Ischnocnema guentheri is a forest ground dweller and is commonly found on the leaf litter during the day or night. This is a species with low mobility. Although it mainly inhabits forest habitats it can also be encountered near the forest edge in surrounding vegetation (Heyer et al. 1990; Pombal 1997; Ramos and Gasparini 2004; Ribeiro et al. 2005).
Males call at late afternoon and early night from low vegetation (20-60 cm) in the rainy season from October to February away from water bodies, but inactive individuals can be found from the very end August throught June (Heyer et al. 1990; Haddad and Sazima 1992; Pombal and Gordo 2004). The advertisement call was described by Heyer et al. (1984; 1990) and can be heard on Haddad et al. (2003). The call is given sporadically, beginning quietly and ending loudly; call duration 1.10-1.75s. Some variations in call structure within the geographic range of I. guentheri and its taxonomic implications are discussed in Kwet and Solé (2005).
This species has direct development, laying small clutches (usually 20-30 eggs) in small hollows, like miniature roofed caves, in banks of earth (Lynn and Lutz 1946; Lutz 1947; Izecksohn and Carvalho-e-Silva 2001; mode 23 of Haddad and Prado 2005).
Dixo and Verdade (2006) reported that they found 12 individuals during 32 days in their study site. Van Sluys et al. (2007) found 6 individuals during one year of sampling, at a density of 1.3 individuals/100m2 using small plots. Rocha et al. (2007) found similar results; I. guentheri was the dominant species within the leaf-litter frog fauna in their study site, comprising 29.5% of the anuran fauna, with a density of 2.71 ind/100m2. Steinicke (2008) found 383 specimens in four forest fragments during two rainy season sampling periods in southeastern Brazil. Additionally, I. guentheri was more commonly found inside small forest fragments, compared with a control site (a forest reserve). Furthermore, it tended to have a higher survival rate in fragmented habitats, demonstrating to be an intermediate habitat specialist. Giaretta et al. (1997) found that I. guentheri was more common at a higher altitude locality in their study site, due to more leaf-litter accumulation and humidity, moreover, I. guentheri comprised 83% of the individuals caught, being the dominant species at this site.
There are reports of infection by nematodes in a population of I. guentheri from Rio de Janeiro. Five species of worms infected the frogs and were found in the lungs and intestine (Martins and Fabio 2005).
An analysis of food items ingested by the pirapitinga do sul (Brycon opalinus, an endangered fish in rivers of the Atlantic Forest of the Serra do Mar, in southeastern Brazil) revealed the occurrence of Ischnocnema guentheri as a prey item, but the authors pointed out that this fish is an opportunistic omnivore (Gomiero et al. 2006).
The defense strategy is death feigning (Haddad et al. 2008).