Bioacoustics of Cochranella erminea

Distribution and ecology. This species is widely distributed throughout the east-Andean versant in Peru , occurring from roughly 11° south latitude to 5° south latitude, at elevations between 349 and 923 m ( Fig. 18 ). However, Cochranella erminea appears to be patchily distributed within this region. For example, this species has not been registered from the mountains surrounding Tarapoto, Peru , despite frequent searches in this area. Some of this patchiness may be attributable to the presence of the closely related Co. guayasamini . These two species are sister taxa, have similar calls, occur at similar elevations, and appear to overlap in the montane regions extending from northern San Martín to central Amazonas. However, these two species have never been found together in the same site (N = 7 sites for Co. erminea and N = 8 sites for Co. guayasamini ). It is possible that competitive exclusion or microhabitat preferences could be important regulators of community structure at small spatial scales. Cochranella erminea occurs in a wide variety of habitats ranging from primary premontane forest to relatively disturbed, lowland foothill habitats. The site where we have witnessed the highest density of this species was an overgrown cacao plantation at 349 m . The only notable behavior we have observed in this species has been male calling activity. Males call from the tops of leaves, typically in groups of 2–5 individuals, although solitary males have also been observed calling. When calling in groups, males seem to stagger their calls sequentially and calls of different males do not typically overlap. At one site, males called sequentially downstream, with the chorus starting with an upstream male and finishing with a downstream male. See details below on Co. guayasamini for noted similarities among Cochranella . We observed two egg clutches near a chorus of Co. erminea males that correspond to Cochranella eggs; a globular cluster of pigmented eggs dangling from leaf tips. At the type locality as well as our record from near Juanjui, Cochranella erminea was the only centrolenid species registered ( Torres-Gastello et al. 2007 ). In the Río Shunté site, Co. erminea was found alongside Hyalinobatrachium carlesvilai and Rulyrana cf. flavopunctata . In northern Peru , Co. erminea has been found alongside Centrolene charapita , Teratohyla amelie , T. midas , and Rulyrana mcdiarmidi . Taxonomic remarks. Based on results from our phylogenetic analysis ( Fig. 2c ), Cochranella erminea is wellsupported as a member of the genus Cochranella (JK = 100; GB = 16) and is similar in overall morphology to Co. granulosa . Furthermore, this species shows substantial similarity in advertisement call to other members of Cochranella , most notably Co. granulosa and Co. guayasamini .

Variation. Cochranella erminea exhibits moderate morphological variation over its large range. While our records from near Juanjui and Tocache appear nearly identical to material from the type locality, individuals from northern Peru are notable in that they have a distinctly pinkish-red iris, and they show variation in the number and distribution of dorsal spots ( Fig. 17 ). Furthermore, the white enameled spots as mentioned in the holotype are less notable in these northern populations. Vocalizations. The following call description is based on a single call from a male recorded by SC-F and ET on 3 April 2010 from Pongo de Rentema ( 5°18'3.86"S , 78°23'44.57"W , 682 m ), temperature 21.4°C. The call consists of two harsh buzz-notes given in quick succession. The first of these notes starts quietly and increases in amplitude throughout, with a duration 0.313 s , 14 pulses, dominant frequency 4870 Hz. This is followed by a single “chirp” given 0.173 s after the first note. This chirp is 0.054 s in duration, with 3 pulses, dominant frequency 4866 Hz. In the field, this sounds like a “zzzZZZT ZT”. We have heard calls from other populations ( i.e. , Juanjui and the type locality), and the calls all sound similar to the ear, with the only noticeable difference is that the number of trailing chirps can vary from zero to two. This call is similar to the call of Cochranella granulosa , which has a “pulsed primary note followed by 0–5 shorter pulsed secondary notes” ( Ibáñez 1991 ). The call of Co. guayasamini new species (see below) is superficially similar to Co. erminea , except that Co. guayasamini tends to use a two-note call only in groups (often just one note when alone), whereas Co. erminea typically uses a two-note call even when alone. In addition, in Co. guayasamini the first and second notes are equal in duration, and not amplitude modulated (vs. first note amplitude modulated and longer than second note in Co. erminea ).