Diet of Dendropsophus microcephalus and Scarthyla vigilans (Anura: Hylidae) at a locality in north-western Venezuela with notes on microhabitat occupation

DISCUSSION

The results of the present study indicate a high 

probability of competition for calling or prey-am-

bushing perches (but see below) and a relatively low 

probability of competition over food between D. mi-

crocephalus and S. vigilans at the study site. Both spe-

cies use emergent plants and show identical vertical 

distribution. The species share approximately 42% of 

the prey categories identified (15 out of 36) but their 

relative importance varies between them; the most im-

portant categories in one species are usually amongst 

the least important in the other. In D. microcephalus, 

arachnids of Agelenidae and dipterans of Thachinidae 

are the most important (RII ≈ 10%), while the most 

important prey in S. vigilans are orthopterans of the 

family Grillydae. Our results contrast with those of 

Muñoz-Guerrero et al. (2007) with regards to micro-

habitat use and diet composition; we discuss potential 

factors favoring the differences between studies.

At our study locality, we found total micro 

spatial overlap between D. microcephalus and S. vigi-

lans; both species occupy the same type of perch and 

their vertical distribution coincides. We often found 

individuals of both species on the same plant sepa-

rated by as much as 20 cm, as well as on neighboring 

plants less than one meter apart. In addition, during 

the study season, the abundance of both species (esti-

mated from acoustic surveys and captures) was simi-

lar, despite the fact that D.  microcephalus has often 

been regarded as more abundant than S. vigilans (S. 

Boher, pers. comm.). While habitat use suggests high 

potential for space competition between these spe-

cies, we do not take this for granted because competi-

tion depends on resource abundance (Pianka, 1994) 

and nightly activity rhythms. If suitable perches are 

abundant and/or their activity patterns are disjointed 

(within the night and/or along the season), both spe-

cies might coexist without major interference. We did 

not estimate perch abundance in relation to popula-

tion numbers, but qualitatively, at the height of the 

rainy season, emergent vegetation formed a con-

tinuous cover along the lagoon margins; thus calling 

perches did not seem to be limited. Additionally, dur-

ing the study period we never observed any type of ag-

gressive interaction (vocal or physical) between D. mi-

crocephalus and S. vigilans. We believe that acoustical 

cues may help to avoid direct interspecific encounters 

and maintain interindividual distances much as it has 

been demonstrated in intraspecific spacing (Whitney 

& Krebs, 1975; Wilczynski & Brenowitz, 1988). We 

understand, however, that our characterization of the 

microhabitat was not detailed enough because we did 

not identified plants to species level, or estimated the 

size and shape of the leaves and stems. For instance, 

Jiménez & Bolaños (2012) found similitude in mi-

crohabitat use between D. ebraccatus and D. phlebodes 

but they detected microhabitat segregation when they 

considered other more specific variables such as leaf 

size and shape (long-thing, short-wide) and plant type 

(herb, sedge, shrub, vine).

Our results contrast with those of Muñoz-Guer-

rero et al. (2007), who found some evidences of spatial 

segregation between D. microcephalus and S. vigilans 

at a locality in a dry forest in Colombia; while both 

species preferentially perched from 40-50  cm above 

shallow water, D. microcephalus preferred herbaceous 

plants whereas S.  vigilans preferred heliconias (al-

though it also used herbs). We propose that floristic 

and physiognomic differences between sites (Colom-

bia and Venezuela) may explain these differences. 

Nevertheless, the striking differences in microhabitat 

species-segregation between our study and that of Mu-

ñoz-Guerrero et al. (2007) identify the need of more 

extensive studies encompassing more habitat and mi-

crohabitat types to better understand potential space 

interactions between D. microcephalus and S. vigilans.

While the microhabitat-niche dimension of 

D. microcephalus and S. vigilans at our study locality 

coincides, the food dimension differentiates. Both 

species rely on arthropods, but at the taxonomic level 

TABLE 3:

 Comparison of the diet of of Dendropsophus microcephalus 

and Scarthyla vigilans at two localities: La Guáquira (Venezuela, this 

study) and El Botillero, Colombia (Muñoz-Guerrero et al., 2007) 

based on RII (%). RII for El Botillero were calculated from data 

shown in Table 1. pp 420, Muñoz-Guerrero et al. (2007). Other 

includes unidentified items and larvae. “?” indicates incomplete 

data not allowing calculation. RII > 15% are shown in bold.

Order

D. microcephalus

S. vigilans

This study El Botillero This study El Botillero

Acari

1.46

Araneae

26.56

17.74

11.02

24.37

Collembola

10.62

Coleoptera

14.41

15.68

3.56

11.51

Dyctioptera

6.1

19.80

Diptera

15.68

16.55

10.60

4.21

Hemiptera

?

5.54

4.87

Homoptera

15.79

27.67

Hymenoptera

5.28

9.52

3.64

19.07

Lepidoptera

10.26

10.31

Neuroptera

6.31

Mantodea

?

Orthoptera

5.93

10.31

22.95

16.68

Psocoptera

?

Isopoda

4.7

Other

2.64

8.66

Fonseca-Pérez, K.A. 

et

 

al

.: Diet and microhabitat Hylinae

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