Species Description: Kraus F 2017 A New Species of Oreophryne (Anura: Microhylidae) from the Mountains of Southeastern Papua New Guinea. Current Herpetology. 36:105-115.
Oreophyrne brunnea is an arboreal frog species described from 10 specimens, 9 male and 1 female. Oreophyrne brunnea has a relatively wide head with a snout-vent length ranging from 16.0 - 19.0 mm for adult males and a snout-vent length of 18.2 mm for the adult female. The holotype is described to have an oblique and flattened loreal region and a broadly rounded canthus rostralis. The snout is shallowly rounded in lateral view and broadly rounded in dorsal view. Furthermore, its nostril is directed anterolaterally and is closer to the tip of the snout than the eye. It has rather large eyes and rather small tympana. In the holotype, the weak supratympanic fold is apparent from the right side of the holotype but not on the left. The fingers are unwebbed and have finger discs approximately twice the width of the penultimate phalanges and larger than the toe discs. The relative finger lengths are 3 > 4 > 2 > 1. The relative toe lengths are somewhat similar, with 4 > 3 = 5 > 2 > 1. The length of the webbing between toes measure I 1.9 – 1.2 II 1.5 – 2.0 III 2.5 – 3.3 IV 3.3 – 2.0 V, with the webbing reaching to the middle or distal to the penultimate tubercle of the fifth toe. It has low sub-articular tubercles; the inner metatarsal is shaped like a narrow oval and there are no outer metatarsals. The species has relatively smooth skin, scattered with warts, and moderately long hind legs (Kraus 2017).
This species is differentiable from other species mostly from its combination of having a ligamentous connection between the procoracoid and the scapula, well-webbed toes, and the third and fifth toes subequal in length. Although there are eleven other species, who each have the same combination of features, O.brunnea defends its uniqueness through its call. The call of O. brunnea consists of a rattling sound, a trait that only three other species (O. biroi, O.furu, and O. matawan) in the family share. Oreophryne brunnea is further differentiated from these three other similar species through slight variations in size, proportion, and patterns on the skin. Compared to O. biroi, O. brunnea is smaller in size; O. brunnea has a snout-vent length of 16 - 19 mm compared to O. biroi which has a snout vent length of 22 - 28 mm. Oreophyrne brunnea also has a broader snout, larger eyes, and a call with faster note delivery and higher pitch. Moreover the color of O. brunnea’s dorsum is a dark brown, compared to the uniform yellow or pale-brown dorsum characteristic in O. biroi. Compared to O. furu, O. brunnea is also smaller in size with a snout vent length of 16 - 19 mm compared to 20 - 25 mm. It has a broader snout, larger eyes, and skin with scattered tubercles which is absent on the skin of O. furu. It also has a slightly longer call and has various slight color discrepancies, including a large brown scapular smudge, which is absent in O. furu, brown at the top of the snout, and a darker anterior region. Compared to O. matawan, O. brunnea has a broader snout, larger eyes, and is darker brown in dorsal color. Oreophyrne brunnea also lacks dark bars on its thighs and has a shorter call with a faster note-delivery rate. Compared to other Oreophryne species lacking in call data, O. brunnea differs from O. albopunctata in having scattered tubercles on the skin, a wider head, a longer and broader snout, larger eyes, and the absence of a white spot on each shank. Oreophryne brunnea differs from O. ampelos only in its smaller size with a snout vent length of 16 - 19 mm compared to 26 - 35 mm, broader snout, and its dark-brown dorsum, differing from the tan or light brown dorsum with brown mottling of O. ampelos. Oreophyrne brunnea is differentiated from O. mertoni by having scattered tubercles on the skin which is smooth on the latter. Oreophyrne brunnea also has a wider head and a darker brown dorsal color, compared to the dark orange-red and dark-brown dorsal region of O. mertoni (Kraus 2017).
In preservative, the dorsum ranges from dark brown to a paler brown, dappled with darker brown between the shoulders, the back of the head, and the snout. Some of the specimens have a defined W shape on the dorsal scapular region of darker brown. The upper eyelids are a blackish dark brown and the front and rear of the thigh is an unpatterned dark brown. The venter is a beige color, but is so densely spotted with dark brown that it appears a uniform dark brown to the naked eye. The appearance of the postocular dash varies between specimens with some having a dark smudge, some having a distinct dash, and some having none at all. The palmar and plantar surfaces and the postocular dash are dark brown as well, except for the pale gray discs and subarticular tubercles and the hidden surfaces of the thighs more or less match the dorsal color of the specimen. The lower part of tympanum is a paler brown than the surrounding area and the iris is black. (Kraus 2017).
In life, the color of the dorsal region ranges from pale reddish brown, dark umber, dark brown, or dark orange brown. The color of the venter and the rear of the thighs typically matches the respective dorsal color, but with some variation. The venter color ranges from pale reddish brown, dark orange brown with pale gray flecks and dark purple brown (Kraus 2017).
There is variation in color and pattern (Kraus 2017)
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Papua New Guinea
Oreophryne brunnea is found in the mountains of southeastern Papua New Guinea, more specifically in the uplands of Cape Nelson and the nearby Mt. Dayman and Mt. Suckling Massif. They are known to be found from 820 - 1000 meters above sea level on Mt. Trafalgar on Cape Nelson, Oro Province and 900 - 1430 meters above sea level on the saddle between Mt. Suckling and Mt. Dayman, Milne Bay Province. This species is typically found in primary rainforest on shallow and steep slopes (Kraus 2017).
Life History, Abundance, Activity, and Special Behaviors
This species can be found active at night in primary rainforests. Males were observed calling while perched on tree trunks 1 - 2 meters above the forest floor. Although they called infrequently, they weren’t particularly wary (Kraus 2017).
Their calls were recorded at a temperature range of 21.5 - 21.9 degrees Celsius with a call duration ranging 2.11 - 3.10 seconds. The number of notes per call ranges from 48 - 75 notes per call with each note lasting 0.004 - 0.010 seconds. The duration between each note ranges from 0.027 - 0.048 seconds with a repetition rate of 22.3 - 24.0 notes per second. Finally, the dominant frequency of the call ranges from 3.04 to 3.6 kilohertz. The intensity of the notes increases sharply, giving the note a triangle shaped amplitude envelope. The notes lack pulsing, frequency modulation, and harmonics (Kraus 2017).
Trends and Threats
The conservation status of Oreophryne brunnea seems to be of "Least Concern" at the moment because its habitat is extensive and largely unaffected by agriculture, logging, or other human activities. The primary rainforests that O. brunnea reside in are remote and are usually inaccessible to humans due to steep slopes. However, should rapid climate change occur and alter its habitat, O. brunnea could become threatened, with the populations on Mt. Trafalgar and Mt. Victory being put at the greatest risk (Kraus 2017).
Possible reasons for amphibian decline
Climate change, increased UVB or increased sensitivity to it, etc.
The species authority is: Kraus, F. (2017). “A New Species of Oreophryne (Anura: Microhylidae) from the Mountains of Southeastern Papua New Guinea.” Current Herpetology 36(2): 105–115
Morphologically, O. brunnea is most similar to O. matawan. Possibly, the sympatry between the two species may be due to partitioning of diet. Both species also tend to occupy lower elevations of the forest compared to other species in the same genus, suggesting habitat partitioning may play a role as well (Kraus 2017).
The species epithet, “brunnea” is Latin, meaning “dusky” or “dark”, after the dark dorsal color pattern (Kraus 2017).
Including O. brunnea, there is a total of 16 known Oreophryne species from Milne Bay Province (Kraus 2017).
Kraus, F. (2017). ''A New Species of Oreophryne (Anura: Microhylidae) from the Mountains of Southeastern Papua New Guinea.'' Current Herpetology, 36(2), 105-115.
Originally submitted by: Michael Chou (first posted 2017-10-05)
Edited by: Ann T. Chang (2017-10-10)
Species Account Citation: AmphibiaWeb 2017 Oreophryne brunnea <https://amphibiaweb.org/species/8679> University of California, Berkeley, CA, USA. Accessed May 17, 2021.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 17 May 2021.
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