (HW). CL (- 9.10; t = serving and collecting specimens between 7 pm to 12 pm. Captured 3.791; p < 0.05) and HW (-10.16; t = 3.907; p < 0.05) were in- specimens were preserved in 10% formalin, and later transferred to versely correlated to perch height, while TL (10.385; t = 70% ethanol. All specimens were deposited at the Laboratório de 3.642; p < 0.01) was directly correlated to perch height (Fig. Fauna e Unidades de Conservação (LAFUC) at the University of 2). AIC values for all other possible values are listed in Ap- Brasília.