Abstract
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. 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. 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.
Highlights
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
Reproductive activity In total, 169 specimens were collected from Bach Ma National Park, Thua Thien-Hue Province, central Vietnam
This femalebiased sexual size dimorphism is common in anurans (Shine 1979); it tends to be more pronounced in larger species (Salthe and Duellman 1973) and is usually explained as the effect of different selective pressures acting on male and female body sizes
Summary
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 Asian common toad Duttaphrynus melanostictus (formerly Bufo melanostictus) is a widely distributed species in South Asia. It inhabits Taiwan and southwestern and southern China, including Hainan Island, southward through Southeast Asia to Indonesia, and westward to India and Sri Lanka (Shieh 1993). According to Pratihar and Kundu (2010), some adult females of this species grow to almost 20 cm long (from the tip of the snout to the tip of the fourth toe). This species is commonly distributed in villages, towns, and open areas, and only seen occasionally in primary forest. The species can hibernate in mud holes (Nguyen et al 2005; Lin et al 2011)
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