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

of order, and especially at the level of family, their di-

ets segregate. Agelenidae, Tachinidae and Lepidoptera 

larvae represent 28.4% of the diet of D. microcephalus, 

but only 15.7% of the diet of S. vigilans. On the other 

hand, Gryllidae, Cicadidae, Cicadellidae and Delpha-

cidae represent 39.5% of the diet of S. vigilans (but 

only 15.1% of the diet of D.  microcephalus). These 

seven prey categories are consumed by both species, 

but there are 21 additional prey categories which are 

not shared (Table 1). This differentiation is expressed 

in a relative low index of food-niche overlap (approx. 

30%). Reduced niche overlap between syntopic hylids 

has been documented in several anuran communities 

(e.g., Toft, 1980a,b; 1985; Van Sluys & Rocha, 1998).

With regards to diet composition, our results 

partially differ from those of Muñoz-Guerrero et al. 

(2007): they found 15 orders as a whole, 11 orders in 

D. microcephalus and 7 in S. vigilans while we found 

only 10 orders as a whole, 8 orders in D. microcepha-

lus and 9 in S. vigilans. In addition, the orders Acari, 

Collembola, Mantodea, Neuroptera and Psocoptera 

were not found in our study populations, while the 

relative important order Homoptera in our study 

was not quantified in theirs. Muñoz-Guerrero et al. 

(2007) did not calculate the %RII of each prey cat-

egory but from their published data we estimated that 

Dyctioptera, Araneae, Diptera and Coleoptera (all 

with similar importance, altogether 70% of the diet) 

were the most important prey in D.  microcephalus 

(Table 3), while Araneae, Hymenoptera and Orthop-

tera were the most important in S. vigilans (Table 3). 

We found similitude between studies in the compo-

sition of the diet of D. microcephalus (Araneae, Co-

leptera and Diptera represent 56% of the diet in our 

study), with the remarkable difference that Araneae 

was the most important prey in ours (instead of Dyc-

tioptera) and that Homoptera, the second category in 

our study, was absent in the Colombian study. The 

largest differences in diet between studies correspond 

to S. vigilans, in which Homoptera and Orthoptera 

represent 50% of the diet at our study locality but 

only 16% in the Colombian site, where, on the other 

hand, Araneae and Hymenoptera altogether represent 

43% of the diet (but only 15% in our study). In addi-

tion, Muñoz-Guerrero et al. (2007) estimated a much 

higher niche overlap (O = 0.82) than we did (0.411, 

when calculated at the taxonomic level of order). It is 

very interesting that in our study, niche overlap calcu-

lated from family-level prey categories was even lower 

than that from order-level categories, as we expected. 

This result raises a caution on conclusions about po-

tential food competition between species based on 

coarsely identified prey categories. From our results, 

based on family-level analysis, the probability of com-

petition for food is relatively low between D. micro-

cephalus and S. vigilans, and we expect that a finer-

scale identification of preys (to genus or species) could 

reveal wider diet segregation. The differences in diet 

composition between studies surely relate to variation 

in prey diversity and availability between localities, 

and support our conclusion that both species are food 

generalists (see below) that opportunistically capture 

prey as they pass by their ambushing perch; this for-

aging strategy does not imply that frogs do not select 

perch sites with high probability of prey capture, on 

the contrary. It is very interesting that Araneae and 

Diptera are also amongst the most important prey in 

the diets of D. ebraccatus and D. phlebodes (Jiménez & 

Bolaños, 2012), D. sanborni and D. nanus (Macale et 

al., 2008) suggesting that these prey are the most or 

among the most abundant in wet habitats (Candia, 

1997; Aiken & Coyle, 2000).

Diet diversity, equitability and niche breath 

indexes of both species roughly correspond to those 

expected for species toward the generalist end of the 

diet-specialization continuum. Despite the fact that 

most studies on anuran diet have not estimated prey 

availability, most authors agree that most anurans are 

generalist consumers based on the assumption that 

their diets represent prey availability (Duellman & 

Trueb, 1994; Menéndez-Guerrero, 2001). Nonethe-

less, in a multispecies study with hylids, Parmelee 

(1999) found that some species have wide diets while 

others seem to be specialized in “large” preys. Further 

study is necessary to address feeding preferences varia-

tion in this abundant and diverse group.

In our study, a number of stomachs was empty 

(approx. 17%); this proportion is below the interval 

documented for other hylids (36-78%, Parmelee, 

1999; Menin et al., 2005; Jiménez & Bolaños, 2012). 

Information on time budgets in anurans is lacking, 

but high proportions of empty stomachs have been 

regarded to specific feeding schedules (Parmelee, 

1999). For instance, males may feed before beginning 

their calling activity each night, or later at night, after 

calling, or alternate feeding nights with calling nights 

(e.g., Ryan, 1985; Anderson et al., 1999). In addition, 

it has been documented that males do not feed while 

calling (Woolbright & Stewart, 1987; Solé & Pelz, 

2007). The high proportion of empty stomachs to-

gether with that of stomachs with digested contents 

suggest that D. microcephalus and S. vigilans alternate 

feeding nights and calling nights or feed quite early 

before beginning to call.

Surprisingly we did not find difference in prey 

size and volume between species, despite the fact that 

Papéis Avulsos de Zoologia, 57(7), 2017

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