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

---

D

iet

 

of

 D

enDropsophus

 

microcephalus

 

anD

 s

carthyla

 

vigilans

 

(a

nura

: H

yliDae

) 

at

 

a

 

locality

 

in

 

nortH

-

western

 

V

enezuela

 

witH

 

notes

 

on

 

microHabitat

 

occupation

K

imberlyn

 a. f

onseca

-p

érez

¹²³

c

ésar

 m

olina

¹

†

z

aiDa

 t

árano

²⁴

ABSTRACT

The coexistence of species with similar ecological requirements (food, space, time) has typically 

drawn attention of researchers because competition for resources is expected to be high. The diet and 

microhabitat occupation of two morphologically and ecologically similar species of Hylidae (Anura), 

Dendropsophus microcephalus and Scarthyla vigilans, were analyzed at a locality in north-

western Venezuela, with the aim of addressing the potential for space and food competition between 

them. Diet was estimated through the analysis of stomach contents and microhabitat occupation 

was estimated through recordings of perch type, height and horizontal distance to water. Thirty-six 

prey categories (32 families, 4 orders) of arthropods were identified: 30 categories in D. microceph-

alus and 21 categories in S. vigilans. The most important prey (RII) in D. microcephalus were 

Agelenidae (11.1%), Tachinidae (9.32%) and Lepidoptera-larvae (7.96%). Gryllidae (14.13%), 

Cicadidae (9.1%), Cicadellidae (8.3%) and Delphacidae (8.02%) were the most important in 

S. vigilans. Diet overlap was relatively low (0.32). Both species have relatively generalist diets. Both 

species occupied the same type of perches (leaves and stems of Dicotyledons and Monocotyledons) and 

heights (average: S. vigilans, 24 ± 16.2 cm; D. microcephalus, 22.7 ± 9.5 cm). The potential for 

space competition is high if perches are limited and food competition is expected to be low.

Key-Words: Diet; Generalist; Niche overlap; Resource partitioning; Microhabitat; Mor-

phometry.

INTRODUCTION

Morphological and ecological similarity between 

species is believed to hinder their coexistence because 

competition for resources is likely. It is thought that 

at least one ecological difference in resource use be-

tween them (i.e., food, time or space partitioning) is 

necessary to allow coexistence (Pianka, 1994; Gor-

www.mz.usp.br/publicacoes

www.revistas.usp.br/paz

ISSN impresso: 0031-1049

ISSN

1807-0205

on-line:

Museu de Zoologia da Universidade de São Paulo

Papéis Avulsos de Zoologia

http://dx.doi.org/10.11606/0031-1049.2017.57.07

Volume 57(7):93‑104, 2017

1. Laboratorio de Biología y Conservación de Anfibios, Instituto de Zoología y Ecología Tropical, Facultad de Ciencias, 

Universidad Central de Venezuela.

2. Laboratorio de Comportamiento Animal, Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela.

3. E-mail: [e-mail].

4. Correspondence autor. E-mail: [e-mail].

†  This is a posthumous publication for César Molina.

---

don, 2000; Vignoli & Luiselli, 2011). The relative 

importance of food, time and space use in structur-

ing animal communities varies from one another and 

between habitats. Several authors have suggested that 

the space dimension is often more important than 

the food dimension, and that the latter is often more 

important than the temporal dimension (Schoener, 

1974; Giller, 1984); however, this ordering is by no 

means universal. For instance, food is the main di-

mension in structuring several anuran communities 

(Toft, 1980a,b; Lima, 1998), while microhabitat is in 

others (e.g., Crump, 1974; Toft, 1985; Cardoso et al., 

1989).

Amphibians, and specially anurans, are remark-

ably abundant in tropical ecosystems and have been 

considered extremely important in food webs and 

energy flow (Stebbins & Cohen, 1995). Nonethe-

less, there are relatively few studies of feeding pref-

erences and behavior in this group (Toft, 1980a,b; 

Duellman, 1993; Piñero & Durant, 1993; Lima & 

Magnusson, 1998; Caldwell & Vitt, 1999; Parmelee, 

1999), and most of them have focused on a limited 

number of taxa. With regards to habitat occupation, 

available literature indicates that in general, there are 

substantial differences in microhabitat and activity 

periods both within and among species (Schoener, 

1974; Drewry & Rand, 1983; Toft, 1985; Muñoz-

Guerrero et al., 2007; Tárano, 2010). Several stud-

ies with hylids have demonstrated that microhabitat 

segregation is associated to body size (Bevier, 1997), 

which in turn has a strong impact on the diet and 

prey-capture behavioral strategies (Toft, 1980a, 

1981).

In anurans, diet composition is usually related 

to body size, sex, and habitat and microhabitat pref-

erences (Toft, 1980a,b; Christian, 1982; Woolbright 

& Stewart, 1987; Piñero & Durant, 1993; Bevier, 

1997; Hirai & Matsui, 2000). The diet typically 

changes with age (e.g., Labanick, 1976; Christian, 

1982; Strussmann et al., 1984; Woolbright & Stew-

art, 1987; Donnelly, 1991; Wiggins, 1992), season 

(da Rosa et  al., 2002) and the size and behavior of 

preys (Freed, 1980; Lima, 1998; Parmelee, 1999). 

Since anurans swallow whole prey, mouth width pos-

es an upper limit to the maximum size or volume of 

prey. Therefore, as an individual grows, the maximum 

size of its preys may increase concomitantly (Lima & 

Moreira, 1993; Parmelee, 1999). In general, anurans 

that consume relatively small and slow-moving prey 

have narrow mandibles and symmetric feeding cycles 

(i.e., the time devoted in capturing is similar to that 

devoted in retrieving to the mouth). On the other 

hand, anurans feeding on relatively large slow-moving 

prey have wide mandibles and asymmetric feeding 

cycles (Emerson, 1985).

Most anurans analyzed so far feed upon inverte-

brates as adults while a few also prey upon small verte-

brates (Duellman & Trueb, 1994). A great majority of 

the anurans analyzed have been labeled as food-gener-

alists based on estimations of diet richness and equi-

tability, despite the fact that prey availability has not 

been estimated in most studies (but see Toft, 1980b, 

1981; Christian, 1982; Hirai & Matsui, 2000). With 

regards to prey specificity, anurans can be arranged 

in a continuum ranging from ant specialists through 

non-ant specialists to generalists (Toft, 1981).

In the present study we aimed to describe the 

diet and microhabitat occupation of two hylid frogs 

of similar morphology which occur syntopically over 

a wide range in northern Venezuela, Scarthyla vigilans 

and Dendropsophus microcephalus. Scarthyla vigilans is 

an arboreal anuran traditionally thought to be restrict-

ed to the Maracaibo Lake basin in northwestern Ven-

ezuela (Barrio-Amorós, 1998). It is currently known 

for inhabiting the northern Caribbean lowlands, the 

Magdalena River basin in Colombia and the llanos 

of Colombia and Venezuela (Barrio-Amorós et  al., 

2006; Lotzkat, 2007; Rojas-Runjaic et al., 2008). The 

species is currently expanding into the Orinoco River 

Delta (Rojas-Runjaic et al., 2008) and Trinidad and 

Tobago (Smith, J.M. et al., 2011). Dendropsophus mi-

crocephalus has been regarded as widely distributed in 

Venezuelan lowlands (Barrio-Amorós, 2009). There-

fore, both species coexist in vast areas of their distri-

bution providing opportunity to assess the potential 

for food and space segregation. Previous studies in 

Colombia have documented similar microhabitat 

preferences (Lomolino et al., 2006, Muñoz-Guerrero 

et al., 2007; Armesto et al., 2009), overlapping diets 

(Muñoz-Guerrero et al., 2007) and partially disjoint 

activity patterns throughout the rainy season (Mu-

ñoz-Guerrero et al., 2007). Nonetheless, so far there is 

scarce information on the habits of both species. With 

this study we aimed to add to the comprehension of 

the coexistence of D. microcephalus and S. vigilans and 

to address potential regional differences.

METHODS

Study Site and Subjects

We performed the study at Hacienda La Guá-

quira (10°20’4”N, 68°39’17”W), in the mountain 

complex Macizo de Nirgua, at the western-most edge 

of the Coastal Mountain Chain (Cordillera de la Cos-

Fonseca-Pérez, K.A. 

et

 

al

.: Diet and microhabitat Hylinae

94

---