Reproductive activity and advertisement calls of the Asian common toad Duttaphrynus melanostictus (Amphibia, Anura, Bufonidae) from Bach Ma National Park, Vietnam

Abstract

Background: We examined differences in reproductive activities and intraspecific variations in advertisement calls of Duttaphrynus melanostictus (Schneider, 1799) that lives in a tropical region of central Vietnam. The snout-vent length (SVL) of sexually mature males ranged from 50.2 to 70.3 mm, while that of females ranged from 65.2 to 97.3 mm. Histological analyses of testes revealed that sperm was not present throughout the year, indicating discontinuous reproductive activity for adult males. Adult females were captured year-round, but reproductive females were observed only during months of the auxiliary rainy season (mainly April to July), indicating that females reproduce seasonally. We also estimated levels of within-male variation of each call property and the influences of the ambient temperature, humidity, and the SVL of calling males on acoustic features. Results: The call rate and pulse rate showed intermediate levels of variation, whereas the dominant frequency and call duration were the most stereotyped properties. One-way analyses of variance for six acoustic properties showed that the call rate, pulse rate, and rise time significantly differed (p < 0.05) among localities. Advertisement calls were a series of groups of 56 to 244 (145 ± 54) pulses with an average call duration of 26.722 s, an average pulse rate of 11.69 pulses/s, and an average dominant frequency of 1.293 kHz. The results of the multiple regressions for possible effects of temperature, humidity, and SVL on the six acoustic properties indicated that the dominant frequency, pulse rate, call duration, and rise time were positively significant. Conclusions:In Bach Ma National Park, when air temperature in the recording area decreased to <16.6°C, and advertisement calls of adult males virtually ceased in all three populations.

Tracing a toad invasion: lack of mitochondrial DNA variation, haplotype origins, and potential distribution of introduced Duttaphrynus melanostictus in Madagascar

“…Competition for reproduction sites seems to be an issue as well, given that this species has a high rate of fecundity with up to nine thousand eggs per clutch (Cai, 1979; Van Leeuwen, personal observation; sup-plementary table S1). Further, it uses all available water bodies including ponds and streams (Ngo and Ngo, 2013) that native amphibians usually inhabit. Given the toxicity of the secretions of bufonid toads, D. melanostictus might also pose threats to native Madagascan predators, including the many frog-eating snakes, birds and mammals (Glaw and Vences, 2007).…”

Feeding ecology of the common sun skink,Eutropis multifasciata(Reptilia: Squamata: Scincidae), in the plains of central Vietnam

“…We estimated the volume (V) of food items using an ellipsoid formula (with π = 3.14159; Biavati et al 2004;Caldart et al 2012;Borges et al 2013;Ngo and Ngo 2013):…”

Signals of forest degradation in the demography of common Asian amphibians

“…Toads were measured and weighed, and sex was determined. Male D. melanostictus reach sexual maturity by 50 mm in size ( Huang, Lin & Yu, 1997 ; Ngo & Ngo, 2013 ), and we used this as a lower size limit for making a sex determination. Sex in this species can be determined by relative size of forelimbs, which are notably larger in males even outside of the breeding season, and by presence of nuptial pads, which often remain apparent beyond the breeding season.…”