Bioacoustics of Ameerega yoshina

Distribution and natural history. Ameerega yoshina is known from two premontane regions with an elevational range of 195-873 meters: east of Ucayali River in the Serranía de Contamana (near the Sierra del Divisor National Park) and then west of the Ucayali River in the northern Cordillera Azul. Within Cordillera Azul it is found at two disjunct locations: Callanayacu in the northern Cordillera Azul near the Huallaga River, and near Shamboyacu at two isolated sites. Near Callanayacu, A. kuriinti sp. nov. occurs only north of the Huallaga River, while A. yoshina is only known from a small stream, Quebrada Pucayacu, south of the Huallaga River. In the southernmost localities, near Shamboyacu, this species is restricted to rocky and steep gallery forests due to extensive deforestation surrounding more accessible habitats. At all known localities, this species is absent from surrounding lowland habitats and appears to be confined to these upland forests adjacent to small and medium-sized streams. We expect that this species occurs at other localities within north-central Cordillera Azul, however this is unverified, as much of this area has not been surveyed. Further, even if an area is surveyed, this species is often exceedingly difficult to observe. In late July 2021 , B. Geralds and J. Brown surveyed the forests between Shamboyacu and Tocache in Alto Biavo District of San Martin, with the particular aim of discovering additional populations of A. yoshina (and perhaps A. pepperi ). We surveyed the road SM108 from Bellavista until the road became impassable at km. 53 ( 7°31’37.4”S 76°18’49.9”W , before the town of Nuevo Arica), we also surveyed a side road, the road to Israel Uriate (Valle de Pavo), and traveled past the village until km. 44 where the road was blocked by the high waters of a small river (ca. 7°23’17.3”S 76°14’20.6”W ). During the three days of survey, we only observed larvae of A. trivittata , which was also occasionally calling along the road. No other dendrobatid (adult or larvae) was observed or heard calling. Based on these observations, it does not appear that members of ABSG are abundant in this region during the time of our survey. Elsewhere in San Martin, adult A. yoshina are frequently heard calling at multiple sites and routinely observed as tadpoles. Conservation status. Following the IUCN Red List criteria 3.1 (IUCN 2012), we suggest A. yoshina be listed as Endangered (EN) under the following criteria: (1) we estimate its extent of occurrence at 1,163 km 2 (as shown in Fig. 1 ), however only four populations have been confirmed to be this species across its entire range (our map has two additional locations marked with * that are likely A. yoshina and are coordinates for other researchers/databases. However, when we surveyed these sites, we did not find any evidence of this species’ existence). However, this species likely occurs in two large reserves: Parque Nacional Cordillera Azul and Parque Nacional Sierra del Divisor, which have not been extensively surveyed for this shy species; (2) it only occurs largely undisturbed habitat (3); population sizes are small in known habitats likely range from 100-1000 adult individuals; (4) populations do not appear to be declining in areas where habitat is protected and (5) demand for the pet trade is presumed to be moderate to low. Under the international CITES agreement this species is listed under Appendix II; limiting international trade. Currently this species has never been legally exported, nor been observed in the US and European hobby markets.

Distribution and natural history. Ameerega yoshina is known from two localities, one in the Serranía de Contamana and the other in the Huallaga Canyon 1 in the northern Cordillera Azul ( Fig. 3 ). These two localities are 130 km apart and separated by the Ucayali floodplain, which may represent a significant barrier between these two populations. We have not found A. yoshina in lowland habitats and expect that this species is restricted to premontane forests of the Serranía de Contamana and northeastern Cordillera Azul. At their closest points, the Cordillera Azul and Serranía de Contamana are separated by 26 km of lowland forest (and Río Ucayali), and it is unlikely that there is currently gene flow across this barrier. In the lower Huallaga Canyon, we have only found A. bassleri on the north-bank and A. yoshina on the south-bank of Río Huallaga. Therefore, it is possible that A. bassleri is absent from the northeastern Cordillera Azul and that this area is inhabited exclusively by A. yoshina . Ameerega yoshina occurs in undisturbed premontane forests, particularly in habitats which are adjacent to streams ( Fig. 15 h & j). This species appears to have extremely specific habitat requirements, as we were only able to find them in isolated pockets near Contamana and Callanayacu. For example, in Callanayacu we hiked for several kilometers along Quebrada Pacuyacu (a small stream), and only heard A. yoshina calling along a ~200-m stretch of habitat adjacent to the stream. In Contamana we were able to find this species alongside three different streams, but only in small areas along these streams. This species is exceedingly cryptic and is nearly impossible to detect if males are not calling. In Callanayacu we spent roughly 68 person-hours searching within the 200-m stretch of habitat and were only able to capture three individuals, despite the fact that numerous males were calling in the vicinity the entire time we were searching. In Contamana we searched for 60 person-hours in 2006 and 48 person-hours in 2007, yet we were only able to encounter a total of six frogs, one of which was a metamorph. Most adults were found under logs or under piles of leaf litter, although two were found moving about the leaf litter after a heavy rain. Reproduction appears to take place near small streams and forest pools. In the same spot where we found A. ignipedis transporting tadpoles, we also found one A. yoshina metamorph at the edge of the water. There were no other water sources nearby and we assume this metamorph emerged from the stream. We also found a shallow forest pool at the base of a small waterfall, around which many A. yoshina males were calling. In this pool were numerous tadpoles which were A. yoshina (confimed by DNA sequencing). Males appear to call from the leaf litter throughout the day. In Callanayacu males called incessantly the entire day, but were wellhidden. 1. The term “Huallaga Canyon” refers to a narrow section of the river which forms between the Cordillera Oriental and Cordillera Azul, starting at Chumia and ending when the river reaches the lowlands. Callanayacu and Chazuta are both towns located within this section of river. Conservation status. Following the IUCN Red List criteria (IUCN 2001), we tentatively suggest that A. yoshina should be listed as Near Threatened (NT) based on the following: (1) we estimate the extent of occurrence to be less than 4,500 km 2, (2) populations appear to be fragmented, as we have only encountered two disjunct populations which are restricted to small areas, and (3) there has been a small amount of potential habitat loss in the Cordillera Azul near Río Huallaga, although this species probably occurs throughout the northern part of the Cordillera Azul National Park. Further investigation may warrant a revised classification, as the above estimate on extent of occurrence assumes that this species occurs at elevations from 280–600 m and also occurs in the Ojo de Contaya ( Fig. 3 ). While this species may range widely throughout the Cordillera Azul and Sierra del Divisor, it may just as likely be restricted to the Serranía de Contamana and extreme northern Cordillera Azul.

Etymology. The species name is formed as an adjective, derived from the Panoan word ‘ Yoshín ’ which means ‘devil or evil spirit’, in reference to the cryptic nature of this species and its haunting, penetrating call. The Panoan language is spoken by the Shipibo-Conibo people who are indigenous to the upper Río Ucayali and the Sierra del Divisor. Definition and diagnosis. Assigned to the genus Ameerega on the basis of the following: first finger longer than second, webbing absent between the toes, dorsal skin granular ( Myers 1982 , Grant et al. 2006 ). This is a medium-large species of Ameerega with an adult SVL of approximately 26–35 mm . Dorsum has a black ground color, stippled brick-red to bright red or orange, stippling less dense near sacral region. Bright yellow dorsolateral stripes extend from the eyelid to the groin; a yellow labial stripe is also present starting near nares and extending posterior to the axillary region. Bright yellow-green spot present above groin in some populations, shank spots and axillary spots absent. Limbs greenish-bronze or black; venter ranges from greenish-gold to blue, black marbling weak or absent. Teeth present. Appressed first finger longer than second; finger discs moderately expanded, hands and feet lacking webbing between digits. Vocalization consists of a ‘burst’ of loud, whistle-like notes, each burst consisting of 4–31 notes, given at a rate of 4.0–4.5 notes per second; dominant frequency 3210– 3060 Hz ( Fig. 4 , Table 2 ).

Ameerega yoshina can be distinguished from most other species of Ameerega by its red dorsum. It is similar in appearance to the following species: A. bassleri , A. bilinguis , A. cainarachi , A. macero , A. pepperi sp. nov. (description below), and A. parvula , all of which have (or can have) a red dorsum. Ameerega parvula and A. bilinguis both lack distinct dorsolateral stripes (vs. dorsolateral stripes present and conspicuous in A. yoshina ). Ameerega cainarachi is smaller, females up to 31.3 mm SVL (vs. 35 mm SVL in A. yoshina ), and has an advertisement call consisting of a regular chain of notes which are not frequency–modulated, repeated at a rate of 9 notes per second (vs. ‘bursts’ of frequency-modulated notes, repeated 3.7–4.1 notes per second in A. yoshina ). Ameerega macero is smaller than A. yoshina , females up to 29.5 mm SVL, and has a call consisting of a series of harsh ‘peeps’, repeated regularly at a rate of 10 notes per second. Ameerega bassleri and A. pepperi have an advertisement call consisting of a series of regularly-spaced whistle-like notes given continuously for several minutes at a rate of 1.6–2.1 notes per second in A. bassleri and 0.9–1.3 notes per second in A. pepperi (vs. bursts of 4–31 notes, given at a rate of 3.7–4.1 notes per second, each burst less than 8 seconds in total duration in A. yoshina ). max, pairwise significance). Species Calling rate (notes/min) Note Duration (sec) Silence between notes (sec) Dominant Frequency (Hz) N A. pepperi 62.1 ± 9.4 (51.0–75.9, a) 0.17 ± 0.05 (0.13–0.22, a) 0.80 ± 0.20 (0.56–1.03, a) 2970 ± 130 (2800–3160, a) 6 indiv., 4 local. A. bassleri 95.3 ± 10.0 (95.3–127.8, b) 0.15 ± 0.03 (0.09–0.19, a) 0.42 ± 0.08 (0.30–0.42, b) 2750 ± 190 (2400–3070, b) 18 indiv., 6 local. A. yoshina 235.2 ± 5.6 (227.3–243.2, c) 0.13 ± 0.02 (0.09–0.15, a) 0.13 ± 0.02 (0.11–0.15, c) 3140 ± 50 (3060–3210, a) 6 indiv., 2 local. ANOVA F2,27=597.02, P <0.001 F2,21=2.54, P = 0.102 F2,21=56.97, P <0.001 F2,27 = 13.83, P <0.001 Measurements (in mm) of holotype . The female holotype ( Fig. 1 ) has SVL 34.8; FL 16.3; TL 17.6; KK 29.5; FoL 14.6; HaL 8.3; HL 8.1; HW 10.2; BW 12.1; UEW 7.3; IOD 4.9; TD 3.2; ED 5.3; DET 0.8; L1F 7.6; L2F 4.5; W3D 1.0; W3F 0.5. Measurements of paratypes are given in Table 4 . Description of holotype . Size large, SVL 34.8 mm ( Table 4 ). Dorsal skin coarsely granular, pigmented black with brick red mottling densest near the snout. Thin light-yellow dorsolateral stripes extend from eyelids to groin; posterior to eyes the stripes blend into the red dorsum. Dorsolateral stripes slightly wider at groin. Flanks are solid black along the entire length of the body and head. Yellow labial stripe present extending from nares to axillae and upper forelimb. Forelimbs are weakly granular and are metallic-brown in color. Legs are granular, dark brown with faint olive green stippling. On each leg there is a large yellow spot present on the anterodorsal surface of the thigh. Hands, feet, and digits colored as limbs. The ventral skin is smooth and uniformly olive-gold in color on the belly and limbs; the head and chest are slightly darker than the belly. No distinct black markings present on the venter. Iris black. Widest part of head between jaw articulations and tympanum, head narrower than body; greatest headwidth 29.3% of SVL. Eyes protuberant. Tongue medium sized, oval. Premaxillary and maxillary teeth present. Vocal slits absent. Snout sloping laterally; bluntly rounded dorsally; truncate ventrally. Nares situated and directed posterolaterally to the tip of snout; nares visible from front and below but not from above. Canthus rostralis sloped, slightly rounded; loreal region nearly vertical and slightly concave. Upper eyelid 1.5 times wider than interorbital distance. Eye large and prominent with a maximum diameter of 9.3 % of the snout vent length; pupil rounded and horizontally elliptical. Tympanum circular; without tympanic annulus its diameter is less than 60.2 % of ED; supratympanic fold present. Hands relatively small, length being 23.7% of SVL. Relative length of appressed fingers II ≈ IV <I <III (with I being interior-most finger). Discs moderately expanded on all fingers. Disc on finger III is twice as wide as distal end of adjacent phalanx. A large, circular outer metacarpal tubercle present on median base of palm; a smaller inner metacarpal tubercle on base of finger I absent; one well developed subarticular tubercle on fingers I and II, two on fingers III and IV. Hind limbs short, with heel of appressed limb reaching the axillary region. Tibia length 50.7% of SVL. Relative lengths of appressed toes I <II <V<III <IV; first toe extending past subarticular tubercle on base of second toe; discs on toes I, II, III, IV barely expanded (much smaller than finger discs), and toe V expanded (disc 1.2 times wider than adjacent phalanx). Moderate-sized inner and outer metatarsal tubercles, protuberant with rounded surfaces. One protuberant subarticular tubercle on toes I and II, two on toes III, IV, and V. Hands and feet lacking supernumerary tubercles and lateral fringes. No basal webbing on toe fringes. Tarsal tubercles absent. In 70% alcohol the color is similar to the living animal described above, except the red dorsum changed to black, yellow dorsolateral stripes changed to silver-white, and gold coloration on venter changed to black and grey-green. Variation. Little variation has been observed in the two known populations of A. yoshina . Frogs from near Contamana vary somewhat with respect to dorsal coloration; some individuals are brick-red while others are more orange. These frogs also possess a venter which varies from greenish-gold to pale yellow-green, although black ventral markings are absent or not well-defined. Frogs from Callanayacu tend to be more orange as opposed to red on the dorsum ( Fig. 14 ), and have blue venters that have diffuse and irregular black markings. The limbs vary in color from black to pale olive. Vocalizations. The advertisement call for A. yoshina ( Fig. 4 ) can be classified as a ‘retarded trill’ following Lötters et al. (2003). The call consists of a series of musical notes resembling short ‘whistles’ which are given in short bursts of 4–31 notes at a rate of 3.7–4.1 notes per second. Notes are 90–156 ms long, spaced 110–150 ms apart, and frequency-modulated by about 325 Hz (notes start at 2925 Hz, end at 3250 Hz, overall dominant frequency 3140 Hz). The call of A. yoshina can be very easily distinguished from the advertisement call of A. bassleri , which is a series of whistle-like notes repeated at a much slower rate and for much longer. Our recordings of A. bassleri have notes repeated at a rate of 1.6–2.1 notes per second for 7.5 seconds or longer, although on several occasions we have heard A. bassleri calling continuously for several minutes at a time. Ameerega bassleri also has an aggressive call which consists of 3–5 notes given in quick succession. However, even this aggressive call differs from the advertisement call of A. yoshina , as notes are repeated at a slower rate (1.6 notes per second in A. bassleri vs. over 4 notes per second in A. yoshina ) and are spaced further apart (notes spaced 420 ms in A. bassleri vs. 130 ms in A. yoshina ). In the field, the call differences between the two species are immediately recognizable and fixed in a given geographic region. For example, during several days in Callanayacu and Contamana, we never heard a call which sounded like A. bassleri . Conversely, in areas containing A. bassleri , we have never heard a call which sounded like A. yoshina .